Co-reporter:Gaoming Mo, Ruoyu Zhang, Yanfei Wang, Liu He
European Polymer Journal 2017 Volume 92(Volume 92) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.eurpolymj.2017.04.034
•Gelation in phase separating blends could suppress the phase separation kinetics.•Critical gels have both lower and upper length scale limits.•Homogeneous gel has wider size limits than those of inhomogeneous ones.•The stiffness of homogeneous gel is stronger than that of inhomogeneous ones.•Activation energy of gelation has no dependence on the average composition of the system.Isothermal aging experiments are carried out in Polyacrylonitrile/Dimethylsulfoxide/H2O (PAN/DMSO/H2O) blends, and rheological and optical methods are used to investigate the interplay between phase separation and gelation. Two types of gel structures are found. In most samples, gelation is induced by phase separation in PAN concentrated regions, yet it will subsequently slow the kinetics of phase separation down by altering the concentration balance and fluctuation. As a result, the drop of light transmittance becomes slower and a phenomenon called “RT reversal” is observed. At last, the phase separated morphology is replaced by gel structure, which inherits the inhomogeneity in PAN content distribution. Another type of gel grows from homogeneous solution and its structure disperses uniformly in space. Moreover, the temperature dependence of critical gel properties, like its size limits and thermodynamics, is discussed. It is found that the self-similar structure in homogeneous critical gel covers wider length scales and possesses stronger gel stiffness than those of inhomogeneous ones. The activation energy for gelation is also calculated, which reveals no obvious dependence on original PAN concentration or temperature.Download high-res image (70KB)Download full-size image
Co-reporter:Yong Yang, Juncheng Huang, Ruoyu Zhang, Jin Zhu
Materials & Design 2017 Volume 126(Volume 126) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.matdes.2017.04.005
•Isosorbide diesters with varying alkyl chain length were evaluated as bio-based alternatives to petro-based phthalates.•The plasticizing efficiency of isosorbide diesters were in the order of dibutyrate > dihexanoate > dioctanoate > didecanoate.•The thermostability of isosorbide diesters followed the order of dibutyrate < dihexanoate < dioctanoate < didecanoate.•The isosorbide diester with longer alkyl chain length is more difficult to volatilize.A series of bio-based plasticizers based on isosorbide, a renewable monomer derived from glucose, were successfully synthesized. The chemical structures of the synthesized isosorbide diesters with different alkyl chain length were confirmed by FTIR and 1H NMR. The influence of varying alkyl chain length on thermal and mechanical properties of isosorbide diesters in poly(vinyl chloride) (PVC) was investigated in detail. It was found that the plasticizing efficiency of isosorbide diester decreased as the alkyl chain length increased, reflecting on the gradually increased Tg and the decreased elongation at break of PVC blend. However, the longer alkyl chain length of isosorbide diester improved the thermal stability of PVC blend and simultaneously depressed its volatility from PVC. Besides, the bio-based isosorbide diesters rivaled those petro-based phthalates, and they could be potential candidates to replace phthalates in the future industry.Download high-res image (132KB)Download full-size image
Co-reporter:Yu Long, Ruoyu Zhang, Juncheng Huang, Jinggang Wang, Junwu Zhang, Nissim Rayand, Guo-hua Hu, Jian Yang, Jin Zhu
Polymer 2017 Volume 125(Volume 125) pp:
Publication Date(Web):8 September 2017
DOI:10.1016/j.polymer.2017.08.004
•Retroreflection occurs in PLA/PBF blends through several processing methods.•Surface area of PLA crystal largely affects the reflection ratio.•Amorphous PBF droplet is one of the most important optical geometry in retroreflection.•Refraction index difference between PLA and PBF is required to have retroreflection phenomenon.Corn starch based polylactide acid (PLA) and 2,5-furandicarboxylic acid (FDCA) based poly(butylene 2,5-furan dicarboxylate) (PBF) are melt blended together, and the binary bio-based blends show high reflectivity by several processing methods, including hot pressing, injection molding and 3D printing. We use optical microscopy to study the underlying structures and find that the phase separated and semi-crystallization morphology in the blends is the key structure. The large surface area of PBF droplets and smooth surface of PLA lamellar compose a retro-reflection geometry, which is similar to the tapetum lucidum in a cat's eyes. The conclusion in this study is applicable to other polymer pairs, and is adaptable in many processing technologies.Download high-res image (158KB)Download full-size image
Co-reporter:Wei Xu, Ruoyu Zhang, Wei Liu, Jin Zhu, Xia Dong, Hongxia Guo, and Guo-Hua Hu
Macromolecules 2016 Volume 49(Issue 16) pp:5931-5944
Publication Date(Web):August 1, 2016
DOI:10.1021/acs.macromol.6b01172
Shape memory thermoplastic polyurethane (SMTPU) containing isophorone diisocyanate (IPDI) in hard segment has excellent shape recoverability even after large strain deformation. However, the underlying mechanism of shape recovery remains unclear. In this study, 1,4-phenylene diisocyanate (PPDI) in the polyurethane is gradually substituted by IPDI, and multiscale effects are examined by normal and dichroic Fourier transform infrared spectroscopy (FTIR), small-angle X-ray scattering (SAXS), single-molecule force spectroscopy (SMFS), and mechanical test. Contradictory to the traditional conclusion, the degree of microphase separation decreases as the content of IPDI increases, while the macroscopic shape recoverability is largely improved. With dichroic FTIR and SAXS, we find that the morphology of hard phases changed from lamellar-like to fibrillar-like, which is more stable under stretching. SMFS experiments discover that IPDI could increase the elasticity of polymer chain and could endow the hard phases with “elastic” under stress. With these two factors, we are able to explain the high recoverability of the SMTPU containing IPDI.
