Gel formation in free-radical crosslinking copolymerization

Polymer gels with varying amounts of crosslinker and solvent were prepared by solution free-radical crosslinking copolymerization of methyl methacrylate/ethylene glycol dimethacrylate (MMA/EGDM) and styrene/p-divinyl benzene (S/p-DVB) comonomer systems. The structural characteristics of the gels were examined using equilibrium swelling in toluene and gel fraction measurements. Experimental results were compared with the predictions of a kinetic model developed recently for free-radical crosslinking copolymerizations. Experimental data on S/EGDM networks reported by Hild, Okasha, and Rempp were also used to test this model. It was found that the model correctly predicts the development of the gel properties in free-radical crosslinking copolymerization. © 1995 John Wiley & Sons, Inc.     

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     

Gamma‐rays induced copolymerization of vinyl triethoxy silane and methyl methacrylate: Their spectroscopic characterization

The γ‐ray–induced copolymerization of vinyl triethoxy silane (VTES) with methyl methacrylate (MMA) was developed to be used in the simultaneous preservation and consolidation of archeological artifacts. A detailed analysis was performed to characterize the copolymerization reaction and conversion. The copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), and elemental analysis techniques. The mol fraction of VTES units in the synthesized copolymers were determined by elemental analysis of silicone pertaining to VTES segments using inductive coupling plasma spectroscopy (ICP). The effect of VTES mol fraction in the initial feed and the irradiation dose (6.5, 8.5, 10.0 kGy) on the yield of copolymerization was investigated. The yield of the copolymerization was found to decrease with increasing the VTES mol fraction in the monomer feed, and to increase with increasing the irradiation dose at each monomer composition. However, using the data obtained from the ICP measurements, the mol fraction of the VTES units in synthesized copolymers was determined to increase with increasing the VTES concentration in the initial monomer feed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 141–147, 1999     

In situ fast transient fluorescence technique (FTRF) to study swelling of gels made of various crosslinker contents

The fast transient fluorescence technique (FTRF), which uses the strobe master system (SMS), was employed to study the swelling of disc‐shaped PMMA [poly(methyl methacrylate] gels. Seven gels were prepared by free radical copolymerization (FCC) of methyl methacrylate (MMA) with various ethylene glycol dimethacrylate (EGDM) contents. Pyrene (P_y) was introduced as a fluorescence probe during polymerization. After drying these gels, swelling experiments were performed in chloroform at room temperature. P_y lifetimes were measured from fluorescence decay traces during the in situ swelling experiments. An equation was derived for low quenching efficiencies to interpret the behavior of lifetimes in the gel during swelling. It was observed that P_y lifetimes in the gel decreased as swelling proceeded. The Li–Tanaka equation was used to determine the cooperative diffusion coefficients, D_c, which were found to decrease as the crosslinker content was increased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 464–472, 2003     

Fast transient fluorescence technique for studying swelling of gels made at various crosslinker contents and exposed to organic vapour

Fast transient fluorescence technique (FTRF) was employed for studying swelling of disc‐shaped poly(methyl methacrylate) (PMMA) gels, which were prepared by free radical copolymerization of methyl methacrylate (MMA) using various ethylene glycol dimethacrylate (EGDM) contents at 60 °C. Pyrene (P) was introduced as a fluorescence probe during polymerization. Swelling experiments were performed by using P‐doped PMMA gels under chloroform vapor. Decay curves of P were measured during in situ swelling experiments. Exponential fits were performed to measure pyrene lifetimes, τ, inside the PMMA gels. It was observed that τ values decreased as swelling proceeded. An equation is derived for low quenching efficiencies to interpret the behaviour of P lifetimes during swelling. The Li–Tanaka equation was used to determine the cooperative diffusion coefficients, D_c, for the gels made at various crosslinker contents. It is observed that D_c values decrease as the crosslinker content is increased. © 2002 Society of Chemical Industry     

Effect of molar size and solubility parameter of solvent molecules on swelling of a gel: a fluorescence study

