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

Employing transfer-dominated branching radical telomerisation (TBRT) and atom transfer radical polymerisation (ATRP) to form complex polyester-polymethacrylate branched-linear star copolymer hybrids via orthogonal initiation

TBRT and ATRP are orthogonal initiation chemistries used in vinyl polymerisations. Here, we present the first combination of these techniques to readily create high molecular weight branched polyester macroinitiators capable of forming star copolymers from a range of methacrylate monomers.

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.

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.

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.

Facile Synthesis of Functionalised Hyperbranched Polymers for Application as Novel, Low Viscosity Lubricant Formulation Components

A novel, previously unreported, method for synthesising hyperbranched (HB) materials is detailed. Their use as additives to produce lubricant formulations that exhibit enhanced levels of wear protection and improved low-temperature oil viscosity and flow is also reported. The lubricant formulations containing HB additives were found to exhibit both significantly lower viscosities and improved in-use film-forming properties than the current industry standard formulations. To achieve this, alkyl methacrylate oligomers (predominantly dimers and trimers) were synthesised using catalytic chain transfer polymerisation. These were then used as functional chain transfer agents (CTA) to control the polymerisation of divinyl benzene (DVB) monomers to generate highly soluble, high polydispersity HB polymers. The level of dimer/trimer purification applied was varied to define its influence on both these HB resultant structures and the resultant HB additives’ performance as a lubricant additive. It was shown that, while the DVB acted as the backbone of the HB, the base oil solubility of the additive was imparted by the presence of the alkyl chains included in the structure via the use of the oligomeric CTAs.

Accessing new and scalable high molecular weight branched copolymer structures using transfer-dominated branching radical telomerisation (TBRT)

Three new synthesis strategies for branched statistical copolymers containing analogues of step-growth backbones are shown using free radical chemistries and transfer-dominated branching radical polymerisation (TBRT) conditions.

Impact of multi-vinyl taxogen dimensions on high molecular weight soluble polymer synthesis using transfer-dominated branching radical telomerisation

The creation of branched polymers by TBRT is influenced by the molecular dimensions of the polymerising species. A mechanistic understanding is presented that includes a radical lifetime sphere model that is unique to telomerisation conditions used.