Yi Gu

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Name: 顾宜; Gu, Yi

Organization: Sichuan University , China

Department: College of Polymer Science and Engineering

Title: Professor(PhD)

TOPICS

Polymer

Polyimide Polysulfone

Chemicals
References

Polybenzoxazines: Thermal Responsiveness of Hydrogen Bonds and Application as Latent Curing Agents for Thermosetting Resins

Co-reporter:Shuai Zhang, Po Yang, Yun Bai, Tao Zhou, Rongqi Zhu, and Yi Gu

ACS Omega April 2017? Volume 2(Issue 4) pp:1529-1529

Publication Date(Web):April 19, 2017

DOI:10.1021/acsomega.7b00075

This work aims at exploring the application of polybenzoxazines as thermal latent curing agents for epoxy resins. Thorough studies have shown that hydrogen bonds of polybenzoxazines block the reactivity of phenolic hydroxyl at ambient temperatures and break at elevated temperatures to release the free phenolic hydroxyl. On the basis of these findings, polybenzoxazines are used as thermal latent curing agents. Mixtures of polybenzoxazines and epoxy resins exhibit a long shelf life at room temperature, and the corresponding copolymers possess enhanced properties. This novel insight into using polybenzoxazines as thermal latent curing agents for epoxy resins is anticipated to help researchers explore novel latent curing agents and apply polybenzoxazines more widely.Topics: Analytical chemistry; Epoxy resins; Materials science; Mechanical properties; Molecular structure; Polyamines; Resins; Ring-opening polymerization; Thermal properties;

Modification of benzoxazine with aryl-ether-ether-ketone diphenol: preparation and characterization

Co-reporter:Yiqing Xia;Yifeng Lin;Qichao Ran;Rongqi Zhu

RSC Advances (2011-Present) 2017 vol. 7(Issue 3) pp:1617-1625

Publication Date(Web):2017/01/04

DOI:10.1039/C6RA27493E

A highly active aryl-ether-ether-ketone diphenol intermediate (m-DHPBP) was synthesized by molecular design. Then it was introduced into benzoxazine (BA-a) as a modifier and a new modified benzoxazine resin system (BA-a/m-DHPBP-X) with varying contents of m-DHPBP was prepared. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the curing behaviour and to explore the polymerization mechanism of the BA-a/m-DHPBP-X mixtures by following major changes in the functional groups during the curing process. A significant reduction in the peak reaction temperature in the DSC curves and in the gel-time of BA-a/m-DHPBP-X indicated that m-DHPBP was an effective catalyst for the ring-opening polymerization (ROP) of benzoxazine. As the amount of m-DHPBP increased, the variation in benzene ring substituents of poly(BA-a/m-DHPBP-X) implied that m-DHPBP reacted with BA-a and finally embedded in the three dimensional networks of poly(BA-a). The thermal properties of the BA-a/m-DHPBP-X mixtures were evaluated by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA); they exhibited a higher initial storage modulus, maintained a high glass transition temperature (Tg) and displayed a higher char yield compared with the neat poly(BA-a). Furthermore, the tensile properties of poly(BA-a/m-DHPBP-X) were good. Thus a modified benzoxazine resin system with “high strength, high modulus and high toughness” was prepared, and a more than 60% increase in tensile strength and 78% increase in elongation at break were observed by incorporating 20 wt% m-DHPBP into poly(BA-a). We believe that this modified benzoxazine system can be applied as a matrix for high-performance composites due to its excellent processibility and superior comprehensive mechanical properties.

Greatly improved thermal properties of polybenzoxazine via modification by acetylene/aldehyde groups

Co-reporter:Yi Xu, Jie Dai, Qichao Ran, Yi Gu

Polymer 2017 Volume 123(Volume 123) pp:

Publication Date(Web):11 August 2017

DOI:10.1016/j.polymer.2017.07.021

•A novel benzoxazine resin bearing acetylene/aldehyde groups was developed.•The cured product has outstanding thermal properties and lower curing temperature.•Its Tg and char yield at 800 °C under N2 are as high as 459 °C and 77.2%.•The above high values is a breakthrough for thermosetting resins.•This benzoxazine has great potential as a matrix for high performance composite.A novel benzoxazine resin (PHB-apa) with low curing temperature, high Tg and excellent thermal stability was developed. Be different from other benzoxazines, PHB-apa contains both aldehyde group and acetylene group on the phenol ring and the aniline ring, respectively. Other benzoxazine monomers contain only one aldehyde group or one acetylene group were chosen for comparison. Their chemical structures were proved by 1H and 13C Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). The polymerization reaction monitored by Differential Scanning Calorimetry (DSC) and FTIR suggests that the presence of the aldehyde group in PHB-apa leads to a low curing temperature that is benefit for processing. Besides, it is noticeable that this new polybenzoxazine has outstanding thermal property due to the cooperative reaction of the aldehyde group and the acetylene group. Its Tg from Dynamic thermo mechanical analysis (DMA) and char yield at 800 °C under N2 from Thermogravimetric Analysis (TGA) are as high as 459 °C and 77.2%, respectively. Such kind of high values is a breakthrough for thermosetting resins, which will allow its application as a heat-resistant material at a much high temperature.A novel benzoxazine resin (PHB-apa) via modification by acetylene/aldehyde groups was successfully prepared and it exhibits excellent performance for low curing temperature, high Tg and excellent thermal stability.Download high-res image (220KB)Download full-size image

Hydrogen bonds in the blends of polybenzoxazines and N,N′-(pyridine-2,6-diyl)diacetamide: Inter- or intra-molecular hydrogen bonds?

Co-reporter:Yun Bai, Po Yang, Tao Wang, Yi Gu

Journal of Molecular Structure 2017 Volume 1147(Volume 1147) pp:

Publication Date(Web):5 November 2017

DOI:10.1016/j.molstruc.2017.06.081

•Effect of additional hydrogen-bond donors on polybenzoxazine blends were studied.•Additional hydrogen-bond donors benefit the hydrogen bonds of polybenzoxazines.•Hydrogen bonds form between polybenzoxazines and additional hydrogen-bond donor.This work aims at probing the formation of hydrogen bonds in the blends of polybenzoxazines and additional hydrogen-bond donor moieties-containing compounds. Based on experimental study and computer simulations, we found that the dominant hydrogen bonds of p-cresol-aniline-based dimer (pC-a-D) and polybenzoxazines (PpC-a) were OH⋯N while N,N′-(pyridine-2,6-diyl)diacetamide (DAA) was NH⋯OC hydrogen bond. After blending pC-a-D or PpC-a with DAA, additional hydrogen bonds formed, i.e., OH⋯OC and OH⋯NH. Moreover, the total quantity of hydrogen bonds of the blends increased. These results suggested that hydrogen bonds formed between polybenzoxazines and the additional hydrogen-bond donor moieties-containing polymers or compounds, and furthermore would be desirable to foster the promoted performance. This novel insight about polybenzoxazine blends is anticipated to help researchers explore more blends of polybenzoxazines with excellent properties.Download high-res image (795KB)Download full-size image

A study on the chain propagation of benzoxazine

Co-reporter:Hongyuan Wang, Rongqi Zhu, Po Yang and Yi Gu

Polymer Chemistry 2016 vol. 7(Issue 4) pp:860-866

Publication Date(Web):20 Nov 2015

DOI:10.1039/C5PY01397F

The chain propagations of Bisphenol A-aniline benzoxazine (defined as BA-a) polymerized by thermal induction and in the presence of various catalysts or curing agents during the curing process before gelation were investigated in this paper. DSC, gel time test and GPC were used to measure the curing behavior, number-average molecular weight (n), glass transition temperature (Tg), gel time (tgel) and curing conversion (α) of different benzoxazine systems. By comparing the experimental results (n and Tg) with the models of step polymerizations and chain polymerizations proposed by Flory et al., three kinds of chain propagations of benzoxazine were observed and confirmed. The step polymerization occurred in the thermal induction or in the presence of catalyst N,N-dibenzylaniline (tAm), and then the non-living chain polymerization and the living chain polymerization occurred, respectively, when indole (Id) and other additives such as phenol (tBp), acid (HA), imidazole (IMZ) etc. were added to benzoxazine as catalysts or curing agents. Moreover, the relationship between the chain propagation and curing kinetics of benzoxazine was also established. The chain propagation of benzoxazine systems involves step polymerization, non-living chain polymerization andliving chain polymerization, the conversion of the gel point (αgel) is almost equal to, less than and greater than the value of the conversion at which the polymerization rate reaches a maximum (αmax), respectively. The results may contribute to a better understanding of the polymerization mechanism of benzoxazine and provide new approaches to effective control of the polymerization kinetics and growth crosslink structures of benzoxazine.

