Influence of a functional group situated along the n-alkyl side chain on the γ-transition of comb-like polymers: Poly[ N-(5-n-alkyloxycarbonyl-n-pentyl)maleimides)—a comparative study

Abstract

The γ-transition temperature T γ has been studied by differential thermal analysis in a series of 11 poly[ N-(5-n-alkyloxycarbonyl-n-pentyl)maleimides] (PEMIS 5). Side chains containing even numbers of carbon from ethyl to n-docosyl were used. The γ-transition temperature decreases continuously as the number of methylene groups in the n-alkyl side chain increases. A method for estimating the T γ of (CH 2) polyethylene (PE) was employed using γ-transition temperatures of an amorphous series of comb-like polymers with long n-alkyl side chains. The relationships between T γ and chemical structures of comb-like polymers are discussed in terms of the number of participating groups within the movements of the n-alkyl side chain of the polymers. A comparative study has been made with some other comb-like polymers having oxy-n-alkyl moieties in the side chain, such as poly[ N-(10-n-alkyloxycarbonyl-n-decyl)maleimides] (PEMIS 10), poly(n-alkylmethacrylates) (PAMAS) and poly(n-alkyl vinyl ethers) (PAVES). This internal motion is presumably made possible by the partial rotation of the various groups which link the side chains to the main chain of the comb-like polymers: for PAVES the link is the oxy-n-alkyl moiety; for PAMAS the link is a carboxy group; and for PEMIS 5 and PEMIS 10 the link is a carboxy-n-alkyl group. It is concluded that this transition is comb-like polymers with functional groups situated along the n-alkyl side chain is attributed to internal motions within the outer part of the n-alkyl side chain. Interactions with the main chain or with the neighbouring n-alkyl side chains belonging to adjacent structural units are therefore not important.