Rapid synthesis of well-defined all-acrylic diblock copolymer nano-objects via alcoholic photoinitiated polymerization-induced self-assembly (photo-PISA)

Abstract

A series of well-defined all-acrylic poly(hydroxyethyl acrylate)-poly(isobornyl acrylate) (PHEA-PIBOA) diblock copolymer nano-objects were prepared by photoinitiated polymerization-induced self-assembly (photo-PISA) of isobornyl acrylate in ethanol/water at 40 °C using poly(hydroxyethyl acrylate)-based macromolecular chain transfer agents (macro-CTAs). Polymerizations proceeded rapidly upon exposure to visible light irradiation (λ_max = 405 nm, 0.46 mW cm⁻²) with high monomer conversion being achieved within 30 min. Gel permeation chromatography (GPC) demonstrated that good control was maintained throughout the photo-PISA process, and the final block copolymers exhibited relatively low polydispersities (M_w/M_n ≤ 1.55). By virtue of the high T_g value of PIBOA, a diverse set of block copolymer nano-objects having different morphologies (e.g. spheres, worms, and vesicles) were prepared and characterized by conventional transmission electron microscopy (TEM). Two phase diagrams were constructed by varying the DP of the PIBOA block or monomer concentration or the DP of the PHEA macro-CTA. Worm-like micelles were prepared by monitoring the viscosity of the reaction mixture in a proof-of-concept experiment. Finally, poly(acrylic acid) (PAA) and poly(2-(dimethylamino)ethyl acrylate) (PDMAEA) macro-CTAs were also utilized to mediate the photo-PISA process, demonstrating the versatility of this method.