The structural flexibility and efficacy of thiourea-amine catalysts for the supramolecular activation and ring-opening polymerization (ROP) of lactide are described. The nature of the hydrogen bonding group and its strength as well as the steric congestion have been altered, leading to shorter polymerization times, better control, and pathways to influence the stereochemistry of the resulting polymer. The tolerance to functionality and the mild conditions of the ROP mechanism allow for block copolymer synthesis by combination of nitroxidemediated polymerization as well as reversible addition fragmentation and chain transfer polymerization using dual-headed initiators. Tandem hydrogen bond activation to organocatalyze ROP of lactide is an effective, versatile means to generate polymers with predictable molecular weights, narrow polydispersities, control of microstructure and a variety of complex architectures and block copolymers.

Presently, the majority of reports deal with combining chemical reactions, in a stepwise fashion, to obtain well‐defined polymers. In the future, chemists need to address new challenges such as increase in the range of available efficient reactions, developing libraries of compatible one‐pot reactions, and the application of obtained materials in key industries. Indeed, the rising importance of the click concept has now devised robust synthetic approaches in various fields of research. The unique selectivity of the click reaction is today a new found toolbox for scientists to investigate one‐pot multi‐step systems. Several accelerated protocols have elegantly been reported to obtain a library of advanced polymers.magnified image

Histamine functionalized poly(allyl glycidyl ether)-b-poly(ethylene glycol)-b-poly(allyl glycidyl ether) (PAGE-PEO-PAGE) triblock copolymers represent a new class of physically cross-linked, pH-responsive hydrogels with significant potential for biomedical applications. These telechelic triblock copolymers exhibited abrupt and reversible hydrogelation above pH 7.0 due to a hudrophilic/hydrophobic transition of the histamine units to form a network of hydrophobic domains bridged by a hydrophilic PEO matrix. These hydrophobic domains displayed improved ordering upon increasing pH and self-assembled into a body centered cubic lattice at pH 8.0, while at lower concentrations formed well-defined micelles. Significantly, all materials were found to be non-toxic when evaluated on three different cell lines and suggests a range of medical and biomedical applications.

Photocured thiol-ene hydrogel coatings based on poly(ethylene glycol) (PEG) were investigated for marine antifouling purposes. By varying the PEG length, vinylic end-group, and thiol cross-linker, a library of hydrogel coatings with different structural composition was efficiently accomplished, with or without ester linkages. The thiol-methacrylate and thiol-allyl systems were evaluated with respect to curing, degradation, as well as antifouling properties. Methacrylate-based systems exhibited homopolymerization, whereas allyl-based systems reacted more selectively through thiol-ene couplings reaction. The ester-free hydrogels elucidated higher hydrolytic stability whereas longer PEG chains accelerated the degradation process. The antifouling properties were evaluated by protein adsorption with Bovine serum albumin (BSA) and bioassays with the marine bacteria, Cobetia marina, and the marine diatom, Amphora coffeaeformis; in all tests, longer PEG lengths improved the antifouling properties.