Preparation of novel macromonomers and study of their polymerization

Novel macromonomers of polystyrene and poly(tert‐butyl acrylate) containing a methacryloyl group as a polymerizable unit and two chains of the same length were prepared in two steps: the synthesis of the precursors through the atom transfer radical polymerization of styrene and tert‐butyl acrylate initiated by 1‐hydroxymethyl‐1,1‐di[(2‐bromoisobutyryloxy)methyl] ethane and the esterification of the hydroxyl group in the precursors with methacryloyl chloride. The molecular weight and polydispersity of the macromonomers were controllable because of the living nature of the atom transfer radical polymerization. Gel permeation chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and hydrolysis confirmed the structure of the novel macromonomers. The homopolymerization and copolymerization of the macromonomers were investigated to prepare branched copolymers in which two chains were grafted from every repeating unit. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3887–3896, 2004     

Reactive surfactants in heterophase polymerization

The mechanism for the formation of polymer particles in the dispersion polymerization of methyl methacrylate and styrene in alcohol-water mixtures has been investigated. Methacrylic based poly(ethylene oxide) macromonomers and poly(vinyl-pyrrolidone) have been used as steric stabilizers. Dynamic light scattering as well as transmission electron microscopy have been applied to determine the evolution of the average particle size at the beginning of the polymerization. Stable nuclei from 80 to 400 nm in diameter size were detected. The nucleation process was quite rapid and completed within less thanca. 0.1% monomer conversion. The experimental results are compared with those predicted by the multibin kinetics model for coalescence developed by Paine [(1990) Macromolecules 23: 3109].A series of publication from the EU program Human Capital and Mobility (CHRX CT 93-0159)     

Anionic polymerization and copolymerization of macromonomers: Kinetics,structure control

The present paper discusses the ability of macromonomers to undergo polymerization and copolymerization with acrylic and vinylic monomers. These macromonomers have been synthesized by classical deactivation reactions. Special interest was devoted to macromonomers fitted with polymerizable methylmethacrylate end-groups. The anionic homopolymerization of ω-methacryloyloxy-polystyrene macromonomers was studied in detail and the influence of the molar mass of the macromonomer on the apparent propagation constant was determined. The anionic homopolymerization of ω-methacryloyloxy poly(ethylene oxide) macro-monomers was also examined. In both cases, lithium chloride has to be added in order to reach a better control of the reaction. The dilute solution properties of these polystyrene polymacromonomers have been studied. Some preliminary attempts to apply that anionic homopolymerization of macromonomers to the preparation of “dumbbell” and “palmtree” polymers were presented.     

Amphiphilic cationic block copolymers via controlled free radical polymerization

N-oxyl terminated vinylbenzyl chloride macromonomers, available via controlled free radical polymerization, were used to synthesize AB-block copolymers of vinylbenzyl chloride and styrene with low polydispersity and different block lengths and block length ratios. The vinylbenzyl chloride blocks were quantitatively converted into cationic polyelectrolytes by reactions with tertiary amines. The micellization of the synthesized amphiphilic cationic block copolymers was investigated using different techniques such as static light scattering, ultracentrifugation and size exclusion chromatography.     

Hydrogels by atom transfer radical polymerization. I. Poly(N-vinylpyrrolidinone-g-styrene) via the macromonomer method

Atom transfer radical polymerization has been used to prepare well-defined vinyl macromonomers of polystyrene using vinyl chloroacetate as an initiator. Because styrene and vinyl chloroacetate do not copolymerize, no branching or incorporation of the initiator into the backbone was observed. Macromonomers of several molecular weights were prepared and copolymerized free radically with N-vinylpyrrolidinone in varying feed ratios in order to produce poly(NVP-g-Sty) graft copolymers. The macromonomers used were of sufficiently high molecular weight to form physical crosslinks in solvents which favor the hydrophilic NVP, such as water, which prevent the copolymer from dissolving and cause it to swell. These materials, therefore, formed hydrogels of swellabilities in water exceeding 95%, depending on the amount of styrene that was incorporated into the copolymer. Limitations of and alternatives to this method are also discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 823–830, 1998     

One-step synthesis of poly(methacrylic acid) macromonomers and application to soap-free emulsion copolymerization with styrene

Allylic sulfides such as α-(tert-butylthiomethyl)styrene and α-(2-hydroxyethylthiomethyl)styrene worked as effective chain transfer agents in the radical polymerization of methacrylic acid, to afford a one-step synthesis of water-soluble macromonomers with the 2-phenylallyl end groups. The macromonomers were found to be effective, particularly in the partially neutralized form, in emulsion copolymerization with styrene in water, to give stable emulsions with nearly monodisperse, submicron-sized particles. The microspheres thus obtained are considered to have carboxyl groups densely bound on the surface as a result of an organized copolymerization.     

