DYNAMICAL OBSERVATION OF STRUCTURAL TRANSITION OF POLYMERS USING AN X-RAY-DIFFRACTION SYSTEM WITH IMAGING PLATES .1. REVERSIBLE HELIX HELIXTRANSFORMATION OF POLY(VINYL CYCLOHEXANE)/

Two different crystalline forms were caused by drawing an unoriented i sotactic poly(vinylcyclohexane) film, Form I and Form II, depending on the drawing temperature. Form II was changed into Form I thermally an d Form I was converted into Form II by drawing. This reversible phase transformation was followed by dynamical X-ray observation. The X-ray measurements were carried out with an X-ray diffraction system with im aging plates, which was designed to record X-ray diffraction patterns over a series of short time spans while the samples were being heated or drawn. When samples were drawn at temperatures below about 110 degr ees C, Form I was produced, and Form II was formed at higher temperatu res. Through dynamical observations with the X-ray diffraction system, it was found that Form I occurred at an early stage of drawing indepe ndently of the drawing temperature and that the crystalline form was c hanged into Form II by further drawing at high temperatures, e.g., 130 degrees C. Form II was transformed into Form I by heat treatment at t emperatures above 248 degrees C. When the heat-treated sample of Form I was drawn at, e.g., 133 degrees C, the crystalline form was transfor med into Form II. Thus, the transformation of Form II into Form I occu rred thermally at temperatures above 248 degrees C and the inverse tra nsformation was induced by applying the stress at temperatures above a bout 110 degrees C.