Self-assembly scenarios of block copolymer stars

Abstract

We examine the self-organization scenarios of star-shaped AB-block copolymers, consisting of a solvophilic A-block and a solvophobic B-block, in which f such blocks are chemically anchored on a common centre on their A-parts, leaving the B-blocks exposed on their exterior. We employ a lattice model and we perform Grand Canonical Monte Carlo simulations for the case f = 6, varying thereby the percentage of attractive monomers as well as the concentration of stars. In agreement with previous studies on the low-functionality case f = 3 [F. Lo Verso, A.Z. Panagiotopoulos, and C.N. Likos, Phys. Rev. E 79, 010401(R) (2009)], we find that when the majority of monomers in the star are attractive, macrophase separation between two fluid phases at different concentrations of stars occurs below a system-dependent critical temperature. When the majority of monomers is repulsive, novel forms of self-organization arise, which include not only well-defined spherical micelles but also the coexistence of a multiply-connected percolating cluster with smaller micelles having a well-defined size. The morphological characteristics and the sizes of the ensuing aggregates are quantitatively analysed and a critical comparison with the case f = 3 and f = 10 is presented.

Keywords:

• block copolymer stars
• self-assembly
• microphase structuring
• macrophase separation
• lattice model

Acknowledgements

It is a pleasure to dedicate this paper to Professor Luciano Reatto on the occasion of his formal retirement from his Chair in Theoretical Physics at the Università degli Studi di Milano. Professor Reatto has been a pioneer in the field of classical and quantum fluids, and his contributions have never ceased to inspire and guide us in our own research. This work has been supported by the REA through the Marie Curie ITN-COMPLOIDS, Grant Agreement No. 234810. AZP acknowledges support from the Princeton Center for Complex Materials (NSF grant DMR-0819860).