Glass transition in the lower homologues of polyethyleneoxide

Experimental measurements of T_g for two series of lower homologues of polyethyleneoxide. differing in their end-groups, are discussed in terms of existing theories. Simple free-volume considerations predicting linear dependence of T_g on (molecular weight)^?1 are inadequate in systems with end-groups capable of specific interactions (hydrogen bonding). Thermodynamic arguments show that the true T_g of infinitely long PEO chain is 220 ± 5°K. Suitable modification of parameters of the Gibbs-DiMarzio equations to account for the dependence of the free volume fraction on the concentration of end-groups results in good fit of the experimental data for hydroxyl-terminated samples and correctly predicts T_g(∞). Analysis of the data for chlorine-substituted oligomers suggests the existence of specific intermolecular interactions in the latter, involving chlorine atoms.