Binary Polymer Brushes of Strongly Immiscible Polymers

Abstract

The phenomenon of microphase separation is an example of self-assembly in soft matter and has been observed in block copolymers (BCPs) and similar materials (i.e., supramolecular assemblies (SMAs) and homo/block copolymer blends (HBCs)). In this study, we use microphase separation to construct responsive polymer brushes that collapse to generate periodic surfaces. This is achieved by a chemical reaction between the minor block (10%, poly(4-vinylpyridine)) of the block copolymer and a substrate. The major block of polystyrene (PS) forms mosaic-like arrays of grafted patches that are 10-20 nm in size. Depending on the nature of the assembly (SMA, HBC, or neat BCP) and annealing method (exposure to vapors of different solvents or heating above the glass transition temperature), a range of "mosaic" brushes with different parameters can be obtained. Successive grafting of a secondary polymer (polyacrylamide, PAAm) results in the fabrication of binary polymer brushes (BPBs). Upon being exposed to specific selective solvents, BPBs may adopt different conformations. The surface tension and adhesion of the binary brush are governed by the polymer occupying the top stratum. The "mosaic" brush approach allows for a combination of strongly immiscible polymers in one brush. This facilitates substantial contrast in the surface properties upon switching, previously only possible for substrates composed of predetermined nanostructures. We also demonstrate a possible application of such PS/PAAm brushes in a tunable bioadhesion-bioadhesive (PS on top) or nonbioadhesive (PAAm on top) surface as revealed by Escherichia coli bacterial seeding.

Homopolymer Nanolithography

“…In particular, brush‐like polymer molecules attached to the surface at one end in an extended configuration offer a promising system for surface patterning. [1b,11] Nanopatterning realized by segregation in binary polymer brushes in selective solvent has been used to tune surface wetting properties,[11b,12] prepare membranes,[11b,13] and control cell adhesion,[11b,14] however, this patterning method afforded limited access to the underlying substrate.…”

Micrometre and nanometre scale patterning of binary polymer brushes, supported lipid bilayers and proteins

“…Perhaps the simplest approach is to exploit phase separation in copolymer blends formed from immiscible polymers, 42 but for top-down control of architecture, lithographic processing is required.…”

Targeted grafting of thermoresponsive polymers from a penetrative honeycomb structure for cell sheet engineering

“…20 Because of the inflammatory response and their cellular filling ratio faced by the former two methods, thermoresponsive pNIPAAm films have more potential use as confluent cell sheets. 26 Appropriate architectures and porosity are of fundamental importance to biointerfaces. 24,25 As pointed out in a previous work, a biointerface with suitable roughness can stimulate cell growth.…”

“…[21][22][23] However, many studies have been performed on flat substrates. [26][27][28][29][30] The breath figure method is an emerging method for the preparation of highly ordered hexagonal pore arrays. 26 Appropriate architectures and porosity are of fundamental importance to biointerfaces.…”