Effect of porosigen and hydrophobic monomer on the fast swelling–deswelling behaviors for the porous thermoreversible copolymeric hydrogels

A series of porous thermoreversible copolymeric hydrogels were prepared from N‐isopropylacrylamide (NIPAAm) and hydrophobic monomers such as 2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate (OFPMA) and n‐butyl methacrylate (BMA) and CaCO₃ or poly(ethylene glycol) 8000 (PEG8000) as porosigen by emulsion polymerization. The effect of hydrophobic monomers and porosigens on the fundamental properties, such as equilibrium swelling ratio, swelling kinetics, gel strength, crosslinked densities, etc., and fast swelling–deswelling behavior for the present copolymeric hydrogels were investigated. Results showed that the deswelling rates for the gels porosigened by CaCO₃ were more rapid than those gels foamed by PEG8000. Results also showed that the swelling rates for the gel foamed by CaCO₃ were higher than those for the gel foamed by PEG8000. At the same time, results also showed that the gels with OFPMA foamed by CaCO₃ exhibit a faster swelling–deswelling behavior than those gels with BMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3152–3160, 2006     

Effect of silane coupling agent on swelling behaviors and mechanical properties of thermosensitive hybrid gels

A series of organic–inorganic hybrid thermosensitive gels with three different structures were prepared from N‐isopropylacrylamide (NIPAAm), and N, N′‐methylenebisacrylamide (NMBA) and tetraethoxysilane (TEOS) [N‐IPN]; NIPAAm, 3‐(trimethoxysilyl) propyl methacrylate (TMSPMA) as coupling agent and TEOS [NT‐IPN]; and NIPAAm, TMSPMA, and TEOS [NT‐semi‐IPN] by emulsion polymerization and sol–gel reaction in this study. The effect of different gel structures and coupling agent on the swelling behavior, mechanical properties, and morphologies of the present gels was investigated. Results showed that the properties of the gels would be affected by the gel networks such as IPN or semi‐IPN and with or without existence of TMSPMA as the bridge chain between networks. The NT‐semi‐IPN gel had higher swelling ratio and faster diffusion rate because poly(NIPAAm) moiety in the semi‐IPN gels was not restricted by NMBA network. However, the IPN gels such as N‐IPN and NT‐IPN had good mechanical properties and lower swelling ratio, but had a poor thermosensitivity due to the addition of coupling agent, TMSPMA, into the gel system that resulted in denser link between organic and inorganic components. The morphology showed that IPN gels had partial aggregation (siloxane domain) and showed some denser phases. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of TEOS contents on swelling behaviors and mechanical properties of thermosensitive hybrid gels

A series of organic‐inorganic hybrid thermosensitive gels with three different structures and different contents of tetraethoxysilane (TEOS) were prepared from N‐isopropylacrylamide (NIPAAm), and N,N′‐methylene‐bis‐acrylamide (NMBA) and TEOS [N‐IPN]; NIPAAm, 3‐(trimethoxysilyl) propyl methacrylate (TMSPMA) as coupling agent and TEOS [NT‐IPN]; and NIPAAm, TMSPMA and TEOS [NT‐semi‐IPN] by emulsion polymerization and sol‐gel reaction in this study. The effect of TEOS content on the swelling behavior, mechanical properties, and morphologies of the present gels was investigated. Results showed that the properties of the gels would be affected by the gel networks such as IPN or semi‐IPN, existence of TMSPMA as the bridge chain between networks, and content of TEOS. The NT‐semi‐IPN gel had higher swelling ratio because poly (NIPAAm) moiety in the semi‐IPN gels was not restricted by NMBA network. However, the IPN gels such as N‐IPN and NT‐IPN had good mechanical properties and lower swelling ratio, but had bad thermosensitivity due to the addition of coupling agent, TMSPMA, into the gel system that resulted in denser link between organic and inorganic components. Increasing TEOS content would also reduce the thermosensitivity of the hybrid gels. The morphology showed that IPN gels had partial aggregation (siloxane domain) and showed some denser phases. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Investigation of mechanical and thermodynamic properties of pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels prepared with different crosslinking agents

pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels were synthesized by free‐radical crosslinking polymerization using two different crosslinking agents; tetraethylene glycol dimethacrylate (TEGMA) and N,N′‐methylenebis(acrylamide) (BAAm). The influence of the polymerization factors such as the type of the crosslinking agent and the gel preparation concentration on the swelling behavior, the gel strength, the effective crosslinking density and the average chain length between the crosslink points for the resulting hydrogels was investigated. The results of the equilibrium swelling measurements in water showed that the linear swelling ratio of the resulting hydrogels increases with increasing gel preparation concentration. The swelling ratio of PDMAEMA hydrogels crosslinked with BAAm is larger than those for hydrogels crosslinked with TEGMA over the entire range of the polymer network concentration. The hydrogels exhibit very sharp pH‐sensitive phase transition in a very narrow range of pH between 7.7 and 8.0. From the mechanical measurements, it was also found that the linear swelling ratio of resulting hydrogels depends on the crosslinking density and also the type of the crosslinker used in the preparation. The resulting hydrogels are thought to be good candidates for pH‐sensitive drug delivery systems. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Rapid pH‐dependent phase transition and elasticity of stimuli‐responsive cationic poly(N,N‐dimethylaminoethyl methacrylate) hydrogels prepared with a dimethacrylate crosslinker

Stimuli‐responsive hydrogels prepared from poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) and its copolymers have attracted much interest to serve in biomedical and pharmaceutical applications. To investigate pH‐dependent swelling and elasticity, a series of cationic hydrogels based on N,N‐dimethylaminoethyl methacrylate were prepared by free radical crosslinking copolymerization at 60 °C in the presence of tetraethylene glycol dimethacrylate as the crosslinker. The equilibrium swelling and the mechanical properties of the PDMAEMA hydrogels were investigated as a function of the gel preparation concentration. To explain the effect of pH on the equilibrium swelling of the hydrogels, pH‐dependent swelling studies were carried out in solutions of pH ranging from 2.1 to 10.7. It was found that the PDMAEMA hydrogels exhibit a rapid pH‐dependent phase transition in aqueous solutions; that is, the gels first remain in the swollen state at acidic pH then collapse in a very narrow range of pH. The results showed that the volume of PDMAEMA hydrogels in acidic conditions is about 10‐ to 40‐fold larger than that in the basic pH region. By using the Flory–Rehner theory, the characteristic network parameters of the PDMAEMA hydrogels were calculated and good agreement obtained between the swelling equilibria of hydrogels and their mechanical properties over the whole range of gel preparation concentration. © 2012 Society of Chemical Industry     

Preparation and properties of thermosensitive organic‐inorganic hybrid gels containing modified nanosilica

A series of thermosensitive organic–inorganic hybrid gels containing nanosilica or modified nanosilica were prepared from N‐isopropylacrylamide (NIPAAm), and N,N′‐methylene‐bis‐acrylamide (NMBA) and nanosilica (AE200) or modified AE200 (mAE200); and NIPAAm, NMBA, 3‐(trimethoxysilyl) propyl methacrylate (TMSPMA) as coupling agent and AE200 or mAE200 in this study. The effect of inorganic nanosilica on the swelling behaviors and mechanical properties were investigated by adding different amount of nanosilica and modified nanosilica. Results showed that the swelling ratios of the hybrid gels decrease with increasing nanosilica content. Existence of silane coupling agent would also reduce the swelling ratios of the hybrid gels. Adding coupling agent or nanosilica would improve the gel strength. Modification of nanosilica by grafting amino‐silane via sol–gel process was carried out and the effect of addition of modified silica on gel properties was also investigated. Results showed that the hybrid gels containing modified silica would have higher swelling ratios and moduli than those containing unmodified silica. Gels containing both silane coupling agent and silica would have higher crosslinking density because the silica would be better crosslinked with coupling agent. POLYM. COMPOS., 31:1712–1721, 2010. © 2010 Society of Plastics Engineers.     

