Project description:Living organisms can synthesize a wide range of macromolecules from a small set of natural building blocks, yet there is potential for even greater materials diversity by exploiting biochemical processes to convert unnatural feedstocks into new abiotic polymers. Ultimately, the synthesis of these polymers in situ might aid the coupling of organisms with synthetic matrices, and the generation of biohybrids or engineered living materials. The key step in biohybrid materials preparation is to harness the relevant biological pathways to produce synthetic polymers with predictable molar masses and defined architectures under ambient conditions. Accordingly, we report an aqueous, oxygen-tolerant RAFT polymerization platform based on a modified Fenton reaction, which is initiated by Cupriavidus metallidurans CH34, a bacterial species with iron-reducing capabilities. We show the synthesis of a range of water-soluble polymers under normoxic conditions, with control over the molar mass distribution, and also the production of block copolymer nanoparticles via polymerization-induced self-assembly. Finally, we highlight the benefits of using a bacterial initiation system by recycling the cells for multiple polymerizations. Overall, our method represents a highly versatile approach to producing well-defined polymeric materials within a hybrid natural-synthetic polymerization platform and in engineered living materials with properties beyond those of biotic macromolecules.
Project description:The complexity of polymer-protein interactions makes rational design of the best polymer architecture for any given biointerface extremely challenging, and the high throughput synthesis and screening of polymers has emerged as an attractive alternative. A porphyrin-catalysed photoinduced electron/energy transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerisation was adapted to enable high throughput synthesis of complex polymer architectures in dimethyl sulfoxide (DMSO) on low-volume well plates in the presence of air. The polymerisation system shows remarkable oxygen tolerance, and excellent control of functional 3- and 4-arm star polymers. We then apply this method to investigate the effect of polymer structure on protein binding, in this case to the lectin concanavalin A (ConA). Such an approach could be applied to screen the structure-activity relationships for any number of polymer-protein interactions.
Project description:The immense application potential of amphiphilic protein-polymer conjugates remains largely unexplored, as established "grafting from" synthetic protocols involve time-consuming, harsh and disruptive deoxygenation methods, while "grafting to" approaches result in low yields. Here we report an oxygen tolerant, photoinduced CRP approach which readily affords quantitative yields of protein-polymer conjugates within 2 h, avoiding damage to the secondary structure of the protein and providing easily accessible means to produce biomacromolecular assemblies. Importantly, our methodology is compatible with multiple proteins (e.g. BSA, HSA, GOx, beta-galactosidase) and monomer classes including acrylates, methacrylates, styrenics and acrylamides. The polymerizations are conveniently conducted in plastic syringes and in the absence of any additives or external deoxygenation procedures using low-organic content media and ppm levels of copper. The robustness of the protocol is further exemplified by its implementation under UV, blue light or even sunlight irradiation as well as in buffer, nanopure, tap or even sea water.
Project description:This work presents a new method for the synthesis of antifouling polymer brushes using surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain-transfer polymerization with eosin Y and triethanolamine as catalysts. This method proceeds in an aqueous environment under atmospheric conditions without any prior degassing and without the use of heavy metal catalysts. The versatility of the method is shown by using three chemically different monomers: oligo(ethylene glycol) methacrylate, N-(2-hydroxypropyl)methacrylamide, and carboxybetaine methacrylamide. In addition, the light-triggered nature of the polymerization allows the creation of complex three-dimensional structures. The composition and topological structuring of the brushes are confirmed by X-ray photoelectron spectroscopy and atomic force microscopy. The kinetics of the polymerizations are followed by measuring the layer thickness with ellipsometry. The polymer brushes demonstrate excellent antifouling properties when exposed to single-protein solutions and complex biological matrices such as diluted bovine serum. This method thus presents a new simple approach for the manufacturing of antifouling coatings for biomedical and biotechnological applications.
Project description:Recycling vinyl polymers is essential to mitigate the environmental impact of plastic waste. However, typical polymerization strategies to construct vinyl polymers lack the ability to incorporate degradable linkers throughout the main chain. We report a RAFT step-growth polymerization through the Z-group approach that is directly carried out by using a common class of symmetric trithiocarbonate based RAFT agents and commercially available bismaleimide monomers. Such synthesized RAFT step-growth polymers contain embedded RAFT agents in every structural unit, allowing chain expansion of the step-growth backbone via controlled chain growth to yield linear multiblock (co)polymers. These polymers can undergo deconstruction via the RAFT interchange process with exogeneous RAFT agents, generating smaller uniform species with narrow molecular weight distribution. In addition, the telechelic bifunctional RAFT agent nature after deconstruction allows repolymerization, showing a promising method for recycling common vinyl polymers.
