Co-reporter:Jun Liang;Guo-rong Shan 单国荣;Peng-ju Pan
Chinese Journal of Polymer Science 2017 Volume 35( Issue 1) pp:123-129
Publication Date(Web):2017 January
DOI:10.1007/s10118-017-1874-0
Controlled and homogeneous free-radical polymerization of acrylamide (AM) in aqueous phase was realized by using S,S′-bis(α,α′-dimethyl-α″-acetic acid)-trithiocarbonate as a reversible addition-fragmentation transfer (RAFT) agent. Linear increases in molecular weight with conversion and narrow molecular weight distribution were observed for polyacrylamide (PAM) throughout the polymerization. By this method, PAMs with controlled molecular weight (up to 1.0 × 106) and narrow molecular weight distribution (Mw/Mn < 1.2) were prepared. This study provides an effective method for synthesis of PAMs with narrow molecular weight distribution under environmentally friendly conditions.
Co-reporter:Jinjin Cheng, Guorong ShanPengju Pan
Industrial & Engineering Chemistry Research 2017 Volume 56(Issue 5) pp:
Publication Date(Web):January 25, 2017
DOI:10.1021/acs.iecr.6b03626
Poly(N-isopropylacrylamide-co-maleic acid-co-1-vinylimidazole), P(NIPAM-MA-VI), has been prepared in water by free radical polymerization. The aqueous solution of low-molecular-weight P(NIPAM-MA-VI) has four distinct phases above a critical concentration. Effects of monomer ratio, copolymer concentration, and pH on the phase transition temperatures of P(NIPAM-MA-VI) were studied. The addition of divalent metal ions promoted the gelation process of P(NIPAM-MA-VI). Therefore, the adsorption behavior of P(NIPAM-MA-VI) to Cu2+ ions was further investigated; this adsorption behavior was pH-dependent, and the adsorption isotherm could be well fitted by the Freundlich model. The maximum adsorption capacity reaches 21.1 mg g–1 dried copolymer at 60 °C and pH 5. The adsorbed P(NIPAM-MA-VI) can be regenerated by the treatment of hydrochloric acid and reused in the following adsorption process. X-ray photoelectron spectroscopy (XPS) and synchrotron radiation small-angle X-ray scattering (SAXS) were used to investigate the effect of Cu2+ ions on the phase transition behavior of P(NIPAM-MA-VI). O 1s and N 1s XPS spectra and SAXS results analyzed by the Ornstein–Zernike and generalized Ornstein–Zernike models are in agreement with the proposed mechanisms and adsorption behavior. As a thermo-, pH-, and metal ion-responsive copolymer, P(NIPAM-MA-VI) could be used for the ion recognition, water purification, and enrichment of heavy metal ions.
Co-reporter:Yong Chen;Pengju Pan
Colloid and Polymer Science 2017 Volume 295( Issue 11) pp:2207-2215
Publication Date(Web):23 September 2017
DOI:10.1007/s00396-017-4197-3
The amphiphilic cationic polymer, poly(acryloyloxyethyl dimethylbenzyl ammonium chloride) (PAODBAC), has been studied as an additive for the stabilization of water-in-oil inverse emulsions prepared from mixed surfactants. The interaction behavior of PAODBAC with the surfactants, the effect of the PAODBAC concentration on the stability of the inverse emulsion obtained after polymerization, the characteristics of the polymer particle after polymerization, and the rheological properties with different concentrations of PAODBAC have been systematically investigated. A mechanism is proposed to account for the stabilizing effect of PAODBAC on the inverse emulsion system. The PAODBAC chains can interact with the surfactant molecules. When the concentration of PAODBAC was 0.067% (w/w), the interactions between the polymer chains and surfactant molecules were optimized, resulting in the best stability of the inverse emulsion. The presence of PAODBAC in the inverse emulsion system aided the establishment of a small mean polymer particle size distribution.
