Styrenic butadiene block copolymers

Poly butylene (PB) Styrene-butadiene block copolymer... 

Styrene—butadiene block copolymers are made with anionic chain carriers, and low molecular weight PS is made by a cationic mechanism (110). Analytical standards are available for PS prepared by all four mechanisms (see Initiators). 

Anionic polymerization, if carried out properly, can be truly a living polymerization (160). Addition of a second monomer to polystyryl anion results in the formation of a block polymer with no detectable free PS. This technique is of considerable importance in the commercial preparation of styrene—butadiene block copolymers, which are used either alone or blended with PS as thermoplastics. 

Table 3. Properties of High Styrene—Butadiene Block Copolymers ...

Table 16.6 Some typical properties of styrene-butadiene block copolymer thermoplastics (Phillips K-Resins)...

In order to obtain the desired photoconductive characteristics, toughness and adherence to the substrate it is usual to incorporate additives such as electron acceptors, plasticisers and primers. A typical electron acceptor is 2,4,7-trinitro-fluoronone, plasticisers include benzyltetraline and phenanthrene whilst as primers styrene-butadiene block copolymers (30-35% styrene) and styrene-maleic anhydride copolymers (5-30% maleic anhydride) are of use. 

Styrene isoprene block copolymers Styrene butadiene block copolymers Styrene butadiene random copolymers Polyisobutylene Polysiloxanes... 

Figure 2 Influence of added styrene-butadiene block copolymer (BCP) on the particle size.

Experimentally, the stretching of block copolymer chains has been addressed in two ways by measuring L as a function of N, and by measuring the components of Rg of the block chains both parallel and perpendicular to the interface. The domain dimensions have been studied most extensively for styrene-isoprene and styrene-butadiene block copolymers X-ray and neutron scattering are the methods of choice. The predicted SSL scaling of L N2/3 has been reported for spheres, cylinders and lamellae [99,102-106], but not in all cases. For example, Bates et al. found N0 37 for styrene-butadiene spheres [100], and Hadziioannou and Skoulios observed N0 79 for styrene-isoprene lamellae [107], In the sphere case, kinetic limitations to equilibration were felt to be an important factor [100],... 

Even further advantages in transparency are obtained with special styrene-butadiene block copolymers consisting predominantly of styrene units (88, 89 ). Such products have been in use for a few years now for transparent packagings and other purposes numerous other applications are feasible. 

Stereon Styrene-butadiene block copolymer Firestone... 

Styrene-butadiene block copolymers Liquid crystals Poly(butylene terephthalate)... 

Chemical processes are far more varied and may involve either the formation of radicals or ions along a polymeric backbone. Both cationic processes3 as well as radical processes have been widely used for graft copolymerization of vinyl monomers onto various polymers. Radical graft copolymerization has been reported for many polymers including styrene-butadiene block copolymers, and acrylonitrile-butadiene-styrene terpolymer, ABS.3 7 9... 

In this paper graft copolymerization onto both polystyrene and styrene-butadiene block copolymer will be discussed. It will be shown that radical processes do not permit the addition of monomers onto polystyrene and that one must use anionic initiation in order... 

The vinyl monomers used in this study, methacrylic acid, methyl methacrylate, acrylic acid, methyl acrylate, and acrylonitrile, as well as the solvents, initiators, and polystyrene were supplied by the Aldrich Chemical Company. The styrene-butadiene block copolymer was supplied by Shell as Kraton D1102, known as SBS this contains approximately 75% butadiene and 25% styrene. 

Chemical Initiation of Graft Copolymerization onto Styrene-Butadiene Block Copolymer... 

It appeared attractive to extend the work on emulsification of liquid-liquid systems by BG copolymers to solid-liquid systems. As a first approach a model system was studied which comprises titanium dioxide dispersed in toluene with modified styrene-butadiene block copolymers as dispersants. These studies are reported here. 

The work was planned on the basis of a model of a dispersed solid particle onto which one type of sequences of a BG copolymer is adsorbed selectively while the other type sequence is dissolved in the dispersion medium. A sketch of this model is shown in Figure 1. The model is the result of applying the same arguments which had been advanced (12) in discussing the mechanism of stabilization of polymeric oil-in-oil emulsions by BG copolymers to the problem of stabilization of dispersions of solid particles in organic media. Previously, essentially the same arguments had led to the demonstration of micelle formation of styrene-butadiene block copolymers in organic media under certain conditions (15). 

The block copolymers were AB type styrene-butadiene block copolymers prepared by anionic polymerization. Unless specified differently in the text, a block copolymer of number average molecular weight 110,000 containing 70 wt % styrene and 30 wt % butadiene (S30B) was used. Samples of different composition used in one series of experiments had approximately the same molecular weight. 

In a three-necked flask equipped with stirrer, reflux condenser, and N2 inlet, 200 grams of a 1% solution of carboxylated styrene-butadiene block copolymer in o-dichlorobenzene and 2 grams TiOo were stirred at various temperatures for 3 hours. (Typical temperatures in this treatment were 110°, 150°, and 178°C.) After the heat treatment the Ti02 was isolated from the block copolymer solution by centrifuging for 1-2 hours at 2,000-2,200 rpm. After decanting the supernatant solution, the solid particles were washed with solvent and dried in vacuo for about 16 hours at 50°C. 

Following the guidelines established by Schechter s work, we dispersed titanium dioxide particles in 1% solutions of carboxylated styrene-butadiene block copolymers and stirred the dispersions at elevated temperatures in a nitrogen atmosphere. Typical data are shown in Table I. The dispersions (primary dispersions) in o-dichlorobenzene were quite stable. The titanium dioxide particles were isolated from these primary dispersions by centrifugation and were washed with toluene and finally with methanol. After drying in vacuo, samples of the block copolymer-titanium dioxide composites were submitted for carbon analysis. The... 

The two extremes on the styrene-butadiene block copolymer composition scale are homopolymers of butadiene or styrene, respectively. To test the usefulness of homopolymers as dispersants, polybutadiene (PB) was carboxylated by adding thioglycolic acid, and polystyrene (PS) having carboxylic groups was prepared by copolymerizing small amounts of acrylic acid (AA) into the styrene chain. Adsorption experiments with these carboxylated homopolymers are listed in Table V. In the first... 

This work has demonstrated that carboxylated styrene-butadiene block copolymers are excellent dispersants for titanium dioxide particles in toluene. Combining our results with carboxylated block copolymers and homopolymers and Schechters (18) results with fatty acids, we can... 

The effects of improved wettability, entropic repulsion, and sterical hindrance undoubtedly play a role in stabilizing dispersed solid particles by block or graft copolymers. However, since the dispersions of titanium dioxide in toluene stabilized by carboxylated styrene-butadiene block copolymers are so much more stable than dispersions stabilized by carboxylated homopolymers under otherwise identical conditions, we must assume that an additional factor comes into play when block copolymers are used. The model in Figure 1 is an attempt to explain this additional... 

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