Co-reporter:Wei Liu, Ruoyu Zhang, Miaoming Huang, Xia Dong, Wei Xu, Nissim Ray, Jin Zhu
Polymer 2016 Volume 104() pp:115-122
Publication Date(Web):8 November 2016
DOI:10.1016/j.polymer.2016.09.079
•Facile preparation of a new triple-shape memory polymer material, PCL/PVC blend, was achieved.•The PCL-30% had a broad glass transition and displayed the mechanical properties like an elastomer.•The nano-scale PCL crystals and chain entanglements served as the physical networks.•The amorphous PVC and PCL regions acted as the reversible phase at high and low switch temperatures respectively.Poly(ε-caprolactone) (PCL) and poly (vinyl chloride) (PVC) are miscible with each other, and their glass transition temperatures differ a lot. With this feature, we tried to design a triple-shape memory material by simply blending them together. After carefully examining the glass transition broadness and the tensile behavior of various PCL/PVC blends, PCL-30% (the weight fraction of PCL was 30%) was picked out as the best candidate. It fulfills two criterions that it has a wide glass transition range and it has no strain or stress induced crystallization. Subsequent triple-shape memory procedure proves that it could function as an effective shape memory blend. The structure was studied by SAXS/WAXS and nano-scale periodic structure was found, which was composed of crystalline and amorphous PCL regions of 4.7 nm and 8.4 nm respectively. Such periodic domains would orient along the stretch direction, but it kept stable and could restore to its original state after the stress was released. Dichromic FTIR discerned the orientation of PCL chains at low temperature and PVC chains at high temperature. It can be concluded that both the nano-scale PCL crystalline structures and physical entanglements served as the fixed phase, while the amorphous PVC and PCL regions played as the reversible phase at high and low switch temperatures respectively.
Co-reporter:Yong Yang;Lisheng Zhang;Zhu Xiong;Zhaobin Tang
Science China Chemistry 2016 Volume 59( Issue 11) pp:1355-1368
Publication Date(Web):2016 November
DOI:10.1007/s11426-016-0222-7
Due to its high strength, high modulus, excellent clarity, good biodegradability and biocompatibility, poly(lactic acid) (PLA), a bio-based thermoplastic polyester, has evolved into a competitive commodity material with potential to replace conventional petrochemical-based polymers. However, the wide applications of PLA have been hampered by its native drawbacks, such as low heat distortion temperature (HDT), inherent brittleness and relatively high cost. In recent years, researchers have devoted to breaking above-mentioned bottleneck and attempted to extend the application of PLA. This review will summarize recent work about the modification of PLA, especially focusing on enhancing HDT, toughening and reducing cost.