Preparation and swelling behavior of macroporous poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels

Macroporous superabsorbent hydrogels (SAHs) composed of acrylamide (AAm) and sodium methacrylate (NMA) were prepared by aqueous solution polymerization in the presence of a glucose solution. Their swelling capacity was investigated as a function of the concentrations of the glucose solution, sodium methacrylate, crosslinker, initiator, and activator. The porosity of the poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels was confirmed using scanning electron microscopy. The SAHs were characterized by IR spectroscopy. To estimate the effect on the swelling behavior, three types of crosslinkers were employed: N,N′‐methylenebisacrylamide, 1,4‐butanediol diacrylate, and diallyl phthalate. Network structural parameters such as initial swelling rate, swelling rate constant, and maximum equilibrium swelling were evaluated by water absorption measurement. The equilibrium water content (EWC%) of the AAm–NMA macroporous SAHs was found to be in the range of 93.31–99.68, indicating that these SAHs may have applications as biomaterials in the medicinal, pharmaceutical, and veterinary fields. Most of the SAHs prepared in this investigation followed non‐Fickian‐type diffusion, and few followed a case II– or super–case II‐type diffusion. The diffusion coefficients of these macroporous SAHs were investigated. Further, the swelling behavior of these SAHs also was investigated at different pHs and in different salt solutions and simulated biological fluids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3202–3214, 2006     

Effect of intercalated hydrotalcite on swelling and mechanical behavior for poly(acrylic acid‐co‐N‐isopropylacrylamide)/hydrotalcite nanocomposite hydrogels

A series of nanocomposite hydrogels were prepared from acrylic acid (AA), N‐isopropylacrylamide (NIPAAm), and intercalated hydrotalcite (IHT) by photopolymerization. The influence of the intercalating content of 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) in HT on the swelling and mechanical properties for poly(AA‐co‐NIPAAm)/IHT nanocomposite hydrogels was investigated. The results showed that the higher the content of the AMPS‐HT was, the higher the swelling ratio of the gels and the higher the content of the intercalating agent was, the lower swelling ratio. It was also demonstrated that the swelling ratio of the gel was not affected by the counterion in HT. The gel strength and crosslinking density were not enhanced by adding AMPS‐HT into the gel composition, but the maximum effective crosslink density and shear modulus of the nanocomposite hydrogels were increased with an increase of the content of the intercalating agent in HT. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1572–1580, 2005     

Influence of MEOBiPA content on the properties of novel photoluminescent thermosensitive hydrogels

In order to establish a dual functional hydrogel, a special monomer, methacryloyloxy‐ethylene‐oxy‐carbonyl bis[4‐(phenyl‐isopropyl)phenyl]amine (MEOBiPA), was prepared from bis[4‐(phenyl‐isopropyl)phenyl]‐4‐cyanophenyl amine and 2‐hydroxyethyl methacrylate. Subsequently, a series of thermosensitive hydrogels was obtained through copolymerization of N‐isopropyl acrylamide (NIPAAm) with MEOBiPA by UV irradiation (named the NM series). The effect of MEOBiPA content on the swelling behavior, mechanical properties and drug release behavior of the hydrogels was further investigated. Results showed that the swelling ratios of the NM copolymeric hydrogels decreased from 4.73 to 1.74 g g^?1 when the MEOBiPA content in the hydrogel increased from 0.1 to 0.9 mol%. Both gel strength and crosslinking density of the NM hydrogels increased with increasing MEOBiPA. Conversely, the thermosensitive behavior of NM hydrogels significantly decreased upon increase of MEOBiPA content. Likewise, the caffeine release ratio also decreased from 70% to 25%. Notably, the intensity of photoluminescence increased with increasing MEOBiPA content in the hydrogels. Further, the corresponding copolymers of the hydrogels were prepared using free radical polymerization. The UV absorbance and photoluminescent behavior of the MEOBiPA, NIPAAm/MEOBiPA copolymeric hydrogels and their corresponding copolymers in different polar solvents were also investigated. © 2015 Society of Chemical Industry     

Effect of crosslinking concentration on mechanical and thermodynamic properties in acrylic acid–co–methyl methacrylate hydrogels

