Pendant vinyl group reactivity during the free-radical copolymerization of methyl methacrylate and ethylene glycol dimethacrylate

Summary Methyl methacrylate-ethylene glycol dimethacrylate (MMA-EGDM) copolymerization has been investigated in toluene at a monomer concentration of 22 w/v %. The kinetic models developed recently along with the experimental conversion curve and gel point data provided the calculation of the average reactivity of pendant vinyl groups. It was found that the pendant vinyl reactivity for intermolecular links is much less than the monomeric vinyl reactivity and it decreases further as the EGDM concentration increases. At 5–15 mol % EGDM, the average pendant reactivity is 1–2 orders of magnitude lower than the monomeric vinyl reactivity. The reduced pendant reactivity is mainly responsible for the shift of the gel point towards higher conversions.     

Size distribution of polymers during the photoinitiated free-radical copolymerization of methyl methacrylate and ethylene glycol dimethacrylate

Summary Photoinitiated methyl methacrylate-ethylene glycol dimethacrylate (MMA/EGDM) copolymerization has been investigated in toluene at a monomer concentration of 35 w/v %. Diphenyl-2,4,6-trimethylbenzoylphosphine oxide (DPTPO) was used as a photoinitiator at 0.3 wt% concentration. Monomer conversions and the size distribution of the polymer molecules were measured as a function of the reaction time up to the onset of macrogelation. Compared to the photoinitiators benzoin or benzoin derivatives, gelation process proceeds at much higher rates in the presence of DPTPO. The size distribution curves obtained by size-exclusion chromatography (SEC) change from monomodal to bimodal distributions as the polymerization proceeds. Strongly bimodal SEC curves were obtained in the close vicinity of the gel point. This finding confirms the coagulation type gelation mechanism of compact primary particles. It also indicates that the present gelation theories cannot describe the structure dependent kinetics of free-radical crosslinking copolymerization.     

Kinetics of miniemulsion polymerizations of ethylene glycol dimethacrylate and/or methyl methacrylate

Two types of reactive acrylic microgel particles of methyl methacrylate (MMA)/ethylene glycol dimethacrylate (EGDMA) (66.4/33.6 and 0/100 (mol/mol)) were prepared by miniemulsion polymerization with 2,2′‐azobisisobutyronitrile as the initiator in the temperature range 60–80 °C. Ostwald ripening occurred during the very early stage of polymerization. In addition to the predominant droplet nucleation, homogeneous nucleation was also observed. The polymerization rate for MMA/EGDMA miniemulsion was higher than that for EGDMA miniemulsion. By contrast, comparable apparent limiting conversions were observed for the polymerizations of MMA/EGDMA and EGDMA. The mole fractions of MMA and EGDMA units incorporated into the copolymer product were estimated to be 0.62 and 0.38, respectively, for the polymerization of MMA/EGDMA at 70 °C. The mole fraction of the EGDMA unit containing one ? C?C? within the MMA/EGDMA microgel particle product was estimated to be 0.23, which was comparable to that (0.22) of the EGDMA unit containing one ? C?C? within the EGDMA microgel particle product. © 2015 Society of Chemical Industry     

Crosslinked methyl methacrylate/ethylene glycol dimethacrylate polymer compounds with a macroazoinitiator

A silane‐containing diamine, bis(p‐aminophenoxy) diphenylsilane (BADPS), was prepared by the condensation of p‐aminophenol with dichlorodiphenyl silane in the presence of triethylamine. Then, BADPS was condensed with 4,4‐azobis(4‐cyanopentanoyl chloride) to prepare macroazoinitiators containing silane units (Si–MAIs). A series of poly(methyl methacrylate) gels containing silane were derived by the solution free‐radical crosslinking copolymerization of methyl methacrylate and ethylene glycol dimethacrylate monomers initiated by these macroazoinitiators at a total monomer concentration of 6 mol/L and 80°C. Si–MAIs were characterized with ¹H‐NMR and ¹³C‐NMR spectroscopy, and the structural characteristics of the gels were also examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Branching and gelation in atom transfer radical polymerization of methyl methacrylate and ethylene glycol dimethacrylate

Bulk copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) was initiated by methyl α‐bromophenylacetate (MBPA) and mediated by copper bromide (CuBr) ligated with 1,1,4,7,10,10‐hexamethyltriethylenetetramine (HMTETA). The atom transfer radical polymerization (ATRP) of pure MMA yielded polymers with well controlled molecular weights and the homopolymerization was taken as a reference for the copolymerization analysis. The copolymerization experienced autoacceleration in rate due to a diffusion‐controlled radical deactivation. The onset of autoacceleration came earlier with an increase in the EGDMA fraction. At low EGDMA fractions, the molecular weight versus conversion data deviated from linearity due to branching. The ratio of the copolymer molecular weight over homo‐poly(methyl methacrylate) gave an estimate for the branching density, which increased initially and leveled off at high conversion. At high EGDMA fractions, the ATRP system experienced gelation. The pregel branching density increased with conversion, and at the gel point, it agreed with Flory's gelation theory assuming cross‐linking free of cyclization. The branching densities at the high gel fractions were very close to the maximum values possibly achieved with the added EGDMA fractions. These results suggested that the ATRP system was very effective in preparing homogeneous polymer networks with a high cross‐linking efficiency. POLYM. ENG. SCI., 45:720–727, 2005. © 2005 Society of Plastics Engineers     

