Transformation of copolymerization mechanism of N-phenyl maleimide and ethyl phenylacrylate in the mixture of dioxane and pyridine

The copolymerization of N-phenylmaleimide (NPMI) with ethyl phenylacrylate (EPA) in a mixture of dioxane (DIO) and pyridine (Py) was investigated. The apparent monomer reactivity ratio r₁ (NPMI) = 0.07 ± 0.01 and r₂ (EPA) = 0.09 ± 0.02 in DIO was turned to r₁ (NPMI) = 3.67 ± 0.07 and r₂ (EPA) = 0 ± 0.03 in Py. The copolymerization of NPMI and EPA with the fixed feed ratio (mol/mol 1 : 1) in different volume ratio of DIO/Py showed that the copolymer composition might be varied in a wide range from the 93.5% of NPMI contents in copolymer to 48.7%. When the volume fraction of Py in the mixture of DIO and Py was <10%, the copolymer with nice alternating structure was obtained and the copolymerization could be inhibited completely by hydroquinone; if the fraction of Py was >10%, the following two kinds of copolymers were formed: a copolymer in which the content of NPMI increased with the Py and the copolymerization also could be inhibited by hydroquinone and a copolymer with low molecular weight almost completely composed of homopolymer of NPMI and is not affected by radical inhibitor as hydroquinone. The transformation of the copolymerization mechanism from the radical to anionic, which was dependent on the volume ratio of DIO and Py, was suggested. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2755–2761, 1999     

Reactivity ratios and microstructure determination of vinyl acetate–alkyl acrylate copolymers by NMR spectroscopy

(Vinyl acetate)/(ethyl acrylate) (V/E) and (vinyl acetate)/(butyl acrylate) (V/B) copolymers were prepared by free radical solution polymerization. ¹H-NMR spectra of copolymers were used for calculation of copolymer composition. The copolymer composition data were used for determining reactivity ratios for the copolymerization of vinyl acetate with ethyl acrylate and butyl acrylate by Kelen-Tudos (KT) and nonlinear Error in Variables methods (EVM). The reactivity ratios obtained are r_v = 0.03 ± 0.03, r_E = 4.68 ± 1.70 (KT method); r_v = 0.03 ± 0.01, r_E = 4.60 ± 0.65 (EV method) for (V/E) copolymers and r_v ? 0.03 ± 0.01, r_B ? 6.67 ± 2.17 (KT method); r_v = 0.03 ± 0.01, r_B = 7.43 ± 0.71 (EV method) for (V/B) copolymers. Microstructure was obtained in terms of the distribution of V- and E-centered triads and V- and B-centered triads for (V/E) and (V/B) copolymers respectively. Homonuclear ¹H 2D-COSY NMR spectra were also recorded to ascertain the existence of coupling between protons in (V/E) as well as (V/B) copolymers. © 1995 John Wiley & Sons, Inc.     

An alternating copolymer of maleimide and atropic acid with narrow molecular weight distribution prepared by radical mechanism

Three basic conditions for preparation of alternating copolymer with narrow molecular weight distribution were derived from the element kinetic equations of binary radical copolymerization. Using maleimide (MI) and atropie acid (ATA) as model monomer pairs and dioxane as the solvent the alternating copolymer with molecular weight distribution in the range of 1.09--1.20 was prepared successfully by charger transfer complex (CTC) mechanism in the presence of benzoyl peroxide at 85℃. The monomer reactivity ratioes r_1(MI)=0.05±0.01 and r_2(ATA)=0.03±0.02 were measured. The alternating eopolymerization was carried out through formation of a contact-type CTG and then alternating addition of MI and ATA monomers. The molecular weight of the copolymers is nearly independent of the feed ratio in a large range and the polymerization rate dropped with an increase in ATA in feed ratio.     

Comparative recalculation of the monomer reactivity ratios in copolymerization for styrene and methyl methacrylate

The monomer reactivity ratios (MMRs) in radical copolymerization for styrene and methyl methacrylate were recalculated by five different methods using literature copolymerization data. The use of approximate 95% confidence limits and their visual inspection helps to separate possibly biased copolymer composition data. The recalculated mean MRR values were r₁ (styrene) = 0.501 ± 0.031 and r₂ = 0.472 ± 0.031. The results of the linear least-squares calculation procedures seldom approach the quality of the nonlinear least-squares analysis according to the method of Tidwell and Mortimer.     