Co-reporter:Gaoming Mo, Ruoyu Zhang, Yanfei Wang, Qing Yan
Polymer 2016 Volume 84() pp:243-253
Publication Date(Web):10 February 2016
DOI:10.1016/j.polymer.2016.01.002
•Gelation could happen in phase separated state.•Gelation with phase separation could be studied by Chambon–Winter model.•Heterogeneous gel structure is developed with phase separation.Thermal-induced gelation and phase separation was investigated in PAN/DMSO/H2O semidilute solutions utilizing rheological and optical methods. The incipient precipitation temperature, where a distinct decrease in relative light transmittance occurred, was considered as the cloud point (CP). Phase separation mechanism of nucleation and growth was confirmed by various ramp rates experiments and viscoelastic evolution pattern. On the other hand, the validity of Chambon–Winter model was evaluated in these blends and used to measure the critical gel point (GP). It was found that in the accessible temperature regions CP was always higher than GP, and phase boundaries were constructed accordingly. What's more, the absolute complex viscosity η′ at a low frequency also showed transition points during temperature decreasing experiments, which mostly located between CPs and GPs. The gelation mechanisms with and without phase separation were proposed and the effect of the two transitions on the structures of the ternary blends were shown by SEM pictures.
Co-reporter:Zhu Xiong;Xinyan Dai;Haining Na;Zhaobin Tang, ;Jin Zhu
Journal of Applied Polymer Science 2015 Volume 132( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/app.41220
ABSTRACT
In this manuscript, a toughened PLA/nanosilica composite with good storage stability was obtained in the presence of the epoxidized soybean oil (ESO). The composite was fabricated via a twin-screw extruder, and characterized by the FTIR, selective distribution test, and SEM. The surface of nanosilica was modified by the ESO through the chemical bonding, and this rendered the nanosilica to selectively localize in ESO droplets in the composite. As a result, the PLA/nanosilica composite was changed from brittleness to ductility with the addition of ESO. For example, the elongation and notched impact strength of the PLA/silica/ESO nanocomposite with 5 wt % nanosilica and 15 wt % ESO were ∼42% and ∼11 KJ/m2, respectively, which were much higher than neat PLA or PLA/nanosilica composite without ESO. Furthermore, the change of the brittle fracture of PLA into ductile fracture was investigated by SEM micrographs in detail. A possible toughening mechanism was also proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41220.
Co-reporter:Zhongfei Qi;Yong Yang;Zhu Xiong;Jun Deng;Jin Zhu
Journal of Applied Polymer Science 2015 Volume 132( Issue 23) pp:
Publication Date(Web):
DOI:10.1002/app.42028
ABSTRACT
A series of aliphatic diacyl adipic dihydrazides (ADHs) with different alkyl moieties were synthesized by the reaction between adipic dihydrazide and acyl chloride. Then these ADHs were solution blended with PLA respectively and were evaluated as nucleating agents. Through the investigation of nonisothermal and isothermal crystallization, it was found that both the crystallization rate and the crystallinity of PLA could be enhanced by adding only 1 wt % of ADHs. Especially for ADH-Oc (ADH-Octyl), the crystallization rate of PLA increased about 4 times at 105°C. Optical morphology showed that and the size of PLA spherulites decreased and the nucleation density increased with the existence of ADH-Oc. Meanwhile, the crystal structure of PLA were not discerniblly affected after the addition of ADHs as found by wide-angle X-ray diffraction. Thus, this study suggested these ADHs compounds are simple and potential nucleating agents to enhance crystallization ability of PLA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42028.
Co-reporter:Lisheng Zhang, Zhu Xiong, S. Saqib Shams, Ruilei Yu, Juncheng Huang, Ruoyu Zhang, Jin Zhu
Polymer 2015 Volume 64() pp:69-75
Publication Date(Web):1 May 2015
DOI:10.1016/j.polymer.2015.03.032
•Reactive blending system of PLLA/Bio-TPU/free radical initiator was researched in this work.•The double bonds in Bio-TPU were more prone to react with free radicals.•The ternary blends show excellent ductility and high tensile strength at the same time.The reactive blending system of free radical initiator (L101), polylactide (PLLA) and bio-based polyurethane (Bio-TPU) elastomer containing double bonds was investigated. There existed a competition for free radicals between the PLLA and Bio-TPU, because free radicals could attack both the tertiary hydrogen in PLLA chains and the double bonds in Bio-TPU. The behavior of competition for free radicals between PLLA and toughening phase was pointed out and analyzed in this work for the first time. Observations from all kinds of characterization lead us to believe that the double bonds in Bio-TPU were more prone to react with free radicals. The competition for free radicals played an important role on the interfacial properties of the blending systems, and consequently, on the thermal and mechanical properties of the blends. In PLLA/Bio-TPU/L101 (90/10/0.1, 90/10/0.3) blends, excellent ductility and high tensile strength were found at the same time owing to largely improved compatibility and much higher crystallinity. The elongation at break of these two samples were improved 36 and 34 times compared to pure PLLA separately, accompanied with only 16% and 18% decrease of the tensile strength. This work may be helpful for better understanding of similar reactive blending systems and designing PLLA blends with comprehensive properties.