Effect of hydrogen bonds on the polymerization of benzoxazines: influence and control

Co-reporter:Yun Bai, Po Yang, Yan Song, Rongqi Zhu and Yi Gu

RSC Advances 2016 vol. 6(Issue 51) pp:45630-45635

Publication Date(Web):04 May 2016

DOI:10.1039/C6RA08881C

This work aims to disclose the reason that prohibited the preparation of highly crosslinked polybenzoxazines. Based on experimental study and computer simulations, we found that the dominant –OH⋯N hydrogen bond (Type I –OH⋯N hydrogen bond) of polybenzoxazines blocked high-degree polymerization and resulted in a low crosslink density by decreasing the charge densities of corresponding hydroxyl groups on phenols. As a solution, by introducing additional hydrogen-bond acceptors, the formation of Type I –OH⋯N hydrogen bonds could be suppressed, which enables a high-degree of polymerization of benzoxazines. This novel insight about benzoxazine polymerization is anticipated to help researchers explore more types of polybenzoxazines with enhanced properties.

Influence of curing sequence on phase structure and properties of bisphenol A-aniline benzoxazine/N,N-(2,2,4-trimethylhexane-1,6-diyl) bis (maleimide)/imidazole blend

Co-reporter:Zhi Wang;Ni Cao;Yu Miao

Journal of Applied Polymer Science 2016 Volume 133( Issue 14) pp:

Publication Date(Web):

DOI:10.1002/app.43259

ABSTRACT

The effects of different catalysts on the curing sequences of bisphenol A-aniline benzoxazine (BA-a)/N,N′-(2,2,4-trimethylhexane-1,6-diyl) bis (maleimide) (TBMI) blends were studied, and the influence of curing sequences on the phase structure and properties of products was discussed. In BA-a/TBMI/adipic acid, BA-a homopolymerized first, followed by the copolymerization between TBMI and ring-opened benzoxazine. This curing sequence led to strong copolymerization, which limited the movement of components and resulted in homogeneous structures of the final products. However, in BA-a/TBMI/imidazole, TBMI homopolymerized firstly, followed by the homopolymerization of BA-a. BA-a and TBMI hardly copolymerized, and the products presented phase-separated (bi-continuous phase) structures finally. The degree of copolymerization and phase structures of products differed due to different curing sequences when different catalysts were used. Furthermore, the product with phase-separated structures had improved thermal property and toughness compared to those of the product with homogeneous structures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43259.

A novel benzoxazine/cyanate ester blend with sea-island phase structures

Co-reporter:Xiaodan Li, Xiaoyong Luo and Yi Gu

Physical Chemistry Chemical Physics 2015 vol. 17(Issue 29) pp:19255-19260

Publication Date(Web):19 Jun 2015

DOI:10.1039/C5CP02426A

A novel cardanol-based benzoxazine (C-BOZ)/bisphenol A dicyanate ester (BADCy) blend with sea-island phase structures was successfully prepared via reaction-induced phase separation. The introduction of a long-chain alkyl group on the benzene ring significantly enhanced the thermodynamic differences between C-BOZ and BADCy. With the increase of the BADCy content, the Flory–Huggins interaction parameter (χ) of the blend decreased. By adjusting the ratio of the two components, sea-island phase separations were observed in C-BOZ/BADCy blends during the curing process. The dispersed phase was a C-BOZ rich phase, while the matrix was the crosslinked network composed of triazine rings and ring-opened C-BOZ. On the DMA curves of 9/1, 8/2 and 7/3 cured blends, there were two distinct Tgs. But with the increase of the BADCy content, the extent of phase separation was reduced. When the ratio reached 5/5, there was only one Tg because the viscosity of the blend was too high for phase separation to occur.

Correction: A novel benzoxazine/cyanate ester blend with sea-island phase structures

Co-reporter:Xiaodan Li, Xiaoyong Luo and Yi Gu

Physical Chemistry Chemical Physics 2015 vol. 17(Issue 31) pp:20425-20425

Publication Date(Web):17 Jul 2015

DOI:10.1039/C5CP90128F

Correction for ‘A novel benzoxazine/cyanate ester blend with sea-island phase structures’ by Xiaodan Li et al., Phys. Chem. Chem. Phys., 2015, DOI: 10.1039/c5cp02426a.

Study on the thermal degradation behavior of sulfone-containing polybenzoxazines via Py-GC-MS

Co-reporter:Huachuan Zhang, Wu Gu, Rongqi Zhu, Qichao Ran, Yi Gu

Polymer Degradation and Stability 2015 Volume 111() pp:38-45

Publication Date(Web):January 2015

DOI:10.1016/j.polymdegradstab.2014.10.020

A stepwise-temperature testing method by Py-GC-MS was applied to study the thermal degradation processes of two polybenzoxazines containing sulfone group. This new method can give lots of information about degradation gas products and the variation of chemical structures in bulk. The results showed that (1) for 4,4′-sulfonylbiphenol/aniline based polybenzoxazine (PBS), the thermal degradation fragments tend to form heterocyclic compounds in bulk phase; (2) for 4,4′-sulfonyldianiline/phenol based polybenzoxazine (PBAS), crosslinked phenol and aniline structures were preferentially produced from the thermal decomposition fragments in bulk phase. Therefore, it means that PBS is more likely to generate thermally stable fused rings like chars in bulk during pyrolysis process. As the result, a deep insight into the pyrolysis process of polybenzoxazines was achieved by this method, which probably provides a new way to study the degradation behavior of other polymers.

Effect of phenol on the synthesis of benzoxazine

Co-reporter:Qin Zhang, Po Yang, Yuyuan Deng, Chengxi Zhang, Rongqi Zhu and Yi Gu

RSC Advances 2015 vol. 5(Issue 125) pp:103203-103209

Publication Date(Web):27 Nov 2015

DOI:10.1039/C5RA17395G

This work aims to search the key starting materials and the key step of benzoxazine synthesis using primary amine, phenol and formaldehyde as the starting materials. The reaction kinetics were investigated by gas chromatography. The kinetic parameters of benzoxazine formation, such as reaction order, rate constant and activation energy, were found to approximately equal those of phenol consumption, which revealed that phenol was the key starting material and played an important role in the synthesis of benzoxazine. Furthermore, step 2, the reaction between formaldehyde–amine derivatives and phenol for the production of a mannich base was the controlling step. This improved insight into the benzoxazine synthesis is expected to help researchers explore novel benzoxazines and control their synthesis.

Study on thermal degradation mechanism of a cured aldehyde-functional benzoxazine

Co-reporter:Chao Li, Qichao Ran, Rongqi Zhu and Yi Gu

RSC Advances 2015 vol. 5(Issue 29) pp:22593-22600

Publication Date(Web):18 Feb 2015

DOI:10.1039/C5RA00350D

A cured product of aldehyde-functional benzoxazine has good heat-resistant performance. The thermal degradation process of this polybenzoxazine was actively studied by TGA-FTIR and Py-GC/MS. The temperature range of pyrolysis and the major products were determined by TGA-FTIR. A stepwise-temperature testing method based on Py-GC/MS was employed to identify the structures and contents of the pyrolysis products at different temperature stages. Transformation and chemical structures of the polymer bulk during the pyrolysis process were speculated. The results showed that the reactions of the aldehyde groups can form special crosslinking structures which effectively prevent the release of phenols during the pyrolysis process. Additionally, benzophenone compounds and carbon monoxide were detected.