Co-reporter:Jun Liang;Pengju Pan
Soft Matter (2005-Present) 2017 vol. 13(Issue 22) pp:4148-4158
Publication Date(Web):2017/06/07
DOI:10.1039/C7SM00544J
A novel double network (DN) hydrogel with highly enhanced toughness has been prepared using reversible addition–fragmentation transfer (RAFT)-modified poly(2-acrylamide-2-methylpropane sulfonic acid) (PAMPS) as the first network, and polyacrylamide (PAM) as the second network. The mechanical properties of the first-network-modified PAMPS/PAM DN hydrogels have been studied and the new DN hydrogel shows remarkably high fracture energy (3.3 MJ m−3) in tensile deformation, which is nearly 9 times larger than that of the unmodified PAMPS/PAM DN hydrogel. Synchrotron radiation small-angle X-ray scattering (SAXS) was used to study the microstructures of the first-network single network (SN) and DN hydrogels. It was demonstrated by the SAXS results that the introduction of the RAFT agent into the first network enlarges the size of the ordered cross-linked domains in the SN hydrogel. The large ordered domains are beneficial for entanglement and interpenetration between the first and the second networks to dissipate concentrated stress more efficiently, resulting in the enhanced toughness of the first-network-modified DN hydrogels.
Co-reporter:Weixiao Fan, Kuanxiang Shang, Guorong Shan and Pengju Pan
RSC Advances 2016 vol. 6(Issue 64) pp:59352-59359
Publication Date(Web):21 Jun 2016
DOI:10.1039/C6RA09732D
The aqueous two-phase copolymerization (ATPP) of acrylamide and cationic monomers was carried out in poly(ethylene glycol) (PEG) aqueous solution. The effects of inorganic salts on the ATPP process were systematically investigated and obvious differences were observed between univalent and multivalent anions. For the ATPP system with added univalent anions such as Cl−, the critical conversion for the phase separation decreased as the particle size increased, but the polymerization kinetics and final molecular weight of the copolymers were similar with that of the salt-free system. However, after adding multivalent anions such as SO42− into the ATPP system, the critical conversion for the phase separation decreased sharply, the polymerization rate slowed down, the final molecular weight of the copolymers increased, and the particle size greatly increased. Moreover, the system underwent a unique particle formation process. A mechanism for the role of anions in the ATPP process was proposed. The salting-out effects of the univalent anions screen the electrostatic repulsion between cationic species and lead to the formation of gravel-like particles. But for multivalent anions, when the concentration is low, their salting-out effect is involved in the particle formation process and results in the formation of gravel-like particles as well. When the concentration becomes high, their bridge effect is dominant, making large and spherical particles appear.
Co-reporter:Xianbo Xu;Guorong R. Shan;Pengju Pan
Journal of Applied Polymer Science 2016 Volume 133( Issue 42) pp:
Publication Date(Web):
DOI:10.1002/app.44132
ABSTRACT
Functionalized amphiphilic block copolymers poly(N-isopropyl acrylamide)-b-poly(stearyl methacrylate) (PNIPAM-PSMA) are synthesized. Their self-assembled core-shell nanoparticles have the hydrophilic thermosensitive shell and hydrophobic crystallizable core. Nanoparticles exhibit volume phase transition at temperature of 38 °C and its poly(stearyl methacrylate) (PSMA) moiety could form nano size crystals to retain drugs, making them good carriers for drug co-delivery system. Thermosensitivity and crystallinity of nanoparticles are characterized with dynamic light scattering (DLS), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM). The interactions and relationship between chemical structures of copolymer nanoparticles and loading drugs are discussed. Different loading techniques and combined loading of hydrophobic/hydrophilic drugs are studied. Nanoparticles show a good and controllable drug loading capacity (DL) of hydrophilic/hydrophobic drugs. The drugs release kinetics is analyzed with Fick's law and Weibull model. A general method for analyzing drug release kinetics from nanoparticles is proposed. Weibull model is well fitted and the parameters with definite physical meaning are analyzed. PNIPAM-PSMA nanoparticles show a quite different thermal response, temporal regulation, and sustained release effect of hydrophilic and hydrophobic drugs, suggesting a promising application in extended and controlled co-delivery system of multi-drug. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44132.