Co-reporter:Yanfei Wang, Wei Liu, Gaoming Mo, Ruoyu Zhang
Polymer 2015 Volume 73() pp:149-155
Publication Date(Web):2 September 2015
DOI:10.1016/j.polymer.2015.07.033
•The loss tangent coincided at two different temperatures in different frequency periods as temperature decreased.•A ‘Joint Point to Joint Section’ model was proposed to interpret the mechanism of the growth of the physical linkages.•Phase boundaries of critical gel and the second self-similar structure can be drawn.The gelation process in Polyacrylonitrile (PAN)/Dimethyl Sulfoxide (DMSO)/Water (H2O) systems was studied by rheology. Chambon–Winter criterion was used to detect the critical gelation temperature variation. Interestingly, we found that the loss tangent coincided at two different temperatures in different frequency periods with the temperature decreased. By using the physical and mathematical analysis, we were able to tell that the first one was the critical sol–gel transition temperature, which appeared at higher temperatures under lower frequencies; and the second point was an indication of another self-similar structure, which appeared at lower temperatures under higher frequencies. We analyzed the coarsening mechanism in the gelation process of ternary blends, and considered that the volume growth of the physical linkage can interpret this unusual phenomenon. A ‘Joint Point to Joint Section’ model, similar to nucleation process, was proposed to interpret the mechanism of the growth of the physical linkages. Based on the above data, phase boundaries of critical gel and the second self-similar structure can be drawn. As the PAN or water content increased, both transition temperatures increased, which indicated the non-solvent water favored the aggregation of PAN molecules and promoted the forming of the second self-similar structure.
Co-reporter:Lisheng Zhang, S. Saqib Shams, Yanping Wei, Xiaoqing Liu, Songqi Ma, Ruoyu Zhang and Jin Zhu
Journal of Materials Chemistry A 2014 vol. 2(Issue 47) pp:20010-20016
Publication Date(Web):22 Oct 2014
DOI:10.1039/C4TA05126B
In this work, SMPUs with non-planar ring structures in the hard segments display a low degree of phase separation but excellent shape recoverability (shape recovery rate ∼99% with 500% strain). The accepted wisdom is that there are two criteria for SMPUs possessing good shape recoverability: (i) high degree of phase separation forming physical crosslinks; (ii) strong physical interactions between hard segments which keep physical crosslinks stable under external stress. However, our results are completely against the accepted wisdom since the asymmetrical non-planar ring structures will depress the micro-phase separation and physical interactions in the hard phase. Thus, the excellent shape recovery could not be attributed to the phase morphology. Based on such results, single molecule force spectroscopy was adopted to study the properties of single polymer chains with non-planar ring structures. We found that the single chain elasticity was largely improved by non-planar rings. It is highly possible that the excellent shape recovery property originates from the elastic non-planar ring structures absorbing the external stress which stabilizes the physical crosslinks. Much work needs to be done in the near future to confirm this assumption.
Co-reporter:Lisheng Zhang, Miaoming Huang, Ruilei Yu, Juncheng Huang, Xia Dong, Ruoyu Zhang and Jin Zhu
Journal of Materials Chemistry A 2014 vol. 2(Issue 29) pp:11490-11498
Publication Date(Web):19 May 2014
DOI:10.1039/C4TA01640H
One of the obvious shortcomings of bio-based shape memory polyurethanes (Bio-SMPUs), which usually use natural oil based polyols as the soft segment, is their low mechanical strength because the long dangling chains (six to eight carbons) in these polyols prevent the Bio-SMPUs from deep micro-phase separation, and consequently deteriorate their mechanical properties. In this work, we prepared a bio-based polyester diol for the soft segment, in which short side chains (CC) were used to tune the transition temperature and the morphology of the Bio-SMPUs. The moderate concentration of short branch chains barely affects the micro-phase separation, and the mechanical properties of the Bio-SMPUs are quite satisfactory. With the same 70 wt% soft segment content, the tensile strength in this work is 13.2 MPa, while the one using ricinoleate-based soft segments reported 2.8 MPa. Through proper shape memory programming, the synthesized Bio-SMPUs show good shape memory properties with a shape fixing rate of greater than 98% and a shape recovery rate of 85% in the first cycle and greater than 90% in the following cycles. This study provides a framework for developing bio-based SMPUs with high mechanical and good shape memory properties at the same time.
