Conformational and topological correlations in the gyroid morphology formed by non-frustrated triblock copolymers with homopolymers

The gyroid morphology is often only stable in a narrow region of the phase diagram, in part due to the high packing frustration, where blocks are stretched to fill the volume of the networks. Here, we investigate whether the stability of the gyroid phase can be improved by relieving the packing frustration using homopolymers. The effect of topology on the chain conformation is studied using dissipative particle dynamics (DPD) simulations. In a non-frustrated ABC, the A-blocks stretch to fill deep within the A-rich region. To relieve this stretching, A-selective homopolymers of different lengths were co-assembled with the ABC copolymer at several compositions. Topological analysis showed that homopolymers with lengths shorter than the A-block length filled the middle of the A-networks as hypothesized. The block copolymer chains exhibited some stretching, but the homopolymers did not. Since entropy is additive, the effect of the stretched block copolymer decreases by adding more homopolymers. Thus, entropic benefits can be tuned by choosing the amount and size of the homopolymer. From a macroscopic perspective, the domain size of the network can also be tuned using different lengths and amounts of added homopolymers, offering greater control over the final stable phase and bridging two separate regions in the phase diagram, making it more practical. Broadly, our method of analyzing the topology can be applied to other mixtures and blends to analyze questions pertaining to chain residence within the gyroid.