Synthesis and pH and salinity-controlled Self-assembly of Novel Amphiphilic Block-Gradient Copolymers of Styrene and Acrylic Acidстатья

Статья опубликована в высокорейтинговом журнале

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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.

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[1] Synthesis and ph and salinity-controlled self-assembly of novel amphiphilic block-gradient copolymers of styrene and acrylic acid / O. Borisova, L. Billon, M. Zaremski et al. // Soft Matter. — 2012. — Vol. 8. — P. 3649. A novel type of amphiphilic ionic copolymers comprising a hydrophilic poly(acrylic acid) PAA block and an amphiphilic poly(acrylic acid)-grad-poly(styrene) PAA-grad-PS copolymer block were synthesized using one step direct Nitroxide-Mediated Polymerization (NMP). A strong influence of the macroinitiator on the values of the reactivity ratios of the co-monomers is confirmed by 1H NMR. The aggregation behaviour of the copolymers in aqueous medium was studied by Small-Angle Neutron Scattering and Dynamic Light Scattering (SANS, DLS) and by Transmission Electron Microscopy (TEM) in a wide range of pH and ionic strength. It has been demonstrated that PAA-b-(PAA-grad-PS) copolymers are soluble in alkaline water at room temperature without special experimental procedures (addition of co-solvent, heating, etc.) which are usually required for solubilisation of classical PAA-b-PS diblock copolymers. The self-assembly of the PAA-b-(PAA-grad-PS) copolymers into nano-scale aggregates at low/moderate pH and/or high ionic strength was demonstrated by SANS and DLS experiments. The SANS spectra for the copolymer solution exhibit a correlation peak pointing to the formation of micelles with repulsive coronae. TEM images indicate that the micelles have approximately spherical shape and exhibit wide size distribution. Our results prove, that in contrast to “frozen” aggregates formed by PAA-b-PS copolymers in aqueous media, the micelles of PAA-b-(PAA-grad-PS) amphiphilic copolymers exhibit “dynamic”, pH-responsive properties, i.e., they can reversibly change the aggregation number upon variation of pH or salinity in the solution. [ DOI ]

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