Co-reporter:Lijing Han, Jinyue Dai, Lisheng Zhang, Songqi Ma, Jun Deng, Ruoyu Zhang and Jin Zhu
RSC Advances 2014 vol. 4(Issue 90) pp:49471-49477
Publication Date(Web):26 Sep 2014
DOI:10.1039/C4RA08665A
This paper reported the synthesis of bio-based unsaturated poly(ester-urethane)s via a nonisocyanate route, by metal-catalyzed melt polycondensation of itaconic acid with urethanediols. Three novel types of bio-based unsaturated poly(ester-urethane)s, namely, poly(urethanediol 2-itaconic acid), poly(urethanediol 4-itaconic acid) and poly(urethanediol 6-itaconic acid) (poly(U2-IA), poly(U4-IA) and poly (U6-IA) for short code, respectively), were prepared by a green synthetic route. The urethane linkage was formed by the reaction of two equivalent of ethylene carbonate with 1,6-hexanediamine, 1,4-butanediamine and 1,2-ethanediamine to form urethanediols. The urethanediols underwent polymerization with itaconic acid (IA) in the presence of metal catalyst dibutyltin dilaurate (DBTL) to produce low-molecular-weight bio-based unsaturated polyurethanes. Then, these bio-based unsaturated poly(ester-urethane)s were formulated with free radical photoinitiator and curing promoter to prepare UV curable polyurethane systems. After UV curing, the tensile properties, thermal properties and general coating properties of the three UV-cured polyurethane films were similar to that of UV cured polyurethane films prepared by polyurethane-acrylate (PUA). The results suggested that the obtained bio-based unsaturated polyurethanes could serve as coating materials.
Co-reporter:Rui-lei Yu;Li-sheng Zhang;Yu-hong Feng 冯玉红
Chinese Journal of Polymer Science 2014 Volume 32( Issue 8) pp:1099-1110
Publication Date(Web):2014 August
DOI:10.1007/s10118-014-1487-9
Polylactide (PLA) was successfully toughened by blending with bio-based poly(ester)urethane (TPU) elastomers which contained bio-based polyester soft segments synthesized from biomass diols and diacids. The miscibility, mechanical properties, phase morphology and toughening mechanism of the blend were investigated. Both DSC and DMTA results manifested that the addition of TPU elastomer not only accelerated the crystallization rate, but also increased the final degree of crystallinity, which proved that TPU has limited miscibility with PLA and has functioned as a plasticizer. All the blend samples showed distinct phase separation phenomenon with sea-island structure under SEM observation and the rubber particle size in the PLA matrix increased with the increased contents of TPU. The mechanical property variation of PLA/TPU blends could be quantitatively explained by Wu’s model. With the variation of TPU, a brittle-ductile transition has been observed for the TPU/PLA blends. When these blends were under tensile stress conditions, the TPU particles could be debonded from the PLA matrix and the blends showed a high ability to induce large area plastic deformation before break, which was important for the dissipation of the breaking energy. Such mechanism was demonstrated by tensile tests and scanning electron microcopy (SEM) observations.
Co-reporter:Lisheng Zhang, Yanhua Jiang, Zhu Xiong, Xiaoqing Liu, Haining Na, Ruoyu Zhang and Jin Zhu
Journal of Materials Chemistry A 2013 vol. 1(Issue 10) pp:3263-3267
Publication Date(Web):24 Jan 2013
DOI:10.1039/C3TA01655B
Improving the phase separation and stability of the hard segment domains at the same time is the novel method reported here to improve the recovery of thermoplastic shape memory polyurethanes (SMPUs) at high strain (>1000%). The shape recovery of the corresponding SMPUs with a more than 1000% strain can reach about 96% at room temperature in 3 min, the recoverable strain (εmax − εpermanent) is more than 960%, which is nearly 2.5 times that of the best value (400%) previously reported.
