No abstract

The click‐coupling reaction was applied to polycondensation, to synthesize a high‐molecular weight prepolymer having benzoxazine moieties in the main chain. For the polycondensation, a bifunctional N‐propargyl benzoxazine was synthesized from bisphenol A, propargylamine, and formaldehyde. The propargyl group was efficiently used for the copper(I)‐catalyzed alkyne‐azide “click” reaction with p‐xylene‐α,α′‐diazide, to give the corresponding linear polycondensate having 1,2,3‐triazole junctions. The polycondensation proceeded in N,N‐dimethylformamide (DMF) at room temperature. By this highly efficient “click‐” polycondensation reaction, the benzoxazine ring in the monomer was successfully introduced into the polymer main chain without any side reaction. The obtained polymer (=prepolymer) underwent thermal crosslinking to afford the corresponding product, which was insoluble in a wide range of organic solvents and exhibited higher thermal stability than the polymer before crosslinking. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2316–2325, 2008

Polyrotaxanes with a low threading ratio of α-cyclodextrin (α-CD) on a poly(ethylene glycol) chain effectively acted as both the relaxation and reinforcing reagents in Novolac-type epoxy resin. The polyrotaxanes were incorporated into the epoxy resin during the curing process to produce transparent and rigid epoxy resin/polyrotaxane (E/PR) alloys. From dynamic mechanical analysis (DMA) of the E/PR alloys, it was found that the polyrotaxane contributed not only as a stress-relaxation component but also as a reinforcing modifier in the epoxy resin matrix. The morphology and chemical structures of polyrotaxanes in the epoxy resin matrices were assumed to be in a nanoscale dispersion, forming an interpenetrate network structure with multi cross-linking bonds on threaded α-CDs. This assumption was made based on their transparency, differential scanning calorimetry, small-angle X-ray scattering, and DMA analyses. This is the first report on the unique properties of polyrotaxanes added in a rigid matrix.

Summary: A novel semi‐interpenetrating polymer network (semi‐IPN) with photomechanical switching ability was developed by a cationic copolymerization of azobenzene‐containing vinyl ethers in a matrix of a linear polycarbonate (PC). The semi‐IPN film showed reversible deformation upon switching the UV irradiation on and off and responded with unprecedented rapidity. The photomechanical effect is attributed to a reversible change between the highly aggregated and dissociated states of the azobenzene groups.The reversible UV response of the length of the semi‐IPN film at 25 °C.magnified imageThe reversible UV response of the length of the semi‐IPN film at 25 °C.