Polybutadiene segment

A large volume usage of S—B—S-based compounds is ia footwear. Canvas footwear, such as sneakers and unit soles, can be made by injection mol ding. Frictional properties resemble those of conventionally vulcanised mbbers and are superior to those of the flexible thermoplastics, such as plasticized poly(vinyl chloride). The products remain flexible under cold conditions because of the good low temperature properties of the polybutadiene segment. 

Ba-Li and Ba-Mg-Al, which provide unique steric control of the trans-1,4/cis-l,4 ratio of polybutadiene segments ( 6). Although Alfin rubbers ( 7) contain trans contents at 70-757., their vinyl contents are much greater (20-257.) than is characteristic of the new rubbers reported here. 

The synthesis and characterization of a series of dendrigraft polymers based on polybutadiene segments was reported by Hempenius et al. [15], The synthesis begins with a linear-poly(butadiene) (PB) core obtained by the sec-butyllithium-initiated anionic polymerization of 1,3-butadiene in n-hexane, to give a microstructure containing approximately 6% 1,2-units (Scheme 3). The pendant vinyl moities are converted into electrophilic grafting sites by hydrosilylation with... 

The polybutadiene microstructure was examined by NMR spectroscopy (27). It was estimated that the polybutadiene segment contained about 7% 1,2-addition and 93% 1,4-addition. The relative amounts of cis and trans structures in the 1,4-adduct could not be resolved by this method. 

Tg of polystyrene = 100°C) linked together by rubbery polybutadiene segments (see Fig. 8.5). The polystyrene domains thus serve as effective cross-links and stabilize the structure against moderate stresses. They can be softened sufficiently at T > 100°C to enable molding and when cooled the rigid polystyrene domains reform. 

Subsequently the polybutadiene segment was functionalized by quantitatively converting the olefin double bonds of the 1,2-polybutadiene block via a hydroboration reaction to hydroxyl functions. In the last step various azobenzene-chromophores were attached via a polymeranalogous reaction. The synthesis and characterization as well as photophysical aspects of block copolymers based on an amorphous polystyrene block and a functionalized 1,2-polybutadiene block... 

A copolymer like SBS has properties of both polymers of which it is composed. In the case of SBS, the polystyrene segments give the product strength and durability, while the polybutadiene segments provide flexibility. The substance acts like natural rubber at room temperature, but becomes... 

I indicates compatible with polyisoprene segments B, compatible with polybutadiene segments EB, compatible with poly(ethylene-butylene) segments and S, compatible with polystyrene segments. 

The unusual physical properties of these copolymers stem from the inherent incompatibility of the S and B blocks. In the bulk material the two different blocks aggregate into separate domains leading to a dispersion of polystyrene domains (as the lesser component) in a continuous matrix of polybutadiene. At ordinary temperatures the polystyrene domains are rigid and immobilize the ends of the polybutadiene segments, in effect serving both as cross-links and filler particles. Thus the system has the strength of a filler-reinforced vulcanized amorphous elastomer. (See Table 18.1.) At temperatures above the glass-transition temperature of polystyrene (lOO C), the polystyrene domains are readily disrupted and the material may be melt-processed. The maximum service temperature of components fabricated from the copolymers is about 60°C. 

Increase in the length of the polybutadiene segment above a critical value does not appear to influence mechanical properties either when the S B ratio is held constant (Holden et af., 1%9) or when only the length of the centre block is varied (Bishop and Davidson, 1%9). This suggests that above a critical value the modulus is controlled by physical entanglements. 

Before the advent of NMR, qualitative information related to monomer sequence distribution was obtained primarily by the chemical method of Kolthoff. In this procedure, the copolymer is oxidatively degraded at the double bonds of the polybutadiene segments. Polystyrene blocks are not attacked and are isolated and determined... 

The union of polybutadiene segments with the rubber is accountable if the two polymers intermingled or if sulfur from the NR member entered into crossbridging reactions. A likely role for the methacrylic acid moiety would be in adsorbing on the steel substrate. 

Chlorinated rubber Polymeric blends containing polybutadiene segments Polybutadiene blends with ... 

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