Proton lineshape and proton spin-lattice relaxation, Tip, measurements were made on blends of bisphenol chloral polycarbonate and perdeutero poly(methyl methacrylate) (PMMA). The solution-cast blends are optically clear and display a single thermal glass transition temperature, T v as reported. The proton lineshape and proton relaxation data are used to follow the dynamics of the polycarbonate in the blend. The glass transition process is monitored by lineshape collapse as a function of temperature and the sub-glass transition process associated with rr flips of the phenylene group is monitored by the proton T~p values as a function of temperature. The glass transition as viewed from the polycarbonate remains similar in character to the behaviour observed in pure polycarbonate. Below T v the lineshape consists of a broadened Pake doublet and above Tg a narrow Lorentzian grows in on top of the Pake pattern. The bimodal behaviour and the growth of the narrow line with temperature can be described by the Vogel-Tamman-Fulcher equation with T O values which decrease with PMMA concentration. The proton T~p data show antiplasticization in the form of suppression of the ~ flip process as PMMA is added. In addition, a new minimum associated with the motion of the polycarbonate is observed at the temperature and time scale of the ester group rotation of the PMMA. This apparent coupling of the sub-Tg relaxation processes is related to the behaviour of polycarbonate upon addition of low-molecular-weight ester diluents. The level of antiplasticization and the amount of coupling is underestimated by a lattice model and an assumption of random mixing. On the very local scale of the n flip motion and at the higher concentrations of PMMA, there are apparently fewer PMMA-polycarbonate contacts than a random mixing assumption indicates.
Посилання на статтю:
Coupled relaxations in a blend of PMMA and a polycarbonate / H. de los Santos Jones, Y. Liu, P. T. Inglefield and A. A. Jones // Polymer. – 1994. – Vol 35. – P. 57-65.