Characterization of PMMA-b-PDMAEMA aggregates in aqueous solutions
Abstract
Diblock amphiphilic copolymers form aggregates in some solvents. Such aggregates exhibit different morphologies, depending mainly on the polar/apolar block ratios. Aggregation of copolymers with polar block excess leads to micelle-like aggregates, known as polymeric micelles, which can be used as vehicles for drug and gene delivery, water decontamination, and catalysis. Here, we synthesized by RAFT polymerization three different polymers namely [dimethyl 2-(aminoethyl) methacrylate] (PDMAEMA), poly (methyl methacrylate) (PMMA) copolymers, and PDMAEMA-block-PMMA and characterized their aggregates by NMR spectroscopy and pH titrations. We investigated correlations between their chemical structure, aggregation behavior, protonation degree, and chain conformation in the corona. Decreased amine protonation in the copolymers reduced the electrostatic repulsion, and the apparent pKa of the amino groups approached that of isolated amine. These effects increased compactness and sizes of the polymers and their aggregates at higher pH as reflected by the increased NMR line widths.