Influence of Preparation Conditions on the Self-Assembly by Stereocomplexation of Polylactide Containing Diblock Copolymers

Self-assembly of diblock copolymers having a crystallizable block can yield particles of complex shapes. Here, particles have been obtained by mixing two solutions of poly(l-lactide)−poly(ε-caprolactone) and poly(d-lactide)−poly(ε-caprolactone) diblock copolymers, in a good solvent of polycaprolactone. We have proved that these particles result from the cocrystallization of the polylactide blocks (stereocomplexation). At the highest concentration investigated (10 g/L), the stereocomplexation is in competition with a solvophobically driven aggregation process. However, the latter process is reversible and does not seem to affect the stereocomplexation to a large extent. At lower concentrations, stereocomplexation is the only process involved. Temperature also has a strong influence both on kinetics and on the structure of the particles. At low temperature, the growth of the particles is stopped at a particular size. This effect may be related to the properties of the polycaprolactone block.