Phase Behavior of Binary Blends of Diblock Copolymers: Progress and Opportunities

Abstract

The phase behavior of binary blends of diblock copolymers has been examined extensively in the past decades.Experimental and theoretical studies have demonstrated that mixing two different block copolymers provides an efficient and versatile route to regulate their self-assembled morphologies. A good understanding of the principles governing the self-assembly of block copolymer blends has been obtained from the study of A 1 B 1 / A 2 B 2 diblock copolymer blends. The second (A 2 B 2 ) diblocks could act synergistically as fillers and cosurfactants to regulate the domain size and interfacial properties, resulting in the formation of ordered phases not found in the parent (A 1 B 1 or A 2 B 2 ) diblock copolymer melts. The study of A 1 B 1 /A 2 B 2 block copolymer blends further provides a solid foundation for future research on more complex block copolymer blends.

Architectural Design of Block Copolymers

“…When the blending strategy is used to manipulate the nonuniformities in the domain size and interfacial curvature, block copolymer can be an alternative additive. While the homopolymer additive only serves as the filler, the block copolymer additive serves as both the filler and cosurfactants to regulate the volume fraction and interfacial properties simultaneously. − Thus, binary blending of block copolymers may provide a more efficient route in modulating the packing frustration to stabilize novel ordered phases. Liu et al have purposely designed a binary blend composed of two AB diblock copolymers (A 1 B 1 /A 2 B 2 ) with different volume fractions and molecular weights, which clearly elucidated the effect of blending diblock copolymers in stabilizing complex spherical phases (Figure a) .…”

Regulating the self‐assembly of AB/CD diblock copolymer blends via secondary interactions

“…[28][29][30][31][32][33][34] Extensive experimental and theoretical studies have revealed that the ability of polymeric blends to stabilize these complex spherical phases could be attributed to the differential distribution of the second component. 35 Specifically, the added homopolymers could act as fillers swelling the spherical domains thus aiding the formation of large domains with different sizes, whereas the added copolymers could act as fillers and co-surfactants at the same time to regulate both the size of the spherical domains and the properties of the AB interface. 35 The complexity of polymeric blends containing block copolymers could be dramatically increased by introducing new chemically distinct components.…”

“…35 Specifically, the added homopolymers could act as fillers swelling the spherical domains thus aiding the formation of large domains with different sizes, whereas the added copolymers could act as fillers and co-surfactants at the same time to regulate both the size of the spherical domains and the properties of the AB interface. 35 The complexity of polymeric blends containing block copolymers could be dramatically increased by introducing new chemically distinct components. For example, going from the binary A 1 B 1 =A 2 B 2 blends to AB/B 0 C or AB/CD blends enlarges the phase space and thus alters the phase behaviors tremendously.…”

Theory of Complex Spherical Packing Phases in Diblock Copolymer/Homopolymer Blends

“…19−23 The discovery of these complex morphologies has greatly enriched the array of possible spherical packing phases accessible in polymeric systems containing block copolymers. 14 Since the discovery of the FK phases in AB diblock copolymer systems, substantial efforts have been made to understand their formation mechanisms. There are two key features that distinguish the FK phases from the classical spherical phases, i.e.…”

“…Given the richness of crystalline structures, a natural question arises: can complex spherical packing phases or nonclassical spherical phases emerge from the self-assembly of block copolymers? An early instance of a nonclassical spherical phase in block copolymers is the self-assembly of a Frank–Kasper (FK) A15 phase from miktoarm AB n block copolymers, which was predicted theoretically by Grason et al − and observed experimentally by Cho et al A significant breakthrough in the search of nonclassical spherical phases in block copolymers was the discovery of a FK σ phase in linear polyisoprene- block -polylactide diblock copolymer melts by Lee et al Since then, a large number of experimental and theoretical studies on the emergence and stability of complex spherical packing phases self-assembled from block copolymers have been carried out. ,, Besides their appearance in neat block copolymer melts, these complex spherical phases, including two other FK phases, namely, the Laves C14 and C15 phases, have been found to be stable in binary AB diblock copolymer/A homopolymer (A 1 B 1 /A 2 ) blends − and binary blends of AB diblock copolymers with different block compositions and/or degrees of polymerization (A 1 B 1 /A 2 B 2 ). − The discovery of these complex morphologies has greatly enriched the array of possible spherical packing phases accessible in polymeric systems containing block copolymers …”