The molecular weight dependence for the chain conformation of diphilic copolymers

Abstract

Viscosity measurements have been made for copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) in mixtures of the selective solvents ethylene dichloride (EDC) and N,N′-dimethyl formamide (DMF). The dependence of [η] on DP v and copolymer composition ( a) has been established. The data for samples quite different in DP v and a can be represented by a single master curve using reduced co-ordinates [η] PMMA − [η]CP −c/a DP ̄ v a where c is the volume % DMF in the solvent. This means that the relative coil contraction due to intramolecular hydrogen bonds is proportional to the absolute MAA content in the copolymer chains. The location of the master curve depends only on the method of preparation for the copolymer (partial random hydrolysis of PMMA or direct radical copolymerization of monomers). This can be explained by the different types of distribution of the MAA units along copolymer chains. Analysis of the data suggests that, for the polymer series with fixed MAA content in selective solvents, it is impossible to obtain the Mark-Kuhn-Houwink type equations for [η] CP − M ̄ v . The proposed method for tracing a master curve allows formulation of equations for the [η] CP − M ̄ v relationships for MMA-MAA copolymers having a particular molar composition.