Co-reporter:Jinjin Cheng, Guorong Shan and Pengju Pan
RSC Advances 2015 vol. 5(Issue 76) pp:62091-62100
Publication Date(Web):20 Jul 2015
DOI:10.1039/C5RA09965J
Poly(N-isopropylacrylamide-co-acrylamide-co-maleic acid) (P(NIPAM-AM-MA)) hydrogel has been synthesized by free radical polymerization. The incorporation of functional monomer in the hydrogel was confirmed by Fourier transform infrared spectrometer (FTIR). Swelling measurements and differential scanning calorimeter (DSC) were employed to investigate the volume phase transition of P(NIPAM-AM-MA) hydrogel. P(NIPAM-AM-MA) shows higher swelling ratio and LCST than poly(N-isopropylacrylamide) (PNIPAM) and poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-AM)). The adsorption behavior of copper(II) (Cu2+) ions on P(NIPAM-AM-MA) hydrogel is temperature and pH-dependent. The adsorption isotherm is well fitted by the Freundlich model and the adsorption kinetics can be described by the pseudo-second order equation. In 20 mL of CuSO4 solution containing 4 mg Cu2+, the adsorption capacity reaches 24.4 mg g−1 dry hydrogel at 30 °C and pH = 5. After the volume phase transition, the Cu2+-loaded P(NIPAM-AM-MA) hydrogel can release almost 90% of absorbed water containing few heavy metal ion. Synchrotron radiation small-angle X-ray scattering (SAXS) was used to study the effect of temperature and Cu2+ ions on the microstructure of P(NIPAM-AM-MA) hydrogel. The occurrence of volume phase transition increases the size of cross-linked domains and mass fractal dimension, while the presence of Cu2+ ions has an opposite effect. The adsorbed hydrogel can be easily regenerated by hydrochloric acid and reused in the following adsorption process. This pH and temperature sensitive hydrogel may be used for water purification and enrichment of heavy metal ions.
Co-reporter:Xianbo Xu, Guorong Shan and Pengju Pan
RSC Advances 2015 vol. 5(Issue 62) pp:50118-50125
Publication Date(Web):05 Jun 2015
DOI:10.1039/C5RA07087B
A facile and nontoxic strategy for the preparation of amphiphilic quasi-block copolymers and nanoparticles has been developed utilizing miniemulsion polymerization. By volume phase transition behavior of poly(N-isopropyl acrylamide) (PNIPAM) and thermally induced interfacial absorption, amphiphilic copolymer was generated, which can self-assemble into core–shell nanoparticles in situ. Stearyl methacrylate (SMA) was used as hydrophobic monomer and to form crystalline core, because it has pendent long alkyl side chain and can form crystalline domain to synthesize comb-like polymers. A volatile organic cosolvent was used to enhance the formation process and particles size, and the formation mechanism was investigated. Impacts of cosolvent concentration, monomer feed ratio and polymerization temperature on the morphology and thermal characteristics of particles were studied by DLS, TEM and DSC. 1H NMR, 13C NMR and GPC were carried out to analyze the chemical structure and composition of copolymers. The triads sequence and average block length are analyzed to determine the sequence distribution of copolymers. Volume phase transition temperature (VPTT) of PNIPAM copolymer was first increased to nearly 40 °C with hydrophobic monomer rather than hydrophilic monomer. In addition, hydrophilic property of copolymer and the drug release behavior were studied to understand further applications. These amphiphilic quasi-block copolymers show great potential in the controlled delivery system for drugs.
Co-reporter:Yue Shang;Pengju Pan
Macromolecular Chemistry and Physics 2015 Volume 216( Issue 8) pp:884-893
Publication Date(Web):
DOI:10.1002/macp.201400563
Co-reporter:Long Cai
Journal of Porous Materials 2015 Volume 22( Issue 6) pp:1455-1463
Publication Date(Web):2015 December
DOI:10.1007/s10934-015-0026-6
The use of N,N-dimethylformamide (DMF) as a drying control chemical additive was found to be effective in obtaining methyltrimethoxysilane (MTMS) based silica aerogels in terms of excellent monolithic property, hydrophobicity and elasticity. The aerogels were produced by hydrolysis and condensation of methanol diluted MTMS in presence of ammonia catalyst followed by ambient drying. The molar ratio of DMF/MTMS varies from 0 to 1. It has been observed that higher DMF/MTMS value leads to lower density (~0.15 g/cm3) and higher porosity of aerogels with excellent hydrophobicity. For DMF/MTMS (~0.6) values, monolithic and elastic aerogels which can recover to their original shapes after compression were obtained. Narrower and more uniform pore size distribution was observed for the DMF modified aerogels in our study.