Gels were swollen in various solvents with different molar volume V and solubility parameter δ. In situ steady state fluorescence (SSF) measurements were performed for swelling experiments in gels formed by free radical crosslinking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM). Gels were prepared at 75 °C with pyrene (Py) as a fluorescence probe. After drying these gels, swelling and slow release experiments were performed in various solvents with different V and δ at room temperature by time monitoring of the Py fluorescence intensity. The Li–Tanaka equation was used to produce time constant τ₁ values. Cooperative diffusion coefficients (D_c) were measured and found to be strongly correlated to the molar volume of the solvents used. Solvent uptake and degree of swelling were found to be dependent on the solubility parameter of the solvent. © 2000 Society of Chemical Industry     

Copolymerization of methyl methacrylate and allyl acetate Part I. Rate of reaction

Free radical bulk copolymerization of methyl methacrylate (MMA) and allyl acetate (AAc) has been investigated using electron spin resonance (ESR) and FT–near infrared (FTNIR) spectroscopy. Data are used to evaluate the rate constants. The mole fraction of AAc plays an important role in the copolymerization of these two monomers. AAc not only delays the Trommsdorff effect but also increases the onset of percentage total conversion at which the Trommsdorff region begins. With AAc fraction 0.5 and higher, no Trommsdorff effect was observed. Inclusion of AAc into copolymer structure mainly occurs in the Trommsdorf region or when the AAc fraction in the comonomer feed is dominant. This is associated with a drop in the concentration of propagating radicals. However, ESR spectra indicate that the MMA propagating radical is predominant during the reaction. In the comonomer mixtures where a Trommsdorff region can be observed, the addition of AAc does not produce any significant change in k_p and k_t in the steady state region. Major changes in k_p and k_t are observed after the gel point and glassy state, respectively. © 2001 Society of Chemical Industry     

Swelling of porous copolymers based on alkyl methacrylate esters in water

Porous copolymers based on alkyl methacrylate esters (AMA) were prepared in the presence of toluene as the inert diluent, and their swelling properties in water were investigated by measuring the water uptake of the copolymers with or without being pretreated with methanol. With ethylene glycol dimethacrylate (EGDM) being used as the crosslinking agent, the obtained AMA/EGDM copolymers, regardless of their inherent hydrophobic nature, were found to be able to swell in water directly. The swelling was negligible in the lower degree of crosslinking region. However, once it increased to a value beyond a certain EGDM percentage, the swelling transition occurred, and the water uptake, which was measured by direct contact of the copolymers with water for all three kinds of AMA/EGDM copolymers based on methyl MA (MMA), ethyl MA (EMA), and butyl MA (BMA), reached very high values. The direct swelling of highly crosslinked AMA/EGDM copolymers in water was very fast at the beginning of the swelling with the swelling rate order of MMA/EGDM > EMA/EGDM > BMA/EGDM, but thereafter it progressed very slowly with most swelling being achieved. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 250–258, 2000     

Copolymerization of 2-(4-tert-butylphenoxy)-2-oxo-ethyl Methacrylate with Methyl Methacrylate and Styrene: Synthesis, Characterization, and Monomer Reactivity Ratios

A tertierbutylphenoxy group containing methacrylate based monomer 2-(4-tert-butylphenoxy)-2-oxo-ethyl methacrylate (TBPOEMA) was synthesized by reacting 4-tertierbutylphenyl chloroacetate (TBPClAcO) with sodium methacrylate in acetonitrile. TBPClAcO was prepared by reacting tertierbutylphenol dissolved in benzene with chloroacetylchloride. The free-radical-initiated copolymerization of TBPOEMA, with methyl methacrylate (MMA) and styrene (ST) was carried out in dimethylsulphoxide (DMSO) solution at 65°C using 2,2-azobisisobutyronitrile (AIBN) as an initiator with different monomer-to-monomer ratios in the feed. The monomer TBPOEMA and copolymers were characterized by FTIR, ¹H- and ¹³C-NMR spectral studies. The copolymer composition obtained from the ¹H-NMR spectra led to the determination of reactivity ratios. The reactivity ratios of the monomers were determined by the application of Finemann–Ross and Kelen–Tüdös linear methods and the Behnken nonlinear least-squares method. The analysis of reactivity ratios revealed that MMA and ST are more reactive than TBPOEMA, and copolymers formed are statistical in nature. The molecular weights _w and _n) and polydispersity index of the polymers were determined using gel permation chromagtography. Thermogravimetric analysis of the polymers reveal that the thermal stability of the copolymers increases with an increase in the mole fraction of TBPOEMA in the copolymers. Glass transition temperatures of the copolymers were found to decrease with an increase in the mole fraction of TBPOEMA in the copolymers. The apparent thermal decomposition activation energies (E _d) were calculated by Ozawa method using the SETARAM Labsys TGA thermobalance.     

