Blockiness and sequence polydispersity effects on the phase behavior and interfacial properties of gradient copolymers

We consider the influence of sequence polydispersity upon the phase behavior and interfacial characteristics of gradient copolymers. By adapting the algorithmic procedure proposed for random copolymers, we design sequences of varying blockiness and compositional polydispersities for specified composition profiles of the gradient copolymers. Using the sequences so generated, we studied the dependence of the spinodals, the phase behavior, and interfacial properties of gradient copolymers as a function of gradient strengths and blockiness of the sequences. We demonstrate that the interplay between compositional polydispersity and the overall blockiness of the sequences can play a significant role in determining the morphologies, phase behavior, and interfacial activity of gradient copolymer systems. In systems wherein the inherent blockiness of the sequences is small, such as in gradient copolymers with weak gradient strengths, the introduction of such polydispersity and blockiness effects leads to substantial changes in the self-assembly behavior and interfacial properties. In contrast, in systems for which the inherent blockiness is already large, such as in gradient copolymers with strong gradient strengths, the effects of sequence correlations upon the self-assembly characteristics and interfacial properties are seen to be much more mitigated.