Co-reporter:Luyi Wang, Guorong Shan and Pengju Pan
Soft Matter 2014 vol. 10(Issue 21) pp:3850-3856
Publication Date(Web):14 Apr 2014
DOI:10.1039/C4SM00206G
A novel interpenetrating network (IPN) hydrogel with ultrahigh compressive strength and fracture strain has been prepared using the copolymer of 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and acrylamide (AM) [P(AMPS-co-AM)] or N-isopropylacrylamide (NIPAM) [P(AMPS-co-NIPAM)] as the primary network and polyacrylamide (PAM) as the secondary network. The as-prepared IPN hydrogel of P(AMPS-co-AM)/PAM has a significantly high compressive strength (91.8 MPa), which is 4 times greater than that of the common PAMPS/PAM IPN hydrogel as well as the compressively strongest hydrogel reported in the literature. The P(AMPS-co-AM)/PAM IPN hydrogel is tough enough not to fracture even when the compressive strain reaches 98%. Synchrotron radiation small-angle X-ray scattering (SAXS) analysis has indicated that the presence of an AM comonomer changes the size of the physically cross-linked domains in the IPN hydrogel, which may partially account for its unique mechanical properties. This study has presented the compressively strongest hydrogel reported to date and also provided a novel and feasible method to prepare the highly strong and tough hydrogel.
Co-reporter:Kuanxiang Shang, Guorong Shan and Pengju Pan
Soft Matter 2014 vol. 10(Issue 44) pp:8913-8922
Publication Date(Web):03 Oct 2014
DOI:10.1039/C4SM01866D
A unique phenomenon of multiple soluble–insoluble phase transitions was found in the two-phase copolymerization of acrylamide (AM) and a weakly charged comonomer, N,N-dimethylaminoethyl methacrylate (DMAEMA), in the aqueous solution of poly(ethylene glycol) (PEG). As the DMAEMA molar fraction increased from 0 to 0.30, the insoluble–soluble (I–S) phase transition first appeared and then disappeared. Varying the PEG concentration, the salt concentration, or the pH of reaction mixture, the phase transitions were tuned dependently. The volume fractions and refractive indices of continuous and disperse phases, as well as the viscosity change in the phase transitions were investigated, and the results showed that phase reentrance had occurred in the I–S phase transition. The transitional conversion for the first S–I phase transition increased with the DMAEMA molar fraction, indicating the solubility enhancement of charged polyelectrolytes. The content of DMAEMA in the resulting copolymer first increased and then decreased as the polymerization progressed. Accordingly, the droplet size increased in the two S–I phase transitions and decreased in the I–S phase transition. And it was proved that the copolymers were molecularly solubilized after the I–S phase transition. The multiple soluble–insoluble phase transitions were ascribed to the synergistic effect of polymer concentration, solubility enhancement of charged copolymers, and the salting-out effect of ionic comonomers. A generalized mechanism for the multiple soluble–insoluble phase transitions was proposed, which showed that the effects of polymer concentration were dominant in the two S–I phase transitions, while the effects of solubility enhancement played a key role in the I–S phase transition.
Co-reporter:Luyi Wang, Guorong Shan and Pengju Pan
RSC Advances 2014 vol. 4(Issue 108) pp:63513-63519
Publication Date(Web):24 Nov 2014
DOI:10.1039/C4RA11494A
An interpenetrating network (IPN) hydrogel with a highly enhanced elongation-at-break has been prepared using poly(ethylene glycol) (PEG)-swollen poly(2-acrylamide-2-methylpropane sulfonic acid) (PAMPS) as the first network and polyacrylamide (PAM) as the second network. The new IPN hydrogel of PAMPS–PEG/PAM has remarkably high elongation-at-break (∼2100%) in tensile deformation, which is 4 times larger than common PAMPS/PAM IPN hydrogel and PAMPS/PAM–PEG IPN hydrogels synthesized by incorporating PEG into the second network. The microstructures of single network (SN) and IPN hydrogels were investigated by synchrotron radiation small-angle X-ray scattering (SAXS). SAXS results were analyzed by Guinier, Ornstein–Zernike (OZ), and generalized Ornstein–Zernike (GOZ) models. It was found that the incorporated PEG increases the size of cross-linked domains and decreases the fractal dimension of domains. The toughening mechanism of PEG on IPN hydrogel was discussed. It is proposed that the largely enhanced toughness of PAMPS–PEG/PAM IPN hydrogel is due to the increased size of physical cross-linked domains, hydrogen bonding between the first and second network, and the increased pull-out resistance of PAM chains under deformation.