Free-radical emulsion copolymerization of styrene with butadiene and vinyl triethoxysilane with a cumene hydroperoxide redox initiator

The emulsion free-radical copolymerization of vinyl triethoxysilane (VTES) with styrene (St) and butadiene (Bd) was initiated by cumene hydroperoxide and ferrous sulfate at 0 °C. The effects of VTES on the copolymerization conversion, reaction time, gel content, latex particle size, thermal stability, and mechanical properties were thoroughly investigated. The success of this reaction was confirmed by the peaks attributed to both Si─O─Si groups at 1065 cm⁻¹ and the Si─O─C bond at 1046 cm⁻¹. A kinetics analysis showed that the conversion decreased with increasing VTES mass in the monomer feed. Compared with that in the St–Bd copolymer, the latex particle size increased slightly with increasing VTES mass. The Mooney viscosity and gel content results show that a large fraction of precrosslinking molecular chains was formed in the rubber particles. The thermogravimetric analysis results indicate that the thermal stability of the copolymers increased with increasing VTES concentration. The 300% modulus and tensile strength of the St–Bd–VTES copolymer increased with the mass of VTES at first and then decreased after 3 phr VTES, whereas the elongation at break decreased with increasing VTES mass. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47896.     

Modeling of swelling by fluorescence technique in poly (methyl methacrylate) gels

A novel technique based on in-situ steady-state fluorescence (SSF) measurements is introduced for studying swelling processes in gels formed by free radical cross-linking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) in toluene. Gels were prepared at 75°C for various toluene contents with pyrene (Py) as a fluorescence probe. After drying these gels, swelling and desorption experiments were performed in toluene at 50°C by real-time monitoring of Py fluorescence intensity. A correction method was developed to obtain pure swelling curves, by using desorption curves of Py molecules. Li-Tanaka equation was employed to produce swelling parameters. Cooperative diffusion coefficients (D_c) were measured and found to be around 10⁻⁶ cm²/s for gels swollen in toluene. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1777–1784, 1997     

Synthesis of chiral polymers containing the acetoxybornyl group and their applications on the asymmetric induction

Optically active 2-endo-actoxy-5-endo-bornyl methacrylate (ABMA) was prepared from (+)-camphor. The homopolymerization of ABMA and copolymerization of ABMA with achiral methyl methacrylate (MMA) or styrene (St) were carried out with 2,2′-azobisisobutyronitrile (AIBN) in benzene. Effects of temperature, solvents, and reaction time on the copolymerization were discussed. The monomer reactivity ratios(r₁, r₂) for poly(ABMA-co-MMA) and poly(ABMA-co-St) and Q and e values for the chiral ABMA in the copolymerization systems were evaluated by the Fineman—Ross method. The absolute value of the specific rotation of poly(ABMA-co-MMA) increased with increasing ABMA unit content. A small deviation from linearity was observed, which suggests that asymmetry is not introduced into the copolymer main chain. Temperature and solvent effects on the specific rotation of the chiral homopolymer and copolymers were investigated. The results suggest that the chiral polymers synthesized in this investigation did not show a strong preference for a particular helical conformation. Applications of the chiral polymers on the asymmetric addition of n-butyllithium to aldehydes were also discussed.     

Mechanical stability of trimethylolpropane trimethacrylate-based polymers

Trimethylolpropane trimethacrylate (TRIM) was homopolymerized and copolymerized with methyl methacrylate (MMA), glycidyl methacrylate (GMA), and acrylamide (AA), respectively, in various solvents and at various temperatures. For comparison, poly(styrene-co-divinyl benzene) [poly(S-co-DVB)] gels were selected. The mechanical stability was measured by compression of the swollen gels. The porogen served as swelling agent. The compression moduli increased with increasing TRIM concentration in the polymerization. The compression moduli of poly(TRIM) could be increased by copolymerization with low concentrations of comonomer. Low polymerization temperature decreased the mechanical strength of poly(TRIM). A good solvent increased the compression modulus. TRIM-based gels were at least as mechanically stable as were poly(S-co-DVB) gels.     

