Nathaniel Corrigan

Copper-Mediated Living Radical Polymerization (Atom Transfer Radical Polymerization and Copper(0) Mediated Polymerization): From Fundamentals to Bioapplications

Radical Polymerization and Copper(0) Mediated Polymerization): From Fundamentals to Bioapplications Cyrille Boyer,*,†,‡ Nathaniel Alan Corrigan,‡ Kenward Jung,‡ Diep Nguyen,‡ Thuy-Khanh Nguyen,‡ Nik Nik M. Adnan,†,‡ Susan Oliver,†,‡ Sivaprakash Shanmugam,‡ and Jonathan Yeow†,‡ †Australian Centre for Nanomedicine, and ‡Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering, University of New South Wales, Sydney 2052, Australia

Photocatalysis in organic and polymer synthesis

This review, with over 600 references, summarizes the recent applications of photoredox catalysis for organic transformation and polymer synthesis. Photoredox catalysts are metallo- or organo-compounds capable of absorbing visible light, resulting in an excited state species. This excited state species can donate or accept an electron from other substrates to mediate redox reactions at ambient temperature with high atom efficiency. These catalysts have been successfully implemented for the discovery of novel organic reactions and synthesis of added-value chemicals with an excellent control of selectivity and stereo-regularity. More recently, such catalysts have been implemented by polymer chemists to post-modify polymers in high yields, as well as to effectively catalyze reversible deactivation radical polymerizations and living polymerizations. These catalysts create new approaches for advanced organic transformation and polymer synthesis. The objective of this review is to give an overview of this emerging field to organic and polymer chemists as well as materials scientists.

Aqueous photoinduced living/controlled polymerization: tailoring for bioconjugation

We report a photoinduced living polymerization technique able to polymerize a large range of monomers, including methacrylates, acrylates and acrylamides, in water and biological media as well as organic solvents. This polymerization technique employs ultra-low concentrations of a ruthenium-based photoredox catalyst (typically 1 ppm to monomers) and enables low energy visible LED light to afford well-defined polymers with narrow polydispersities (Mw/Mn < 1.3). In this paper, different parameters, including photocatalyst concentrations and solvent effects, were thoroughly investigated. In addition, successful polymerizations in biological media have been reported with good control of the molecular weights and molecular weight distributions (Mw/Mn < 1.4). Finally, protein–polymer bioconjugates using a “grafting from” approach were demonstrated using bovine serum albumin as a model biomacromolecule. The enzymatic bioactivity of the protein was demonstrated to be maintained using a standard assay.

Precise synthesis of poly(N-acryloyl amino acid) through photoinduced living polymerization

Amino acid-based polymers possess exceptional physical structures, chemical properties, and biocompatibility and have shown great potential in applications, including drug delivery, chiral recognition, and sensor materials, among others. The precise synthesis of amino acid-based polymers with defined chemical structure and functionality facilitates the exploration of prospective properties and therefore potential practical applications. Controlled/“living” radical polymerization techniques are powerful tools for the synthesis of amino acid-based polymers due to their tolerance toward functional groups and versatility of polymerisable monomer families. In this work, we used photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization to polymerize various N-acryloyl amino acid monomers with diverse chirality and functionality to prepare a library of amino acid-based polymers with controlled molecular weights and narrow molecular weight distributions (Mw/Mn < 1.20) under mild conditions. Different solvents, RAFT agents and photocatalysts have been investigated to show the robustness and versatility of this process. Amino acid monomers with unprotected di-carboxylic acid moieties were directly polymerized in methanol to provide a facile approach to prepare various well-defined homo- and di-block amino acid-based polymers.

Discrete and Stereospecific Oligomers Prepared by Sequential and Alternating Single Unit Monomer Insertion

Natural biopolymers, such as DNA and proteins, have uniform microstructures with defined molecular weight, precise monomer sequence, and stereoregularity along the polymer main chain that affords them unique biological functions. To reproduce such structurally perfect polymers and understand the mechanism of specific functions through chemical approaches, researchers have proposed using synthetic polymers as an alternative due to their broad chemical diversity and relatively simple manipulation. Herein, we report a new methodology to prepare sequence-controlled and stereospecific oligomers using alternating radical chain growth and sequential photoinduced RAFT single unit monomer insertion (photo-RAFT SUMI). Two families of cyclic monomers, the indenes and the N-substituted maleimides, can be alternatively inserted into RAFT agents, one unit at a time, allowing the monomer sequence to be controlled through sequential and alternating monomer addition. Importantly, the stereochemistry of cyclic monomer insertion into the RAFT agents is found to be trans-selective along the main chains due to steric hindrance from the repeating monomer units. All investigated cyclic monomers provide such trans-selectivity, but analogous acyclic monomers give a mixed cis- and trans-insertion.

Seeing the Light: Advancing Materials Chemistry through Photopolymerization

The application of photochemistry to polymer and material science has led to the development of complex yet efficient systems for polymerization, polymer post-functionalization, and advanced materials production. Using light to activate chemical reaction pathways in these systems not only leads to exquisite control over reaction dynamics, but also allows complex synthetic protocols to be easily achieved. Compared to polymerization systems mediated by thermal, chemical, or electrochemical means, photoinduced polymerization systems can potentially offer more versatile methods for macromolecular synthesis. We highlight the utility of light as an energy source for mediating photopolymerization, and present some promising examples of systems which are advancing materials production through their exploitation of photochemistry.