Co-reporter:Yi Liu, Yue Shang, and Guorong Shan
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 50) pp:19533-19539
Publication Date(Web):2017-2-22
DOI:10.1021/ie503009d
On the basis of the Van Deemter model of the chromatographic process, the infinite dilution diffusion coefficients of dichloromethane, chloroform, and carbon tetrachloride in poly(ethylene terephthalate) (PET) have been measured over a wide range of temperatures from 373.15 to 413.15 K by inverse gas chromatography. The relationships between the infinite dilution diffusion coefficients and molecular size of the solvent, as well as the temperature, were investigated. Meanwhile, the measured diffusion data were compared with the theoretical predictions by free-volume theory. The results indicated that neglecting the molecular interactions, i.e., the diffusivity energy term in the free-volume equation, may result in a poor prediction of the diffusion coefficient for PET-chlorinated methane systems because of the strong molecular interactions. The good agreement between the experimental data and the theoretical predictions by the proposed method showed that it is reasonable to take the diffusivity energy term into consideration for those systems with strong molecular interactions, and, furthermore, the infinite dilution diffusion coefficients at different temperature can be predicted accurately with this method.
Co-reporter:Kuanxiang Shang, Guorong Shan, and Pengju Pan
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 38) pp:14664-14672
Publication Date(Web):September 11, 2014
DOI:10.1021/ie502388b
A series of cationic polyacrylamides (CPAMs) with different charge densities have been prepared via the stabilizer-free two-phase copolymerization of acrylamide (AM) and 2-methylacryloylxyethyl trimethylammonium chloride (DMC) in the aqueous solution of poly(ethylene glycol) (PEG). Systematical investigations were carried out on the role of electrostatic interactions in the phase separation, product stability, and droplet formation. It was found that, with the introduction of a DMC unit into the polyacrylamide chains, the critical conversion and stability of the product greatly improved and the droplets of the final dispersion became smaller and more uniform. Scanning electron microscopy and ζ-potential results indicated that two growth stages and a transition stage existed in the droplet formation and growth process, and the aggregation degree of droplets in the transition region was controlled by the electrostatic repulsion. The cationic copolymer acted as a stabilizer in the stabilizer-free two-phase copolymerization process, which facilitated the formation of smaller and more uniform droplets. A novel four-step mechanism for the droplet formation and growth was proposed, which could illustrate the role of electrostatic interactions in the stabilizer-free aqueous two-phase copolymerization system.
Co-reporter:Kuanxiang Shang, Guorong Shan, and Pengju Pan
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 26) pp:10681-10687
Publication Date(Web):2017-2-22
DOI:10.1021/ie501617j
The two-phase copolymerization of acrylamide (AM) and anionic comonomer, sodium 2-(acrylamido)-2-methylpropanesulfonate (NaAMPS), in a poly(ethylene glycol) (PEG) aqueous solution was investigated. An unusual soluble–insoluble–soluble phase transition was found. The effects of the monomer ratio, PEG concentration, initiator concentration, salt concentration, and pH value of the reaction media on the phase transition behavior were studied. As the NaAMPS molar fraction increased or the PEG concentration decreased, the insoluble–soluble phase transition first appeared and then disappeared. However, all of the aqueous two-phase polymerization systems underwent a soluble–insoluble–soluble phase transition with increasing initiator concentration. The results of critical conversion and copolymer composition indicated that there were two competitive effects governing the phase separation, that is, the solubility enhancement of a polyelectrolyte and Debye–Hückel screening effect of an anionic monomer. The insoluble–soluble phase transition disappeared at higher salt concentration. A mechanism for the unique soluble–insoluble–soluble phase transition was proposed, which was ascribed to the synergistic effects of the polymer concentration, solubility enhancement of a polyelectrolyte, and screening effect of an anionic comonomer. On the basis of this mechanism, the phase transition was successfully tuned by varying the pH value of reaction media.
