Regulation of Cross-Domain Chirality Transfer in Chiral Triblock Copolymers

The formation of the helical phase from the self-assembly of chiral diblock copolymers is attributed to the twisting and shifting of the microphase-separated domain. With the introduction of midblock in-between achiral and chiral blocks, the mechanism of twisting and shifting would be steered by the capability of cross-domain chirality transfer from the chiral block. This work aims to systematically investigate the cross-domain chirality transfer by synthesizing a variety of chiral diblock copolymers, polystyrene-<i>block</i>-poly(l-lactide) (PS-<i>b</i>-PLLA), with various midblocks including poly(d,l-lactide) (PLA), poly(ethylene oxide) (PEO), polycaprolactone (PCL), poly(4-vinylpyridine) (P4VP), poly(4-chlorostyrene) (P4CS) and poly(methyl methacrylate) (PMMA). The capability of the cross-domain chirality transfer is found to be dependent upon the interaction parameter of the midblock and chiral block but less affected by the interaction parameter of the midblock and achiral block. With the increase of the interaction parameter, the driving force for the cross-domain chirality transfer will deteriorate, resulting in a smaller cross-domain distance for chirality transfer.