Synthesis and microphase separation of polystyrene-b-polylactide block copolymers aimed at preparation of ordered nanoparticle/block copolymer hybrid materials

A new nanoparticle/block copolymer (NP/BCP) hybrid material combining the unique properties of BCP poly(styrene)-b-poly(D-lactide) (PS-b-PDLA) and inorganic NP quantum dots CdSe was developed. A systematic study on the microphase separation of a series of PS-b-PDLAs by small-angle X-ray scattering showed that the degree of order of the separated microdomains depended on the initial state of the BCP and the measurement temperature and can be improved through isothermal crystallization of PDLA, thermal annealing and shear field etc. Incorporating a small amount of NPs into the BCP matrix can improve the mobility of the polymer chains and thus promote self-assembly of the BCP, which leads to hierarchically ordered structures. Excess NPs, however, cannot be completely incorporated into the PDLA domains, resulting in the phase transformation of the BCP, destruction of the ordered structure and even macroscopic phase separation due to the aggregation of NPs. An important observation is that stereocomplexation between PDLA and poly(L-lactide) could provide a driving force to promote microphase separation of the BCP. The strategy presented in the current work has potential applications for developing highly ordered NP/BCP hybrid materials. (C) 2014 Society of Chemical Industry