Pressure-induced In-glass structural transformation in the amorphous polymer poly(methylmethacrylate)

Inelastic x-ray scattering data have been collected in the polymeric glass 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 behavior 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 length scales shorter than L-0 approximate to 1 nm.