Isoprene graft copolymers

Table 9.4 Characteristics of arborescent polystyrene substrates used in the preparation of isoprene graft copolymers (adapted from ref. 16)...

The microphase separation of (styrene-g-isoprene) graft copolymers with a large number of grafted chains was investigated by Price and coworkers [349]. Those films were cast from benzene, a nonselective solvent, and a relatively well-defined microphase separated morphology was observed, but the structure was less regular compared with dispersions in hexane on carbon films [350]. In the... 

Poly(methyl methacrylate) Hexane Isobutylene-co-isoprene graft copolymer 73... 

A combination of TEMPO living free radical (LFRP) and anionic polymerization was used for the synthesis of block-graft, block-brush, and graft-block-graft copolymers of styrene and isoprene [201]. The block-graft copolymers were synthesized by preparing a PS-fo-poly(styrene-co-p-chloromethylstyrene) by LFRP [Scheme 110 (1)], and the subsequent re-... 

A graft copolymer, comprising a polyisoprene backbone grafted with isoprene and acrylonitrile units in an unspecified arrangement that contains 85 mol % of isoprene units and 15 mol % of acrylonitrile units polyisoprene-grq/Z -poly(isoprene-co-acrylonitrile) (0.85 0.15 x)... 

Non-aqueous (or-oil-in-oil) emulsions, where the phases are two immiscible organic liquids, have received relatively little attention in the literature. Riess et al. [116-119] have studied the stabilisation of waterless systems with block and graft copolymers, where one of the liquids is a good solvent for one of the blocks and a non-solvent for the other, and vice versa. Thus, poly(styrene-b-methylmethacrylate) copolymers could emulsify acetonitrile/cyclohexane mixtures, and poly(styrene-b-isoprene) was effective for DMF/hexane systems [116]. These, however, are not HIPE systems. 

Ober and coworkers117 have grafted siloxanes onto a styrene-isoprene block copolymer via hydrosilylation of the pendant vinyl groups of the diene block with pentamethyldis-iloxane (30) (equation 12). 

Natural rubber, graft copolymers of natural rubber with acrylic or methacrylic acid esters of mono-functional CiC4 alcohols butadiene and isoprene polymers polymers... 

Isobutylene was copolymerized with methylbenzenes by cationic methods to give products containing 1-2% of the comonomer. Attachment of polyplvalolactone grafts was accomplished using the same chemistry as that for Isoprene block-graft copolymers. 

The graft copolymers could be spun Into fibers at 250-260 0. These fibers, after orientation by drawing, were not as strong as fibers from the Isoprene compositions, but they had tenacities In the 0.4-0.5 g/d range. Stress-decay on these fibers, determined the same way as for those described In Figure 2, was only 11% for the first hour with a further loss of only 5% In the next 22 hours. 

The radical-catalyzed copolymerization of isoprene and maleic anhydride in the presence of polystyrene gives the corresponding alternating copolymer graft copolymer (Table IX). Similar results are obtained with other dienes and appropriate substrate polymers. 

Using anionic polymerization techniques poly[styrene-b-(4-vinyl phenyl-dimethylsiloxane-g-isoprene)), P[S-fr-(VS-,g-I)] block-graft copolymer was prepared [66,67] according to the following reaction sequence (Scheme 20). 

Vinylmagnesiumchloride was also used to produce PMMA macromonomers [115]. Using similar techniques, several macromonomers have been prepared by the anionic polymerization of ethylene oxide, butadiene, isoprene, 2-vinylpyri-dine, a-methylstyrene, vinylpyrrolidone etc. Table 2 summarizes the data reported in the literature concerning the synthesis of graft copolymers with anionically prepared macromonomers. 

Tuzar and coworkers [305] studied the micellization of a poly(isoprene-g-styrene) copolymer in solvent mixtures selective either for the backbone or for the grafts. Their results from static and dynamic light scattering and sedimentation velocity experiments favor the closed association model for the description of the unimers-micelles equilibrium. The graft copolymer micelles were found to have lower aggregation numbers and to be less compact than the micelles formed by linear diblocks. 

For the case of homopolyisoprene/styrene-isoprene copolymer mixtures [364], it was shown that the miscibility increases in the order four-arm star-block < triblock < diblock. Increased incompatibility was observed in the pair poly(isoprene-g-styrene)/polyisoprene [365] even when the molecular weight of the homopolymer was much lower than the PI segment length between junction points of the graft copolymers. 

The film preparation technique has been described elsewhere (3). It should be noted that films are observed directly and by phase contrast microscopy. Thus, we can compare the emulsifying effect of different styrene-isoprene copolymers (random, block, and graft copolymers) of the same overall composition (40 wt % PS, 60 wt % PI) and practically the same molecular weight (Mn — 50,000) in a given PS-PI blend, where Mn of PS is 45,000 and Mn of PI is 25,000. The appearance of the films obtained with different blend compositions is depicted in Figure 1. Hazy or opaque areas are striped. From Figure 1, it appears that random copolymers always cause hazy films which means... 

Furthermore, in an attempt to increase the strength of PHB, the homopolymer was immersed in isoprene solution (using heptane as a solvent) and irradiated with UV radiation. As a result, grafted copolymers showing much better ductility and strength than pure PHB were produced (Jiang and Hu 2001). 

The possibility of producing latex particles whose molecular architecture seems to be thermodynamically unfavourable by combining free-radical and emulsion polymerisation mechanistic knowledge is discnssed. Examples of unusual new materials created using this approach are illustrated. They include extensively grafted copolymers based on isoprene and dimethylaminoethyl methacrylate, spatially-homogeneous copolymers and composite aniline-styrene polymer colloids. 29 refs. AUSTRALIA... 

Model block-double graft copolymers and terpolymers of styrene, butadiene, and isoprene of the type poly[S-6-(PBd-l,2-g-X)] were recently synthesized (28), where X is either S, Bd, I, or S-6-I by a combination of anionic polymerization, hydrosilylation, and chlorosilane linking chemistry. The backbone P(S-6-l,2Bd) was synthesized by sequential addition of the monomers. The vinyl groups of the PBd-1,2 block were hydrosilylated with HSiCH3Cl2 and used for the attachment... 

Fig. 11. Synthesis of exact graft copolymers of styrene and isoprene.

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