Fabrication of microvillus-like structure by photopolymerization-induced self-assembly of an amphiphilic random block copolymer

A microvillus-like structure observed in digestive systems and glands was fabricated by the photopolymerization-induced self-assembly using an amphiphilic random block copolymer consisting of hydrophilic poly(methacrylic acid), PMAA, and hydrophobic poly(methyl methacrylate-random-methacrylic acid), P(MMA-r-MAA). The random block copolymerization of methyl methacrylate and methacrylic acid using a PMAA end-capped with 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl for the photopolymerization-induced self-assembly produced spherical vesicles and micelles during the early stage of the polymerization. These spherical particles transformed into worm-like vesicles, accompanied by the precipitation of a film-like product as the hydrophobic block chain grew according to the polymerization progress. Further extension of the hydrophobic block length produced the microvillus-like structure on the surface of the precipitating film. The finger-like structure in the microvilli had an ca. 8.5-μm height. An inverted cone-like critical packing shape of the copolymer with the hydrophobic block longer than the hydrophilic block contributed to the formation of the microvillus-like structure.