Ronan McHale

Biomimetic radical polymerization via cooperative assembly of segregating templates

Segregation and templating approaches have been honed by billions of years of evolution to direct many complex biological processes. Nature uses segregation to improve biochemical control by organizing reactants into defined, well-regulated environments, and the transfer of genetic information is a primary function of templating. The ribosome, wherein messenger RNA is translated into polypeptides, combines both techniques to allow for ideal biopolymer syntheses. Herein is presented a biomimetic segregation/templating approach to synthetic radical polymerization. Polymerization of a nucleobase-containing vinyl monomer in the presence of a complementary block copolymer template of low molecular weight yields high molecular weight (M(w) up to ~400,000 g mol(-1)), extremely low polydispersity (≤1.08) daughter polymers. Control is attained by segregation of propagating radicals in discrete micelle cores (via cooperative assembly of dynamic template polymers). Significantly reduced bimolecular termination, combined with controlled propagation along a defined number of templates, ensures unprecedented control to afford well-defined high molecular weight polymers.

Metal-containing polymers: building blocks for functional (nano)materials.

The incorporation of metallic units into polymer chains has emerged as a promising route towards functional metal-containing (nano)materials. The resulting polymers possess rich functions derived from their metallic elements, such as redox, optical, catalytic and magnetic properties. In addition, the directional and dynamic nature of metal coordination interactions provides further variables for the exploration of novel materials with designed nanostructures. These types of polymers can be synthesized through direct metal-ligand coordination or chain polymerization of metal containing monomers. Depending on the polymerization techniques and starting components, the resulting polymers, akin to their organic counterparts, can be produced in the form of insoluble networks, processible chain structures, gels or colloids. Research into this rising multidisciplinary subject has benefited from recent progress in several related areas such as supramolecular chemistry, colloidal chemistry etc., with the combination of the relative merits of each ensuring further developments in each individual discipline. For example, as a result of studies into organometallic block copolymers self-assembly behavior, living supramolecular polymerization has been unprecedentedly realized for the architectural design of micelles (see image on the right). Nevertheless, the field is still in a developmental stage and offers ample opportunities for fundamental research, as well as material exploration. In this Feature Article, we intend to overview the field with a brief survey of recent literature.

Synthesis of Prussian Blue Coordination Polymer Nanocubes via Confinement of the Polymerization Field Using Miniemulsion Periphery Polymerization (MEPP)

Miniemulsion periphery polymerization (MEPP) has been used for the synthesis of Prussian blue (PB) nanocubes. Pentacyano ferrate functionalized surfactant in combination with a co-surfactant containing 4-(dimethylamino)-pyridine (DMAP) or OH end groups in lieu of ferrate functionality (EPE-DMAP or EPE-OH) were used to prepare a miniemulsion system comprising 20 wt.-% toluene and 0.5 wt.-% total surfactant. On addition of Fe(3+) to the miniemulsion, metal coordination polymerization occurred with nanocubes generated when the ratio of EPE-Fe:EPE-DMAP (or EPE-OH) was 60:40 (w/w). The resulting nanocubes are apparently amorphous. Particles with irregular shape have been observed on reacting EPE-Fe and Fe(3+) directly in water, thus suggesting that confinement of the polymerization field on the periphery of the miniemulsion droplets is a primary factor in the formation of cubic structures.