Abstract

SANTOS-ROSAS, Rosario; LICEA-CLAVERIE, Angel  and  ARNDT, Karl-Friedrich. Statistical copolymers of methacrylic acid derivatives with hydrophobic spacers and N,N'-dimethylaminoethylimethacrylate: New associating polyampholytes. J. Mex. Chem. Soc [online]. 2006, vol.50, n.4, pp.164-174. ISSN 1870-249X.

Two series of statistical copolymers containing N,N'-(dimethylamino)ethylmethacrylate (DMAEM) and comonomers derived from methacrylic acid with three and five methylene-units as spacers, were prepared by free radical-copolymerization followed by selective saponification. These statistical copolymers prepared showed strong self-associative properties as revealed by viscosity, static and dynamic light scattering studies. The aggregates formed in aqueous solution show classical ampholytic behaviour with aggregate expansion both in acid and alkaline conditions and aggregate contraction at intermediate pH-values, near the isoelectric point of the system. The contraction of aggregates is shifted to higher pH-values when the content on hydrophobic acid comonomer is increased. The aggregates formed are stable to sonication above a concentration of 0.9 g/L and merge to larger structures at very high or very low pH-values. A conceptual model is proposed that accounts for the observed association behaviour of the copolymers. The statistical ampholytic copolymers studied are an easy to prepare alternative to block-copolymers for the formation of nano-sized aggregates for different applications.

Keywords : Polyampholytes; macromolecular aggregates; hydrophobic self-association; pH-sensitive copolymers.

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