Local and cooperative motions at the glass transition of polystyrene : information from one- and two-dimensional NMR as compared with other techniques

摘要: 2 H NMR results are analyzed in terms of different reorientation models applied to the C− bond directions chain-deuterated polystyrene. The dominant mechanism is rotational diffusion by small angular steps where mean correlation time agress with relaxation times from dynamic mechanical experiments over a range 10 decades. methods employed fopr study chain motion compared. It shown that motions or well-defined C−H which probed tightly coupled cooperative α-process. moreover, also monitor separation fast β-process slow α-process when approaching T g colling down melt