Thermal Processing of Diblock Copolymer Melts Mimics Metallurgy



Small-angle x-ray scattering experiments conducted with compositionally asymmetric low

molar mass poly(isoprene)-b-poly(lactide) diblock copolymers reveal an extraordinary

thermal history dependence. The development of distinct periodic crystalline or aperiodic

quasicrystalline states depends on how specimens are cooled from the disordered state to

temperatures below the order-disorder transition temperature. Whereas direct cooling

leads to the formation of documented morphologies, rapidly quenched samples that

are then heated from low temperature form the hexagonal C14 and cubic C15 Laves phases

commonly found in metal alloys. Self-consistent mean-field theory calculations show

that these, and other associated Frank-Kasper phases, have nearly degenerate free

energies, suggesting that processing history drives the material into long-lived metastable

states defined by self-assembled particles with discrete populations of volumes and

polyhedral shapes.
Date made available2017
PublisherData Repository for the University of Minnesota

Cite this