Glass Transitions of Block Copolymers

The chemical stracture of block copolymers is given by the number of blocks, their sequence, and their length, as discussed in Sect. 3.4.1 and Fig. 1.19. A diblock copolymer poly(styrene-/ /ocl -a-methylstyrene) (S/MS) of molar masses 312,000, and 354,500 Da, for example, has the following approximate chemical stmcture  

Enthalpy Relaxation of Block Copolymers of Styrene with a- Methylstyrene 

All polymers have molar masses above 500,000 Da, compare to Fig. 7.78 

AT = Tg - T or T -Tg, where T and T are the beginning and the end of the glass transition regions, respectively, defined in Fig. 2.117. The value of AT increases sharply with the surface area of the microphase. For the transition of the phases surrounded by a surface that connects to a phase of lower glass transition, the glass transition starts at lower temperature (spheres of polystyrene in air and MS surrounded 

Comparing the block copolymers of high molar mass to solutions of the same polymers described, as in Sect. 7.3.2, one expects solubility at lower block lengths. Indeed, Fig. 7.81 shows that this is so, and that Barton s equation describes the data for the bock copolymer solutions (mn number R = 0), blocky copolymers (indicated run numbers R = 6 and 30), as well as random copolymers (o) [36]. 

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