Project description:ATRP (atom transfer radical polymerization) is one of the most robust reversible deactivation radical polymerization (RDRP) systems. However, the limited oxygen tolerance of conventional ATRP impedes its practical use in an ambient atmosphere. In this work, we developed a fully oxygen-tolerant PICAR (photoinduced initiators for continuous activator regeneration) ATRP process occurring in both water and organic solvents in an open reaction vessel. Continuous regeneration of the oxidized form of the copper catalyst with sodium pyruvate through UV excitation allowed the chemical removal of oxygen from the reaction mixture while maintaining a well-controlled polymerization of N-isopropylacrylamide (NIPAM) or methyl acrylate (MA) monomers. The polymerizations of NIPAM were conducted with 250 ppm (with respect to the monomer) or lower concentrations of CuBr2 and a tris[2-(dimethylamino)ethyl]amine ligand. The polymers were synthesized to nearly quantitative monomer conversions (>99%), high molecular weights (M n > 270 000), and low dispersities (1.16 < Đ < 1.44) in less than 30 min under biologically relevant conditions. The reported method provided a well-controlled ATRP (Đ = 1.16) of MA in dimethyl sulfoxide despite oxygen diffusion from the atmosphere into the reaction system.
Project description:It is known that oxygen (O2) stops radical polymerization (RP). Here, it was found that the reaction turn-off occurs abruptly at a threshold concentration of O2, [O2]t, for both free RP and reversible addition-fragmentation chain-transfer polymerization (RAFT). In some reactions, there was a spontaneous re-start of conversion. Three cases were investigated: RP of (i) acrylamide (Am) and (ii) sodium styrene sulfonate (SS) and (iii) Am RAFT polymerization. A controlled flow of O2 into the reactor was employed. An abrupt turn-off was observed in all cases, where polymerization stops sharply at [O2]t and remains stopped when [O2] > [O2]t. In (i), Am acts as a catalytic radical-transfer agent during conversion plateau, eliminating excess [O2], and polymerization spontaneously resumes at [O2]t. In no reaction, the initiator alone was capable of eliminating O2. N2 purge was needed to re-start reactions (ii) and (iii). For (i) and (ii), while [O2] < [O2]t, O2 acts a chain termination agent, reducing the molecular weight (Mw) and reduced viscosity (RV). O2 acts as an inhibitor for [O2] > [O2]t in all cases. The radical-transfer rates from Am* and SS* to O2 are >10,000× higher than the initial chain propagation step rates for Am and SS, which causes [O2]t at very low [O2].
Project description:The ability to reverse controlled radical polymerization and regenerate the monomer would be highly beneficial for both fundamental research and applications, yet this has remained very challenging to achieve. Herein, we report a near-quantitative (up to 92%) and catalyst-free depolymerization of various linear, bulky, cross-linked, and functional polymethacrylates made by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Key to our approach is to exploit the high end-group fidelity of RAFT polymers to generate chain-end radicals at 120 °C. These radicals trigger a rapid unzipping of both conventional (e.g., poly(methyl methacrylate)) and bulky (e.g., poly(oligo(ethylene glycol) methyl ether methacrylate)) polymers. Importantly, the depolymerization product can be utilized to either reconstruct the linear polymer or create an entirely new insoluble gel that can also be subjected to depolymerization. This work expands the potential of polymers made by controlled radical polymerization, pushes the boundaries of depolymerization, offers intriguing mechanistic aspects, and enables new applications.
Project description:A novel raspberry-like γ-Fe2O3@carbon dot (CD) nanocatalyst was prepared and applied for photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The nanocatalyst was found to be an efficient photocatalyst in visible light-regulated PET-RAFT polymerization owing to the oxidative quenching mechanism between the photoexcited γ-Fe2O3@CDs and the RAFT agent in the PET process. Notably, polymerization can be reversibly ceased in the absence of light or under an external magnetic field. The superparamagnetic nature and high saturation magnetization value (∼30.4 emu g-1) of the nanocatalyst contribute to convenient recycling of the nanocatalyst after polymerization. The PET-RAFT polymerization with the nanocatalyst before and after recycling was investigated, which displayed all the characteristics of controlled/living polymerization systems.