Synthesis,Characterization, and Reactivity Ratios of Phenyl Methacrylate-N-vinyl-2-pyrrolidone Copolymers

Free radical solution copolymerization of phenyl methacrylate and N-vinyl-2-pyrrolidone was carried out using benzoyl peroxide in 2-butanone solution at 70°C. The composition of the copolymer was determined using ¹H-NMR spectra by comparing the intensities of aromatic protons to that of total protons. The results were used to calculaie the copolymerization reactivity ratios by both the Fineman-Ross (F-R) and Kelen-Tüdös (K-T) methods. The reactivity ratios are r ₁ = 4.49 ± 1.27 and r ₂ = 0.05 ± 0.09 as determined by the K-T method. These values are in good agreement with those determined by the F-R method. The FT-infrared and ¹³C-NMR spectra of the copolymer are discussed.     

Controllability of radical copolymerization of maleimide and ethyl α‐(n‐propyl)acrylate using 1,1,2,2‐tetraphenyl‐1,2‐bis(trimethylsilyloxy) ethane as initiator

The radical copolymerization of maleimide (MI) and ethyl α‐propylacrylate was performed using 1,1,2,2‐tetraphenyl‐1,2‐bis(trimethylsilyloxy) ethane (TPSE) as initiator. The whole copolymerization process might be divided into two stages: in the first stage, the copolymerization was carried out on the common radical mechanism, the molecular weight of the copolymer increased rapidly in much lower conversion (< 85%), and did not depend on the polymerization time and conversion; in the second stage, molecular weight of the copolymer increased linearly with the conversion and the polymerization time. It was found, however, when the conversion was higher than a certain value, for example, more than 36%, the molecular weight of the copolymer was nearly unchangeable with the polymerization time and the molecular weight distribution was widened. The effect of reaction conditions on copolymerization was discussed and the reactivity ratios were calculated by the Kelen–Tudos method, the values were r_MI = 0.13 ± 0.03, r_EPA = 0.58 ± 0.06 for TPSE system and r_MI = 0.12 ± 0.03, r_EPA = 0.52 ± 0.06 for AIBN system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2872–2878, 2000     

Determination of the reactivity ratios of methyl acrylate with the vinyl acetate,vinyl 2,2-dimethyl-propanoate,and vinyl 2-ethylhexanoate

The course of composition drift in copolymerization reactions is determined by reactivity ratios of the contributing monomers. Since polymer properties are directly correlated with the resulting chemical composition distribution, reactivity ratios are of paramount importance. Furthermore, obtaining correct reactivity ratios is a prerequisite for good model predictions. For vinyl acetate (VAc), vinyl 2,2-dimethyl-propanoate also known as vinyl pivalate (VPV), and vinyl 2-ethylhexanoate (V2EH), the reactivity ratios with methyl acrylate (MA) have been determined by means of low conversion bulk polymerization. The mol fraction of MA in the resulting copolymer was determined by ¹H-NMR. Nonlinear optimization on the thus-obtained monomer feed–copolymer composition data resulted in the following sets of reactivity ratios: r_MA = 6.9 ± 1.4 and r_VAc = 0.013 ± 0.02; r_MA = 5.5 ± 1.2 and r_VPV = 0.017 ± 0.035; r_MA = 6.9 ± 2.7 and r_V2EH = 0.093 ± 0.23. As a result of the similar and overlapping reactivity data of the three methyl acrylate–vinyl ester monomer systems, for practical puposes these data can be described with one set of reactivity data. Nonlinear optimization of all monomer feed–copolymer composition data together resulted in r_MA = 6.1 ± 0.6 and r_VEst = 0.0087 ± 0.023. © 1994 John Wiley & Sons, Inc.     

