Phase transition phenomena in polymers

The variation in the o-Ps intensity (I3) with temperature is more complex than that of the o-Ps lifetime. A number of authors have reported that the I3 values increases below the Tg of the polymers and then flattens out above the Tg [25, 42, 27] This has lead to the suggestion that in the melt (above Tg) the increase in total free volume with temperature involves the growth in hole size rather than an increase in the number of holes. On the other hand since t3 increases only slightly below Tg while I3 increases significantly, it has been suggested that the variation in free volume below Tg primarily results from hole formation [25]. 

A number of discontinuities in the r3-temperature and I3-temperature curves have been observed for polymers at temperatures well below the Tg of 

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Although morphologies from thermally-induced phase transitions in polymer-polymer systems were not examined heretofore, van Aarsten (6), Smolders (7), and van Emmerik et al. (8,9) investigated phase transition phenomena in polymer-solvent systems. Their findings indicate that both nucleation and growth and spinodal decomposition occur. Further, their work supports the assertion that the key to understanding the nature of the phase transition lies in the thermodynamics of the system. 

Licjuid-liquid phase transition phenomena in polymer-polymer systems were studied. Evidence is presented which suggests that spinodal decomposition occurs in this system. It was not possible to prove that nucleation and growth also occurred for the dispersed-phase structure because of the rapid rate of phase equilibration. 

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