A range of poly(butyl methacrylate-<i>stat</i>-methacrylic acid) [P(BMA-<i>st</i>-MAA)] copolymers of various compositions and molecular weights from 5-30 kDa has been synthesised in order to establish a relationship between self-assembled morphologies, molecular architecture and composition of statistical copolymers. Small-angle X-ray scattering (SAXS) analysis together with transmission electron microscopy (TEM) have demonstrated that the copolymers form spherical micelles in aqueous media. More importantly, it was found that the resulting micelle radii are copolymer composition-dependent, but independent of molecular weight. These results, along with aqueous electrophoretic measurements, have demonstrated that all the stabilizing (MAA) units are located on the micelle surface. A proposed structural model describes the experimental data well and enables the micelle radii to be predicted from the content of stabilizing units which could make this model universal and applicable for other statistical copolymer systems. Additionally, the effect of solvent composition and copolymer concentration on the self-assembled morphology was monitored using SAXS and rheology. SAXS models of different levels of complexity, including inhomogeneous structure of the micelle core and the formation of mass fractals, have been developed. These studies revealed that the copolymers are present in solution as molecularly-dissolved Gaussian chains when the solvent composition is IPA-rich. However, the copolymer chains self-assemble into spherical micelles when the solvent composition is water-rich. At intermediate solvent compositions, SAXS analysis confirmed the formation of an interconnected micelle network. A good correlation between the structure, detected by SAXS, and the rheological properties of the materials has been observed.

Control of self-assembly of amphiphilic statistical copolymers by their composition

255th National Meeting (2018)

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