Quantifying and Controlling the Composition and ‘Randomness’ Distributions of Random Copolymers

The effect of disparity in the reactivity ratios of monomer pairs on the composition distribution and microstructure of the resultant copolymer formed through free‐radical polymerization is quantified computationally. This correlation has been determined for the monomer pairs of styrene/methyl methacrylate and styrene/2‐vinyl pyridine for a variety of monomer feed ratios. These monomer pairs were chosen as they represent systems that have been utilized to experimentally examine the importance of copolymer architecture on its ability to compatibilize an immiscible polymer blend. Moreover, their respective random copolymers show conflicting results for this examination. The results of this work show that the difference in the reactivity ratios of styrene and 2‐vinyl pyridine copolymer (r₁ = 0.5, r₂ = 1.3) significantly broadens the composition and randomness distribution of the resultant copolymer. This breadth is not easily avoided as it evolves even in the early stages of the copolymerization. Conversely, for the styrene/methyl methacrylate pair, the reactivity ratios are similar (r₁ = 0.46, r₂ = 0.52) and this results in a copolymer with a narrow composition distribution and sequence distribution dispersion. Stopping the polymerization at early conversion further narrows both distributions. The presented results, therefore, provide fundamental information that must be considered when planning an experimental procedure to evaluate the relative importance of sequence distribution and composition distribution of a random on its application.     

Radical copolymerization behavior of a highly fluorinated cyclic olefin with vinyl ether

The copolymerization of a highly fluorinated cyclic monomer, octafluorocyclopentene (OFCPE, M₁), with ethyl vinyl ether (EVE, M₂) was investigated with a radical initiator in bulk. Despite the poor homopolymerizability of each monomer, the copolymerization proceeded successfully, and the molecular weights of the copolymers reached up to more than 10,000. Incorporation of the OFCPE units into the copolymer led to an increase in the glass‐transition point. The copolymer composition was determined from ¹H NMR spectra and elemental analysis data. The molar fraction of the OFCPE unit in the copolymer increased and approached but did not exceed 0.5. The monomer reactivity ratios were estimated by the Yamada–Itahashi–Otsu nonlinear least‐squares procedure as r_1,OFCPE = ?0.008 ± 0.010 and r_2,EVE = 0.192 ± 0.015. The reactivity ratios clearly suggest that the copolymerization proceeds alternatively in the case of an excessive feed of OFCPE. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1151–1156, 2002     

Copolymerization of glycidyl methacrylate with alkyl acrylate monomers

A newer approach to obtaining acrylic thermoset polymers with adequate hydrophilicity required for various specific end uses is reported. Glycidyl methacrylate (GMA) was copolymerized with n-butyl acrylate (n-BA), isobutyl acrylate (i-BA), and 2-ethylhexyl acrylate (2-EHA) in bulk at 60°C. with benzoyl peroxide as free radical initiator. The copolymer composition was determined from the estimation of epoxy group. Reactivity ratios were calculated by the Yezrielev, Brokhina, and Roskin method. For copolymerization of GMA (M₁) with n-BA (M₂) the reactivity ratios were r₁ = 2.15 ± 0.14, r₂ = 0.12 ± 0.03; with i-BA (M₂) they were r₁ = 1.27 ± 0.06, r₂ = 0.33 ± 0.031; and with 2-EHA (M₂) they were r₁ = 2.32 ± 0.14, r₂ = 0.13 ± 0.009. The reactivity ratios were the measure of distribution of monomer units in a copolymer chain; the values obtained are compared and discussed.     

Radical copolymerization of N-vinylformamide with unsaturated carboxylic acids

Radical precipitative copolymerization of N-vinylformamide with acrylic and methacrylic acids in isopropanol at 60°C, with azobisisobutyric acid dinitrile as initiator, was studied. The conditional values of the relative reactivities were found: r ₁ = 0.068 ± 0.008 and r ₂ = 1.638 ± 0.025 for the N-vinylformamide-methacrylic acid copolymer and r ₁ = 0.15 ± 0.03 and r ₂ = 0.19 ± 0.09 for the N-vinylformamide-acrylic acid copolymer.     

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.     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. III. NMR study of methyl methacrylate–styrene copolymer

The copolymer composition curve of the methyl methacrylate–styrene copolymer obtained by the copolymerization in the presence of ZnCl₂ has more alternating tendency than that of ordinary methyl methacrylate–styrene copolymer obtained by radical copolymerization. The fine structure of the copolymer was examined by NMR, and the mechanism of the propagation step of the copolymerization in the presence of ZnCl₂, which was proposed in the first report of this series, was verified.     