Reactive surfactants in heterophase polymerization. Part XXII—incorporation of macromonomers used as stabilizers in styrene dispersion polymerization

The effect of several parameters on the incorporation yield of poly(ethylene oxide) macromonomers at the surface of the particles, for the dispersion polymerization of styrene in ethanol–water mixtures, has been studied. The reactivity of the macromonomer is a key parameter in the mechanism of stabilization of the micrometer-size polymer particles, because it partly determines the amount and the composition of the copolymer stabilizer available at any moment during the process. The polarity of the reaction medium also strongly influences the polymerization process: higher incorporation yield and grafting density were obtained in medium of lower polarity. Besides, a chain length of around 50 ethylene oxide units for the macromonomer were needed to produce stable monodisperse particles with a significant incorporation yield. Thus, an incorporation yield as high as 53% and a grafting density corresponding to a surface area of 232 Ų/molecule have been obtained in a one-step process by using a methacrylate macromonomer. In an optimized two-step process resulting in monodisperse polymer particles, 80% incorporation yield with a very high grafting density (175 Ų/molecule) were reached. The particles with high grafting density (surface area lower than 600 Ų/molecule) could be transferred in water and exposed to a freeze–thaw cycle without massive flocculation, illustrating the efficiency of the steric stabilization. © 1997 John Wiley & Sons, Ltd.     

Miniemulsion polymerization of styrene using a pH-responsive cationic diblock macromonomer and its nonreactive diblock copolymer counterpart as stabilizers

The miniemulsion polymerization of styrene has been carried out using two pH-responsive cationic diblock macromonomers as reactive stabilizers. As a comparison, the analogous nonpolymerizable cationic diblock copolymer was also investigated. Each of these three stabilizers based on 2-(diethylaminoethyl)methacrylate and quaternized 2-(dimethylaminoethyl)methacrylate residues were prepared via oxyanionic polymerization and had relatively low polydispersities. It was found that all three copolymers were grafted to the polystyrene latex particles, as judged by X-ray photoelectron spectroscopy, aqueous electrophoresis and FTIR spectroscopy studies. Kinetics studies and colloidal characteristics indicated poorer stabilization properties of the partially quaternized diblock macromonomer and electron microscopy confirmed that the latexes invariably had relatively broad particle size distributions.     

Emulsion polymerization of styrene using polystyrene‐block‐poly(ethylene oxide) macromonomers as stabilizers

New diblock macromonomers were used as reactive emulsifiers in the emulsion polymerization of styrene. The nature of the reactive group, the molecular weight, the length of the poly(ethylene oxide) (PEO) block, and the molecular structure of the macromonomer were systematically investigated during this process by analyzing the evolution of the conversion and particle diameters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2819–2827, 2002     

Anionic polymerization of styrenic macromonomers of polyisoprene,polybutadiene, and polystyrene

Anionic polymerization and high‐vacuum techniques were used to prepare a series of well‐defined polyisoprene, polybutadiene, and polystyrene polymacromonomers. The procedure involved (1) the synthesis of styrenic macromonomers in benzene by the selective reaction of the corresponding macroanion with the chlorine of 4‐(chlorodimethylsilyl)styrene (CDMSS) and (2) the in situ anionic polymerization of the macromonomer without previous isolation. The synthesis of the macromonomers [polyisoprene macromonomer: 11 samples, weight‐average molecular weight (M_w) = 1000–18,000; polybutadiene macromonomer: 5 samples, M_w = 2000–4000; and polystyrene macromonomer: 2 samples, M_w = 1300 and 3600] was monitored by size exclusion chromatography with refractive index/ultraviolet detectors. Selectivity studies with CDMSS indicated that polybutadienyllithum had the highest selectivity, and polystryryllithium the lowest. From kinetic studies it was concluded that the polymerization half‐life times were longer but comparable to those of styrene, and they appeared to only slightly depend on the molecular weight of the macromonomer chain (at least for low degrees of polymerization of the polymacromonomer and for M_w < 7000 for the macromonomer side chain). Dependence on the polymerization degree of the polymacromonomer product was also observed. All the prepared polymacromonomers were characterized by size exclusion chromatography with refractive index, ultraviolet and two‐angle laser light scattering detectors, and NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1038–1048, 2005     

Macromonomers and coordination polymerization

The present work discusses the synthesis of well-defined comb-shaped polymers or graft copolymer structures based on coordination (co)polymerization of macromonomers. Polystyrene macromonomers with various polymerizable entities were synthesized first by induced deactivation reactions. The homopolymerization of these macromonomers in the presence of selected early or late transition metal catalysts was examined. Comb-shaped polymers could be obtained over a large range of DP values. The results were compared to those obtained by anionic homopolymerization. Some results on the copolymerization of these PS macromonomers with ethylene in the presence of VERSIPOL^TM type catalysts were presented.     