Co-reporter:Xianbo Xu;Yue Shang ;Pengju Pan
Journal of Applied Polymer Science 2014 Volume 131( Issue 15) pp:
Publication Date(Web):
DOI:10.1002/app.40589
ABSTRACT
A thermo-sensitive nanocapsule, containing the hydration layer, was synthesized through introducing N-isopropylacrylamide into the system of styrene miniemulsion polymerization and hexadecane as liquid template. The properties and content of the water in the hydration layer were investigated by differential scanning calorimetry. With dynamic light scattering and transmission electron microscope, the effects of temperature and solvent on the particle size and morphologies were studied. The results showed that the increase of temperature and the ethanol–water mixed solvent could decrease the thickness of hydration layer and caused the polymer chain in the shell coil-to-globule transition, which switched on the pathway to loading and releasing substances in the nanocapsules. By using UV-visible spectroscopy to monitor the tracer, the diffusion coefficients were determined and verified the switching process above. In addition, the ethanol–water molecule cluster can form a stable associative structure around ethanol mole fraction of 0.4, and destroyed the hydration of the hydrophilic group. The solvent interactions were proved to be the main driving force for the coil-to-globule transition of poly(N-isopropylacrylamide). Moreover, an appropriate latex particle size should exclude the hydration layer but stable dispersed in the solvent was suggested. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40589.
Co-reporter:Lei Xu and Guorong Shan
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 24) pp:8216
Publication Date(Web):June 5, 2013
DOI:10.1021/ie3026168
Simultaneous interpenetrating polymer networks (SIPNs) of linear polyurethane (PU) and linear poly(methyl methacrylate) (PMMA) were synthesized. Kinetic studies were carried out by means of titration of −NCO functional groups for PU and gas chromatography for methyl methacrylate (MMA). Factors that influence the kinetics of SIPN formation, such as the composition ratio, temperature, initiator concentration, catalyst concentration, time of initiator addition, and presence of the chain extender 1,4-butanediol, were investigated. It was found that all of the factors that influenced the system viscosity also affected the kinetics of SIPN formation and that the step-growth polymerization process was related to the radical polymerization process. If too much of the catalyst was added to the system, SIPNs would not completely form. The kinetics of polyurethane formation obeyed a second-order function during the early period of the reaction and a third-order function at high −NCO functional group conversions.
Co-reporter:Yiming Shi, Guorong Shan, and Yue Shang
Langmuir 2013 Volume 29(Issue 9) pp:3024-3033
Publication Date(Web):February 22, 2013
DOI:10.1021/la304847a
Through zeta potential and surface tension measurements and a series of polymerization experiments, the role of poly(ethylene glycol) (PEG) in the process of surfactant-free polymerization of styrene (St)/methyl methacrylate (MMA) has been investigated experimentally. Nanoscale and stable copolymer particles were formed after an abnormal process, in which the nucleation and growth of particles was different from that in previously proposed mechanisms. It has been observed that PEG can exist in both the monomer and the aqueous phases at high temperature. PEG in the aqueous phase could form copolymer particles with a loose structure, making them prone to enter the monomer phase. Entry of these copolymer particles into the monomer phase would introduce excess PEG. From the ternary phase diagram, a solubility curve could be delineated in the ternary system of PEG/monomer/copolymer. The system used the ternary solubility property to regenerate copolymer particles in the monomer phase, which maintained their morphology until the end of the polymerization. At the end, consumption of the monomer resulted in the volume contraction of the particles, and the surface potential increased. This increasing potential is a driving force to prevent particles from stacking, leading to the formation of nanoscale and stable particles.
