Poly block copolymers spherulites

The synthesis and characterization of poly(hexamethylene sebacate-tiimethyl-siloxane) block copolymers, prepared by coupling Cl- or McjNH-terminated dimethylsiloxanes with OH-terminated poly(hexamethylene sebacate), have been studied. The copolymers containing 19—90% siloxane were characterized by n.m.r., viscosity, DSC and CPC. All the polymers were found to be crystalline. The copolymers containing <69% siloxane, when cast from solution or melts, indicated a reduction in spherulite size as the siloxane concentration increased, although only a small m.pt. depression was observed. All the copolymers have critical surface tensions similar to dimethylsiloxane homopolymers. Polycarbonate-Siloxane Copolymers.—A model has been proposed to predict the micromorphology and mechanical properties of block copolymers of bisphenol-A polycarbonate and poly(dimethylsiloxane). N.m.r. data upon 65 35 (wt%) copolymer of poly(dimethylsiloxane) and bisphenol-A polycarbonate, with block lengths of 20—100 monomer units, were found to be in agreement with the predictions of a spin-diffusion model. ... 

The influence of block length on the spherulite growth rate can be found in a set of urethane linked poly(ethylene oxide) block copolymers.(75) The copolymers consisted of uniform block length of either 34,45 or 90 repeating units with total molecular weights that varied from several thousand to 3-6 x 10. The 34 repeating unit blocks (M = 1500) always crystallized in extended form. In contrast the 90 repeating unit blocks (M = 3900) crystallized in a folded structure at all... 

Fig. 10.32 Plot of spherulite growth rate against weight average molecular weight, Mw, for poly(ethylene oxide) D and segmented block copolymers A, B, C. Block length in repeating units (A) 34 (B) 45 (C) 90. (From Friday and Booth (75))...

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