PRESSURE-INDUCED IN-GLASS STRUCTURAL TRANSFORMATION IN THE AMORPHOUS POLYMER POLY(METHYLMETHACRYLATE)

Inelastic x-ray scattering data have been collected in the polymeric g lass poly(methylmethacrylate) in the P = 0-4.5 kbar and Q = 1-15 nm(-1 ) pressure and momentum transfer regions. At P = P-0 approximate to 1. 6 kbar, the elastic intensity at Q values smaller than approximate to 5 nm(-1) and the sound excitation energy at Q = 2 nm(-1) show a cusp b ehavior in their pressure dependences. These findings could indicate a pressure-induced structural transition in this polymeric glass, which does not affect, however,interparticle static correlations with lengt h scales shorter than L-0 approximate to 1 nm.