Co-reporter:Ting Lü;Songmin Shang
Journal of Applied Polymer Science 2011 Volume 122( Issue 2) pp:1121-1133
Publication Date(Web):
DOI:10.1002/app.34243
Abstract
A poly(acrylamide) (PAM) aqueous dispersion with high solid was successfully synthesized through two-phase polymerization of acrylamide (AM) in aqueous poly(ethylene glycol) (PEG) solution. To prepare stable PAM aqueous dispersion, the effects of initiator, monomer and PEG concentration on the stability of the aqueous two-phase polymerization system were investigated in detail. Dynamic light scattering (DLS) was applied to study the evolution of the size and size distribution of the aqueous PAM droplet in the initial stage of polymerization. A droplet aggregation period was found in the initial stage, in which the PAM coagulum is easy to be generated below the conversion of about 5% due to high polymerization rate. By analyzing the effects of PEG on the stability of this polymerization system, it was found that PEG plays both precipitant and stabilizer role. When PEG concentration ranges from 12 to 24%, increasing its use would promote the droplet stabilization; however, when PEG concentration exceeds 28%, increasing its use may accelerate the droplet formation which does not further favor the droplet stabilization. Furthermore, the viscosity evolution during the polymerization under various reaction conditions was determined by rotational viscometer on line. When monomer concentration exceeded 8%, increasing the initiator or monomer concentration would result in that the polymer produced in the continuous phase could not be separated in time due to the high viscosity. All these results demonstrated that the slower the polymerization rate is, the more stable PAM aqueous dispersion will be. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Ting Lü ;Guo-Rong Shan
Journal of Applied Polymer Science 2010 Volume 116( Issue 3) pp:1747-1758
Publication Date(Web):
DOI:10.1002/app.31628
Abstract
A kind of polyacrylamide (PAM) latex product dispersed in an aqueous solution was successfully prepared through the aqueous two-phase polymerization of acrylamide in an aqueous solution of poly(ethylene glycol) (PEG). The effects of various polymerization parameters on the size and morphology of droplets rich in PAM were systematically investigated. The droplet size and morphology was significantly influenced by the polymerization rate. The high polymerization rate caused the formation of stripe-shaped droplets because of the aggregation of more droplets rapidly separated from the continuous phase. At the same time, the monomer partition behavior mainly relied on the temperature, and the PEG concentration also dramatically affected the droplet size and morphology. The increase in PEG concentration not only changed the monomer partition behavior and restrained droplet aggregation but also shortened the critical PAM radical chain length and accelerated the droplet formation. Furthermore, the stirring speed was also recognized as the correlative factor that affected the droplet stability and monomer diffusion rate from the continuous phase into the droplets. The addition of salt and alcohol altered the droplet stability and the final droplet size and morphology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Ting Lü;Songmin Shang
Journal of Applied Polymer Science 2010 Volume 118( Issue 5) pp:2572-2581
Publication Date(Web):
DOI:10.1002/app.32556
Abstract
The interaction between poly(acrylamide) (PAM) and poly(ethylene glycol) (PEG) in their solid mixture was studied by Fourier transform infrared spectroscopy (FTIR); and their interaction in aqueous solution was investigated by nuclear magnetic resonance spectroscopy (NMR). For the solid PAM/PEG mixtures, an induced shift of the >CO and >NH in amide group was found by FTIR. These results could demonstrate the formation of intermolecular hydrogen bonding between the amide group of PAM and the ether group of PEG. In the aqueous PAM/PEG solution system, the PAM and PEG associating with each other in water, i.e., the amide group of PAM interacting with the ether group of PEG through hydrogen bonding was also found by 1H NMR. Furthermore, the effects of different molecular weight of PAM on the strength of hydrogen bonding between PAM and PEG in water were investigated systemically. It was found that the hydrogen bonding interaction between PAM and PEG in water did not increase with the enlargement of the PAM molecular weight as expected. This finding together with the viscosity reduction of aqueous PAM/PEG solution with the PAM molecular weight increasing strongly indicated that PAM molecular chain, especially having high molecular weights preferred to form spherical clews in aqueous PEG solution. Therefore, fewer amide groups in PAM could interact with the ether groups in PEG. Based on these results, a mechanism sketch of the interaction between PAM and PEG in relatively concentrated aqueous solution was proposed. The fact that the phase separation of aqueous PAM/PEG solution occurs while raising the temperature indicates that this kind of hydrogen bonding between PAM and PEG in water is weak and could be broken by controlling the temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Ting Lü
Journal of Applied Polymer Science 2009 Volume 112( Issue 5) pp:2859-2867
Publication Date(Web):
DOI:10.1002/app.29782
Abstract