Blends of sulfonated polysulfone/polysulfone/4,4-diaminodiphenyl methane-based benzoxazine: multiphase structures and properties

Co-reporter:Yiqing Xia;Po Yang;Yu Miao;Chaoliang Zhang

Polymer International 2015 Volume 64( Issue 1) pp:118-125

Publication Date(Web):

DOI:10.1002/pi.4766

Abstract

To overcome the brittleness of polybenzoxazine and decrease its high curing temperature, sulfonated polysulfone/polysulfone/benzoxazine ternary blends were prepared, and their curing behaviors, phase structures and properties were probed. Sulfonated polysulfone (SPSU) was synthesized firstly, and then SPSU was applied to modify 4,4′-diaminodiphenyl methane based benzoxazine (BZ-m) along with polysulfone. The results obtained from differential scanning calorimetry showed that the addition of SPSU efficiently decreased the curing temperature of BZ-m, and furthermore affected the phase structures of SPSU/PSU/PBZ-m blends. The phase structures of the corresponding blends were confirmed by scanning electron microscopy and dynamic mechanical analysis to probe the relationship between the microstructures and mechanical properties. According to the results, the blends presented complicated phase structures and exhibited good comprehensive mechanical properties. Moreover, all the blends displayed good thermal stability and the blends with SPSU-PBZ-m core − shell particles and a phase inversion structure exhibited the highest comprehensive mechanical properties. We believe these blends can meet the requirement of applications relating to high strength and good toughness matrix for fiber reinforced composites. © 2014 Society of Chemical Industry

Influence of substituent on equilibrium of benzoxazine synthesis from Mannich base and formaldehyde

Co-reporter:Yuyuan Deng, Qin Zhang, Qianhao Zhou, Chengxi Zhang, Rongqi Zhu and Yi Gu

Physical Chemistry Chemical Physics 2014 vol. 16(Issue 34) pp:18341-18348

Publication Date(Web):11 Jul 2014

DOI:10.1039/C4CP02053G

N-Substituted aminomethylphenol (Mannich base) and 3,4-dihydro-2H-3-substituted 1,3-benzoxazine (benzoxazine) were synthesized from substituted phenol (p-cresol, phenol, p-chlorophenol), substituted aniline (p-toluidine, aniline, p-chloroaniline) and formaldehyde to study influence of substituent on equilibrium of benzoxazine synthesis from Mannich base and formaldehyde. 1H-NMR and charges of nitrogen and oxygen atoms illustrate effect of substituent on reactivity of Mannich base, while oxazine ring stability is characterized by differential scanning calorimetry (DSC) and C–O bond order. Equilibrium constants were tested from 50 °C to 80 °C, and the results show that substituent attached to phenol or aniline has same impact on reactivity of Mannich base; however, it has opposite influence on oxazine ring stability and equilibrium constant. Compared with the phenol–aniline system, electron-donating methyl on phenol or aniline increases the charge of nitrogen and oxygen atoms in Mannich base. When the methyl group is located at para position of phenol, oxazine ring stability increases, and the equilibrium constant climbs, whereas when the methyl group is located at the para position of aniline, oxazine ring stability decreases, the benzoxazine hydrolysis tends to happen and equilibrium constant is significantly low.

Reaction-induced phase separation in a bisphenol A-aniline benzoxazine–N,N′-(2,2,4-trimethylhexane-1,6-diyl)bis(maleimide)–imidazole blend: the effect of changing the concentration on morphology

Co-reporter:Zhi Wang, Qichao Ran, Rongqi Zhu and Yi Gu

Physical Chemistry Chemical Physics 2014 vol. 16(Issue 11) pp:5326-5332

Publication Date(Web):20 Jan 2014

DOI:10.1039/C3CP54960G

The effect of the concentration changes on morphology was researched by modulating the molar ratio of bisphenol A-aniline benzoxazine (BA-a) and N,N′-(2,2,4-trimethylhexane-1,6-diyl)bis(maleimide) (TBMI); the relationships between the concentration changes, the curing rate, rheological properties, and morphologies of blends were examined in this paper. The cured blends showed different morphologies at different concentrations, and the morphologies changed from a sea-island structure to a bi-continuous structure followed by a homogeneous structure when the molar ratio of BA-a was decreased. This effect was caused by the relative rates of the phase separation and the curing reaction. Meanwhile, from the thermodynamic calculations, it was found that the concentration changes altered the Gibbs free energy, while the miscibility of blends improved after decreasing the BA-a content. Moreover, from the analysis and the Flory–Huggins equation, it was found that the phase separation of BA-a–TBMI–imidazole occurred due to the molecular weights of the components and the large discrepancy between those weights.

A novel benzoxazine/epoxy blend with multiphase structure

Co-reporter:Pei Zhao, Qian Zhou, Yuyuan Deng, Rongqi Zhu and Yi Gu

RSC Advances 2014 vol. 4(Issue 1) pp:238-242

Publication Date(Web):05 Nov 2013

DOI:10.1039/C3RA44738C

A novel benzoxazine (BOZ)/epoxy resin (ER) blend with multiphase structure was successfully prepared under the catalysis of imidazole (MZ) via reaction-induced phase separation. The toughness and thermal properties of the novel blend were greatly improved compared with the homogeneous PBOZ and PBOZ/ER systems.

Kinetics of 3,4-Dihydro-2H-3-phenyl-1,3-benzoxazine Synthesis from Mannich Base and Formaldehyde

Co-reporter:Yuyuan Deng, Qin Zhang, Huachuan Zhang, Chengxi Zhang, Wenhu Wang, and Yi Gu

Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 5) pp:1933-1939

Publication Date(Web):January 8, 2014

DOI:10.1021/ie402978s

To study oxazine ring formation in benzoxazine synthesis from phenol, primary amine and formaldehyde, reactions between 2-phenylaminomethylphenol (Mannich base) and formaldehyde in homogeneous dioxane/water solution are researched. Reaction orders, rate constants at different temperatures, and activation energy are calculated, the process of reaction is proposed, and the influence of acid and base is discussed. The reaction can occur at low temperature and generate the product 3,4-dihydro-2H-3-phenyl-1,3-benzoxazine. No intermediate 2-(N-hydroxymethyl-N-phenylamino)methylphenols are observed. The concentration of a Mannich base has little effect on the reaction rate, while the reaction is first-order to formaldehyde. Based on chemical properties of formaldehyde in aqueous solution, the reaction process includes the following three steps: degradation of poly(oxymethylene) glycols to methylene glycol, dehydration of methylene glycol to formaldehyde molecule, and the reaction between a Mannich base and formaldehyde molecule to benzoxazine. Dehydration of methylene glycols to formaldehyde molecules is the rate-controlling step.

Reaction induced phase separation in thermosetting/thermosetting blends: effects of imidazole content on the phase separation of benzoxazine/epoxy blends

Co-reporter:Pei Zhao, Qian Zhou, Yu Yuan Deng, Rong Qi Zhu and Yi Gu

RSC Advances 2014 vol. 4(Issue 106) pp:61634-61642

Publication Date(Web):11 Nov 2014

DOI:10.1039/C4RA10484F

A micro-sized phase separation structure was successfully realized in normally homogeneous benzoxazine (BZ)/epoxy (ER) (mass ratio: 80/20) blending systems in situ by enhancing the content of catalyst, imidazole (MZ). To reveal the internal relationships between the content of MZ and the phase separation, the phase morphology, polymerization activity, rheology and relaxation behaviors of BZ/ER blends with different contents of MZ were investigated by means of turbidity observation, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and rheological and dynamic mechanical thermal analysis (DMA), respectively. The results showed that in the BZ/ER/MZ blending system, when the content of MZ was high enough (≥8 wt%), micro-sized ER-rich domains could be obtained, otherwise a homogeneous structure was obtained. What's more, the curing reaction of BZ/ER/MZ blends at 110 °C was mainly associated with the polymerization of ER with MZ. Increasing the MZ content not only increased the reactivity difference between ER and BZ and accelerated the gelation, but also resulted in branched or looser ER networks and relatively low system viscosity, therefore was beneficial to phase separation.

The catalytic mechanism of benzoxazine to the polymerization of cyanate ester

Co-reporter:Xiaodan Li, Xiaoyong Luo, Ming Liu, Qichao Ran, Yi Gu

Materials Chemistry and Physics 2014 Volume 148(1–2) pp:328-334

Publication Date(Web):14 November 2014

DOI:10.1016/j.matchemphys.2014.07.051

•Two model compounds, PA and s-PA, were successfully synthesized and purificated.•There is no phenolic hydroxyl in the final ring-opened structures of s-PA.•Compared with PA, s-PA also can catalyze the polymerization of BADCy.•The main catalytic process is caused by the oxygen anion.•The catalytic effect from the phenolic hydroxyl is a secondary factor.Two model compounds, 3-Phenyl-3,4-dihydro-2H-1,3-benzoxazine (PA) and 6,8-dimethyl-3-(2,4,6-trimethyl-phenyl)-3,4-dihydro-2H-1,3-benzoxazine (s-PA), were successfully synthesized and purificated. Compared with PA, s-PA also catalyzed the polymerization of BADCy even though there was no phenolic hydroxyl in its final ring-opened structures. It was confirmed that the real mechanism of benzoxazine catalyzing the polymerization of cyanate ester is the nucleophilic addition reaction of the oxygen anion on ring-opened benzoxazine to the positively charged carbon atom on cyano group. The catalytic effect also contains the contribution from the phenolic hydroxyl, but it is a secondary factor.

