Critical roles of molecular dynamics in the superior mechanical properties of isotactic-poly(1-butene) elucidated by solid-state NMR

Isotactic-poly(1-butene) (iPB1) shows superior mechanical properties after crystal–crystal transitions. Recently, Miyoshi et al. found that crystalline stems in metastable tetragonal crystal perform uniaxial rotational diffusions accompanying side-chain conformational transitions in the fast motional limit (correlation time, /scS o10 7 s; Macromolecules 2010, 43, 3986– 3989.). In this study, molecular dynamics in stable trigonal crystal is investigated by solid-state nuclear magnetic resonance, which indicates that crystalline stems and side-chain conformations are completely fixed up to melting points (/scS 410 s). In addition, lamellar thickness, /lS of iPB1 and a low isotacticity iPB1 (low_iPB1) with /mmmmS1⁄478%, respectively, were investigated by small-angle X-ray scattering. The low_iPB1 sample shows very week supercooling dependence of /lS (B5 nm), whereas iPB1 shows strong supercooling dependence of /lS (10–28 nm). On the basis of molecular dynamics and /lS results, molecular dynamics effects on structures and unique mechanical property of iPB1 are discussed. Polymer Journal (2012) 44, 65–71; doi:10.1038/pj.2011.66; published online 10 August 2011