The mechanical and thermodynamic properties of poly(acrylic acid‐co‐methyl methacrylate) hydrogels with varying crosslinker N,N′‐methylenebisacrylamide (NMBA) content are reported. A higher NMBA content generally led to a stronger and harder gel with lower water content. Swelling capacity decreased as the NMBA concentration increased between 0.5% and 2%, remaining constant beyond this range. The temperature changes of the partial molar Gibbs free energy of dilution and enthalpic and entropic contributions were examined. The thermodynamic parameters showed that swelling was an unfavorable and endothermic process. The freezing and nonfreezing water in the hydrogel was determined by differential scanning calorimetry (DSC). Freezing water content decreased with increasing crosslinker (NMBA) content, whereas the ratio of nonfreezing water to total water content increased with NMBA content because of the promoting of hydrophobic interactions in the hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4016–4022, 2006     

Investigation for surface morphology and mechanical property variations of single polymer particles

Monodisperse polymer particles were prepared via one‐step seeded polymerization using polystyrene, poly(methyl methacrylate), or styrene/methyl methacrylate copolymer [poly(ST‐co‐MMA)] as seed particles and 1,6‐hexanedioldiacrylate or divinylbenzene as crosslinking monomer. For the study, the effects of the combination of seed polymer and crosslinking monomer, the ratio of the absorbed monomer to the seed polymer particles (swelling ratio: S/R), and the seeded polymerization rate on the variation of surface morphology and mechanical properties of polymer particles, such as recovery rate, K‐values, breaking strength, and breaking displacement were investigated by using microcompression test. It was observed that the surface morphology could be controlled by changing polymerization rate or combination of seed polymer and crosslinking monomer, and it had a great influence on mechanical properties, especially the breaking strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2350–2360, 2007     

Preparation and pH‐sensitive swelling behavior of physically crosslinked polyampholyte gels

A novel polyampholyte hydrogels were prepared by free radical aqueous copolymerization of ionic complex consisting of acrylic acid (AAc), (N,N‐diethylamino) ethyl methacrylate (DEAEM), and acrylamide (designated as PADA). Without any chemical crosslinker, the formation of PADA network structures was mainly attributed to the electrostatic interaction of AAc (anionic monomer) and DEAEM (cationic monomer). The PADA gels exhibited a typical swelling behavior of polyampholyte gels in buffer solutions. The hysteresis of isoelectric point (pI) for PADA gels was observed after preswollen in alkaline solutions. The swelling behavior of PADA gels in response to change of pH was investigated. It was found that the equilibrium swelling ratio orderly decreased in buffer solutions with alternating pH between 2.2 and 5. An abrupt swelling was observed for the hydrogels at the pH near isoelectric point in the earlier stage of swelling process. The study of swelling kinetics of the hydrogels showed that the swelling process was in agreement with the second‐order swelling kinetics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3857–3861, 2006     

Synthesis and drug‐release studies of low‐fouling zwitterionic hydrogels with enhanced mechanical strength

Reversible addition–fragmentation chain‐transfer polymerization was introduced to prepare a series of zwitterionic poly(hydroxyethyl methacrylate)‐g‐poly(sulfobetaine methacrylate) (PSBMA) hydrogels (HSGs) with different monomer feed ratios. Compared with PSBMA hydrogels, these hydrogels exhibited enhanced mechanical strengths. Then, the HSGs were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and swelling measurements. We found that the equilibrium swelling ratios, mechanical strengths, and drug‐release behaviors were significantly affected by the feed ratios of the gels. The hydrophilic tetracycline hydrochloride release results suggest that the hydrophilic drug release from the HSGs could be prolonged by the variation of the hydroxyethyl methacrylate amount in the gel networks. The bovine serum albumin adsorption data showed that the zwitterionic HSG with 18.2 wt % sulfobetaine methacrylate exhibited good protein‐resistance properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41041.     

