An investigation of the self‐aggregation process of syndiotactic poly(methyl methacrylate) in solution by using infrared spectra

Abstract

AbstractThe time dependence of self‐aggregation of syndiotactic (s) poly(methyl methacrylate) (PMMA) in dilute toluene or CCl4 solutions was investigated using infrared (IR) spectra measurements. The IR spectra were also recorded in s‐PMMA solutions where no self‐aggregation takes place (benzene, acetonitrile). It was found that the helix conformation with a large number of units per turn (near‐tt) in aggregated s‐PMMA is formed in parallel with intermolecular interactions of ester groups of s‐sequences. The connection between the fraction of s‐sequences in the helix conformation determined for unaggregated s‐PMMA in various solvents using IR spectra and the ability of s‐PMMA to form self‐aggregates (double helix) in a certain solvent is discussed. Intersegmental contacts which occur in s‐PMMA in CCl4, i.e. in a thermodynamically poor solvent, lead to a decrease in the equilibrium aggregated fraction, to the slowing‐down of the aggregation process and to the decomposition of the majority of aggregated structures during evaporation of the solvent; their effect is similar to that of chemical crosslinking.