Halloysite nanotubes/polystyrene (HNTs/PS) nanocomposites via in situ bulk polymerization

Serials of halloysite nanotubes/polystyrene (HNTs/PS) nanocomposites with different contents of organo-modified halloysite nanotubes (organo-HNTs) were successfully prepared by the in situ bulk polymerization of styrene with the organo-HNTs as macromonomers. The percentage of grafting (PG%) of more than 230% was achieved, calculated from the results of the thermogravimetric analysis (TG). The TG results also showed that the thermal stabilities of the HNTs/PS nanocomposites prepared via the bulk polymerization were better than the pure polystyrene. And the maximum thermal degradation temperature of the nanocomposites increased with the increasing of the amount of the HNTs fillers added.     

Hyperbranched carbosilane oxazoline-macromonomers: polymerization and coupling to a trimesic acid core

Attachment of oxazoline-based hyperbranched macromonomers to a trimesic acid core affording trimers of the hyperbranched fragments as well as polymerization of the oxazoline groups is reported. Polymerization and copolymerization with 2-phenyl-1,3-oxazoline were investigated for two macromonomers (M _w = 1700 and 8 000, respectively), resulting in hyperbranched analogs of combburst polymers. Homopolymerization of the macromonomers yielded a degree of polymerization DP ≈ 15. Hyperbranched trimers and the polyethyleneimines with apolar hyperbranched carbosilane side-chains form superstructures in solution and in bulk.     

Controlled radical polymerization of styrene mediated by dithiobenzoates as reversible addition-fragmentation chain-transfer agents

The radical polymerization of styrene at 60 and 80°C mediated by benzyl dithiobenzoate and poly(styrene dithiobenzoate) as reversible addition-fragmentation chain-transfer agents has been studied. It has been shown that both agents are characterized by high chain-transfer constants and provide control over molecular-mass characteristics of polymerization products. The number-average molecular mass of polystyrene linearly grows with conversion, and the polymers are characterized by low values of polydispersity indexes. It has been demonstrated that the rate of polymerization significantly decreases with an increase in the concentration of reversible addition-fragmentation chain-transfer agents. This effect is typical of styrene polymerization mediated by dithiobenzoates. The possible reasons for this phenomenon are discussed.     

微乳液中苯乙烯聚合反应的研究

测定了十二烷基磺酸钠(As)/正丁醇/20%苯乙烯/水体系相平衡。用油溶性偶氮二异丁腈(AIBN)和水溶性过二硫酸钾(K~2S~2O~8)为引发剂,研究了油包水(W/O)、双连续(BC)和水包油(O/W)型微乳液介质中苯乙烯的聚合反应。得到了苯乙烯转化率和聚苯乙烯分子量与体系水含量之间的关系,讨论了微乳液结构对聚合作用的影响。并通过电镜观察了聚苯乙烯的形貌,求得了聚苯乙烯的粒径,同时用^1HNMR研究了苯乙烯在微乳液液滴中的增溶位置,分析了聚合作用的实验结果。     

Addition–fragmentation behavior of a capto-dative group-substituted acrylic ester in free-radical polymerization and reactivity of the derived macromonomers

Ethyl-2-(2-cyano-2-ethylthio)-ethyl-propenoate (ECEP) was synthesized and examined as free-radical addition–fragmentation chain transfer agent (AFCTA) in the bulk polymerization of methyl methacrylate (MMA) and styrene at various temperatures. A better chain transfer constant (C_tr) was observed for styrene than for MMA, projecting the potentiality of the compound as a better end-functionalizing agent for the former. In both cases, copolymerization of ECEP with the monomer predominated over fragmentation, the relative proportions of which were dependent on the monomer. The ECEP-terminated radical fragmented to an extent of 26% in the presence of MMA, whereas it was only 9.5% in the case of styrene. The relative extent of fragmentation and copolymerization was in conformation to the calculated reactivity ratios and chain transfer constants. Addition–fragmentation chain transfer resulted in the formation of methacrylic-functional macromonomers. The copolymerizability of the resultant macromonomer was found to depend on the nature of the backbone and on the comonomer. On copolymerizing with MMA, the terminal monomer moiety on polystyrene (PS)-based macromonomers preferred to undergo fragmentation, whereas that of the polymethyl methacrylate (PMMA)-based one copolymerized readily with styrene because of thermodynamic and kinetic factors. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2511–2524, 1999     

Synthesis of well-defined norbornenyl-terminated poly(alkyl methacrylate)s by group transfer polymerization and their grafting-through ring-opening metathesis polymerization

