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Crosslinking is a valuable route to creating new polymeric materials and normally involves introduction of a cross linker or some form of secondary processing. Here we report the discovery and analysis of a self-crosslinking sustainable terpene derived monomer, ?-pinene methacrylate (?PMA). This monomer undergoes crosslinking during free radical homopolymerisation and with comonomers e.g. methyl methacrylate (MMA). ?PMA does not appear to contain any obvious functionality that would induce crosslinking such as vinyl bonds, but we postulate that it may undergo a fortuitous abstraction of a hydrogen atom from the pendant group. A combined computational (DFT) and experimental approach has been applied to investigate this. Further, we used DFT analysis to predict the behaviour of a related monomer, beta-pinene methacrylate (?PMA). To the best of our knowledge this is the first-time that self-crosslinking has been observed in free radical polymerisation of methacrylates via chain transfer through hydrogen abstraction from a pendant group. We have exploited this crosslinking to generate new, renewable poly high internal phase emulsions (polyHIPEs) that could rival those derived from fossil-based styrene- polyHIPEs and we have done this in a process which does not require any additional cross-linking agent.

Silver nanoparticles (AgNP) are widely exploited for their effective antimicrobial activity against a range of pathogens. Their high efficacy in this regard has seen the global demand for AgNP in consumer products steadily increase in recent years, necessitating research into novel low environmental impact synthesis approaches. Here we present a new synthetic methodology to produce polymer-AgNP composite microparticles using supercritical carbon dioxide (scCO2) and avoiding use of any petrochemically derived solvents. Poly(methyl methacrylate)-poly(4-vinylpyridine) (PMMA-b-P4VP) block copolymers were synthesised via RAFT-mediated dispersion polymerisation in scCO2, with in situ thermal degradation of various amounts of a CO2-soluble silver complex. Selective interaction of the silver with the pyridinyl moieties of the block copolymer allowed the formation of AgNP, dispersed within the block copolymer microparticles, leading to homogeneous composites. The by-products of the reaction were also removed by extracting with a flow of CO2 to yield a clean dry product in a single process. The composites were found to be non-cytotoxic and proved to have good antimicrobial activity against two bacterial strains. Though no significant activity was seen for at least the first 24 hours, inhibition of bacterial growth afterwards proved to be extremely persistent, with inhibition observed even after 15 days. Finally, the microparticulate nature of the synthesised composites was exploited and tested for compatibility in the Laser Sintering (LS) 3D printing process. Composite microparticles were fused to produce solid objects, without aggregation of the AgNP. With further optimisation, these composites could prove to be an incredibly versatile ‘ink’ that may be used within additive manufacturing and 3D printing to rapidly produce bespoke medical devices with inherent antimicrobial activity.

New materials chemistries are urgently needed to overcome the limitations of existing biomedical materials in terms of preparation, functionality and versatility, and also in regards to their compatibility with biological environments. Here, we show that Passerini reactions are especially suited for the preparation of drug delivery materials, as with relatively few steps, polymers can be synthesized with functionality installed enabling drug conjugation and encapsulation, self-assembly into micellar or vesicular architectures, and with facile attachment triggerable chemistries. The polymers can be made with a variety of building blocks and assemble into nanoparticles, which are rapidly internalized in triple negative breast cancer (TNBC) cells. In addition, the polymers transport drug molecules efficiently through 3D cell cultures, and when designed with chemistries allowing pH-mediated release, exhibit greater efficacy against TNBC cells compared to the parent drug.

Epoxidized oils are commonly used in the plastics industry as additives in the formulation of polyvinyl chloride (PVC) and as monomers in the coating industry. They are produced from petrochemical feedstocks or by chemical epoxidation of natural oils. Currently, the synthesis processes of these materials are expensive, utilize volatile organic solvents and hazardous oxidants, which are unfavorable for the environment. There is a need to find natural epoxidized oils. Vernonia galamensis (ironweed) is a plant found in abundance in Ethiopia with no commercial value, but its seeds contain 40 wt% epoxide rich triglycerides. V. galamensis oil contains up to 80 wt% of vernolic acid (VA), a mono-unsaturated fatty acid with an additional epoxide functionality. The presence of alkene and epoxide(oxirane) groups offers excellent opportunities to synthesize new building blocks for polymerisations. Here, we report a green and efficient extraction methodology (up to 80% of extraction-efficiency) of the triglyceride vernonia oil from V. galamensis using supercritical carbon dioxide (scCO2). We then report the synthesis of a series of polymerisable monomers (conversion in monomers 64%–99%) based on the VA obtained from the saponification process. Finally, the novel monomers are polymerized into different polymers through polycondensation using a mixture of metal-based and enzyme catalysts.

Reversible addition-fragmentation chain transfer (RAFT) mediated dispersion polymerisation in supercritical carbon dioxide (scCO2) is an efficient and green method for synthesising block copolymer microparticles with internal nanostructures. Here we report for the first time the synthesis of phase separated poly(methyl methacrylate-block-styrene-block-4-vinylpyridine) (PMMA-b-PS-b-P4VP) triblock terpolymer microparticles using a simple two-pot sequential synthesis procedure in scCO2, with high monomer conversions and no purification steps. The microparticles, produced directly and without further processing, show a complex internal nanostructure, appearing as a “lamellar with spheres” [L+S(II)] type morphology. The P4VP block is then exploited as a structure-directing agent for the fabrication of TiO2 microparticles. Through a simple and scalable sol-gel and calcination process we produce hollow TiO2 microparticles with a mesoporous outer shell. When directly compared to porous TiO2 particles fabricated using an equivalent PMMA-b-P4VP diblock copolymer, increased surface area and enhanced photocatalytic efficiencies are observed.

Terpenes are ideal candidates for sustainable polymer feedstocks, due to their natural abundance and availability from existing waste streams. Previously, we have shown that a range of terpene(meth)acrylate monomers can be synthesised from the most commonly available terpenes (α-pinene, β-pinenene and limonene) and that these readily undergo radical polymerisation. We now report the synthesis of well-defined polymers and precise di- and multiblock copolymer architectures by use of RAFT control. A very wide range of Tg values are observed for the terpene (meth)acrylate homopolymers, from −3 °C for poly(limonene acrylate), up to +168 °C for poly(α-pinene methacrylate), and we exploit these to create renewably-sourced hard–soft block copolymers. We also report the synthesis of difunctional poly(α- and β-pinene methacrylate) macro-RAFT agents and the preparation of ABA triblock copolymers. Promising adhesive properties are observed for a triblock copolymer comprised of poly(α-pinene methacrylate) and poly(butyl acrylate) blocks. A range of fully terpene-based triblock copolymers containing poly(limonene acrylate) soft blocks are also reported.