A novel polybenzoxazine containing styrylpyridine structure via the Knoevenagel reaction

Co-reporter:Huachuan Zhang;Min Li;Yuyuan Deng;Chengxi Zhang;Qichao Ran

Journal of Applied Polymer Science 2014 Volume 131( Issue 19) pp:

Publication Date(Web):

DOI:10.1002/app.40823

ABSTRACT

In this article, a kind of styrylpyridine-containing polybenzoxazine was obtained via the Knoevenagel reaction between benzaldehyde and methylpyridine groups. The benzoxazine monomer (MPBC) containing the benzaldehyde and methylpyridine groups was synthesized firstly and its structure was characterized by Fourier transform infrared (FTIR) spectra, ¹H NMR and ¹³C NMR. With the aid of differential scanning calorimetry, FTIR, and photoluminescent tests, the interesting curing behaviors were probed. The results showed that the ring-opening polymerization occurred at lower temperature, and the Knoevenagel reaction further took place at elevated temperature. The amine and phenol moieties were bonded together to form the styrylpyridine structure. Due to these special crosslinking structures, the corresponding polybenzoxazine exhibited excellent thermal stability, and had a special high char yield of 74.5%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40823.

Blends of 4,4′-diaminodiphenyl methane-based benzoxazine and polysulfone: morphologies and properties

Co-reporter:Yiqing Xia;Po Yang;Rongqi Zhu;Chaoliang Zhang

Journal of Polymer Research 2014 Volume 21( Issue 3) pp:

Publication Date(Web):2014 March

DOI:10.1007/s10965-014-0387-6

Polysulfone (PSU) was used to modify 4,4′-diaminodiphenyl methane-based benzoxazine (BZ-m) through reaction-induced phase separation. The curing behaviors and kinetics were investigated using differential scanning calorimeter (DSC), and the results showed that the activation energies of PSU/BZ-m mixtures polymerization increased as the amount of PSU increased. Dynamic mechanical analysis (DMA), temperature-modulated differential scanning calorimeter (TMDSC) and scanning electron microscopy (SEM) were applied to study the phase structures of PSU/BZ-m blends. Four different morphologies were obtained by increasing the proportion of PSU in this work. These blends displayed different properties due to the different phase morphologies. The blend with bicontinuous phase structure exhibited excellent mechanical properties and thermal properties, and we believe that these blends can be applied as matrices for high-performance composites.

Effect of hydrogen bonds on the modulus of bulk polybenzoxazines in the glassy state

Co-reporter:Po Yang, Xiaoying Wang, Haojun Fan and Yi Gu

Physical Chemistry Chemical Physics 2013 vol. 15(Issue 37) pp:15333-15338

Publication Date(Web):15 Apr 2013

DOI:10.1039/C3CP51001H

In this paper, the critical role of hydrogen bonds on the modulus of bulk polybenzoxazines in the glassy state was proved through introducing an additional hydrogen bond, CO⋯HO, into the polybenzoxazine. Thorough studies were carried out to resolve the different modulus behaviors of polybenzoxazines with and without this additional hydrogen bond as the temperature increases. With the aid of dynamic mechanical analysis and in situ Fourier transform infrared spectroscopy, we found that the different performances in modulus were in accordance with the changes of CO⋯HO and, therefore, revealed that the hydrogen bonds played a crucial role on the modulus of bulk polybenzoxazines in the glassy state. We believe this improved insight into the roles of hydrogen bonds is expected to help researchers explore novel polybenzoxazine resins with excellent thermal and mechanical properties.

Reaction induced phase separation in a bisphenol A-aniline benzoxazine/N,N′-(2,2,4-trimethylhexane-1,6-diyl)bis(maleimide)/imidazole blend: the effect of initial curing temperature on morphology and properties

Co-reporter:Zhi Wang, Zhen Zhang, Qichao Ran, Rongqi Zhu and Yi Gu

RSC Advances 2013 vol. 3(Issue 33) pp:14029-14036

Publication Date(Web):16 May 2013

DOI:10.1039/C3RA40868J

The effect of initial curing temperature on final morphology, the influence of different morphologies on the properties and the reason for the initial curing temperature's effect on phase separation in a bisphenol A-aniline benzoxazine (BA-a)/N,N′-(2,2,4-trimethylhexane-1,6-diyl)bis(maleimide) (TBMI)/imidazole blend were studied in this paper. The blend showed different morphologies at different initial curing temperatures and the morphologies changed from a clear bi-continuous structure to an obscure structure, followed by an interpenetrating network, with increasing initial curing temperature. This may be mainly caused by the amount of co-reaction of two monomers and the relative rates of phase separation and reaction. At the same time, the Flory–Huggins parameter of blends became smaller and smaller as the initial curing temperature increased, which led to a difficulty in phase separation due to the thermodynamics. Finally, phase separated products showed improved toughness and thermal properties.

A novel benzoxazine/bismaleimide blend resulting in bi-continuous phase separated morphology

Co-reporter:Zhi Wang, Qichao Ran, Rongqi Zhu and Yi Gu

RSC Advances 2013 vol. 3(Issue 5) pp:1350-1353

Publication Date(Web):26 Nov 2012

DOI:10.1039/C2RA22508E

A novel modified polybenzoxazine with bi-continuous phase separated morphology was successfully prepared from the blend of bisphenol A-aniline benzoxazine (BA-a), N,N′-(2,2,4-trimethylhexane-1,6-diyl)bismaleimide (TBMI) and catalyst imidazole. The thermal and toughness properties of the phase-separated blend cast were improved compared with polybenzoxazine.

Effect of Hydrogen Bonds on Structures and Glass Transition Temperatures of MaleimideIsobutene Alternating Copolymers: Molecular Dynamics Simulation Study

Co-reporter:Qian-Hao Zhou;Ming Li;Po Yang

Macromolecular Theory and Simulations 2013 Volume 22( Issue 2) pp:107-114

Publication Date(Web):

DOI:10.1002/mats.201200057

Research on curing mechanism and thermal property of bis-allyl benzoxazine and N,N′-(2,2,4-trimethylhexane-1,6-diyl) dimaleimide blend

Co-reporter:Zhi Wang, Jiacheng Zhao, Qichao Ran, Rongqi Zhu, Yi Gu

Reactive and Functional Polymers 2013 73(4) pp: 668-673

Publication Date(Web):April 2013

DOI:10.1016/j.reactfunctpolym.2013.01.015

The curing behavior and thermal property of graphene oxide/benzoxazine nanocomposites

Co-reporter:Ming Zeng, Jing Wang, Ranran Li, Jianxin Liu, Wei Chen, Qingyu Xu, Yi Gu

Polymer 2013 Volume 54(Issue 12) pp:3107-3116

Publication Date(Web):24 May 2013

DOI:10.1016/j.polymer.2013.03.069

Two series of benzoxazine (BOZ) based composites were prepared with graphene oxide (GO) and graphite via in situ intercalative polymerization. Based on isothermal and non-isothermal mode Differential Scanning Calorimetry results, BOZ with the addition of GO could not only decrease the cure temperature, but also increase the cure rate of BOZ. On the contrary, BOZ with the addition of graphite would delay the polymerization of BOZ monomer. It was hypothesized that carboxyl groups of GO acted as weak organic acid which accelerated the ring opening procedure. Interestingly, BOZ/GO composite with 1 wt% GO occupied the least time to form polymer networks, attributing to the catalytic effect and good dispersion of GO. Moreover, BOZ with 1 wt% content of GO had relatively higher glass transition temperature and char yield than those of the corresponding BOZ/graphite sample, which was due to relatively stronger intermolecular interactions between GO and BOZ.