Co-reporter:Zhu Xiong, Chao Li, Songqi Ma, Jianxian Feng, Yong Yang, Ruoyu Zhang, Jin Zhu
Carbohydrate Polymers 2013 Volume 95(Issue 1) pp:77-84
Publication Date(Web):5 June 2013
DOI:10.1016/j.carbpol.2013.02.054
Bio-sourced polymers, polylactide (PLA) and starch, have been melt-blended by lab-scale co-extruder with tung oil anhydride (TOA) as the plasticizer. The ready reaction between the maleic anhydride on TOA and the hydroxyl on starch led TOA molecules to accumulate on starch and increased the compatibility of PLA/starch blends, which was confirmed by FT-IR analyses and SEM. The TOA could change the mechanical properties and physical behaviors of PLA/starch blends. DSC and DMA analysis show that the TOA layer on starch has an effect on the thermal behavior of PLA in the ternary blend. The enrichment of TOA on starch improves the toughness and impact strength of the PLA/starch blends. The adding amount of TOA in PLA/starch blends primarily determined the compatibility and mechanical properties of the resulted ternary blends. The tensile and impact fracture modes of the PLA/starch blend with or without TOA has also been investigated by SEM analysis.Graphical abstractThe diagram of TOA layer formed on the starch particle via the possible reaction between hydroxyl groups of starch and maleic anhydride groups of TOA during the melt-blending process.Highlights► Tung oil anhydride could be used as a bio-based reactive plasticizer for PLA/starch compounds. ► TOA could enrich on starch and increase the compatibility of PLA/starch blends via reaction. ► It has no report about tung oil anhydride influencing the properties of PLA/starch blends.
Co-reporter:Lisheng Zhang, S. Saqib Shams, Yanping Wei, Xiaoqing Liu, Songqi Ma, Ruoyu Zhang and Jin Zhu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 47) pp:NaN20016-20016
Publication Date(Web):2014/10/22
DOI:10.1039/C4TA05126B
In this work, SMPUs with non-planar ring structures in the hard segments display a low degree of phase separation but excellent shape recoverability (shape recovery rate ∼99% with 500% strain). The accepted wisdom is that there are two criteria for SMPUs possessing good shape recoverability: (i) high degree of phase separation forming physical crosslinks; (ii) strong physical interactions between hard segments which keep physical crosslinks stable under external stress. However, our results are completely against the accepted wisdom since the asymmetrical non-planar ring structures will depress the micro-phase separation and physical interactions in the hard phase. Thus, the excellent shape recovery could not be attributed to the phase morphology. Based on such results, single molecule force spectroscopy was adopted to study the properties of single polymer chains with non-planar ring structures. We found that the single chain elasticity was largely improved by non-planar rings. It is highly possible that the excellent shape recovery property originates from the elastic non-planar ring structures absorbing the external stress which stabilizes the physical crosslinks. Much work needs to be done in the near future to confirm this assumption.
Co-reporter:Lisheng Zhang, Yanhua Jiang, Zhu Xiong, Xiaoqing Liu, Haining Na, Ruoyu Zhang and Jin Zhu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 10) pp:NaN3267-3267
Publication Date(Web):2013/01/24
DOI:10.1039/C3TA01655B
Improving the phase separation and stability of the hard segment domains at the same time is the novel method reported here to improve the recovery of thermoplastic shape memory polyurethanes (SMPUs) at high strain (>1000%). The shape recovery of the corresponding SMPUs with a more than 1000% strain can reach about 96% at room temperature in 3 min, the recoverable strain (εmax − εpermanent) is more than 960%, which is nearly 2.5 times that of the best value (400%) previously reported.
Co-reporter:Lisheng Zhang, Miaoming Huang, Ruilei Yu, Juncheng Huang, Xia Dong, Ruoyu Zhang and Jin Zhu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 29) pp:NaN11498-11498
Publication Date(Web):2014/05/19
DOI:10.1039/C4TA01640H
One of the obvious shortcomings of bio-based shape memory polyurethanes (Bio-SMPUs), which usually use natural oil based polyols as the soft segment, is their low mechanical strength because the long dangling chains (six to eight carbons) in these polyols prevent the Bio-SMPUs from deep micro-phase separation, and consequently deteriorate their mechanical properties. In this work, we prepared a bio-based polyester diol for the soft segment, in which short side chains (CC) were used to tune the transition temperature and the morphology of the Bio-SMPUs. The moderate concentration of short branch chains barely affects the micro-phase separation, and the mechanical properties of the Bio-SMPUs are quite satisfactory. With the same 70 wt% soft segment content, the tensile strength in this work is 13.2 MPa, while the one using ricinoleate-based soft segments reported 2.8 MPa. Through proper shape memory programming, the synthesized Bio-SMPUs show good shape memory properties with a shape fixing rate of greater than 98% and a shape recovery rate of 85% in the first cycle and greater than 90% in the following cycles. This study provides a framework for developing bio-based SMPUs with high mechanical and good shape memory properties at the same time.
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