Mechanical and thermal induced chain conformational transformations in syndiotactic polypropylene (sPP)

Stretching a stacked sPP lamellar morphology at room temperature leads to a mechanical induced transformation from the (t(2)g(2))(2) (helical) into th e (tttt) (zigzag) chain conformation of the polymer. The so prepared sample s exhibit after annealing above 80 degreesC a thermal induced retransformat ion into the cell I and cell III crystal structure of the helical chain con formation. The mechanical induced chain conformational transformation as we ll as the thermal induced retransformation was studied by means of transmis sion electron microscopy and electron diffraction. (C) 2001 Kluwer Academic Publishers.