Crystallization induced microphase separation

Zhu et al. showed that polypropylene crystallization is not induced until the isotactic block length exceeds a critical number of sequential isotactic propylene units, iso crit- Based on the Doi-Edwards theory for isotropic-to-nematic transitions of liquid crystals " and the proposal of Imai et al. " that a parallel order of polymer segments induces a spinodal composition-type microphase separation prior to crystallization, they calculated the persistence length L of the helical... 

The infrared and mechanical data all indicate that in the case of DBDI based PU, the conformational mobility of the two benzene rings around the ethylene bridge induces a specific stress - strain and stress relaxation behaviour in PU, both in tensile and compression experiments. Experimental DSC, IR diehroism, and X-ray diffraction techniques were employed to study the influence of the compatibility of PU microphases (hard and soft blocks) on the PU physical/ mechanical properties, by the study of the structural modifications which appear during mechanical stresses i.e. phase separation, crystallization and orientation phenomena. The morphological study on such polymers have proved a high tendency of crystallisation and hard segment blocks phase separations [2,4]. ... 

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