Controlling enzyme hydrolysis of branched polymers synthesised using transfer-dominated branching radical telomerisation via telogen and taxogen selection.

With the ever-growing reliance on polymeric materials for numerous applications, new avenues to induce, design and control degradation are clearly important. Here, we describe a previously unreported approach to controlling enzymatic hydrolysis of high molecular weight branched polymers formed from the new free-radical polymer synthesis strategy transfer-dominated branching radical telomerisation (TBRT). Modifying the chemical nature of TBRT polymers may be accomplished through telogen selection and multi-vinyl taxogen (MVT) design, and we show telogen-driven control of enzyme-catalysed hydrolysis and the impact of careful placement of hydrolytically susceptible groups within readily synthesised MVTs. Our results indicate that utilising conventional free-radical chemistries and unsaturated monomers as feedstocks for highly branched polymer architectures has considerable potential for the design of future materials that degrade into very low molecular weight byproducts at variable and controllable rates.

Controlling the pH-response of branched copolymer nanoprecipitates synthesised by transfer-dominated branching radical telomerisation (TBRT) through telogen chemistry and spatial distribution of tertiary amine functionality.

Amine functionality offers the modification of polymer properties to enable stimuli-responsive behaviour, and this feature has been utilised in numerous studies of self-assembly and disassembly. The ability to place amines as pendant groups along linear polymer backbones within distinct blocks, at chain ends or as statistical mixtures with other functionalities, has allowed fine tuning of responses to pH. Here we study and compare the placement of amines within the backbones or as pendant groups within polyesters synthesised by the newly reported transfer-dominated branching radical telomerisation (TBRT). Branched polymers with backbone amines are clearly shown to undergo dissolution that is determined by pH and telogen selection; they undergo nanoprecipitation only when hydrophilic telogens are present within their structure and provide nanoprecipitates that are highly sensitive to the addition of acid. In contrast, TBRT polymers with pendant amines form uniform nanoparticles with remarkable stability to pH changes, under identical nanoprecipitation conditions. The behaviour differences shown here open new avenues of synthetic flexibility for pH-responsive polymer design using TBRT.

Using temperature to modify the reaction conditions and outcomes of polymers formed using transfer-dominated branching radical telomerisation (TBRT).

Transfer-dominated Branching Radical Telomerisation (TBRT) enables the production of branched polymers with step-growth backbones using radical telomerisation chemistry. By conducting identical TBRTs over a broad temperature range, the role of temperature in telomer formation and branching has been evaluated. Elevated temperature limits telomer length, thereby allowing a >10% reduction in the amount of telogen required to produce near identical high molecular weight branched polymers.

Quantification of branching within high molecular weight polymers with polyester backbones formed by transfer-dominated branching radical telomerisation (TBRT).

New branched polymerisations offer previously inaccessible macromolecules and architectural understanding is important as it provides insight into the branching mechanism and enables the determination of structure-property relationships. Here we present a detailed inverse gated 13C NMR characterisation of materials derived from the very recently reported Transfer-dominated Branching Radical Telomerisation (TBRT) approach to quantify branching and provide an insight into cyclisation.