PHENYLENE MOTION IN POLYCARBONATE - INFLUENCE OF TENSILE-STRESS AND CHEMICAL MODIFICATION

Deuteron NMR was utilized to study phenylene group motions in glassy p olycarbonate (PC) as a function of tensile stress and chemical modific ation. A special stretching device was constructed allowing the applic ation of forces up to 1500 N during the measurement. While cold drawin g of PC effects motional restrictions equivalent to a temperature shif t of 10 K, a reversible strain near the yield point enhances the ring dynamics slightly. Methyl group substitution at the ortho positions gi ves rise to even more constraints, shifting the onset of fast ring fli ps by about 180 K.