High conversion copolymerization of styrene with methylmethacrylate

A study of the free radical copolymerization of styrene-methylmethacrylate at high conversion is reported. Differences are observed between the experimentally measured compositions and those calculated according to the integrated form of the copolymer composition equation, using published reactivity ratios. Significant differences occur only in situations exhibiting a gel effect, e.g. during bulk copolymerization or with a precipitant like butyl stearate present. Negligible differences are exhibited when a solvent such as benzene is present. Differences have been expressed as changes in copolymer reactivity ratios with conversion; the start of any changes in reactivity ratios is closely related to the onset of gel effects.     

Critical properties for gelation in free-radical crosslinking copolymerization

A kinetic model was used to predict the molecular weight developments and the critical properties in free-radical crosslinking copolymerization. The predictions of the model were compared to the experimental data reported previously. Agreement of the kinetic model with experiments is satisfactory for both low and high crosslinker contents. The model parameters indicate increasing extent of shielding of pendant vinyl groups as the reaction proceeds due to the increasing number of multiple crosslinkages. The calculation results indicate that the real critical exponents can only be observed in the region ε < 10⁻²–10⁻³ where experimental studies are very difficult. Outside of this region, the apparent critical exponent γ describing the divergence of the weight-average molecular weight was found to deviate from the classical value due to the conversion dependent kinetics of free-radical crosslinking copolymerization.     

Sequence selection during copolymerization

We analyze a simple model for the copolymerization of two chemically distinct monomers that displays a wide variety of product sequence compositions depending on the rate coefficients for the stepwise addition of each monomer to a growing polymer chain. We show that in certain regions of parameter space the copolymer sequence composition depends sensitively on these parameter values, and we compute the information content of the resultant sequences. Finally, we show how the model may be used to interpret experimental data on copolymerization reactions.     

Quantitative theory of living chain copolymerization covering anionic and free-radical mechanisms

Main results of our original general theory of a chain copolymerization are presented which enable the calculation of any statistical characteristic of a copolymer prepared. Outlined theoretical approach also permits one to find thermodynamic and scattering properties of solutions and melts of these copolymers.     

Organostibine mediated controlled/living random copolymerization of styrene and methyl methacrylate

The first example of organostibine mediated controlled/living random copolymerization of styrene (St) and methyl methacrylate (MMA) was achieved by heating a solution of St/MMA/organostibine mediator at 100 °C or St/MMA/organostibine mediator/AIBN with various monomer feed ratios at 60 °C. The addition of AIBN significantly decreased the reaction temperature and enhanced the rate of copolymerization. The structure of poly(St-co-MMA) was verified by ¹H NMR. The reactivity ratios at 60 °C were determined by the extended Kelen-Tüd?s method to be γ_St = 0.40 and γ_MMA = 0.44. The ln([M]₀/[M]) increased linearly with increasing reaction time. The number-average molecular weights of poly(St-co-MMA) increased linearly with conversion. Poly(St-co-MMA) with expected number-average molecular weight and low polydispersity index was formed. The living characteristic was further confirmed by chain-extension of poly(St-co-MMA) to form poly(St-co-MMA)-b-PMMA.     

Di(4-isopropenylphenoxy)alkanes as cross-linking comonomers in three-dimensional copolymerization with styrene

Di(4-isopropenylphenoxy)alkanes were synthesized by condensation of 4-isopropenylphenol with symmetrical dihaloalkanes in the presence of KI promoter. Three-dimensional polymeric structures were prepared by compolymerization of these monomers with styrene.     

Model prediction of batch emulsion copolymerization as a function of conversion: A sensitivity analysis

Recently a model has been developed capable of predicting absolute monomer concentrations and their ratios in the polymer, aqueous, and monomer droplet phases as a function of conversion in batch emulsion copolymerizations without using any adjustable parameters. In this article the sensitivity of model predictions of composition drift toward deviations of 10% in all model parameters (maximum swellabilities of monomer in the polymer phase, water solubilities, reactivity ratios, and monomer and polymer densities) was estimated using the monomer combination methyl methacrylate-styrene as an example. From the sensitivity analysis it can be concluded that the reactivity ratios are the most important parameters affecting composition drift. The effects of deviations in maximum swellabilities and monomer and polymer densities on composition drift can be neglected, while the water solubility is important only in those cases where the amount of monomer in the aqueous phase cannot be neglected as compared with the total monomer amount. © 1994 John Wiley & Sons, Inc.     

