Transfer Radical Copolymerization Research Articles

Synthesis of a New Macroperoxy Initiator with Methyl Methacrylate and T-Butyl Peroxy Ester by Atom Transfer Radical Polymerization and Copolymerization with Conventional Vinyl Monomers

In this study, we present the synthesis of poly-MMA macroperoxy initiators obtained by the ATRP of MMA with bromo methyl benzyl t-butyl peroxy ester (t-BuBP) as an initiator, and CuX (X:Br or Cl)/2,2′-bipyridine (bpy) as a catalyst system at 0, 20, 30 and 40°C. The peroxygen groups do not decompose during the ATRP reaction, because low reaction temperatures used for the ATRP reaction are not enough to decompose them. The peroxygen groups of poly-PMMA macroperoxy initiators can lead them to react with a monomer by using appropriate reaction conditions to obtain the block or graft copolymers. For this purpose, poly-MMA macroperoxy initiators were used to synthesize poly(MMA-b-S) block copolymers with S and used for graft copolymerization of polybutadiene (PBd) and natural rubber (RSS-3) to obtain crosslinked poly(MMA-g-PBd) and poly(MMA-g-RSS-3) graft copolymers. Swelling ratio values of the crosslinked graft copolymers in CHCl3 were calculated. The characterizations of the polymers were achieved by FT-IR, 1H-NMR, GPC, DSC, SEM, and the fractional precipitation (γ) techniques. The reaction schemes were also performed using the HYPERCHEM 7.5 program. The mechanical properties of the products were investigated.

Synthesis and large scale fractionation of non-linear polymers: brushes and hyperbranched polymers

Polymer brushes with poly(methyl methacrylate) (PMMA) backbone and polystyrene side chains were synthesized by radical polymerization of ω-methacryloyl-polystyrene macromonomers. Hyperbranched PMMA was obtained by means of self-condensing group transfer copolymerization of methyl methacrylate with an initiator-monomer containing a polymerizable methacryloyl moiety and an initiating silylketeneacetal function. Both non-linear products were fractionated using the method of continuous polymer fractionation, consisting in a particular type of continuous countercurrent extraction. The combination of methyl ethyl ketone (solvent) with acetone (AC) (precipitant) turned out to be suitable for the fractionation of the polymer brushes; in case of the hyperbranched material AC served as the solvent component and methanol as the precipitant. The achieved fractionation was checked by means of GPC measurements and in case of the polymer brushes also by AFM, where the differences in the size of the macromolecules became clearly visible.

Synthesis of Hyperbranched and Highly Branched Methacrylates by Self-Condensing Group Transfer Copolymerization

We report a study of the self-condensing group transfer copolymerization of the initiator−monomer (“inimer”) 2-(2-methyl-1-triethylsiloxy-1-propenyloxy)ethyl methacrylate (MTSHEMA) with methyl methacrylate (MMA). The highly branched polymethacrylates were characterized by multidetector SEC and NMR. Kinetic measurements show that cyclization, i.e., the intramolecular reaction of an active center with the vinyl group of the polymer, limits the molecular weights and lowers the polydispersity. Depending on the comonomer ratio, γ = [MMA]0/[MTSHEMA]0, molecular weights up to Mw = 240 000 at a polydispersity of Mw/Mn ≈ 3 could be obtained. The Mark−Houwink exponent of these branched copolymers depends on the comonomer ratio and is significantly lower (0.45 ≥ α ≥ 0.23) than linear PMMA (α = 0.69). Only 4% of inimer are necessary to lower the Mark−Houwink exponent to half the value of linear PMMA. Using slow addition of the comonomer mixture to the monofunctional initiator 1-methoxy-3-(trimethylsilyloxy)-2-methyl-1-propene (MTS) enables control of the molecular weights and decreases the polydispersity to Mw/Mn ≈ 1.6. Copolymerization of MTSHEMA with tert-butyl methacrylate followed by acid-catalyzed hydrolysis of the tert-butyl groups yields highly branched poly(methacrylic acid).