Poly(benzoxazole-amide-imide) copolymers for interlevel dielectrics: interchain hydrogen bonding, molecular arrangement and properties

Co-reporter:Yongbing Zhuang

Journal of Polymer Research 2013 Volume 20( Issue 6) pp:

Publication Date(Web):2013 June

DOI:10.1007/s10965-013-0168-7

A series of novel random poly(benzoxazole-amide-imide) copolymers were synthesized via the poly(amic acid)s from the reaction of 5-amino-2-(4-aminophenyl)benzoxazole (BOA) and 4-amino-N-(4-aminophenyl)benzamide (DABA) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). The corresponding homopolyimides were also prepared for comparison. The chemical composition, interchain hydrogen bonding and molecular arrangement of the copolyimides in solid films were investigated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, computation techniques and wide angle X-ray diffraction (WAXD). The results indicated that the interchain hydrogen bonds were most likely formed between the amide oxygen atoms and -N-H bands. And the ordered chain packing structures of copolyimide films were completely different from those of the homopolyimide films probably due to the directional interchain hydrogen bonding interactions. The properties of the copolyimides were also well-characterized by tensile tests, dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA) along with water absorption, solubility and peel tests. All of the obtained copolyimide films exhibited high tensile strength (321 ~ 332 MPa) and modulus (6.76 ~ 8.03 GPa) without any stretching. Moreover, the glass transition temperatures (Tgs) and 5 % weight-loss temperatures of the copolyimides in nitrogen were above 322 and 560 °C, respectively. Additionally, the copolyimide films also exhibited low water absorption, excellent chemical resistance and good adhesion properties suitable for interlevel dielectrics in microelectronics.

Phase separation in benzoxazineepoxy resin blending systems

Co-reporter:Pei Zhao;Qian Zhou;Xin Liu;Rongqi Zhu;Qichao Ran;Yi Gu

Polymer Journal 2013 45(6) pp:637-644

Publication Date(Web):2012-10-17

DOI:10.1038/pj.2012.179

Enlarging dynamic asymmetry in situ by controlling the polymerization sequence is known to be a good way to obtain phase separation structures in benzoxazine (BZ)/epoxy resin (ER) blending systems. In this paper, the possible reactions in BZ/ER blends were studied using model components. The results indicated that once phenolic hydroxyl groups (OH) were produced by the polymerization of BZ resin, the copolymerization between BZ and ER resin was unavoidable, which was unfavorable for the phase separation of the BZ/ER system. If ER could polymerize before BZ, the copolymerization between BZ and ER is expected to be suppressed by the lack of phenolic OH, and the dynamic asymmetry between ER and BZ could thus be enlarged, both of which are favorable for phase separation. In the following studies, a series of ER resins having different molecular weights (Mn) were used to study the possibility of phase separation in the BZ/ER systems. The turbidity observation, dynamic mechanical analysis and scanning election microscope experiments indicated that if the Mn of ER 4370 g mol−1, phase separation could take place with the polymerization of BZ resin and different morphologies could be observed by varying the ER content.

The curing procedure for a benzoxazine–cyanate–epoxy system and the properties of the terpolymer

Co-reporter:Xiaodan Li, Yiqing Xia, Wenli Xu, Qichao Ran and Yi Gu

Polymer Chemistry 2012 vol. 3(Issue 6) pp:1629-1633

Publication Date(Web):25 Apr 2012

DOI:10.1039/C2PY20133J

Thermosetting terpolymer composed of benzoxazine (BA-a), cyanate ester (BADCy) and epoxy resin (E44) was prepared via co-curing reactions. The curing procedure for the ternary blend was studied by differential scanning calorimetry (DSC) and Fourier transform-infrared spectroscopy (FT-IR), and the thermal, mechanical and dielectric properties of the terpolymer were also characterized. The DSC results manifested a multiple curing pattern, suggesting the complexity of the reactions in the system. The FT-IR analysis further showed that the curing procedure involves several steps, firstly the cyclotrimerisation of cyanate ester after oxazine ring opening, followed by the isomerization of cyanurate and the reaction of isocyanurate with epoxy to form oxazolidinone, and finally the copolymerization of the remaining epoxy with benzoxazine and the self-polymerization of benzoxazine. Compared to the polybenzoxazine, the higher crosslinking density of the terpolymer led to the higher glass transition temperature (Tg), as well as the 5% and 10% weight loss temperatures (Td5 and Td10), indicating the better thermal stability of the terpolymer at service temperature. And the data for the mechanical and dielectric properties also showed that the terpolymer performs better than polybenzoxazine and the copolymer.

Molecular packing and properties of poly(benzoxazole-benzimidazole-imide) copolymers

Co-reporter:Yongbing Zhuang, Xiangyang Liu and Yi Gu

Polymer Chemistry 2012 vol. 3(Issue 6) pp:1517-1525

Publication Date(Web):25 Apr 2012

DOI:10.1039/C2PY20074K

Novel random poly(benzoxazole-benzimidazole-imide) copolymers were synthesized via the poly(amic acid)s from the reaction of 5-amino-2-(4-aminobenzene)benzoxazole (BOA) and 5-amino-2-(4-aminobenzene)benzimidazole (BIA) with 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA). The corresponding homopolyimides were also prepared for comparison. The resulting polyimides were characterized by different techniques to obtain their molecular packing and properties. The copolyimide films not only showed ordered arrangement of molecular chains, high packing coefficients and low water absorption, they also exhibited extremely high tensile strength (233.64–325.79 MPa) and modulus (5.18–5.75 GPa) without any stretching. The glass transition temperatures (Tgs) and 5% weight-loss temperatures in nitrogen of the copolyimides were in the range of 339–387 °C and 573–577 °C, respectively. The excellent mechanical and thermal properties of these copolyimides have been verified to be mainly attributed to the improving regularity of the interchain packing by the introduction of benzoxazole moieties as well as the enhancement of the hydrogen bonding by the incorporation of benzimidazole moieties. In addition, the copolyimide films also showed excellent adhesion to copper (637.0–960.4 N m−1) without any adhesion promoters. Meanwhile, the deviation of the experimental values of the molecular packing and properties from the expected values indicated the cooperative effects of BOA and BIA moieties on the copolyimide backbone at the molecular level.

Synthesis of a novel benzoxazine-containing benzoxazole structure and its high performance thermoset

Co-reporter:Po Yang

Journal of Applied Polymer Science 2012 Volume 124( Issue 3) pp:2415-2422

Publication Date(Web):

DOI:10.1002/app.35305

Abstract

A novel benzoxazine containing benzoxazole structures (Boz-BOA) was synthesized and its thermoset [P(Boz-BOA)] was prepared. For comparison, another benzoxazine-based 4,4′-diamine diphenyl methane (Boz-MDA) was also synthesized using a simplified procedure. The structure of Boz-BOA and Boz-MDA was confirmed by Fourier transform infrared (FTIR) and ¹H-NMR. Using FTIR and differential scanning calorimetric scans method, the curing behavior of Boz-BOA was probed, and the structure of P(Boz-BOA) was addressed, which was similar to that of P(Boz-MDA). Data of dynamic mechanical analysis showed that P(Boz-BOA) exhibited a better modulus retention at high temperature than P(Boz-MDA), which was attributed to benzoxazole structure restricting the mobility of chains, even at high temperature. P(Boz-BOA) also exhibited high glass transition temperature (T_g), excellent thermal stability, and low coefficient of thermal expansion value at wide temperature range. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A novel benzimidazole moiety-containing benzoxazine: Synthesis, polymerization, and thermal properties

Co-reporter:Po Yang

Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 7) pp:1261-1271

Publication Date(Web):

DOI:10.1002/pola.25873

Abstract

A novel benzoxazine-containing benzimidazole moiety (P-PABZ) was synthesized from 2-(4-aminophenyl)-1H-benzimidazole-5-amine and characterized. With the aid of differential scanning calorimetry and insitu Fourier transform infrared, we found the thermal polymerization of P-PABZ in bulk started around 140 °C and its favored polymerization pathway. Compared to the benzoxazine derived from 4,4′-diamine diphenyl methane (P-MDA), P-PABZ exhibited lower processing temperature, and the corresponding polymers had higher glass transition temperature and enhanced thermal stability. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

The structural transformation during polymerization of benzoxazine/FeCl3 and the effect on the thermal stability

Co-reporter:Qi-Chao Ran, Dong-Xia Zhang, Rong-Qi Zhu, Yi Gu

Polymer 2012 Volume 53(Issue 19) pp:4119-4127

Publication Date(Web):31 August 2012

DOI:10.1016/j.polymer.2012.07.033

The mixture of bisphenol A/aniline-based benzoxazine (BA-a) and FeCl3 was prepared at 40 °C and then was cured to get the polymer at elevated temperatures. The thermal stability of the modified polybenzoxazine was improved and its char yield at 800 °C increased by 11%. The reason for the improvement of the thermal stability and the structural transformation during polymerization was systematically investigated by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance spectroscopy (1H NMR), thermo-gravimetric analysis (TGA), pyrolysis-gas chromatography/mass spectrometry (Py/GC–MS), TGA-IR and element analysis (EA). The results show that BA-a can partially undergo the ring-opening polymerization at a low temperature in the presence of FeCl3 and generate some oligomers containing N, O-acetal-type bridge structures. At a high temperature, this structure can be transformed into the arylamine Mannich bridge structure which can delay degradation of the aniline moiety. Besides, the volatilization of fragmented Schiff base structures can be found during cure and more thermostable crosslinked structures are formed in polybenzoxazine. The entire polymerization mechanism of BA-a with FeCl3 was proposed.Graphical abstract

