Polystyrenes methacrylate-terminated

The GPC traces that were taken during the course of a copolymerization reaction of vinyl chloride and an 11,000 MW polystyrene methacrylate-terminated macromonomer are shown in Figure... 

The best test for functionality would be in a copolymerization study. A polystyrene with a methacrylate terminal functional group was prepared. A review of relative reactivity ratios indicated that vinyl chloride reacts very rapidly with methacrylates. Therefore, a copolymerization of the polystyrene terminated with a methacrylate functional group in vinyl chloride would be a good test case, and one should observe the disappearance of the MACROMER if the reaction is followed by using GPC analysis. 

Apart from the nse of a polymerizable alkoxysilane, silica/polystyrene composite particles with a raspberry-like morphology have been elaborated in the presence of a methyl methacrylate-terminated polyethylene glycol macromonomer. This macromonomer is mainly hydrophilic due to the presence of ethylene oxide repeat units (n 23), which are able to form hydrogen bonds with the silanol groups of silica and adsorb on its snrface. In addition, this molecnle contains a methacrylate functionality able to copoljmerize with styrene thus... 

PSLi) as shown in Eq. 41. This well-characterized methacrylate-terminated polystyrene (PS) has been copolymerized with various vinyl monomers, using free radical initiators, to form comb-type graft copolymers as shown in Eq. 

Yamasita et al. utilized the chain transfer reaction in the radical polymerization of styrene to synthesize methacrylate terminated polystyrene. 

In general it is found that both types of termination take place in any particular system but to different extents. For instance it is found that polystyrene terminates principally by combination whereas poly(methyl methacrylate) terminates almost exclusively by disproportionation at high temperatures and by both mechanisms at lower temperatures. 

Comb-shaped polymers are derived from polymerizing or copolymerizing macromonomers. Macromonomers can be synthesized by a variety of synthetic techniques. Asami and co-workers prepared a methacrylate-terminated polystyrene by anionic polymerization. The macromonomer was then polymerized using GTP [41] to yield an oligomer with a polystyrene backbone and PMMA grafts. McGrath and co-workers prepared a poly(dimethyl siloxane) macromonomer end-capped with a methacrylate group. This macromonomer was polymerized by GTP to yield a comb-shaped polymer with PDMS branches [19]. 

Combination and disproportionation are competitive processes and do not occur to the same extent for all polymers. For example, at 60°C termination is virtually 100% by combination for polyacrylonitrile and 100% by disproportionation for poly (vinyl acetate). For polystyrene and poly (methyl methacrylate), both reactions contribute to termination, although each in different proportions. Each of the rate constants for termination individually follows the Arrhenius equation, so the relative amounts of termination by the two modes is given by... 

Formation of block polymers is not limited to hydrocarbon monomers only. For example, living polystyrene initiates polymerization of methyl methacrylate and a block polymer of polystyrene and of polymethyl methacrylate results.34 However, methyl methacrylate represents a class of monomers which may be named a suicide monomer. Its polymerization can be initiated by carbanions or by an electron transfer process, the propagation reaction is rapid but eventually termination takes place. Presumably, the reactive carbanion interacts with the methyl group of the ester according to the following reaction... 

In contrast to the behaviour of living polystyrene, the slow termination of living polymethyl methacrylate is least pronounced inDME, more in THF, and is most perturbing in THP 55). It seems that in THF the termination is faster for Na+ than for Cs +. ... 

Both termination mechanisms have been shown to occur experimentally, the method being to examine the polymer molecules formed for fragments of initiator. In such a way polystyrene has been found to terminate mainly by combination and poly(methyl methacrylate) entirely by disproportionation at temperatures above 60 °C. 

II. B polyethylene glycol, ethylene oxide, polystyrene, diisocyanates (urethanes), polyvinylchloride, chloroprene, THF, diglycolide, dilac-tide, <5-valerolactone, substituted e-caprolactones, 4-vinyl anisole, styrene, methyl methacrylate, and vinyl acetate. In addition to these species, many copolymers have been prepared from oligomers of PCL. In particular, a variety of polyester-urethanes have been synthesized from hydroxy-terminated PCL, some of which have achieved commercial status (9). Graft copolymers with acrylic acid, acrylonitrile, and styrene have been prepared using PCL as the backbone polymer (60). 

The ultrasonic irradiation of a mixture of polymers also produces block copolymers, when chain fragments combine with each other and cross termination is predominant in the case of a benzene solution of polymethyl methacrylate and polystyrene, Henglein showed that 33% of the radicals produced combine (101). 

Terminal air oxidation of polystyrene has recently been carried out by degradation of polystyrene in the presence of azo-bis-isobutyronitiile and air oxygen the polystyrene dihydroperoxide can initiate the polymerization of methyl methacrylate and acrylonitrile [193, 194). The yield of homopolymer is very low, indicating an exceptional difference of efficiency between the macroradical and the OH radical. 

An equimolecular amount of tertbutyl oxide and tert-butyl peroxide radicals are formed, which can initiate the polymerization of styrene consequently, considering that the chain termination reaction of polystyrene proceeds by coupling, it results that most of the polystyrene molecules will contain one or two terminal peroxide groups. These have been used for a second step polymerization, e.g. of methyl methacrylate. In this case also, it seems that the macro end radical should be much more efficient for initiating polymerization than the small tert-butyl oxide radical (47). The styrene content of the block copolymer was about 35%. 

Another interesting example belonging to the same general principle was described by Graham (56). On one hand he prepared an amine terminated polystyrene (sodium amide initiation in liquid ammonia) and showed that it contained only one terminal primary amine group per polymer chain. On the other hand copolymers were prepared by free-radical initiated solution copolymerization of small amounts of /S-iso-cyanatoethyl methacrylate with several other monomers as methyl, butyl and lauryl methacrylates, acrylonitrile and styrene. 

Graham, R. K. Preparation of graft copolymers by the reaction of primary amine-terminated polystyrene with copolymers containing /3-isocyanatoethyl methacrylate. J. Polymer Sci. 24, 367 (1957). 

The case of "living polystyrene and methyl methacrylate is somewhat similar. It was shown, as should be expected, that "living polymethyl methacrylate does not initiate styrene polymerization (70), i. e. methyl-methacrylate is a terminator for the latter polymerization, although its addition to living poly-styrene initiates its polymerization. Hence, one may produce a block polymer by adding methyl methacrylate to "living polystyrene but not vice-versa (9,10). 

Carboxylated polyesters were prepared by extending hydroxyl-terminated polyester segments with dianhydrides. Carboxylated polyesters which were soluble in common lacquer solvents were effective in improving the adhesion of coatings on a variety of substrates when 1-10% was blended with cellulose acetate butyrate, poly(vinyl chloride), poly(methyl methacrylate), polystyrene, bisphenol polycarbonates, and other soluble polymers. 

Finally, some termination step occurs, two of which are shown in the scheme. The most common is coupling, in which two radicals combine, leading to one larger macromolecule. Polystyrene radicals typically undergo termination by coupling. Another reaction that is common with some monomers (e.g., methyl methacrylate) is called disproportionation in which on the reaction of two radicals, a hydrogen atom transfers from one species to the other. 

The reactions are just like the ones that produce polystyrene. First, a molecule of methyl methacrylate reacts with a polystyryl anion to form a methyl methacrylate anion (crossover). Then the methyl methacrylate block grows in a series of propagation steps, followed by the addition of methanol to effect termination as before. We can draw the structure for the block copolymer, named poly styrene-6/oe -methyl methacrylate) as is shown here. 

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