Effects of complexing agents in radical copolymerization

Radical copolymerization of methyl methacrylate (MMA, M₁) with various monomers has been studied in presence of modifiers, i.e., complexing agents (CA): ZnCl₂, AlCl₃, AlBr₃, Al(C₂H₅)₂Cl, forming coordinate complexes with ester group of the monomer and of the propagating radical. The comonomers of the first group form complexes of similar structure and stability as MMA, methyl acrylate, or butyl acrylate. The comonomers of the second group do not form complexes with the modifiers (vinylidene chloride, 2,6-dichlorostyrene, p-chlorostyrene, styrene). For all systems studied the copolymer composition follows the Mayo-Lewis equation. In the first group of the systems the effective reactivity ratios (r₁, r₂) approach unity with increase of the CA molar content (r₁ = r₂ ? 1 at [(CA)/MMA] + [MA] ≥ 0,3) In the second group of the systems the values of r₁ either increase to a limit value (at [CA]/[MMA] ≥ 0.3), pass through maximum, or decrease to a limiting value with the CA molar content. The values of r₂ decrease in all systems. The character of variation of r₁ and r₂ has been explained in terms of effects of the CA's on reactivity of MMA and PMMA radical. The equations for the copolymer compositions in these systems have been derived.     

Copolymerization of 2-Hydtoxypropyl Methacrylate with Alkyl Methacrylates

2-Hydroxypropyl methacrylate (2 HPMA) has been copolym-erized with ethyl methacrylate (EMA), n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (EHMA) in bulk at 60°C using benzoyl peroxide as initiator. The copolymer composition has been determined from the hydroxyl content. The reactivity ratios have been calculated by the YBR method. For copolymerization of 2-HPMA (M₁) with EMA (M₂), the reactivity ratios are: r₁=1.807 ± 0.032, r₂=0.245 ± 0.021; with BMA (M₂) they are r₁=2.378 ± 0.001, r₂=0.19 ± 0.01; and with EHMA the values are r₁=4.370 ± 0.048, r₂=0.103 ± 0.006. Since the reactivity ratios are the measure of distribution of monomer units in a copolymer chain, the values obtained are compared and discussed. This enables us to choose a suitable copolymer for synthesizing thermoset acrylic polymers, which are obtained from cross-linking of hydroxy functional groups of HPMA units, for specific end uses.     

Alternating Copolymerization of Styrene and N-(4-Bromophenyl)Maleimide

Abstract

Free radical copolymerization of styrene (St) and N(4-bro-mophenyl)maleimide (4BPMI) in dioxane solution gave an alternating copolymer in all proportions of feed comonomer compositions. The monomer reactivity ratios were found to be r ₁, = 0.0218 ± 0.0064 (St) and r ₂, = 0.0232 ± 0.0112 (4BPMI), and the activation energy of the copolymerization reaction for the equimolar ratios of comonomer was E _a, = 51.1 kJ/mol. The molecular weights of the copolymers obtained are relatively high, the T _g's showed similar values (490 K), and the thermal stability is higher than that of polystyrene. The initial rate of copolymerization depends on the total concentration of the comonomers and the maximum occurred at higher 4BPMI mol fractions; however, the overall conversion is highest at equimolar comonomer composition. It has been shown that a charge-transfer complex participates in the process of copolymerization. The initial reaction rate was measured as a function of the monomer molar ratios, and the participation of the charge-transfer complex monomer and the free monomers was quantitatively estimated.     

Copolymers of α-Methylstyrene with N-Cyclohexylacrylamide: Synthesis,Monomer Reactivity Ratios,and Mean Sequence Length

Abstract

Copolymerization of α-methylstyrene and N-cyclohexylacrylamide was carried out in toluene at 60 ± 1°C using azobisisobutyronitrile as the free-radical initiator. The total concentration of the comonomers was 1.5 mol·L^?1 in the solvent. The copolymers were characterized by ¹H-NMR and ¹³C-NMR spectroscopy, and the copolymer compositions were determined primarily from the ¹H-NMR spectra. The reactivity ratios were found to be r ₁ = 0.08 ± 0.01 and r ₂ = 2.45 ± 0.03 by the Fineman-Ross method, and r ₁ = 0.06 ± 0.01 and r ₂ = 2.43 ± 0.08 by the Kelen-Tüdös method. Mean sequence lengths in the copolymer were estimated from r ₁ and r ₂ values.     

