Role of Chain Length in the Formation of Frank-Kasper Phases in Diblock Copolymers

Ronald M Lewis; Akash Arora; Haley K Beech; Bongjoon Lee; Aaron P Lindsay; Timothy P Lodge; Kevin D Dorfman; Frank S Bates

doi:10.1103/PhysRevLett.121.208002

Role of Chain Length in the Formation of Frank-Kasper Phases in Diblock Copolymers

Phys Rev Lett. 2018 Nov 16;121(20):208002. doi: 10.1103/PhysRevLett.121.208002.

Authors

Ronald M Lewis¹, Akash Arora¹, Haley K Beech¹, Bongjoon Lee¹, Aaron P Lindsay¹, Timothy P Lodge^{1

2}, Kevin D Dorfman¹, Frank S Bates¹

Affiliations

¹ Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
² Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.

PMID: 30500248
DOI: 10.1103/PhysRevLett.121.208002

Abstract

The phase behavior of poly(styrene)-b-poly(1,4-butadiene) diblock copolymers with a polymer block invariant degree of polymerization N[over ¯]_{b}≈800 shows no evidence of Frank-Kasper phases, in contrast to low molar mass diblock copolymers (N[over ¯]_{b}<100) with the same conformational asymmetry. A universal self-concentration crossover parameter N[over ¯]_{x}≈400 is identified, directly related to the crossover to entanglement dynamics in polymer melts. Mean-field behavior is recovered when N[over ¯]_{b}>N[over ¯]_{x}, while complex low symmetry phase formation is attributed to fluctuations and space-filling constraints, which dominate when N[over ¯]_{b}<N[over ¯]_{x}.