Characterization of Highly Branched Poly(methyl methacrylate) by Solution Viscosity and Viscoelastic Spectroscopy

Highly branched poly(methyl methacrylate) with an estimated degree of branching = 0.074 (i.e., 3.7 branchpoints per 100 monomer units) was prepared using self-condensing group transfer copolymerization (SCVCP) of methyl methacrylate (MMA) and 2-(2-methyl-1-triethylsiloxy-1-propenyloxy)ethyl methacrylate (MTSHEMA) and fractionated by means of preparative SEC. The fractions were characterized in solution by SEC−viscosity coupling and in the melt by viscoelastic spectroscopy. In THF solution, a Mark−Houwink exponent of α = 0.40 was determined for the branched polymer, which is considerably lower than that of linear PMMA (α = 0.688). In the region between the relaxation times of the chain, τc, and of the segments, τs, of the viscoelastic spectrum of the branched polymer, both the storage and the loss moduli (log G‘ and log G‘ ‘) are nearly equal, and the complex viscosities show a practically linear dependence on log ω with a slope of −0.54. This is attributed to a broad distribution of relaxation times and t...

Well-defined sulfobetaine-based statistical copolymers as potential antibioadherent coatings.

The potential use of novel poly(sulfobetaine) copolymers as antibioadherent coatings was investigated using Pseudomonas aeruginosa as a model microorganism and human macrophages and 3T3 mouse embryonic fibroblasts. Two well-defined statistical copolymers with narrow molecular weight distributions were prepared by group transfer copolymerization of n-butyl methacrylate (nBuMA) with either 10 or 30 mol % 2-(dimethylamino)ethyl methacrylate (DMAEMA). Sulfobetainized nBuMA-DMAEMA copolymers (poly[sulfobetaine-stat-nBuMA]) were obtained by treating these precursor polymers with 1,3-propanesultone under mild conditions. Both proton NMR spectroscopy and elemental microanalyses indicated that essentially all the DMAEMA residues were derivatized in both copolymers. Poly(methyl methacrylate) (PMMA) discs were coated with the sulfobetainized nBuMA-DMAEMA copolymers and the bioadherent properties of these coated materials were compared with those of PMMA. Statistically significantly fewer (p<.05) bacteria, macrophages, and fibroblasts adhered to the poly(sulfobetaine-stat-nBuMA)-coated PMMA than to the uncoated PMMA. The poly(sulfobetaine-stat-nBuMA) copolymer containing the higher proportion (30 mol %) sulfobetainized DMAEMA residues proved to be the more effective antibioadherent coating. The antibioadherent properties of these coating materials may allow the cost-effective production of dirt-resistant, easy to clean work surfaces, bioinert coatings for medical devices, and antifouling coatings for marine, agricultural, and industrial applications.

Well-defined sulfobetaine-based statistical copolymers as potential antibioadherent coatings

The potential use of novel poly(sulfobetaine) copolymers as antibioadherent coatings was investigated using Pseudomonas aeruginosa as a model microorganism and human macrophages and 3T3 mouse embryonic fibroblasts. Two well-defined statistical copolymers with narrow molecular weight distributions were prepared by group transfer copolymerization of n-butyl methacrylate (nBuMA) with either 10 or 30 mol % 2-(dimethylamino)ethyl methacrylate (DMAEMA). Sulfobetainized nBuMA-DMAEMA copolymers (poly[sulfobetaine-stat-nBuMA]) were obtained by treating these precursor polymers with 1,3-propanesultone under mild conditions. Both proton NMR spectroscopy and elemental microanalyses indicated that essentially all the DMAEMA residues were derivatized in both copolymers. Poly(methyl methacrylate) (PMMA) discs were coated with the sulfobetainized nBuMA-DMAEMA copolymers and the bioadherent properties of these coated materials were compared with those of PMMA. Statistically significantly fewer (p<.05) bacteria, macrophages, and fibroblasts adhered to the poly(sulfobetaine-stat-nBuMA)-coated PMMA than to the uncoated PMMA. The poly(sulfobetaine-stat-nBuMA) copolymer containing the higher proportion (30 mol %) sulfobetainized DMAEMA residues proved to be the more effective antibioadherent coating. The antibioadherent properties of these coating materials may allow the cost-effective production of dirt-resistant, easy to clean work surfaces, bioinert coatings for medical devices, and antifouling coatings for marine, agricultural, and industrial applications.

