Synthesis of Isotactic-block-Syndiotactic Poly(methyl Methacrylate) via Stereospecific Living Anionic Polymerizations in Combination with Metal-Halogen Exchange, Halogenation, and Click Reactions.

Isotactic (-) and syndiotactic (-) poly(methyl methacrylate)s (PMMAs) form unique crystalline stereocomplexes, which are attractive from both fundamental and application viewpoints. This study is directed at the efficient synthesis of - and -stereoblock (---) PMMAs via stereospecific living anionic polymerizations in combination with metal-halogen exchange, halogenation, and click reactions. The azide-capped -PMMA was prepared by living anionic polymerization of MMA, which was initiated with -BuMgBr in toluene at ⁻78 °C, and was followed by termination using CCl₄ as the halogenating agent in the presence of a strong Lewis base and subsequent azidation with NaN₃.

Linear-cyclic polymer structural transformation and its reversible control using a rational rotaxane strategy.

Linear-cyclic polymer structural transformation and its reversibility are demonstrated by a simple but rational strategy using the structural characteristics of crown ether-based rotaxanes. The structure of a polymer containing a [1]rotaxane unit at one end was controlled by conventional protection-deprotection reactions, giving rise to a reversible linear-cyclic polymer structural transformation.