Adaptive Nanomechanical Response of in situ Grown Living Polymer Brush: from Monte Carlo Simulation to Experiment

Small changes in the external environment (e.g., temperature, pH, or solvent quality) can generally trigger a sharp and large response in the structure and properties of the stimuli-responsive polymer brushes made of surface tethered macromolecules. A coarse-grained off-lattice Monte Carlo (MC) simulation study of polydisperse living polymer brushes, created by surface-initiated living polymerization grafted to a planar substrate under good solvent conditions is presented. The living brush is created by end-monomer (de)polymerization reaction after placing an array of initiators on a grafting plane in contact with a solution of initially nonbonded segments (monomers). A high-density, ultrathin (~ 50 nm) polymer brush of (2-hydroxyethyl methacrylate) (PHEMA) was precisely prepared as a model responsive polymer brush on the surface of a flexible poly(dimethylsiloxane) (PDMS) substrate via SI-ATRP. The elastic properties and dynamic response of PHEMA brush within a two-dimensional polymer thin film structure are investigated using in situ atomic force microscopy (AFM) nanoindentation analysis under external stimuli