Dielectric studies on allyl methacrylate-methyl methacrylate copolymers in a slightly polar medium

Dielectric constants of allyl methacrylate-methyl methacrylate copolymers are measured in toluene solution at a constant frequency of 2 MHz, within a wide temperature range (20–70°C). Soluble copolymers have been prepared by group transfer copolymerization. Dipole moments are calculated from Guggenheim-Smith equation. The effects of allyl group on the dipole moments of copolymers in a slightly polar medium are discussed.

Statistical group transfer copolymerization of acrylates with methacrylates

Statistical group transfer copolymerization (GTP) of acrylates with methacrylates have been performed for four binary systems using 1-methoxy-2-methyl-1-trimethylsilyloxypropene (initiator) and tetrabutylammonium bibenzoate (catalyst) in tetrahydrofuran solution. The copolymer compositions were determined by 1H n.m.r. spectroscopy and the results evaluated by the extended Kelen-Tüdős method. The monomer pairs concerned are (1) ethyl acrylate (EA) and methyl methacrylate (MMA), (2) methyl acrylate (MA) and ethyl methacrylate (EMA), (3) MA and butyl methacrylate (BMA) and (4) MA and iso butyl methacrylate (i-BMA). The reactivity ratios were found to be γ EA = 14.15, γ MMA = 0.01, γ MA = 14.41, γ EMA = 0.01, γ MA = 13.96, γ BMA = 0.23, γ MA = 8.66 and γ iBMA = 0.08, respectively. Statistical anionic copolymerizations were also carried out for two monomer pairs to compare with the results for GTP. The reactivity ratios are γ EA = 9.67, γ MMA = 0.11, γ MA = 3.51 and γ EMA = 0.20. It was found that acrylate is much more reactive than methacrylate; the reactivity ratios are quite different from unity and show a high similarity in GTP and anionic polymerization.

Statistical group transfer copolymerization of methyl methacrylate with acrylates

Statistical group transfer copolymerization of acrylates with methyl methacrylate have been performed for two binary systems using 1-methoxy-2-methyl-1-trimethylsilyloxy propene (initiator) and tetrabutylammonium bibenzoate (anionic catalyst) in toluene solution. The copolymer compositions were determined by 1H NMR spectroscopy and the results evaluated by the Kelen-Tudos method. The monomer pairs concerned are (1) methyl acrylate and methyl methacrylate (MMA), (2) butyl acrylate and MMA. The reactivity ratios were found to be γ ma = 8.29, γ mma = 0.04 and γ ba = 6.74, γ mma = 0.14.

Reactivity ratios in group transfer copolymerization of methyl methacrylate/ethyl methacrylate and methacrylonitrile/methyl methacrylate systems obtained by semi‐integral and integral methods

AbstractThe monomer reactivity ratios for the methyl methacrylate/ethyl methacrylate (MMA/EMA) and methacrylonitrile/methyl methacrylate (MAN/MMA) systems are calculated by linearized semi‐integral and nonlinear fully integral methods. For the MMA/EMA system, rMMA values obtained by various methods are between 1.24 and 1.25 and rEMA values between 0.30 and 0.34. For MAN/MMA system, rMAN values are between 3.2 and 3.8 and for rMMA an upper bound can be determined, i.e., rMMA&lt;0.05. The results show that previous values obtained by the linearized method (the initial Kelen‐Tüdős method) overestimate the reactivity of the less active monomer.

