Structural reorganization of cylindrical nanoparticles triggered by polylactide stereocomplexation.

Liang Sun,Jeremy Sloan,Tara L Schiller,Rachel K O’Reilly,Ana M Sanchez,Andrew P Dove,Nigel Kirby,Anaïs Pitto-Barry,M Adam Dyson,Neil R Wilson

doi:10.1038/ncomms6746

Abstract

Co-crystallization of polymers with different configurations/tacticities provides access to materials with enhanced performance. The stereocomplexation of isotactic poly(L-lactide) and poly(D-lactide) has led to improved properties compared with each homochiral material. Herein, we report the preparation of stereocomplex micelles from a mixture of poly(L-lactide)-b-poly(acrylic acid) and poly(D-lactide)-b-poly(acrylic acid) diblock copolymers in water via crystallization-driven self-assembly. During the formation of these stereocomplex micelles, an unexpected morphological transition results in the formation of dense crystalline spherical micelles rather than cylinders. Furthermore, mixture of cylinders with opposite homochirality in either THF/H2O mixtures or in pure water at 65 °C leads to disassembly into stereocomplexed spherical micelles. Similarly, a transition is also observed in a related PEO-b-PLLA/PEO-b-PDLA system, demonstrating wider applicability. This new mechanism for morphological reorganization, through competitive crystallization and stereocomplexation and without the requirement for an external stimulus, allows for new opportunities in controlled release and delivery applications.

Highlights

Co-crystallization of polymers with different configurations/tacticities provides access to materials with enhanced performance
Stereocomplexation is of great interest in materials science, as the stereocomplex formed between the left-handed PLLA and right-handed PDLA polymeric helices has been shown to possess improved mechanical and thermal properties when compared with the homochiral polymers[2,6,8,9]
In an attempt to form more stable cylinders through stereocomplexation, we explore the assembly of a mixture of PLLA-b-PAA and PDLA-b-PAA diblock copolymers, under the same assembly conditions and surprisingly observed the formation of spherical micelles with stereocomplex cores

Summary

Introduction

Co-crystallization of polymers with different configurations/tacticities provides access to materials with enhanced performance. In an attempt to form more stable cylinders through stereocomplexation, we explore the assembly of a mixture of PLLA-b-PAA and PDLA-b-PAA diblock copolymers, under the same assembly conditions and surprisingly observed the formation of spherical micelles with stereocomplex cores.

Results

Conclusion