The interfaces in incompatible A/B homopolymer blends with graft copolymer: a dissipative particle dynamics simulation study

Abstract

The use of graft copolymers as surfactants offers a promising approach to enhance the interfacial properties of polymer blends or fluid blends. The effectiveness of these copolymers is closely related to their topologies. In this study, we employed dissipative particle dynamics (DPD) simulations to investigate the interfaces in incompatible A/B homopolymer blends with graft copolymer AB. In particular, we kept the molecular weights of the “A4B4 series” and “A8B8 series” copolymers constant but varied their architecture. The results show that the "A4B4 series" copolymers exhibit greater efficacy in reinforcing the interface (reduce interfacial tension), as compared to the "A8B8 series". The reduction in interfacial tension achieved by the diblock copolymer is comparatively lower than that achieved by the graft copolymer. Among the various graft copolymers studied, it has been observed that A1A1[B2]A2[B2]/a-S3 graft copolymers exhibit the highest efficiency in reducing interfacial tension. As the graft copolymer A1A1[B2]A2[B2]/a-S3 concentration varies from 0.05 to 0.15, a notable inverse relationship between the degree of copolymer enrichment at the central region of the interface and the corresponding interfacial tension was observed. Specifically, an increase in the concentration of A1A1[B2]A2[B2]/a-S3 graft copolymers led to a discernible decrease in interfacial tension. Due to the saturation of the interface at c_cp = 0.15, upon increasing the concentration of the graft copolymers A1A1[B2]A2[B2]/a-S3 from 0.15 to 0.2, the added copolymers mainly enriched in the homopolymer phase. As a result, there is an absence of further reduction in interfacial tension. These studies allow us to predict the reduction in interfacial tension produced by a wide variety of copolymers and thereby permit a rational design of effective compatibilizers.