Light induced grafting-from strategies as powerfull tool for surface modification

Abstract

Chemical-induced grafting processes can be performed either by a grafting-to method, where preformed polymer chains are grafted on the surface previously activated, or alternatively, the polymer chains can be grown from the surface via a grafting-from method. The last one can be considered a bottom-up approach in which polymers are generated directly on the surface starting from their precursors. As a preliminary process, the substrate is functionalized with specific groups that can initiate a polymerization reaction. Although surface-initiated polymerizations are conventionally induced by a thermal initiator or directly by radicals formed by high energy treatment of the surface, they can be triggered by light. In this regard, light-induced grafting reactions have recently found increasing interest. With this review, by placing emphasis on the initiating system, we aim to show the significant feasibility of photografting-from method to properly functionalize any type of surface.

Engineered Bioactive Polymeric Surfaces by Radiation Induced Graft Copolymerization: Strategies and Applications

“…Several types of photo-initiators have been used and details of their classification can be found in Ref. 7 [ 13 ]. Grafting is commonly carried out using the immersion technique, where UV irradiation is used in the presence of vinyl monomer diluted with water or methanol.…”

“…The classification of antimicrobial polymers and their interaction mechanisms were reviewed extensively [9][10][11][12]. Reviews with limited scope, such as those addressing individual surface modification techniques such as photo-grafting for surface modification [13], plasma treatment [14], modification of specific polymers such as silicon [15], fabrics (cotton and wool) [16], antimicrobial biomaterials containing quaternary ammonium [17], modification of biomaterials (polymer, ceramics, and metals) to impart biocompatibility and cellular interaction [18] have been published. Other articles reviewed strategies pertaining to bio-fouling prevention on silicon and silicon-based materials [15] and the use of nanometals to impart antimicrobial properties to polymers and textile fibers [19].…”

Photografting Coating: An Innovative Approach to “Non‐Migratory” Active Packaging

“…The unimolecular photoinitiator undergoes a cleavage reaction, generating two reactive species (free radicals), both of which possess the same reactivity, although only one species can tether to the surface. [ 61,62 ] The bimolecular photoinitiator tends to abstract the hydrogen from a donor upon absorbing the UV energy ( Figure ). [ 50 ] It generates two free radicals, both of which can initiate polymerization; this implies that this type of photoinitiator can generate more reactive species.…”

“…Photoinitiators can also be divided into Norrish type I (α‐cleavable) and Norrish type II (hydrogen abstraction or non‐cleavable) (Schematic). [ 16a,62,63 ] The Norrish type II photoinitiating system is the effective and convenient method for surface‐initiated polymerization. [ 63 ]…”

“…[ 66 ] Upon absorption of UV energy, BP is excited from a single state to a triple state (biradical state), resulting in hydrogen abstraction from a donor and affording a surface radical (R • ) that is ready for surface graft polymerization. [ 62,67 ] In addition, the resulting benzopinacol does not chemically react to initiate radical polymerization but tends to terminate via a coupling reaction ( Figure ). [ 31 ] Moreover, BP is thermally and chemically more stable than its counterparts, and can be modified to be activated by mild UV treatment under ambient condition.…”