Block copolymerization of poly(ethylene glycol) with methyl methacrylate using redox macroinitiators

A series of block copolymers of poly(ethylene glycol) (PEG) with methyl methacrylate (MMA) were prepared using a redox system consisting of ceric ion and PEG of various molecular weights in aqueous medium. The block copolymerization experiments were carried out under such conditions in which there was no homopolymerization of MMA by Ce⁴⁺ alone. The intermediacy of the PEG macroradical in the redox process was substantiated by ESR spectroscopy and a polymerization proceeding through ‘blocking from’ mechanism was postulated. The formation of the block copolymers was confirmed by chemical test and fractional precipitation as well as by FT-IR and FT-NMR (¹H and ¹³C-(¹H)) spectroscopy. The triblock nature of the block copolymers was ascertained through the cleavage of the ether linkage of the PEG segment. Simultaneous TG/DTA studies of the block copolymers revealed multiple stage decomposition patterns and their DSC curves exhibited two glass transition temperatures. GPC investigation of the block copolymers revealed unimodal molecular weight distribution with M_n values showing a smooth increase with ascending molecular weights of PEG. SEM studies indicated a fine dispersion of PEG in the continuous PMMA matrix.     

Frontal copolymerization of 2‐hydroxyethyl methacrylate and ethylene glycol dimethacrylate without porogen: comparison with suspension polymerization

Networked, crosslinked poly[(2‐hydroxyethyl methacrylate)‐co‐(ethylene glycol dimethacrylate)] (HEMA‐EGDM) was synthesized by frontal polymerization (FP) using azobisisobutyronitrile as initiator. HEMA‐EGDM copolymers of similar composition were also synthesized by suspension polymerization. The two sets of copolymers were characterized for functional groups (IR), pore volume (mercury intrusion porosimetry), surface area (nitrogen adsorption) and morphology (scanning electron microscopy). FP‐generated polymeric network structures had higher internal pore volumes and surface areas but their surface morphologies were inferior to those of copolymers synthesized by suspension polymerization. Copyright © 2004 Society of Chemical Industry     

Poly(methyl methacrylate)/poly(ethylene glycol)/poly(ethylene glycol dimethacrylate) micelles: Preparation,characterization, and application as doxorubicin carriers

A crosslinked amphiphilic copolymer [poly(ethylene glycol) (PEG)–poly(methyl methacrylate) (PMMA)–ethylene glycol dimethacrylate (EGDM)] composed of PMMA, PEG, and crosslinking units (EGDM) was synthesized by atom transfer radical polymerization to develop micelles as carriers for hydrophobic drugs. By adjusting the molar ratio of methyl methacrylate and EGDM, three block copolymer samples (P0, P1, and P2) were prepared. The measurement of gel permeation chromatography and ¹H‐NMR indicated the formation of crosslinked structures for P1 and P2. Fluorescence spectroscopy measurement indicated that PEG–PMMA–EGDM could self‐assemble to form micelles, and the critical micelle concentration values of the crosslinked polymer were lower than those of linear ones. The prepared PEG–PMMA–EGDM micelles were used to load doxorubicin (DOX). The drug‐loading efficiencies of P1 and P2 were higher than that of P0 because the crosslinking units enhanced the micelles' stability. With increasing drug‐loading contents, DOX release from the micelles in vitro was decreased, and in the crosslinked formulations, the release rate was also slower. An in vitro release study indicated that DOX release from the micelles for the linear samples was faster than that for crosslinked micelles. The drug feeding amount increased and resulted in an increase in the drug‐loading content, and the loading efficiency decreased. These PEG–PMMA–EGDM micelles did not show toxicity in vitro and could reduce the cytotoxicity of DOX in the micelles; this suggested that they are good candidates as stable drug carriers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39623.     