Mechanical properties and water vapor permeation of vinyltriethoxysilane/methyl methacrylate copolymers

Methyl methacrylate (MMA) was copolymerized with vinyltriethoxysilane (VTES) using ⁶⁰Co-γ-radiation at varying volume fractions of the liquid monomers in the feed. Thin copolymer films were prepared by casting tetrahydrofuran solutions of the copolymers on a mercury surface. The effect of the mole fraction of VTES in the copolymer on the glass transition temperatures, mechanical properties and water vapor permeabilities were investigated. Glass transition temperatures and mechanical properties decreased with increasing VTES content in the copolymer. However, the water vapor permeabilities were found to increase with the VTES content. The increased water vapor permeation was attributed to increased water solubility in the copolymers due to the presence of Si-O-bonds.     

Toughening effect of comonomer on acrylic denture base resin prepared via suspension copolymerization

In this article, three copolymers used as denture base resins were prepared via suspension copolymerization using butyl acrylate (BA), butyl methacrylate (BMA), or methyl acrylate (MA) with methyl methacrylate (MMA), respectively. The homopolymers and copolymers were characterized by ¹³C nuclear magnetic resonance (¹³C NMR). The influence of the three comonomers on the mechanical property was investigated in details and the fracture surfaces of copolymer specimens were examined using scanning electron microscopy (SEM). Meanwhile, the T_g values of three copolymers were examined by differential scanning calorimetry (DSC). The results indicate that, poly(methyl methacrylate) (PMMA) copolymers with BA, BMA, or MA have been successfully prepared via suspension copolymerization. The presence of BA, BMA, or MA could improve the mechanical property especially the impact strength, the toughness of the materials was remarkably improved. The toughening effect of BMA monomer is most significant. When the content of BA is 2 wt %, the flexural strength improves by 51% and the impact strength improves by 81.3%. The T_g values of three copolymers all decrease. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Initiation system effects in the cationic copolymerization of tetrahydrofuran (THF)

Summary Macromonomeric peroxy initiator, poly tetrahydrofuran (poly-THF=inimer) were synthesized via cationic polymerization of THF by the mono- (t-BuBP) and tetra-bromo methyl benzoyl peroxides (BDBP)/ZnCl₂ initiating system. The macromonomers were characterized by ¹H-NMR, IR, and GPC techniques. Methyl methacrylate (MMA) polymerization initiated by poly-THF inimers at 80°C and different times in bulk gave crosslinked poly-THF-b-polymethyl methacrylate block copolymers. Swelling ratios of the crosslinked block copolymers obtained by taking in same amounts of poly-THF inimer and MMA monomer in CHCl₃ were decreased versus time. It was compared the results obtained from t-BuBP-, BDBP-ZnCl₂ initiating systems with t-BuBP-, BDBP-AgSbF₆ initiating systems for THF monomer. Poly(THF-b-MMA) crosslinked block copolymers containing undecomposed peroxide groups initiated the thermal polymerization of styrene, S, were used to obtain poly(THF-b-MM_A-b-S) crosslinked multicomponent copolymers at 90°C. The crosslinked multi component copolymers were investigated sol-gel analysis and swelling ratios in CHCl₃. "Active" poly(THF-b-MM_A) having peroxygen group were used in the free radical coupling reaction of poly butadien (Poly Bd). Poly(THF-b-MM_A)-polybutadien crosslinked blend soluble graft copolymers were obtained. Received: 31 July 2001/Revised version: 16 June 2002/ Accepted: 5 July 2002     

In situ fluorescence study of slow release and swelling processes in gels formed by solution free radical copolymerization

A novel method based on steady state fluorescence (SSF) measurements is introduced for studying slow release and swelling processes in gels formed by free radical crosslinking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) in toluene. Gels were prepared at 75°C with various toluene contents with pyrene (P_y) as a fluorescence probe. After drying these gels, slow release and swelling experiments were performed in toluene at 50°C by real-time monitoring of the pyrene fluorescence intensity. Li-Tanaka and Fickian type equations were used to obtain swelling and slow release parameters. It was observed that slow release takes place after the gel is swollen. Cooperative and desorption (slow release) diffusion coefficients (D_c and D) were measured and found to be 10^-6cm²s^-1 in both cases. ©1997 SCI     

