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Engineering, Vim Diotisalvi 2,561 00 h a , Italy synopsis The dielectric behavior of amine-terminated butadiene acrylonitriie rubber/DGEBA epoxy resin blenda of ditrerent formulations has been studied in the temperature range -12&16O0C at 10 IJIZ. h indicatd by the constancy of the giasa transition temvatures of the two components, the degree of segmeutal mixing wan vary low or nil. irrespective of cure schedulea The h d t y of the a-relaxation of the rubber wan much leee than that predicted by the Simple series model (lower bound). Thia hm been attributed to incomplete phase separation at gelation. Meaeurementa cnrried out with a nonreactive rubber support this conclusion. Part of the rubber remain6 mol&ly dieperaed within the gh?ay matrix, thus contributing to the modification of the maehrnical p r o m of epoxy resina brought about by reactive rubbers.

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Previous papers from this laboratory') have shown that poly(4-biphenylyl acrylate)" (2a) is characterized by a smectic-like structure in the solid state and displays properties usually considered typical of highly crystalline polymers. It has also been demonstrated that the long-range smectic organization of the macromolecules of 2a takes place independent of the stereoregularity, although the smecticisotropic transition (which, for this polymer, presents all the features of a melting phenomenon) is observed at lower temperatures for isotactic samples (ca. 220 "C) than for atactic ones (ca. 270°C).Since it is known that biphenyl derivatives containing only one, reasonably small, para-substituent are not mesogenic, it is understandable that 4-biphenylyl acrylate

The dynamic mechanical properties of four aromatic polyesters were measured at temperatures in the 78–540°K region at 103–104 cps. The polymers studied were: poly(1,3 phenylene isophthalate), poly(1,4 phenylene terephthalate), poly(4,4′ diphenylene isophthalate), and poly(4,4′ diphenylene terephthalate). All four polymers had β loss peaks at about 280°K. Distinct β* mechanical processes were found for the two terephthalate esters. Broad‐line nuclear magnetic resonance measurements were carried out in the 150–440°K temperature range on the four polyesters mentioned above in addition to poly(4,4′ diphenylene 4,4′ biphenyl dicarboxylate). A change in NMR second moment takes place in the 190–330°K region, the magnitude of which is dependent on the polymer structure. The results are compared with those found for a series of aromatic polyamides and are discussed in terms of possible motional processes.