A new crystal form favored in low molecular weight biodegradable poly(3-hydroxypropionate)

作者：Zhu B; He Y; Asakawa N; Nishida H; Inoue Y^*

来源：Macromolecules, 2006, 39(1): 194-203.

DOI：10.1021/ma051922v

The crystalline structure of biodegradable poly(3-hydroxypropionate) (PHP) has been found to quite depend on the molecular weight (MW) and crystallization conditions. In particular, a new crystal form (the delta-form) has been successfully prepared by casting and optimal melt-crystallizing the low-MW PHP. The overwhelming growth of the delta-form in the cast low-MW PHP possibly arises from the conformational restriction of the intramolecular interaction between terminal groups. As for the melt-crystallization of low-MW PHP, the temperature of the melt (T-f) and the crystallization temperature (T-c) jointly decide the crystalline structure. It has been found that the T-f-dependent nucleation of the delta-form competes with T-c-dependent nucleation of the beta- and gamma-form and then plays a very important part in the T-f- and T-c-dependent polymorphism of PHP. With the aid of the FTIR analysis and the conformation prediction, the delta-form PHP are suggested to take on the 21 helix conformation rather than the trans one adopted by the gamma-form PHP. Interestingly, although the delta-form has a higher melting temperature and is more thermally stable than the gamma-form, no phase transition can be detected in the mixed phase of the delta-form and the gamma-rich phase during heating.

• 出版日期2006-1-10