Highly efficient syntheses of poly(alkyl methacrylate)-based brush polymers were accomplished via a facile group transfer polymerization (GTP) and a consecutive grafting-through ring-opening metathesis polymerization. The GTP system, composed of the norbornenyl-methyl trimethylsilyl ketene acetal initiator and the N-(trimethylsilyl) bis(trifluoromethanesulfonyl)imide catalyst, rapidly and quantitatively generates norbornenyl-terminated poly(alkyl methacrylate) macromonomers with very narrow polydispersities (M_w/M_n < 1.10). The ring-opening metathesis polymerization of methacrylate macromonomers using Grubbs third generation catalyst successfully generated a group of methacrylate-based brush polymers, which assured the high quality of the macromonomers obtained from GTP.     

Radiation-induced grafting polymerization by the ionic mechanism

A technique of radiation-induced grafting under conditions of extreme drying of monomers has been developed. Under such conditions, radiation-induced grafting polymerization of isobutylene, -methylstyrene, vinyl-n-butyl ether, styrene, acrylonitrile, and 4-vinylpyridine by the ionic mechanism at room temperature has been performed. The grafted copolymers of polyethylene, Teflon and polyvinyl chloride with monomers polymerized only ionically (isobutylene, -methylstyrene, vinyl-n-butyl ether) have been obtained for the first time. The kinetics of the radiation-induced grafting of vinyl-n-butyl ether on to polyethylene have been studied; the ionic mechanism has been confirmed. It has been found that the rates of the radiation-induced ionic grafting of styrene, acrylonitrile, and 4-vinylpyridine are much greater than those for radical grafting. The highest grafting rates are observed for 4-vinylpyridine. The mechanism of radiation-induced ionic grafting polymerization has been discussed; generalized kinetic equations have been derived to account for the contributions from radical and ionic processes.     

Synthesis of well‐defined macromonomers by the combination of atom transfer radical polymerization and a click reaction

This article presents a new strategy for synthesizing a series of well‐defined macromonomers. Bromine‐terminated polystyrene and poly(t‐butyl acrylate) with predetermined molecular weights and narrow distributions were prepared through the atom transfer radical polymerization of styrene and t‐butyl acrylate initiated with ethyl 2‐bromoisobutyrate. Then, azido‐terminated polymers were obtained through the bromine substitution reaction with sodium azide. Catalyzed by CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine, the azido end group reacted with propargyl methacrylate via a 1,3‐dipolar cycloaddition reaction, and ω‐methacryloyl‐functionalized macromonomers were thus obtained. The end‐group transformation yields were rather high, as characterized by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra and ¹H NMR analysis. By this effective and facile approach, some novel macromonomers that otherwise are difficult to achieve, such as poly(ethylene oxide)‐block‐polystyrene, were easily prepared. Radical homopolymerizations of these macromonomers were performed, and a series of comb polymers were prepared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6103–6113, 2006     

Near-monodisperse poly(2-(methacryloyloxy)ethyl phosphorylcholine)-based macromonomers prepared by atom transfer radical polymerization and thiol-ene click chemistry: novel reactive steric stabilizers for aqueous emulsion polymerization

Poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) macromonomers have been prepared by the atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) using a bifunctional disulfide-based initiator. To attach a terminal polymerizable methacrylate group, the central disulfide bond was cleaved and the resulting thiols were conjugated to 3-(acryloyloxy)-2-hydroxypropyl methacrylate using tris(2-carboxyethyl)phosphine (TCEP) in water. Here TCEP serves as both the disulfide cleavage agent and also the catalyst for the subsequent Michael addition, which is highly selective for the acrylate group. The resulting methacrylate-terminated macromonomers were used as a reactive steric stabilizer for the aqueous emulsion polymerization of styrene, yielding near-monodisperse PMPC-stabilized polystyrene (PS) latexes of around 100-200 nm in diameter. As a comparison, the disulfide-containing PMPC homopolymer precursor and the intermediate thiol-functional PMPC homopolymer (PMPC-SH) were also evaluated as potential steric stabilizers. Interestingly, near-monodisperse latexes were also obtained in each case. These three sterically-stabilized latexes, prepared using either PMPC macromonomer, disulfide-based PMPC homopolymer, or PMPC-SH homopolymer as a reactive steric stabilizer, remained colloidally stable after both freeze-thaw experiments and the addition of an electrolyte, indicating that a coronal layer of PMPC chains prevented flocculation in each case. In contrast, both a charge-stabilized PS latex prepared in the absence of any steric stabilizer and a PS latex prepared in the presence of a nonfunctional PMPC homopolymer exhibited very poor colloidal stability when subjected to a freeze-thaw cycle or the addition of an electrolyte, as expected.