Chain stiffness, polymer glass formation

The chain stiffness inflnences the height of the glass-rnbber transition temperatnre (and of the melting point), bnt not the stiffness of the polymer below Tg (in the glassy state). Extremely stiff chains show the effect of the formation of LCP s (liqnid-crystalline polymers), by which very high stiffness is reached, bnt only in the direction of the orientation. 

The onset of glass formation in a polymer melt is associated with the development of orientational correlations that arise from chain stiffness. At the temperature Ta, there is a balance between the energetic cost of chain bending and the increased chain entropy, and below this temperature orientational correlations are appreciable while the melt still remains a fluid. Such a compensation temperature has been anticipated based on a field theoretic description of semiflexible polymers by Bascle et al. [120]. The temperature 7a is important for describing liquid dynamics since the orientational correlations (and dynamic fluid heterogeneities associated with these correlations) should alter the polymer dynamics for T < Ta from the behavior at higher... 

E is also independent of chain stiffness and chain interactions, these factors play a role in the height of the glass-rubber transition temperature and the melting point. A stiffer chain, therefore, does not result in a stiffer polymer except, sometimes, in an indirect way, namely when stiff chains enable the formation of high orientation, such as in liquid-crystalline polymers (see 4.6). 

---