A series of enthalpy relaxation measurements were carried out for the pure polymers polystyrene (PS) and poly(oxy-2,6-dimethy¡-1,4-phenylene) (PPE) and for homogeneous blends thereof. The data were analyzed using Moynihan's four-parameter approach.4 For the pure components the best fit parameter values for the simple cooling/heating experiments differ somewhat from those for the annealing experiments at least partly due to thermal lag. The amount of enthalpy relaxation during annealing of the blends turned out to be considerably lower than for the corresponding homopolymers. Moreover, the annealing experiments on the blends could not be fit satisfactorily with the Moynihan model. The first observation agrees with a similar result found by Cowie and Ferguson17 for blends of PS and poly (vinyl methyl ether). Since this effect is not present for a number of polymer blends involving polymers with comparable glass transition temperatures, it seems to be related to the large difference in glass transition temperatures of the blend components. The presence of concentration fluctuations, with a corresponding range of T¡ values, is the most obvious explanation for both observations.
Macromoleculesrange of dielectric constants (3.5-35) used here. Since the calculated quantities show the same qualitative trends throughout this range of dielectric constants, we would expect our conclusions to hold when a more sophisticated electrostatic potential is employed.Added in Proof If bolaform electrolytes were studied a t a temperature different from the 0 temperature for polymethylene, an additional perturbation would arise from the excluded-volume effect. Since the interaction of the charged chain ends becomes negligible as n becomes infinite, the expansion arising from the excluded-volume effect would dominate for large bolaform electrolytes. Acknowledgment.ABSTRACT: Flory's equation-of-state theory is applied to a PVF2/it-PEMA system with a lower critical solution temperature. A comparison is made between the observed irregular asymmetric cloud point curve and the calculated spinodals. The agreement is good for values of the mixing parameters, which are in accordance with melting point depression data.ABSTRACT: A review of the preparation and structure/property relationships of various polyquinolines is preaented. The monomer and polymer syntheses and the kinetics, solution properties, morphology, thermal analyses, and cross-linking reactions of polyquinolines are discussed.
This study completes the investigation of the phase behaviour of polymer blends involving styrene (S), ortho-ftuoro styrene IoFS) and para-fluoro styrene (pFS). As before, due to the proximity of the glass transition temperatures of most blends investigated, the miscibility or immiscibility is established using the alternative thermal analysis method based on enthalpy recovery of samples annealed in the glassy state. In most respects the phase behaviour is similar to that of the corresponding chlorinated systems. The value of the Flory-Huggins parameter ~s,ovs is much smaller than ZS,pFS. However, the latter is approximately the same as XoFS,pFS and, as a consequence, a miscibility window as found in the system PS/P (oC1S-co-pC1S) is only present in PS/P(oFS-co-pFS) blends for rather low molecular weights.
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