Effect of La2O3 on the thermal stability of polybenzoxazine based on 4,4′-diaminodiphenyl methane

Co-reporter:Yongfei Zhu;Hong Ling

Journal of Polymer Research 2012 Volume 19( Issue 7) pp:

Publication Date(Web):2012 July

DOI:10.1007/s10965-012-9904-7

La2O3/polybenzoxazine composite was prepared through incorporating La2O3 into benzoxazine based on phenol and 4,4′-diaminodiphenyl methane (BB) to study the effect of La2O3 on the thermal stability of crosslinked polybenzoxazines. The ring-opening polymerization of BB benzoxazine was analyzed by DSC and measurement of viscosity. The structure and the thermal stability of BB polybenzoxazine were characterized by FTIR, TGA and DMA. The thermal degradation processes of polybenzoxazine were investigated using TGA-FTIR. The results showed that La2O3 could form coordination interaction with the nitrogen atoms of BB and thus promoted the polymerization of BB benzoxazine. The coordination interaction could not influence the volatilization of the amine degradation gases during the thermal degradation process of BB polybenzoxazine due to the amine structure existing in the chemical crosslinking network of polybenzoxazine and being stable. Furthermore, the coordination interaction weakened the C-N and C-C bonds in CH2-NR-CH2- of BB polybenzoxazine and thus accelerated the appearance and volatilization of the phenolic gases during the thermal degradation process, resulting in the decrease of the thermal stability and char yield at 800 °C of BB polybenzoxazine.

Probing structural evolution of the poly(amic acid) containing benzoxazole moieties in backbone during thermal imidization

Co-reporter:Yongbing Zhuang

Journal of Polymer Research 2012 Volume 19( Issue 11) pp:

Publication Date(Web):2012 November

DOI:10.1007/s10965-012-0014-3

Structural evolution of a poly(amic acid) based on 5-amino-2-(4-aminophenyl)benzoxazole (BOA) and 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) in solid film during thermal imidization was investigated using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), ultraviolet–visible spectroscopy and computation techniques. The results of FTIR and geometries of the model compounds optimized using density functional theory (DFT) method revealed the changes of the chemical functionalities and electrical effect accompanying the thermal imidization reaction. The electronic charges of both the para-disubstituted phenyl and oxazole rings in BOA residues would be simultaneously withdrawn towards the BPDA residues as the imidization reaction proceeded. The WAXD results suggested that the molecular aggregation structures evolved from an overall amorphous morphology to a mixture of a highly ordered crystalline domain and an amorphous matrix. The highly ordered structures evolved via a three-step process: initial formation of a face-to-face π-stacking order in the short range, subsequent formation of an interchain ordered packing and final formation of crystalline structure by simultaneous improvement of the two orders. In particular, the formation of the interchain ordered packing required a very high imidization degree. Meanwhile, the average interchain distances in the amorphous matrix decreased with the evolution of the ordered structures in the ordered domain. Additionally, the cut-off wavelength and the transmittance (%) at 500 nm of the films changed obviously due to the structural evolution during the thermal imidization.

The co-curing process of a benzoxazine-cyanate system and the thermal properties of the copolymers

Co-reporter:Xiaodan Li and Yi Gu

Polymer Chemistry 2011 vol. 2(Issue 12) pp:2778-2781

Publication Date(Web):19 Oct 2011

DOI:10.1039/C1PY00379H

Investigations confirmed the co-reactions between oxazine rings and triazine rings formed a crosslinking network composed of triazine rings as part of the polybenzoxazine matrix. The copolymers have higher initial storage modulus compared to polycyanate ester and exhibit better thermal stabilities than the polybenzoxazine.

Thermal stability of polybenzoxazines with lanthanum chloride and their crosslinked structures

Co-reporter:Qi-Chao Ran, Nian Gao, Yi Gu

Polymer Degradation and Stability 2011 Volume 96(Issue 9) pp:1610-1615

Publication Date(Web):September 2011

DOI:10.1016/j.polymdegradstab.2011.06.002

Lanthanum chloride (LaCl3) was incorporated into five kinds of benzoxazines by different preparation methods. The thermal stability and the structures of polybenzoxazines were characterized by thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The evolved gases from the degradation process of polybenzoxazines were analyzed by FTIR. The results showed that the thermal stability and char yields of three kinds of polybenzoxazines containing LaCl3 can be improved obviously. LaCl3 has an important effect on the polymerization reactions of benzoxazines. More stable arylamine Mannich bridges were observed in the chemical structures of the polybenzoxazines. It is these structures that can effectively retard the volatilization of aniline derivatives and result in the improvement of the thermal stability of the polybenzoxazines.

Influence of electronic effects from bridging groups on synthetic reaction and thermally activated polymerization of bisphenol-based benzoxazines

Co-reporter:Xiaoying Wang;Feng Chen

Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 6) pp:1443-1452

Publication Date(Web):

DOI:10.1002/pola.24566

Abstract

Six bis-benzoxazines based on bisphenols with different bridging groups, C(CH₃)₂, CH₂, O, CO, SO₂, and single bond, were synthesized in toluene. The influence of electronic effects from bridging groups on ring-forming reaction and thermal ring-opening polymerization were relatively discussed in detail. Their structures were characterized by high-performance liquid chromatography, Fourier transform infrared, ¹H NMR, differential scanning calorimetry, and elementary analysis. The quantum chemistry parameters of the bisphenols and bis-benzoxazines were calculated by molecular simulation. The results indicated that the electron-withdrawing groups inhibited the synthetic reaction by decreasing the charge density of α-Cs of bisphenols and increasing energy barriers of the synthetic reactions. However, the electron-withdrawing groups promoted the thermally activated polymerization, which resulted from their activation energy and curing temperature decrease by increasing the bond length and lowering the bond energy of CO on oxazine rings. Besides, because of stronger electron-withdrawing sulfone group, there were more arylamine methylene Mannich bridge structure in the polybenzoxazine. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Concerted reactions of aldehyde groups during polymerization of an aldehyde-functional benzoxazine

Co-reporter:Qi-Chao Ran

Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 7) pp:1671-1677

Publication Date(Web):

DOI:10.1002/pola.24593

Abstract

Polymerization reactions of a new aldehyde-functional benzoxazine (4HBA-a) were investigated in detail. The curing behavior of 4HBA-a was studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) methods. The results indicate that the disappearance of the aldehyde group from 4HBA-a and the ring-opening reaction of 4HBA-a occur simultaneously. Gases evolved during the curing process of 4HBA-a were analyzed by thermogravimetric analyzer interfaced with FTIR spectra. The elimination of CO₂ is attributed to the oxidation and decarboxylation of the aldehyde groups. In addition, the crosslink sites of the aldehyde groups in the polymer structure are confirmed by model reactions. A possible reactive position should be sited in ortho position of phenol rather than ortho and/or para positions of N-phenyl ring. Finally, the crosslinked structures of polymerized 4HBA-a have been proposed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Study on morphology control and how to affect mechanical properties of polyimide/silica hybrid films

Co-reporter:Qin Jiaqiang;Li Zhen ;Gu Yi

Journal of Applied Polymer Science 2010 Volume 118( Issue 5) pp:2772-2777

Publication Date(Web):

DOI:10.1002/app.32158

Abstract

A series of polyimide (PI)/silica hybrid films were prepared by sol–gel method, using hydrolyzed tetraethoxysilane and poly amic acid-imides (PAA-Is), which were different imidization degree controlled by chemical imidization method. The imidization degree was characterized by Fourier transform infrared spectra and their corresponding morphology was characterized by scanning electron microscopy. The results show that there are two kinds of silica particles and their formative morphology obeys the double phase separation mechanism. According to the increase of PAA-I imidization degree, amount of nano silica particles decreased and the diameter of macro silica particles increased in the hybrid films. Tensile testing, dynamic mechanical analysis, and thermal mechanical analysis results show that, according to the amount of nano silica particles increasing, the hybrids have the higher the mechanical properties, glass transition temperature (T_g), and thermal expansion coefficient. Through controlling PI/silica hybrid films microstructure, its mechanical properties can be controlled. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Investigation of processing, thermal, and mechanical properties of a new composite matrix-benzoxazine containing aldehyde group

