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本公司與中國清華大學合作發表之papers

Marcomolecular
Article
Left- or Right-Handed Lamellar Twists in Poly[(R)-3-hydroxyvalerate]
Banded Spherulite: Dependence on Growth Axis
Hai-Mu Ye, Jun Xu, Bao-Hua Guo, and Tadahisa Iwata
Macromolecules, 2009, 42 (3), 694-701 • DOI: 10.1021/ma801653p • Publication Date (Web): 18 November 2008
Downloaded from http://pubs.acs.org on February 4, 2009

Institute of Polymer Science & Engineering, Department of Chemical Engineering, School of Materials
Science and Technology, Tsinghua UniVersity, Beijing 100084, China, and Department of Biomaterial
Sciences, Graduate School of Agricultural and Life Sciences, The UniVersity of Tokyo,
Tokyo 113-8657, Japan
ReceiVed July 22, 2008; ReVised Manuscript ReceiVed October 31, 2008

ABSTRACT: Novel morphology of banded spherulite was observed in poly[(R)-3-hydroxyvalerate) (PHV) during its isothermal crystallization at temperatures between 50 and 80 °C. A novel optical technique, Polscope was applied to obtain both the birefringence retardation and azimuth angle of the slow optical axis at each pixel in the
micrograph of the polycrystalline specimen. It is revealed that two different morphological regions, normal and eye-like regions, are derived from different growth axes of the lamellae along the radial direction. In the normal region, lamellae grow and twist along b axis, leading to the alternative strong and weak positive birefringence.
In the eye-like region, they grow and twist along a axis, resulting in the alternative positive and negative birefringence. It is of particular interest to note that PHV lamellae in the two regions exhibit the opposite twist senses. To the best of our knowledge, it is the first report that an optically pure chiral polymer contains two lamellar twist senses in one spherulite. We attribute the driving force of lamellar twist in PHV spherulite to the
unbalanced anisotropic surface stresses. A mechanical model is proposed to interpret the opposite twisting senses along the two orthogonal growth axes. The results demonstrate that the growth axis is one of the factors determining the twist handedness of the lamellae of chiral polymers.



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