SynopsisThe iduence of annealing processes on the thermal behavior of organic glasses in the glass-transition interval has been investigated and analyzed quantitatively. In detailed annealing studies of atactic polystyrene and Aroclor 5460, the absorption of thermal energy superposed on the increase in the specific heat at the glass transition, observed with suitably chosen heating rates, was followed by the differential thermal method. It is concluded that the absorption of thermal energy observed under these conditions parallels the extent of molecular relaxation that has taken place during the annealing period. It is not necessary to postulate a first-order process to account for the energy absorption. Moreover, such a postulate leads to severe conceptual difficulties regarding the development of crystallinity in crystallizable materials. The areas and the shapes of the endotherms are considered in terms of the original physical properties of the quenched glasses and the anticipated equilibrium properties. Relationships between the extent of energy absorption and timedependent processes such as volume relaxation are discussed.

In order to obtain information concerning the effect of molecular weight on the molecular mobility involved in the relaxation processes associated with the nonequilibrium thermodynamic state of glassy polymers. enthalpy-relaxation studies have been undertaken on glassy atactic polystyrenes of various molecular weights, ranging from 2.0X 10 3 to 811 X 10 3 • As was found in previous studies of enthalpy relaxation in organic glasses, the glass transition temperature Tg is the principal rate-determining factor. From a more detailed analysis of the data, however, it is evident that the relaxation processes at corresponding temperature intervals below Tg are a function of the molecular weight. The relaxation rate decreases somewhat with increasing molecular weight and approaches a limiting value at molecular weights in the vicinity of SOX 10 3 , the critical molecular-weight range in the molecular-weight dependence of glass transformation. For ArocJor 5460, a non polymeric material of lower molecular weight but having a Tg comparable to that of atactic polystyrene of molecular weight 2.0X 10 3 , a slightly faster relaxation rate was observed.

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In an attempt to formulate a general picture of the influence of diluents on the physical properties of polymers without invoking specific molecular characteristics of the diluents, a systematic study has been undertaken of the mobility of both the polymer and the diluent in polymer-diluent systems, and of the resulting effects on the physical properties of these systems. In dynamic mechanical and dielectric loss studies of polymer-diluent systems, the influence of the mobility of the diluent on the background loss as well as on the loss associated with subsidiary relaxation transitions has been followed as a function of temperature and correlated with the temperature dependence of the modulus, over temperature ranges which include the low-temperature y and {3 transitions. The temperature ranges of plasticization and antiplasticization have been established for bisphenol A polycarbonate and atactic polystyrene plasticized with various phthalates and chlorinated biphenyls and terphenyls, which were selected to have a wide range of glass transition temperatures and plasticizing efficiencies.