Polymerization in magnetic field: XVIII. Influence of surfactant nature on the synthesis and thermal properties of poly(methyl methacrylate) and poly[(methyl methacrylate)‐co‐(epoxypropyl methacrylate)]

BACKGROUND: The possibility to use β‐cyclodextrin as biodegradable tensioactive and an electromagnetic field in order to improve the kinetic parameters of radical emulsion polymerization is of interest. Thus, the influence of different surfactants—sodium lauryl sulfate (SLS) and β‐cyclodextrin (CD)—on the pathway of emulsion polymerization of methyl methacrylate (MMA) and emulsion copolymerization of MMA with 2,3‐epoxypropyl methacrylate (GMA) performed with or without the presence of a continuous electromagnetic field (MF) was studied. RESULTS: The presence of the MF leads to a considerable increase of the conversion during the first part of the reaction if the classic surfactant (SLS) is used. The reactions performed without MF and with CD exhibit a decrease of the conversion and of the polymerization rate as compared with the variants using SLS. The swelling rate and the maximum degree of swelling vary with the surfactant nature and with the reaction conditions and MF presence. Data from thermogravimetry and differential scanning calorimetry evidence the dependences between the polymer characteristics and the preparation conditions. CONCLUSION: This research underlines the coupling possibilities of the influence of a MF—growth of the reaction rate and conversion explained through radical pairs mechanism—with a combination of the ‘cage’ effect and ‘conformational control’ afforded by CD. The presence of MF and CD during the syntheses leads to an increase of T_g and an increase of PMMA and P(MMA‐co‐GMA) thermal stability. Copyright © 2007 Society of Chemical Industry     

Temperature‐, pH‐, and ion‐stimulus‐responsive swelling behaviors of poly(dimethylaminoethyl methacrylate) gel containing cholic acid

Poly(dimethylaminoethyl methacrylate) hydrogels containing cholic acid (PDMAEMA–CA) were synthesized by radiation crosslinking. The introduction of 10 and 20 mol% cholic acid (CA) into the poly(dimethylaminoethyl methacrylate) (PDMAEMA) hydrogel decreased the maximum swelling ratio (SR) of the gel from 40 to 6 and 5, respectively. The incorporation of CA with dimethylaminoethyl methacrylate led to a decrease in the lower critical swelling temperature of the gel from 44 to 42°C but did not exert big influence on the ion‐stimulus‐responsive properties of the gel. However, the pH sensitivity of the PDMAEMA–CA gel was quite different from that of PDMAEMA gel. The SR of PDMAEMA gel decreased at pH 2.5, whereas the SRs of the PDMAEMA–CA gels showed a convex‐upward function of pH; that is, SR of the PDMAEMA–10% CA gel first increased (pH 1.2–3.2) and then decreased (pH 3.2–11.9) with increasing pH. The pH‐stimulus‐responsive swelling behavior of the PDMAEMA–20% CA gel was similar to that of the PDMAEMA–10% CA gel except for the unique swelling behavior exhibited in the lower pH region. The unique decrease in SR in strong acidic solutions was attributed to aggregations driven by the hydrophobic interactions between CA molecules. Phase separation of the gel in strongly acidic solutions was observed; that is, the margin of the swollen gel was transparent and elastic (cellular structure), whereas the core of it was opaque (aggregated structure) as recorded by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39998.     

Observation for mechanical property variations of single polymer particles

Monodisperse polymer particles were prepared via conventional microsuspension polymerization or one‐step seeded polymerization, using 1,6‐hexanedioldiacrylate or its mixture with ethylene glycol dimethacrylate (EGDMA) as crosslinking monomer and poly(methyl methacrylate) synthesized by soap‐free polymerization as seed particles. For the study, the effects of the ratio of the absorbed monomer or monomer mixture to the seed polymer particles (swelling ratio), the ratio of EGDMA in absorbed monomer mixture, the dosage of initiator, polymer particle structure, and the electroless Ni plating on the mechanical properties of polymer particles, such as recovery rate, K‐values, breaking strength, and breaking displacement were investigated using micro compression test. It was observed that monomer swelling ratio influenced only on breaking strength, whereas EGDMA ratio in monomer mixture, dosage of initiator, polymer structure and electroless Ni plating did on both K‐values and breaking strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and properties of silicone‐containing poly(methyl methacrylate) gels

