Organic-Inorganic Poly(N-vinylpyrrolidone) Copolymers with Double-Decker Silsesquioxane in the Main Chains: Synthesis, Glass Transition, and Self-Assembly Behavior

An organic-inorganic copolymer with polyhedral oligomeric silsesquioxane (POSS) and xanthate moieties in the main chain was synthesized via the polycondensation between 3,13-di(2-bromopropionate) propyl double-decker silsesquioxane (DDSQ) and 1,4-di(xanthate potassium) butane. This hybrid copolymer was used as the macromolecular chain transfer agent to obtain the organic-inorganic poly(N-vinylpyrrolidone) (PVPy) copolymers via a reversible addition fragmentation chain transfer/macromolecular design via the interchange of xanthates (RAFT/MADIX) polymerization approach; the polymerization behavior of N-vinyl pyrrolidone was investigated by means of gel permeation chromatography. It was found that the polymerization was in a living and controlled manner. Transmission electron microscopy (TEM) showed that the organic-inorganic PVPy copolymers with DDSQ in the main chains were microphase-separated in bulks. Compared to plain PVPy, the organic-inorganic PVPy copolymers displayed the decreased glass transition temperatures (T(g)s); the decreased T(g)s are attributable to the effect of the introduced DDSQ cages on the packing of PVPy chains as evidenced by means of Fourier transform infrared spectroscopy (FTIR). In water, the organic-inorganic PVPy copolymers can self-assemble into the spherical nano-objects with the size of 20-50 nm in diameter. In the self-assembled nano-objects, the aggregates of the hydrophobic DDSQ constituted the cores of the polymeric micelles whereas the PVPy chains between the DDSQ behaved as the coronas of the polymeric micelles. (C) 2016 Wiley Periodicals, Inc.