Stereocomplex nucleating agent

A polymeric implantable device from a PLLA/PDLA blend such as a stent with improved fracture toughness is disclosed. A stereocomplex nucleating agent (a combination of PLLA/PDLA) results in an increase in nucleation density and reduced crystal size, which increases fracture toughness of the formed device. ... 

Schmidt, S.C. and Hillmyer, M.A. (2001) Polylactide stereocomplex crystallites as nucleating agents for isotactic polylactide. Journal of Polymer Science Part B Polymer Physics, 39, 300-313. 

Tsuji, H., Takai, H. and Saha, S.K. (2006) Isothermal and non-isothermal crystallization behavior of poly(L-lactic acid) Effects of stereocomplex as nucleating agent. Polymer, 47, 3826-3837. 

The PLLA crystallization ability can also be improved by adding the polymer molecules as nucleating agents. Hideto Tsuji et al. [229] observed that when the PDLA was added from 0.1 wt% to 10 wt%, the spherulitic size of PLLA was decreased when crystallized at 135°C. Meanwhile, the addition of small amounts of PDLA is effective to accelerate overall PLLA crystallization. The WAXD results show that the stereocomplex crystallites in the melt-quenched PLLA films are formed when PDLA contents is above 1 wt%. 

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