Architecture of hyperbranched polymers consisting of a stearyl methacrylate sequence via a living radical copolymerization

The living radical photocopolymerization of 2-(N,N-diethyldithiocarbamyl)ethyl methacrylate (DCEM) as inimer and stearyl methacrylate (STM) as comonomer was carried out under UV irradiation. According to this method, we synthesized hyperbranched polymers (HP) consisting of a STM sequence having a long alkyl side chain. The gel permeation chromatography distribution of hyperbranched polymers had a unimodal pattern. The reactivity ratios (r(1)=0.79 and r(2)=0.81) were estimated by the Kelen-Tüd?s method (DCEM: [M](1) and STM: [M](2)). These values indicated that the two monomers showed almost equal reactivity toward propagating radical species. The radius of gyration (R(g)) and the hydrodynamic radius (R(h)) of copolymers were determined by static and dynamic light scattering (SLS and DLS), and the values of R(g)/R(h) changed from 0.79 to 1.59 with an increment of the feed amount of STM. These results indicated that the copolymer structures changed from hard spheres to loose branched molecules in solution.     

The linear relations and living feature in cationic ring-opening copolymerization of epoxy/THF system

The cationic copolymerization of diglycidyl ether of bisphenol-A with tetrahydrofuran (THF) initiated by phosphotungstic acid H₃PW₁₂O₄₀ (PW₁₂) was in situ investigated by Fourier transform near infrared spectroscopy. The gelation point of the reaction was determined by rheometrics mechanical spectroscopy. It was found that the conversion of epoxy group at 4,530 and 6,073 cm^?1 increased linearly with reaction time up to a high conversion (~90%), during which gelation (at ~51%) had no effect. The slope-indicating reaction rate of epoxy group also increased linearly with the content of PW₁₂. In addition, the peak splitting pattern of the overlapping C–H vibration region (5,700–6,200 cm^?1) was developed here. The peak-splitting analysis showed that the epoxy behavior agreed with above results, but the reaction rate of THF slowed down gradually with reaction time as the viscosity of the system increased. The results suggest that the kinetic behavior of cationic polymerization shows living feature of the propagating chains in this system and near infrared (NIR) technology could be applied to study such kinetic behavior.     

Applicability of the Mayo–Lewis equation to high conversion copolymerization of styrene and methylmethacrylate

In contradiction to reports from this and other laboratories, this study reports that the integrated Mayo–Lewis equation, or Meyer–Lowery equation, adequately describes the high-conversion free radical copolymerization of styrene and methylmethacrylate. The copolymerization was monitored by following the changes in the feed composition using NMR, as well as determination of the resulting copolymer compositions by NMR and UV. “Error in all Variables” statistical techniques were used to produce estimates of the reactivity ratios. The reactivity ratios estimated were, from feed composition, NMR, r₁ (styrene) = 0.472, r₂ = 0.454, from copolymer composition, UV, r₁ = 0.497, r₂ = 0.464, and NMR, r₁ = 0.432, r₂ = 0.422.     

Ambient temperature living radical copolymerization of styrene and methyl methacrylate with sodium hypophosphite as reducing agent

A facile, safe and economical reducing agent, sodium hypophosphite(Na H2PO2·H2O), has been successfully employed for ambient temperature living radical copolymerization of styrene(St) and methyl methacrylate(MMA). Such effective reducing agent significantly improved the reactivity of low reactive St monomers during the copolymerization, where the reactivity ratios of St and MMA were determined to be 0.50 and 0.36 by Finemann-Ross method. Thus the copolymerizations proceeded fast and showed typical living/controlled features, as evidenced by pseudo first-order kinetics of polymerization, linear increase in molecular weight versus monomer conversion, and low polydispersity index values. Effects of the concentration of reducing agent and the monomer feed ratio on the copolymerization were investigated in detail. Furthermore, gel permeation chromatography and 1H-NMR analyses as well as chain extension experiments confirmed the high chain-end functionality of the resultant copolymer.     

Stereogradient polymers by ruthenium-catalyzed stereospecific living radical copolymerization of two monomers with different stereospecificities and reactivities

Stereogradient polymers, a fundamentally new type of polymers, were prepared by the stereospecific living radical copolymerization of two monomers that have different stereospecificities and reactivities. The ruthenium-catalyzed living radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) and the silyl-capped HEMA [(tert-butyldimethylsilyl)-HEMA] (SiHEMA) in (CF3)2C(Ph)OH afforded stereogradient poly(HEMA), in which the rr content gradually increased from 62 to 77% at 0 degrees C, due to the lower reactivity and the higher syndiospecificity of SiHEMA.     