Synthesis of Poly(Methyl Methacrylate-graft-Isobutylene) Copolymers by the Combination of Living Carbocationic and Group Transfer Polymerization

Abstract The synthesis of poly(methyl methacrylate-graft-isobutylene), p(MMA-g-IB) copolymers was accomplished by group transfer copolymerization (GTP) of MMA and polyisobutenyl methacrylate (PIBMA). The PIBMA macromer was obtained by living carbocationic polymerization (LC+P) of IB using a novel functional initiator 3,3,5-trimethyl-5-chloro-1-hexyl methacrylate. Well-defined macromers with perfect functionalities were obtained in the molecular weight range of 2000 to 50,000. The PIBMA macromers were copolymerized with MMA using GTP. The structure and the properties of the resulting p(MMA-g-IB) copolymers were determined by the [MMA]/[I] and [MMA]/[PIBMA] ratios. The homopolymerization of the macromer resulted in a mixture of dimers and unreacted macromer.

Allyl reactivity in group transfer copolymerization

AbstractStatistical copolymers of allyl methacrylates with methyl and ethyl methacrylates are synthesized. Moderate conversions are used. Reactivity ratios are calculated by linearised methods which take composition drift into account as well as by non‐linear least‐squares approximation. For the allyl methacrylate/methyl methacrylate system, rallyl values obtained by various methods are between 1,62 and 1,60 and rmethyl values between 0,36 and 0,34. For the allyl methacrylate/ethyl methacrylate system, rallyl values are between 1,37 and 1,16 and rethyl values between 0,40 and 0,47.

Aldol Condensation-Type Group Transfer Copolymerizations of Silyl (Di)Enolates

Copolymerizations of two monomers among silyl dienolates, CH2=CR1—CH=CH—OSi(CH3)2R2 and silyl enolates CH2=CH—OSi(CH3)2R2 [R1=H, CH3; R2=CH3, C(CH3)3] were examined under conditions suitable for aldol condensation-type group transfer polymerization (aldol-GTP). Structures of the copolymers were determined mainly by their 1H NMR spectra and by partial desilylation. E-isomers of dienolates (R1=H) showed much higher copolymerizability than enolates, independent of R2 substituent on silicon. Methyl substituent at 3-carbon (R1=CH3) enhanced the copolymerizability of silyl dienolate further. Z-dienolates could hardly react with E-isomers but gave rise to copolymerization with the enolate monomer. 1:1 Aldol-adducts of the above monomers with benzaldehyde were prepared. The adducts were effective initiators for aldol-GTP of other monomers. The results provided evidence for the existence of cross-propagation on aldol group transfer copolymerization.

Statistical group transfer copolymerization. Monomer reactivity ratios for allyl methacrylate and n-butyl methacrylate

Statistical copolymerizations have been performed for allyl methacrylate-butyl methacrylate systems using 1-methoxy-2-methyl-1-trimethylsilyloxypropene (initiator) and tris (dimethylamino) sulphonium bifluoride (catalyst) in tetrahydrofuran solution. Soluble allyl copolymers have been obtained by this method. The copolymer compositions were determined by ultraviolet spectroscopy and the results evaluated by the Kelen-Tüdos and Fineman-Ross methods. The reactivity ratios were found to be r AMA = 2.35, r BMA = 0.08 (Kelen-Tüdos) and r AMA = 2.37, r BMA = 0.08 (Fineman-Ross).

The group transfer copolymerization of alkyl acrylates with acrylates containing electron-donor or -acceptor substituents

N-(2-Hydroxyethyl)carbazolyl acrylate, an electron-donor monomer, or 2-(trimethylsiloxy)ethyl acrylate were copolymerized with methyl acrylate and with n-butyl acrylate, respectively, via group transfer polymerization in tetrahydrofuran. By polymer analogue transformations the trimethylsilyl groups were substituted by 3,5-dinitrobenzoyl groups to get the corresponding electron-acceptor (β-hydroxyethyl)-3,5-dinitrobenzoyl acrylate copolymers. The content of the electron-donor (respectively of the electron-acceptor) groups in the acrylate copolymers was in the range of up to 10 mol%. The thermal behaviour of these copolymers obtained via group transfer polymerization is compared with that of the corresponding copolymers obtained by radical copolymerization.