Chiral copolymers of (R)‐N‐(1‐phenylethyl) methacrylamide and 2‐hydroxyethyl methacrylate: copolymerization characteristics and chiroptical properties

The aim of this investigation was the copolymerization of a chiral monomer, (R)‐N‐(1‐phenylethyl) methacrylamide, with an achiral monomer, 2‐hydroxyethyl methacrylate (HEMA). The copolymerization characteristics as well as the chiroptical properties (optical rotation and circular dichroism) and their variation with copolymer composition and temperature are discussed. The copolymers are statistical and enriched in HEMA. The monomer reactivity ratio of the chiral monomer (r₁) is 0.133 whereas that of HEMA (r₂) is 1.042 based on the Kelen–Tudos method. The sequence of consecutive chiral monomer units predominates for a feed composition between 0.5 and 0.9 (mole fraction). On the other hand, the sequence of HEMA is uniform and it predominates for a feed composition of around 0.5 (mole fraction). The chiroptical properties of the copolymers do not vary linearly with the content of chiral units in the copolymers. The optical rotation and circular dichroism attain optimum values above 30–40 mol% of chiral monomer units in the copolymers. However, the circular dichroism of the copolymers varies linearly with the temperature. The chiral monomer being a more bulky structure is less reactive than HEMA. The nonlinear variation of chiroptical properties of the copolymers with the content of chiral units may be due to the secondary interaction in the copolymers associated with the hydrogen bonding involving the amide linkage (CONH) present in the pendant chromophore of the chiral monomer as well as the hydroxyl pendant group of HEMA and also the aromatic π–π interaction. Copyright © 2009 Society of Chemical Industry     

Synthesis and characterization of perfluorinated acrylate–methyl methacrylate copolymers

A novel perfluorinated acrylic monomer 3,5‐bis(perfluorobenzyloxy)benzyl acrylate (FM) with perfluorinated aromatic units was synthesized with 3,5‐bis(perfluorobenzyl)oxybenzyl alcohol, acryloyl chloride, and triethylamine. Copolymers of FM monomer with methyl methacrylate (MMA) were prepared via free‐radical polymerization at 80°C in toluene with 2,2′‐azobisisobutyronitrile as the initiator. The obtained copolymers were characterized by ¹H‐NMR and gel permeation chromatography. The monomer reactivity ratios for the monomer pair were calculated with the extended Kelen–Tüdos method. The reactivity ratios were found to be r₁ = 0.38 for FM, r₂ = 1.11 for MMA, and r₁r₂ < 1 for the pair FM–MMA. This shows that the system proceeded as random copolymerization. The thermal behavior of the copolymers was investigated by thermogravimetric analysis and differential scanning calorimetry (DSC). The copolymers had only one glass‐transition temperature, which changed from 46 to 78°C depending on the copolymer composition. Melting endotherms were not observed in the DSC traces; this indicated that all of the copolymers were completely amorphous. Copolymer films were prepared by spin coating, and contact angle measurements of water and ethylene glycol on the films indicated a high degree of hydrophobicity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and polymerization of a new iodine‐containing monomer

A new iodine‐containing methacrylate monomer, 3,4,5‐triiodobenzoyloxyethyl methacrylate (TIBEM), was synthesized by coupling 2‐hydroxyethyl methacrylate (HEMA) with 3,4,5‐triiodobenzoic acid. The monomer was characterized by ¹H nuclear magnetic resonance, infrared (IR), and ultraviolet spectra. Homopolymerization and copolymerization of the monomer with methyl methacrylate (MMA) were carried out using 2,2′‐azobis isobutyronitrile as the initiator. A terpolymer of TIBEM, MMA, and HEMA was also synthesized. The copolymers were characterized by IR, gel permeation chromatography, differential thermal analysis, and thermogravimetric analysis (TGA). High molecular weight polymers were produced with MMA at different feed compositions of TIBEM. The polymers were found to be freely soluble in common solvents for acrylic polymers. TGA showed little decomposition of the copolymer below 280°C. Copolymers showed good radiopacity at 25 wt % of TIBEM in the feed. These copolymers could find applications in medical and dental areas where radiopacity is a desirable feature of the implants. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2580–2584, 2003