Specific phenomena during the copolymerization of trioxane and ethylene oxide

We, at Asahi Chemical in Japan, have industrialized three types of polyacetal resins, that is, the acetal homopolymer, copolymer and block copolymer using anionic, cationic and anionic polymerization techniques, respectively. During this industrialization, we observed various phenomena, which were not previously reported. First, the authors outline the three technologies for producing each type of polyoxymethylene from an industrial viewpoint. Next, the authors discuss a newly found reaction during the induction period of the trioxane and ethylene oxide copolymerization. Experimental proof of direct ring expansion between the reaction of trioxane and ethylene oxide is discussed and various novel cyclic compounds are also shown. To the best of our knowledge, this reaction may be the world's first experimental proof of direct ring expansion of the reaction of a cyclic monomer. Third, the authors also discuss the newly founded morphospecific polymer from the copolymerization of trioxane and ethylene oxide using boron trifluoride dibutyl ether as an initiator.     

Quantitative theory of living free‐radical polymerization. III. Calculation of copolymerization products' spinodal

The problem of finding conditions of the loss of thermodynamic stability by the reaction system was solved on the basis of the developed theory of living free‐radical copolymerization. The spinodal's calculations were carried out for a significant number of systems differing in the values of kinetic, stoichiometric, and thermodynamic parameters. Analysis of the results of such calculations revealed some regularities in the spinodal curves' behavior and permitted us to classify their possible topological types. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 892–902, 2003     

Controlled/living copolymerization of styrene and acrylamide in DMF with Fe/TMEDA complex as catalyst

In this work, Fe(0)‐mediated single electron‐living radical copolymerization of styrene (St) and acrylamide (AM) was investigated at ambient temperature in N,N‐dimethylformamide using carbon tetrachloride as initiator and tetramethylethylenediamine as ligand. Kinetic studies showed that the copolymerization followed the first‐order kinetics model. The resulting copolymers of St and AM possessed predetermined molecular weights and narrow molecular weight distribution, which agreed with the character of controlled/living polymerization. On the basis of Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (NMR), the monomer reactivity ratios were calculated. The amount of ligand played an important role in copolymerization. The obtained polymer was characterized by FTIR, ¹H NMR, ¹³C NMR, and gel permeation chromatography. The living characteristics were demonstrated by chain extension experiment. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2919–2924     

Block copolymerization of alkoxyallenes by the living coordination system with a π-allylnickel catalyst

Block copolymers of alkoxyallenes were obtained in high yield by the two-stage living coordi-nation polymerization of two kinds of alkoxyallenes using an allylnickel catalyst. The resulting copolymers had narrow molecular weight distributions (～ 1.1), regardless of the order of the monomer additions. When an alkoxyallene-bearing hydrophilic substituent was used as a co-monomer for the block copolymerization with that bearing a hydrophobic one, the resulting copolymer showed amphiphilic properties. For example, a block copolymer obtained by the copolymerization of n-hexyloxyallene with diethylene glycol allenyl methyl ether was soluble in water as well as n-hexane. © 1995 John Wiley & Sons, Inc.     

Calculation of the molecular-mass distribution for hyperbranched macromolecules synthesized by living three-dimensional radical polymerization

Kinetic analysis of the scheme underlying the formation of branched and hyperbranched macro- molecules formed by living three-dimensional radical po lymerization in the pregel period makes it possible to derive some theoretical dependences relating the conditions of polymerization and the molecular-mass distribution of polymers. In this case, a polymer product constitutes a mixture of macromolecules with different degrees of branching, and the fractional weight of macromolecules with hyperbranched structure is no more than one-third with respect to the overall polymer product.     

Effect of the solvent polarity on the living ligated anionic polymerization of tert-butyl methacrylate and copolymerization with methyl methacrylate

An anionic polymerization of t-butyl methacrylate and a copolymerization with methyl methacrylate were initiated with an organolithium ligated with 10 equiv of LiCl. As a rule, the complexation of the active species by LiCl masked the effect that the polarity of the solvent might have on the molecular structure of the chains. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1774–1785, 2001