Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Comprehensive Study on the Controlled Plasmon-Enhanced Photocatalytic Activity of Hybrid Au/ZnO Systems Mediated by Thermoresponsive Polymer Linkers

Hybrid semiconductor/noble metal nanostructures coupled with responsive polymers were used to probe unique plasmon-mediated photocatalytic properties associated with swelling-shrinking transitions in polymer chains triggered by specific external stimuli. Poly(N-isopropylacrylamide) (PNIPAM) brushes were anchored on Au films by atom transfer radical polymerization and ZnO nanoparticles were immobilized on the PNIPAM layer to explore controlled photocatalytic activity. The plasmon-enhanced photocatalytic activity was dictated by two critical parameters, that is, grafting density and molecular weight of PNIPAM involved in Au film-PNIPAM-ZnO. The effect of the areal density of PNIPAM chains on the temperature-responsive UV light photocatalytic activities showed mutually antagonistic trends at two different temperatures. The performance at high density was higher above a lower critical solution temperature (LCST), that is, under contracted configuration, while the sample with low density showed higher activity below LCST, that is, extended configuration. Among all the cases explored, the UV light activity was highest for the sample with thin PNIPAM layer and high density above LCST. The visible light activity was induced only for thin PNIPAM layer and high density, and it was higher above LCST. The efficiency of photocatalytic decomposition of phenol pollutant was dramatically enhanced from 10% to 55% upon the increase in temperature under visible light illumination.