Reconfiguration and Reorganization of Bottlebrush Polymer Surfactants

Abstract

Bottlebrush random copolymers (BRCPs), having randomly distributed hydrophilic and hydrophobic side chains, are shown to reconfigure into hydrophilic-rich and hydrophobic-rich conformations at liquid-liquid interfaces to reduce interfacial energy. Both the degree of polymerization (N BB ) and extent of grafting in these BRCPs were found to impact surface coverage and assembly kinetics. The time-dependence of the interfacial tension is described as the sum of two exponential relaxation functions characterizing BRCP diffusion, interfacial adsorption, and reorganization. Interfacial tension (γ) and fluorescence recovery after photobleaching (FRAP) results showed that higher molecular weight BRCPs require longer time to adsorb to the water-oil interface, but less time for interfacial reorganization. Overall, this work describes fundamental principles of BRCP assembly at liquid-liquid interfaces, with implications pertaining to polymer design with enhanced understanding of emulsification, adhesion, and related properties in fluids and at interfaces.

Bottlebrush Polymers at Liquid Interfaces: Assembly Dynamics, Mechanical Properties, and All-Liquid Printed Constructs

“…35 In our laboratories, we have investigated the jamming behavior of spherical polymer-based Janus NPs, 36 and the assembly dynamics of bottlebrush random copolymers at fluid interfaces as a function of degree of polymerization of the backbone (N BB ) and, hence, shapes (spherical for lower N BB and cylindrical for higher N BB ). 37 Bottlebrush homopolymers containing poly(acrylic acid) side chains functioned as soft nanoparticles (SNPs), giving fluid interfaces that wrinkled upon reduction of interfacial area, demonstrating the ability of cylindrical bottlebrush polymers to bind strongly to fluid interfaces and form elastic films. 15 Such interfacial jamming makes bottlebrush polymers confined to liquid interfaces an ideal platform for realizing "structured liquids", or essentially all-liquid systems with an unusual ability to form patterned objects.…”

Conformation of a Comb-like Chain in Solution: Effect of Backbone Rigidity

“…Comb-like polymers are branched polymers with a linear backbone grafted by multiple side chains − that have emerged as an intriguing class of materials for a wide range of potential applications, including supersoft elastomers, nanocarriers, surfactants, and stimuli-responsive coatings. − Compared with homologous linear polymers, the side chains provide additional steric repulsions, resulting in considerable stiffening of the backbone or even the side chains, which is the origin of many special physical and chemical properties. Three molecular parameters, the degree of polymerization of backbone ( N b ), the degree of polymerization of side chains ( N g ) and the grafting density (σ s ), which is defined as the reciprocal of the degree of polymerization between two neighboring branching points, constitute a set describing the conformations of comb-like polymers.…”

Facilely Control Grafting Density and Side Chain Composition of Bottlebrush Polymer

“…[10][11][12][13][14] Achieving precise control over the graft density and composition of the side chain presents synthetic challenges as well as rich opportunities for materials performance. [15][16][17][18] Despite the importance of grafting density and composition of the side chain cannot be overemphasized, synthetic methods that permit precise control of these parameters are currently limited. Over the past several decades, the development of reversible deactivation radical polymerization (RDRP) including reversible addition-fragmentation chain transfer (RAFT) [19,20] polymerization and atom transfer radical polymerization [21,22] has made it possible to synthesize BPs with complex structures and functionalities.…”