Co-reporter:Qi-chao Ran;Qiao Tian;Cao Li

Polymers for Advanced Technologies 2010 Volume 21( Issue 3) pp:170-176

Publication Date(Web):

DOI:10.1002/pat.1412

Abstract

A new benzoxazine aldehyde group containing monomer 3-phenyl-6-formyl-3, 4-dihydro-2H-1, 3-benzoxazine (Ald-B) was synthesized via the Mannich reaction of formaldehyde, p-hydroxybenzaldehyde, and aniline. The viscosities and curing behavior of the resins were studied. The results indicated that Ald-B has an initial viscosity lower than 0.110 Pa s at 90°C and the maximum temperature of the exotherm was at 196°C. Dynamic mechanical analysis (DMA) of the copolymer of Ald-B and methylenedianiline-type bis-benzoxazine (B-BOZ) showed only one T_g of 251°C and high crosslink density in the matrix. The thermal stability of the copolymer was improved noticeably and the char yield at 800°C is 68.4%. The tensile strength and flexural strength of this resin cast are 72 and 137 MPa, respectively. Copyright © 2009 John Wiley & Sons, Ltd.

Synthesis, characterization, and crystallization of thermoplastic aromatic semi-crystalline poly(ester-imide)s based on bis(trimellitic acid anhydride) phenyl ester

Co-reporter:Guo Yao;Min Wu

Polymers for Advanced Technologies 2010 Volume 21( Issue 12) pp:854-860

Publication Date(Web):

DOI:10.1002/pat.1510

Abstract

A high molecular weight aromatic homopoly(ester-imide) (homoPEI) was synthesized from homopoly(ester-amic acids) (homoPEAA), which was obtained from the reaction of bis(trimellitic acid anhydride) phenyl ester (BTAH) with 4-4'-oxydianiline ether (ODA). This homoPEI was melt-processable semi-crystalline polymer and displayed dual endothermic transitions which were attributed to the different levels of crystal perfection and size in the crystal structures. Four high molecular weight aromatic copoly(ester-imide)s (coPEIs) were synthesized via copoly(ester-amic acids)s (coPEAA) from the reaction of 4, 4'-oxydiphthalic anhydride (ODPA) and BTAH with ODA. The molar percentage of BTAH varied from 10 to 40%. When the molar percentages of BTAH were 30 and 40%, the resulting two coPEIs were crystallinable and their melting temperatures were 361°C and 356/371°C, respectively. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) results indicated that the crystal structures included short segments of BTAH/ODA and ODPA/ODA. The initial crystallization of the two coPEIs took place during imidization process. Thermogravimetric (TA) and mechanical analysis confirmed that both homoPEI and coPEIs showed almost no weight loss until 400°C in N₂ and good mechanical properties. Copyright © 2009 John Wiley & Sons, Ltd.

Synthesis of a novel benzoxazine containing benzoxazole structure

Co-reporter:Po Yang, Yi Gu

Chinese Chemical Letters 2010 Volume 21(Issue 5) pp:558-562

Publication Date(Web):May 2010

DOI:10.1016/j.cclet.2009.12.012

A high-purity benzoxazine (Boz-BOA) containing benzoxazole structure was successfully synthesized by three-step synthetic method using 2-(4-aminophenyl)-1H-benzoxazole-5-amine (BOA) and ortho-hydroxybenzaldehyde. The structure of Boz-BOA was confirmed by FTIR and 1H NMR spectra. The DSC was utilized to probe the curing behavior of Boz-BOA and exhibited a narrow melting peak and curing exothermic peak.

Correlation between hydrogen-bonding interaction and mechanical properties of polyimide fibers

Co-reporter:Xiangyang Liu;Guanqun Gao;Liang Dong;Guangdou Ye

Polymers for Advanced Technologies 2009 Volume 20( Issue 4) pp:362-366

Publication Date(Web):

DOI:10.1002/pat.1232

Abstract

Novel co-polymerization polyimide (PI) fibers based on 4,4′-oxydianiline (ODA)-pyromellitic dianhydride (PMDA) were prepared. 2-(4-Aminophenyl)-5-aminobenzimidazole (PABZ) containing the NH group was introduced into the structure of the fibers as the proton donor. The results of Fourier transform infrared (FTIR) and dynamic mechanical analysis (DMA) showed that hydrogen bonding occured between the NH group and chains, which strongly enhanced interchain interaction. This hydrogen bonding interaction increased the tensile strength and initial modulus of the PI fibers up to 2.5 times and 26 times, respectively, compared to those of homo-PI PMDA-ODA fibers with no hydrogen-bonding interaction because of the absence of proton donors after the imidization process. In the mean time, glass transition temperature (T_g) of the modified PI fibers was found to be 410–440°C, which was higher than that of the homo-PI PMDA-ODA fibers. From the result, a novel access to molecular design and manufacture of high performance PI fibers with good properties could be provided. Copyright © 2009 John Wiley & Sons, Ltd.

Synthesis and properties of novel thermotropic liquid crystalline copoly(ester-imide)s

Co-reporter:Guo Yao, Yi Gu

Chinese Chemical Letters 2009 20(12) pp: 1510-1513

Publication Date(Web):

DOI:10.1016/j.cclet.2009.07.004

Stretching induced steric interaction between backbone and side chain in a novel polyimide fiber

Co-reporter:Xiangyang Liu;Rui Pan;Wei Xu;Guangdou Ye

Polymer Engineering & Science 2009 Volume 49( Issue 6) pp:1225-1233

Publication Date(Web):

DOI:10.1002/pen.21284

Abstract

Stretching induces to form electric interaction between backbone and mesogenic side chain in the bulk of a novel polyimide fiber that was synthesized from 4,4′-oxydiphthalicanhydride (ODPA) and 6-(4-phenyl phenoxy) hexyl-3,5-diaminobenzoate (DABBE6), which results in unusual in situ self-reinforced function, and surprisingly, zigzag undulation of mechanical properties of the annealed polyimide fibers with increasing draw ratios. X-ray scattering and differential scanning calorimetry (DSC) results indicate that some order structures develop in the annealed fibers under tensile stress. Dynamic thermomechanical analysis (DMA) and DSC results also indicate that no phase separation is observed between backbone and side chain. Further results of experiments and computer molecular simulation prove that the biphenyl side chain can be parallel to the backbone via methylene spacers bending and together align orientationally under tensile stress to develop electronic interaction, and the molecular conformations are stabilized to form binding-like molecular structures by the interaction to enhance strength and rigidity of backbone. Meanwhile, formation of the interaction depends on the relative position between backbone and the trail phenyl group of side chain, which contributes to the zigzag undulation of tensile strength and initial modulus of the polyimide fibers. In addition, relationship of draw ratios and formation of the interaction was established, and a corresponding backbone-side chain-packing model was suggested. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Effect of chemical interaction on morphology and mechanical properties of CPI-OH/SiO2 hybrid films with coupling agent

Co-reporter:Jiaqiang Qin;Hui Zhao;Rongqi Zhu;Xinyuan Zhang

Journal of Applied Polymer Science 2007 Volume 104(Issue 6) pp:3530-3538

Publication Date(Web):22 MAR 2007

DOI:10.1002/app.25668

A novel hybrid film composed of copolyimide with hydroxyl group, silica and γ-glycidyloxypropyltrimethoxysilane (CPI-OH/SiO₂/GOTMS) was prepared by the sol–gel process based on hydrolyzed tetraethoxysilane (TEOS) under acidic condition. GOTMS, as the coupling agent, and hydroxyl group in PI chain were used to improve the compatibility between the PI and SiO₂. The components, morphologies, and mechanical properties of the hybrids were investigated by FTIR, UV–vis, SEM, stress–strain tests, and DMA. The results showed that SiO₂ particle size significantly decreased, fractured cross sections of hybrid were rougher, and the surfaces of spherical SiO₂ particles were more widely covered by PI component. The tensile mechanical properties of hybrids increased when adding GOTMS. The critical points of maximum tensile strength and elongation at break move from 11 to 16 wt % SiO₂ content. DMA results showed that the storage moduli of hybrids with GOTMS, when above 260°C, were obviously higher than those without GOTMS; the tan δ transition temperature of hybrid films went up from 317 to 337°C. It suggests that chemical interaction between CPI-OH and SiO₂ is formed and the PI molecular mobility is restricted by the chemical interaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3530–3538, 2007