Aqueous two-phase polymerization of acrylamide has been carried out in an aqueous solution of poly(ethylene glycol) initiated by ammonium persulfate. The chemical composition of the product was characterized by FTIR, and the droplet size distribution in the initial stage of the polymerization was followed by dynamic light scattering. On the basis of the evolution of polyacrylamide aqueous droplets size distribution and morphology at every stage, a new mechanism of droplet formation was proposed. The experimental phenomenon that the small droplets always existed in the process of polymerization and some irregular shape droplets were formed in the product of aqueous two phase polymerization could be successfully explained by the new mechanism. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Shan Guorong;Cao Zhihai
Journal of Applied Polymer Science 2009 Volume 111( Issue 3) pp:1409-1416
Publication Date(Web):
DOI:10.1002/app.29167
Abstract
The concept of aqueous two-phase polymerization and a new polymerization method for the preparation of water-soluble polymers are presented. The phase diagram of poly(acrylamide) (PAAm)-poly (ethylene glycol) (PEG)-water two-phase system was measured by the gel permeation chromatography (GPC). The aqueous two-phase of PAAm-PEG-water system can be easily formed. The critical concentration of phase separation was affected by the molecular weight of PEG. The aqueous two-phase polymerization of acrylamide (AAm) has been successfully carried out in the presence of PEG by using ammonium persulfate (APS) as the initiator. The polymerization behaviors with varying concentration of AAm, initiator and PEG, the polymerization temperature, the molecular weight of PEG, and emulsifier types were investigated. The activation energy of aqueous two-phase polymerization of AAm was 132.3 kJ/mol. The relationship of initial polymerization rate (Rp0) with APS and AAm concentrations was Rp0 ∝ [APS]0.72 [AAm]1.28. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Zhihai Cao
Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 6) pp:1522-1534
Publication Date(Web):
DOI:10.1002/pola.23255
Abstract
A water-soluble comonomer, N-isopropylacrylamide (NIPAM), and an oil-soluble crosslinker, divinylbenzene (DVB), have been combined in a system for the synthesis of nanocapsules with crosslinked shells through interfacial miniemulsion polymerization by encapsulating a liquid nonsolvating hydrocarbon. Oligomers of poly(N-isopropylacrylamide) (PNIPAM) were dehydrated and separated from the aqueous phase and were adsorbed by the nanodroplets or latex particles and then anchored at their interfaces by means of a crosslinking reaction. Nanocapsules were then formed through encapsulation of the hydrocarbon by the newly produced polymers at the interfaces of the droplets. The crosslinked structure gradually grew to stabilize the shell morphology. The incorporation of NIPAM into the shell copolymers has been verified by FTIR and solid-state 13C NMR data. The fact that the number of nanocapsules increases with increasing amounts of DVB and NIPAM supports the formation of nanocapsules following interfacial (co)polymerization. Therefore, a mechanism for the formation of nanocapsules through interfacial (co)polymerization induced by NIPAM and DVB is proposed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1522–1534, 2009
Co-reporter:Jian-Yi Wu;Guo-Rong Shan;Jian-Yi Wu;Guo-Rong Shan
Journal of Applied Polymer Science 2006 Volume 100(Issue 6) pp:4399-4405
Publication Date(Web):8 MAR 2006
DOI:10.1002/app.23793
The gel effect will bring a violent increase of conversion for methyl methacrylate (MMA) polymerization in a short time. It will be very dangerous for the reactor, as it causes an increase of molecular weight and broadens the molecular weight distribution. To unify the kinetics, molecular weight, and its distribution, on the basis of the mathematical models for semibatch polymerization of MMA, three controlled objectives that are the heat load distribution index, the change in molecular weight, and molecular weight distribution index are presented. Three materials (monomer, solvent, and chain transfer agent) and their flow rate and feeding mode are analyzed for the open control of kinetics, molecular weight, and its distribution. The optimum flow rate and mode are obtained. The heat load distribution index and molecular weight distribution index are even less than 2.0 and 2.2, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4399–4405, 2006
Co-reporter:Guo-Rong Shan;Jian-Yi Wu
Journal of Applied Polymer Science 2006 Volume 100(Issue 4) pp:2838-2846
Publication Date(Web):9 FEB 2006
DOI:10.1002/app.23792
There are gel, glass, and cage effects in the methyl methacrylate (MMA) bulk polymerization. These effects will cause the propagation and termination rate constants and initiator efficiency change during the polymerization process, and make the kinetics and molecular weight more complex. A violent increase of conversion will bring a large amount of reaction heat evolved in a short time, and will promote temperature increase if the heat cannot be removed in time. Molecular weight of polymer will raise ten times at the same time. So, the temperature of polymerization system, kinetics of polymerization, and molecular weight and its distribution of polymer cannot be controlled. To control and unify them, the semibatch polymerization method is preferably selected. Furthermore, the kinetic and molecular weight models for MMA semibatch polymerization with the participation of chain transfer agent and new materials addition flow rate are presented. Using the presented models, the effects of temperature, initiator concentration and type, monomer or solvent concentration, and chain transfer agent concentration and type on the kinetics, and molecular weight and its distribution are simulated in this article. Experimental data of kinetics and molecular weight obtained from the published literature are compared with the simulation results to examine the presented models. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2838–2846, 2006
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