Copolymerization of 2-sulfoethyl methacrylate

Copolymers of 2-sulfoethyl methacrylate, (SEM) were prepared with ethyl methacrylate, ethyl acrylate, vinylidene chloride, and styrene in 1,2-dimethoxyethane solution with N,N′-azobisisobutyronitrile as initiator. The monomer reactivity ratios with SEM (M₁) were: vinylidene chloride, r₁ = 3.6 ± 0.5, r₂ = 0.22 ± 0.03; ethyl acrylate, r₁ = 3.2 ± 0.6, r₂ = 0.30 ± 0.05; ethyl methacrylate, r₁ = 2.0 ± 0.4, r₂ = 1.0 ± 0.1; styrene, r₁ = 0.6 ± 0.2, r₂ = 0.37 ± 0.03. The values of the copolymerization parameters calculated from the monomer reactivity ratios were e = +0.6 and Q = 1.4. Comparison of the monomer reactivities indicates that SEM is similar to ethyl methacrylate with regard to copolymerization reactivity in 1,2-dimethoxyethane solution. The sodium salt of 2-sulfoethyl methacrylate, SEM^?Na^⊕, was copolymerized with 2-hydroxyethyl methacrylate (M₂) in water solution. Reactivity ratios of r₁ = 0.7 ± 0.1 and r₂ = 1.6 ± 0.1 were obtained, indicating a lower reactivity of SEM^?Na^⊕ in water as compared to SEM in 1,2-dimethoxyethane. This decreased reactivity was attributed to greater ionic repulsion between reacting species in the aqueous medium.     

Biocompatible polymeric systems: Copolymerization of 4-methacryloyloxy-acetanilide with 2-hydroxyethyl-methacrylate

Soluble copolymers of 4-methacryloyloxy-acetanilide (M), an acrylic derivative of paracetamol, with 2-hydroxyethyl-methacrylate (H) were prepared by free radical polymerization in DMF solution at 50°C, using 2,2′-azobisisobutyronitrile (AIBN) as initiator. The reactivity ratios of both monomers were determined by the application of conventional linearization methods suggested by Fineman-Ross and Kelen-Tudos. The results obtained make clear that this system copolymerizes at random with the reactivity ratios r_m = 2.15 ± 0.05 and r_H = 0.90 ± 0.10. The microstructure of copolymer chains is described on the basis of the first order Markov statistics. The copolymer glass transition temperatures were determined calorimetrically and the variation of T_g with the copolymer composition is discussed according to modern methods, considering the sequence distribution of monomeric units along the copolymer chains. Also the T_g of the corresponding homopolymers were determined giving the values of T_g(M) = 471 K and T_g(H) = 358 K.     

Copolymerization of isopropenyl and isopropylidene oxazolones with styrene

2-Isopropenyl-4-isopropyl-2-oxazolin-5-one (M₂), was copolymerized with styrene (M₁), and the monomer reactivity ratios were determined to be r₁ = 0.31 ± 0.03, r₂ = 1.12 ± 0.10. New isomerized oxazolones (M₂), 2-isopropylidene-4-methyl-3-oxazolin-5-one, 2-isopropylidene-4-isopropyl-3-oxazolin-5-one, and 2-isopropylidene-4-isobutyl-3-oxazolin-5-one were prepared and copolymerized with styrene. The monomer reactivity ratios were: r₁ = 0.36 = 0.07, r₂ = 0.0; r₁ = 0.39 ± 0.06, r₂ = 0.00 ± 0.10; r₁ = 0.39 ± 0.10, r₂ = 0.0, respectively. The isomerized oxazolones showed no tendency towards homopolymerization by radical initiator. From the results of infrared and NMR spectra and hydrolysis of the copolymer, it was indicated that the isomerized oxazolones participated in copolymerization in the form of 1–4 polymerization of the conjugated dienes (exo double bond at C₂ and the C?N in the ring). Copolymers reacted with nucleophilic reagents such as amines and alcohols.