Configurational partition functions and entropies for polyoxide chains having the repeat unit [(CH2)y–O–]

Rotational isomeric state theory is used to calculate values of the configurational partition function z and entropy S for polyoxide chains having the repeat unit [(CH2)y–O–]. The values of z are at least qualitatively useful in interpreting the effect of the number y of methylene groups in the repeat unit on the characteristic ratio 〈r2〉0/nl2 of the unperturbed dimensions relative to the number of skeletal bonds and the average square of their lengths. For example, z has a maximum (corresponding to maximum ’’equilibrium flexibility’’ of the chain) at y=3, where 〈r2〉0/nl2 is at a minimum. The configurational entropy S, however, shows a very poor correlation with either z or 〈r2〉0/nl2; similar difficulties have been noted in comparisons between some polypeptide chains, and between some polysaccharide chains.