ORIENTATIONAL DISTRIBUTION IN STRETCHED POLY(METHYL METHACRYLATE) FROM C-13 NMR-SPECTROSCOPY

The orientational distribution in drawn amorphous poly(methyl methacrylate) extended to the ratio lambda = 3 was measured with one- and two-dimensional carbon-13 NMR spectroscopy. In the analysis, signals from the carboxyl carbons were used as a probe of the orientational distribution. The angular-dependent line shapes were analyzed to determine the orientational distribution function and the order parameter [P2]. The analysis yielded [P2] = 0,21. A two-dimensional rotor-synchronized magic angle spinning experiment was also used to measure the order parameter. The obtained value [P2] = 0,22 is in excellent agreement with the 1D result. The experimental results obtained for [P2] are compared to those proposed by the pseudo-affine model. [P2] predicted by theory is reduced due to conformational disorder present in the glassy state.