Kinetics of graft copolymerization of methyl methacrylate in wool fibers

The graft copolymerization of methyl methacrylate in wool fibers was investigated in the aqueous LiBr–K₂S₂O₈ system without homopolymer. The rate of grafting and the degree of polymerization of graft polymer were determined on varying the extent of reduction of wool fibers and the concentration of monomer. From the graft copolymerization behavior observed at a given concentration of redox catalysts (LiBr and K₂S₂O₈), the thiol groups in wool fibers were considered to play a role as a sort of catalyst of polymerization, not as the chain transfer agent, and also to give the grafting sites. So, the initiation process of grafting was assumed to be started by d[S·]/dt = k_i[SH]_eff, and the kinetic consideration was found to lead to the following expression in agreement with the experimental results: 1/DP = (k_t/k_p²[M]_fib²)R_p, where d[S·]/dt is the rate of formation of thiol radicals by radicalotropy to ? SH from SO₄^?., OH·, or Br·; k_i, k_p, and k_t are the rate constants of initiation, propagation, and termination, respectively; [SH]_eff and [M]_fib are the concentration of the effective thiol groups and the MMA monomers within the wool fibers, respectively; DP is the average degree of polymerization of graft polymers, and R_p the overall rate of grafting.     

Preparation of functional polymer-microspheres by suspension copolymerization of ethylene glycol dimethacrylate with hydrophilic monomers

A study was made of suspension copolymerization of ethylene glycol dimethacrylate (EDMA) with some hydrophilic monomers (M₂) to prepare gel particles having a large number and various kind of functional groups on their surface. Delayed charge of M₂ to partially prepolymerized EDMA suspension resulted in the formation of favorable particles. The polymerization leveled off despite an appreciable amount of remaining M₂ in the aqueous phase, and the amount of copolymerized M₂ and the fraction of on-surface M₂ units depended significantly on the kind of M₂ as well as the mode of M₂ charge. These dependences were explained in terms of the partition coefficient of M₂ between EDMA and water and the monomer reactivity ratio.     

Comparison of reaction kinetics and gelation behaviors in atom transfer, reversible addition-fragmentation chain transfer and conventional free radical copolymerization of oligo(ethylene glycol) methyl ether methacrylate and oligo(ethylene glycol) dimethacrylate

The reaction kinetics and gelation behavior in atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT), and conventional free radical copolymerizations (FRP) of oligo(ethylene glycol) methyl ether methacrylate (OEGMEMA) and oligo(ethylene glycol) dimethacrylates (OEGDMAs) were investigated and compared with respect to the polymerization rate, gel point, and the evolution of network with vinyl conversion. All the three systems experienced autoacceleration in the reaction rate but occurred at different regions of vinyl conversion, caused by diffusion-controlled radical reactions: termination in the FRP, addition in the RAFT, and deactivation in the ATRP, respectively. In the FRP, significant amount of gel materials was collected by solvent extraction far before the onset of macro-gelation detected by an abrupt increase in complex viscosity. However, in the RAFT and ATRP, no gels were found until the systems approached their macro-gelation points. The observation suggests limited intramolecular crosslinking/cyclization reactions in the ATRP and RAFT systems. This is because the slow growth of primary chains (ATRP and RAFT in hours versus FRP in seconds) allowed adequate chain relaxation and diffusion of reacting species. The gel materials thus synthesized by ATRP and RAFT are expected to be more homogeneous in network structure than that by FRP.     

Preparation and applications of the tertiary copolymer poly(ethylene glycol) methacrylate/methyl methacrylate/diethyl allylphosphonate

A novel poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) antistatic and flame‐retardant agent, poly(ethylene glycol) methacrylate/methyl methacrylate/diethyl allylphosphonate (PMMD), was synthesized from poly(ethylene glycol) methacrylate, methyl methacrylate, and diethyl allylphosphonate by free‐radical precipitation polymerization in the aqueous phase to improve the antistatic and flame‐retardant performance at the same time. Through adjustments of the molar ratios of the three monomers, various antistatic, flame‐retardant copolymers (PMMD) were synthesized. The molecular structure and thermal stability of PMMD were analyzed with Fourier transform infrared spectroscopy and thermogravimetric analysis. The electrical resistivity and flame‐retardant and mechanical properties of the ABS/PMMD composites were analyzed by a ZC90 megohmmeter, an oxygen index meter, a vertical burning tester, a memory impact testing machine, and a tensile testing machine. The morphology of PMMD in the ABS blends was characterized with scanning electron microscopy. The compatibilities of PMMD and ABS were characterized by the calculation of the thermodynamic work of adhesion via the measurement of the contact angle. The results show that the antistatic and flame‐retardant performance of ABS were greatly improved by the PMMD copolymer and the mechanical properties of ABS showed little reduction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44126.     

