Effect of Added Homopolymer on the Hexagonal Phase Formed by Cylindrical Block Copolymer Micelles in a Selective Solvent

Abstract

The effect of addition of A homopolymer chains to HEX phases formed by cylindrical micelles obtained by dissolving an AB diblock copolymers in an A selective solvent was investigated. The following general trends were observed: (i) order-order transitions from HEX → Gyroid (G) → Lamellae (LAM); (ii) the inter-cylinder spacing of the HEX phase increased; (iii) when the homopolymer molecular weight and concentration was high, macrophase separation of the system occurred. The A homopolymer chains do not mix significantly with the A domain of the diblock due to excluded volume interactions, causing the corona chain brush to contract. As a result, order-order transitions that reduce the interfacial curvature are observed.

Depletion attraction in colloidal and bacterial systems

“…If these depletion attractions are strong enough, phase separation can occur as demonstrated by several studies (De Hek and Vrij, 1981;Pusey and van Megen, 1986;Yasrebi et al, 1991;Bartlett et al, 1992;Sanyal et al, 1992;Calderon et al, 1993;Duijneveldt et al, 1993;Kaplan et al, 1994;Buitenhuis et al, 1995;Ilett et al, 1995;Imhof and Dhont, 1995;Steiner et al, 1995;Herzfeld, 1996). The effect of overlapped excluded volume has been studied in colloidal solutions for a long time (Hobbie, 1998;Hobbie, 1999;Abbas et al, 2009;Hu et al, 2013;Ray et al, 2015). It has been successfully applied to the separation and purification of substances.…”

“…Apart from the applications mentioned above, depletion attraction could also be used to prepare micelles (Abbas et al, 2009;Lin et al, 2010;Repollet-Pedrosa and Mahanthappa, 2013;Yang et al, 2019), Pickering emulsions (Kim et al, 2017), and limit crystal growth (Ishibe et al, 2019), among others, but we will not list them all here. Depletion attraction has attracted widespread attention and research since its theoretical proposal in the 1950s, and it has been less than a century since then.…”

Controlling the morphology of poly(ethylene glycol)-b-poly(lactide) (PEG-PLA) self-assemblies in solution: Interplay of homopolymer additive and kinetic traps

“…However, to the best of our knowledge, very few studies directly address the concept of effecting morphological changes in the BCP through the addition of these non-adsorbing homopolymers. In an earlier report by Abbas et al [20], the authors investigated the effects of homopolymer additions on the hexagonally packed cylindrical micelles. Using a system comprising of poly(styrene-b-isoprene) BCP and poly(styrene) homopolymer in dibutyl phthalate solvent that is selective for the poly(styrene) blocks, they were able to observe changes in the hexagonal lattice packing, orderorder phase transitions and even phase separation given different compositions of BCP and homopolymer.…”