Poly(methyl methacrylate) (PMMA) gels with varying amounts of silicone and solvent and constant amounts of crosslinker were prepared by solution free radical crosslinking copolymerization of methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM), tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) comonomer systems. They were then studied in benzene at a total monomer concentration of 3.5 mol L^?1 and 70 °C. The conversion of monomer, volume swelling ratio, weight fraction and gel point were measured as a function of the reaction time, silicone concentration and benzene content up to the onset of macrogelation. Structural characteristics of the gels were examined by using equilibrium swelling in benzene, gel fraction and Fourier‐transform infrared (FTIR) analysis. The morphology of the copolymers was also investigated by SEM. Based on the obtained results, it was concluded that the FTIR data did not have the capacity to show the presence of the VTES or TEOS moiety in these kinds of copolymers. On the other hand, the variation of weight fraction of gel, W_g, and its equilibrium volume swelling ratio in benzene, q_v, exhibited the same behaviour as that of MMA/EGDM copolymers. Also, the dilution of the monomer mixture resulted in an increase in the gel point and swelling degree and a decrease in the percent of conversion and gel fraction. Finally, TEOS is not an ideal silicone compound for reaction in the MMA/EGDM copolymerization system, whereas VTES is a suitable silicone comonomer for this system and it has been proved useful. Copyright © 2005 Society of Chemical Industry     

Mechanical properties,water‐swelling behavior,and morphology of water‐swellable rubber prepared using crosslinked sodium polyacrylate

A novel water‐swellable rubber (WSR) has been prepared by blending chlorobutadiene rubber (CR), reactive clay and other additives with crosslinked sodium polyacrylate (CSP), which was modified by interpenetrating polymer networks (IPNs) technology with crosslinked P(AA‐co‐BA). The structure of WSR was characterized by scanning electron microscopy (SEM). The mechanical properties, water‐swelling ratio by mass, and the percentage loss of CSP in the WSR were investigated. The results showed that the modified CSP grains can be dispersed well in the CR, and that it resulted in increase of mechanical properties and water‐swelling ratio and in decrease of percentage loss of CSP, compared with the unmodified one. When the percentage content of crosslinked P(AA‐co‐BA) used to modify CSP reached 30%, the tensile strength, elongation at break, and water‐swelling ratio of WSR exhibited maximum value, and percentage loss of CSP exhibited minimum value. When the content of CSP in WSR was 30 phr, the tensile strength, elongation at break, and water‐swelling ratio and percentage loss of CSP of the WSR containing CSP modified were 7.7 MPa, 1530, 438, and 2.5%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1489–1496, 2006     

Formation and structure of poly(methyl methacrylate) gels containing triphenyl vinyl silane

A series of Poly(methyl methacrylate) gels (PMMA) were prepared for making optical lenses by solution free radical crosslinking copolymerization of 2,2,2,‐trifluoroethyl methacrylate (TFEMA), methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM), and triphenyl vinyl silane (TPVS) comonomer systems. They were then studied in toluene at a total monomer concentration of 5 molL^?1 and 70°C. The conversion of monomer, volume swelling ratio, weight fraction, and gel point were measured as a function of the TPVS concentration, temperature, and chain transfer agents up to the onset of macrogelation. Structural characteristics of the gels were examined by using equilibrium swelling in toluene, gel fraction, and Fourier‐transform infrared (FTIR) analysis. The morphology of the copolymers was also investigated by Scanning electron microscopy (SEM). The dilution of the monomer mixture resulted in an increase in the gel point and swelling degree and a decrease in the percentage of conversion and gel fraction. Finally, TPVS is a compatible vinyl type silicone comonomer for this system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of reactive low‐profile additives on the properties of cured unsaturated polyester resins. II. Glass‐transition temperature and mechanical properties

The effects of reactive poly(methyl methacrylate) (PMMA) and poly(vinyl acetate)‐block‐poly(methyl methacrylate) (PVAc‐b‐PMMA) as low‐profile additives (LPAs) on the glass‐transition temperature and mechanical properties of low‐shrink unsaturated polyester resin (UP) were investigated by an integrated approach of determining static phase characteristics, reaction kinetics, cured sample morphology, and property measurements. The factors that, according to Takayanagi mechanical models, control the glass‐transition temperature in each phase region of the cured samples, as identified by both the thermally stimulated currents method and dynamic mechanical analysis, and the mechanical properties are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 867–878, 2006