Formation of soluble hyperbranched polymer through the initiator-fragment incorporation radical copolymerization of ethylene glycol dimethacrylate with N-methylmethacrylamide

The copolymerization of ethylene glycol dimethacrylate (EGDMA) as a divinyl monomer with N-methylmethacrylamide (NMMAm) as a water-soluble monomer was carried out at 70 and 80 °C in N,N-dimethylformamide (DMF) using dimethyl 2,2′-azobisisobutyrate (MAIB) of high concentrations as initiator. When the concentrations of EGDMA, NMMAm and MAIB were 0.15, 0.50 and 0.35 mol/l, the copolymerization proceeded homogeneously with no gelation at 80 °C to give soluble copolymer in a yield of 50%. EGDMA was polymerized more rapidly than NMMAm as shown by Fourier-transform near infrared spectroscopy. The copolymer formed for 8 h consisted of 20 mol% of EGDMA unit, 47 mol% of NMMA unit and 33 mol% of methoxycarbonylpropyl group unit as MAIB-fragment. The copolymer formed at 80 °C for 30 min showed an upper critical solution temperature (34 °C on cooling) in methanol. The intrinsic viscosity of the copolymer formed for 2 h was very low (0.11 dl/g) at 30 °C in DMF despite high weight-average molecular weight [3.1×l0⁶ by multi-angle laser light scattering (MALLS)]. The copolymer exhibited a very low second virial coefficient (4.2×l0⁻⁶) as determined at 25 °C in DMF by MALLS. The individual copolymer molecules were observed as nanoparticles of 7-20 nm diameter by a transmission electron microscope. These results show that the resulting copolymers are of hyperbranched structure.     

Kinetics of ylide-initiated radical copolymerization of 4-vinylpyridine and methyl methacrylate

The ylide-initiated radical copolymerization of 4-vinylpyridine (4-VP) with methyl methacrylate (MMA) at 60°C using carbon tetrachloride as inert solvent yields non-alternating copolymers. The kinetic parameters, average rate of polymerization (R_p) and orders of reaction with respect to monomers and initiator, have been evaluated and the kinetic equation is found to be R_pα[ylide]^0.94 [MMA]^1.0 [4-VP]^1.5. The values of the energy of activation and k_p²/k_t are 48 kJ mol^?1 and 6.6 × 10^?5 litre mol^?1s^?1, respectively. The copolymers have been characterized by IR and NMR spectroscopy.     

Kinetics for copolymerization of methyl methacrylate with N‐cyclohexylmaleimide

The kinetics for the radical copolymerization of methyl methacrylate (MMA) with N‐cyclohexylmaleimide (NCMI) was investigated. The initial copolymerization rate R_p is proportional to the initiator concentration to the power of 0.54. The apparent activation energy of the overall copolymerization was measured to be 69.0 kJ/mol. The monomer reactivity ratios were determined to be r_NCMI = 0.42 and r_MMA = 1.63. R_p reduces slightly, and the molecular weight of the resultant copolymer decreases with increasing the concentration of the chain transfer agent N‐dodecanethiol (RSH). The more the transfer agent, the narrower the molecular weight distribution of the resulting copolymer. The following chain‐transfer constant of RSH for the copolymerization of MMA with NCMI in benzene at 50°C was obtained: C_s = 0.23. The glass transition temperature (T_g) of the copolymer increases with increasing f_NCMI, which indicates that adding NCMI can improve the heat resistance of Plexiglas. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1293–1297, 1999     

Kinetics and mechanism of emulsion copolymerization. IV. Kinetic modeling of emulsion copolymerization of styrene and methyl methacrylate

Based on the micellar nucleation theory, a mathematical kinetic model for an unseeded emulsion copolymerization system is developed, where the radicals with and without electric charge are discriminated from each other in view of the role in the particle nucleation process. In order to demonstrate the validity and utility of this kinetic model, the experiments of the unseeded emulsion copolymerization of styrene (ST) and methyl methacrylate (MMA) are carried out varying the initial initiator (potassium persulfate) and emulsifier (sodium lauryl sulfate) concentrations and the monomer composition in the initial monomer feed, and various kinetic features observed are compared with the model predictions. It is concluded from this comparison that in this system, almost all the polymer particles are generated by the charged radicals stemming from the initiator, and further that this mathematical kinetic model can provide a satisfactory explanation of the various kinetic features observed.     

Radical copolymerization of ethylene glycol bis(methyl fumarate) with N-vinylcarbazole

Summary For the purpose of elucidating copolymerizability of ethylene glycol bis(methyl fumarate), a new multifunctional monomer, its free-radical Copolymerization with N-vinylcarbazole has been studied. The results show that free-radical Copolymerization of ethylene glycol bis(methyl fumarate) with N-vinylcarbazole produces soluble copolymers at low conversions, the compositions of which vary from 1∶1 to increasingly VCZ rich (below 2.0) with an increase in the VCZ content in the monomer feed. It is suggested that 1∶1 alternating Copolymerization proceeds and that cyclo-propagation becomes predominant when the monomer feed composition becomes rich in VCZ. Gelation occurs at relatively high conversions.