Introduction of side chains containing biphenyl unit on the crystalline morphology and properties of polyimides

Co-reporter:Xikui Liu;Jin Wang;Jialing Tang

Journal of Applied Polymer Science 2006 Volume 101(Issue 4) pp:2255-2260

Publication Date(Web):27 MAY 2006

DOI:10.1002/app.23611

Several polyimides derived from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 3,5-diaminobenzate containing various side chains with biphenyl unit through various flexible spacer were prepared by thermal imidization. By incorporating side chains, the solubility was greatly enhanced and all the polyimides with side chains showed good solubility in polar solvents. During a continuous thermal imidization procedure, the BTDA/MPDA polyimide samples formed a novel banded spherulites with not only zigzag Maltese crosses, but also distinct extinction rings, while the polyimides with side chains revealed only fine grainy crystalline particle. X-ray diffraction of BTDA/MPDA powder showed sharp diffraction peak in the X-ray diffraction and revealed the existence of highly ordered crystalline structure in polyimide, while BTDA/PP0DA, BTDA/PP2DA, and BTDA/PP6DA polyimides with side chains revealed only a broad reflection at the low angle and demonstrated the presence of low-ordered layer structure. DSC confirmed that the introduction of side chains significantly reduced the melting points of the resulted polyimide, thus it greatly enhanced its thermal plasticity. However, the heat-resistant properties such as the thermal stability were generally decreased, and all the polyimide with side chains showed a typical two-step thermal degradation behavior relating to the pyrisis of side chains and polyimide backbone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2255–2260, 2006

Novel aromatic polyimide fiber with biphenyl side-groups: Dope synthesis and filament internal morphology control

Co-reporter:Xiangyang Liu;Wei Xu;Guangdou Ye

Polymer Engineering & Science 2006 Volume 46(Issue 2) pp:123-128

Publication Date(Web):23 DEC 2005

DOI:10.1002/pen.20442

A new organic-soluble aromatic polyimide with biphenyl side-groups has been synthesized from 4,4′-oxydiphthalic anhydride and 3,5-diamino-benzonic-4′-biphenyl ester (DABBE) via a one-step polymerization in m-cresol. A higher molecular weight polyimide has been obtained by the addition of chlorotrimethylsilane (TMSCl) in the solution of DABBE to form, in situ, silylated diamine. The optimum mole amount of TMSCl relative to the number of amino groups is 100%. This polyimide is soluble in m-cresol, allowing fibers to be spun from isotropic solution using a dry-jet wet spinning method. Based on a ternary phase diagram of m-cresol, ethanol, and water, controlling of the internal morphology of as-spun fibers has been achieved by varying the rate of polyimide coagulation through adjustment of nonsolvent/solvent miscibility in the coagulation bath. Scanning electron microscopic pictures show that filament internal morphologies ranged from porous-like to fully solid. The solid as-spun fibers can be drawn at high temperatures (>330°C) under tension to high drawn ratios (up to 6×), which produces a remarkable increase in tensile strength to about 1.0 GPa and an initial modulus higher than 60 GPa. POLYM. ENG. SCI. 46:123–128, 2006. © 2005 Society of Plastics Engineers

Effects of Catalyst Isoquinoline in Polymerization Process on the Aggregation Structures of Polyimide in Solution

Co-reporter:Jin Yang;Xiangyang Liu;Linghong Guo

Macromolecular Rapid Communications 2005 Volume 26(Issue 21) pp:1682-1686

Publication Date(Web):21 OCT 2005

DOI:10.1002/marc.200500485

Summary: A thermoreversible gel or a dendritic crystal has been obtained in a novel polyimide solution at low temperature, depending on the approach taken to add the isoquinoline catalyst during the polymerization process. By adding the isoquinoline at the beginning of polymerization, two kinds of layer structures in the gel are developed. However, by adding the isoquinoline after the polymerization has been carried out for one hour, a perfect dendritic crystalline structure is gradually developed in the polymerization solution.

Formation of new banded spherulites in polyimides

Co-reporter:Xikui Liu;Jialing Tang;Yuanyuan Zheng;Jialing Tang;Xikui Liu;Yuanyuan Zheng

Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 15) pp:1997-2004

Publication Date(Web):21 JUN 2005

DOI:10.1002/polb.20489

The crystalline morphology and structural development of aromatic polyimides during an optimum continuous thermal imidization procedure were examined by means of polarized optical microscopy and X-ray diffraction. During thermal imidization, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride/1,3-diaminobenzene polyimide samples formed complicated spherulites, which, in addition to zigzag Maltese crosses, also showed concentric extinction rings, which are characteristic of banded spherulites. The factors affecting the formation of banded spherulites were studied. The initial imidization conditions dramatically affected the formation of the banded spherulite morphology: slow heating (0.5 °C/min) or fast heating (20 °C/min) led to relatively small polyimide spherulites and less identifiable extinction rings. The morphological features were also affected by the molecular weight of the polyimide: higher molecular weight samples showed typical banded spherulites, whereas low-molecular-weight samples formed degenerated banded spherulites. In all the spherulites formed in 3,3′,4,4′-benzophenonetetracarboxylic dianhydride/1,3-diaminobenzene polyimides, special zigzag Maltese crosses, instead of normal Maltese crosses, were observed. The relationship between the imidization procedure and the spherulite morphology formation was also studied. X-ray and Fourier transform infrared together revealed that after several minutes of thermal treatment, the crystallization was nearly complete, with a 42.5% degree of crystallinity; meanwhile, only some poly(amic acid) converted to the corresponding polyimide, with a 27% degree of imidization. The crystalline morphology and structure formed in the initial stage of the imidization process were maintained during the following imidization processing at an elevated temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1997–2004, 2005

New polyimide–silica organic–inorganic hybrids

Co-reporter:Yi Gu;Yi Huang;Yi Huang

Journal of Applied Polymer Science 2003 Volume 88(Issue 9) pp:2210-2214

Publication Date(Web):13 MAR 2003

DOI:10.1002/app.11885

A series of polyimide–silica hybrid films with silica contents up to 30 wt % were successfully prepared by the sol-gel reaction of tetraethoxysiliane in the presence of poly(amic acid) containing pendent hydroxyl groups. The films were yellow and transparent when the silica content was less than 11 wt %. The chemical structure of the films was characterized by Fourier transform infrared spectroscopy, and the morphology of the films was investigated by scanning electronic microscopy and atomic force microscopy. Thermogravimetric analysis, differential scanning calorimetry, and stress–strain tests were used to measure the performance of the films. The results indicate that the glass-transition temperatures and decomposition temperatures of the hybrid films increased with increasing silica content, whereas the tensile strength had a maximum with the variety of silica contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2210–2214, 2003

Influence of substituent on equilibrium of benzoxazine synthesis from Mannich base and formaldehyde

Co-reporter:Yuyuan Deng, Qin Zhang, Qianhao Zhou, Chengxi Zhang, Rongqi Zhu and Yi Gu

Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 34) pp:NaN18348-18348

Publication Date(Web):2014/07/11

DOI:10.1039/C4CP02053G

A novel benzoxazine/cyanate ester blend with sea-island phase structures

Co-reporter:Xiaodan Li, Xiaoyong Luo and Yi Gu

Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 29) pp:NaN19260-19260

Publication Date(Web):2015/06/19

DOI:10.1039/C5CP02426A

Effect of hydrogen bonds on the modulus of bulk polybenzoxazines in the glassy state

Co-reporter:Po Yang, Xiaoying Wang, Haojun Fan and Yi Gu

Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 37) pp:NaN15338-15338

Publication Date(Web):2013/04/15

DOI:10.1039/C3CP51001H

Co-reporter:Zhi Wang, Qichao Ran, Rongqi Zhu and Yi Gu

Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 11) pp:NaN5332-5332

Publication Date(Web):2014/01/20

DOI:10.1039/C3CP54960G

Correction: A novel benzoxazine/cyanate ester blend with sea-island phase structures

Co-reporter:Xiaodan Li, Xiaoyong Luo and Yi Gu

Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 31) pp:NaN20425-20425

Publication Date(Web):2015/07/17

DOI:10.1039/C5CP90128F

Correction for ‘A novel benzoxazine/cyanate ester blend with sea-island phase structures’ by Xiaodan Li et al., Phys. Chem. Chem. Phys., 2015, DOI: 10.1039/c5cp02426a.