We seek to expand the opportunities to exploit glycerol, a largely untapped renewable feedstock, by exploiting enzymatic catalysis in supercritical carbon dioxide (scCO
2
). This work highlights a ...promising and clean approach to bio-renewable amphiphilic polyester-based biodegradable surfactants. We have developed a low temperature (40, 50 and 60 °C), low energy melt processing route to biodegradable, renewable poly(glycerol succinate) (PGLSA) polymers that importantly have a low degree of branching (3% < DB < 11%). Our approach shows significant advantages over traditional melt polycondensation at 110-120 °C, where the standard catalyst-free approach led only to highly branched (DB > 85%) or insoluble crosslinked materials. We have exploited these linear PGLSA materials to create a library of '
green
' surfactants by end-capping with lauric acid or poly(ethylene glycol). Our approach avoids pre-modification of the monomers and fewer synthetic steps are required. Finally, we evaluate the performance of these new surfactants, focussing upon surface tension, critical aggregation concentration (CAC) and water contact angle.
We exploit enzymatic catalysis in supercritical carbon dioxide to create novel, linear and degradable amphiphilic polymers that can act as surfactants.
The evaluation of two terpene-derived polymers, termed TPA6 and TPA7, as possible consolidants for archaeological wood was carried out. The overall objective of this work was to expand the ...non-aqueous treatment toolkit which is available for the conservation of the highly degraded Oseberg collection. The wood artefacts which were found on the Oseberg ship were treated with alum in the early twentieth century, leading to the formation of sulfuric acid and to the precarious state that they are in today. Some of these artefacts cannot be treated with conventional aqueous consolidants, like polyethylene glycol, due to their highly degraded and/or reconstructed nature. This study sought to examine the level of penetration of the polymers in archaeological wood and to evaluate their consolidative effect. Both TPA6 and TPA7 were soluble in isopropanol and had a M
of 3.9 and 4.2 kDa respectively. A number of archaeological wood specimens were immersed in solutions of these polymers. Their penetration and effects were evaluated using weight and dimensional change, colour change, infrared spectroscopy, scanning electron microscopy and hardness tests. Both polymers successfully penetrated the wood specimens, with a higher concentration found on the surface versus the core. Additionally, both polymers appeared to increase the hardness of the specimen surfaces. Increasing the polymer concentration and soaking time in future investigations could potentially facilitate the penetration to the wood cores.
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The functionalisation of limonene has enabled the synthesis of two renewably-sourced monomers for the formation of terpene-derived polyesters. Three methods for the synthesis of the novel ...hydroxy-acid 6 are reported and their green-credentials scrutinised through comparison of their sustainability-metrics. Step-growth homo-polymerisation of 6 is demonstrated to yield a low molecular weight (2.6 kDa) novel polyester with 100% of its carbon content originating from the terpene starting material. The corresponding diol 2 is shown to act as a co-monomer with a renewable diacid. The resultant polyesters display impressive M n s of up to 30 kDa with T g s between −6 and 24 °C. These materials have been shown to depolymerise under basic conditions for reclamation of the diol monomer 2 .
Objectives: Implantable devices are major risk factors for hospital-acquired infection. Biomaterials coated with silver oxide or silver alloy have all been used in attempts to reduce infection, in ...most cases with controversial or disappointing clinical results. We have developed a completely new approach using supercritical carbon dioxide to impregnate silicone with nanoparticulate silver metal. This study aimed to evaluate the impregnated polymer for antimicrobial activity. Methods: After impregnation the nature of the impregnation was determined by transmission electron microscopy. Two series of polymer discs were then tested, one washed in deionized water and the other unwashed. In each series, half of the discs were coated with a plasma protein conditioning film. The serial plate transfer test was used as a screen for persisting activity. Bacterial adherence to the polymers and the rate of kill, and effect on planktonic bacteria were measured by chemiluminescence and viable counts. Release rates of silver ions from the polymers in the presence and absence of plasma was measured using inductively coupled plasma mass spectrometry (ICP-MS). Results: Tests for antimicrobial activity under various conditions showed mixed results, explained by the modes and rates of release of silver ions. While washing removed much of the initial activity there was continued release of silver ions. Unexpectedly, this was not blocked by conditioning film. Conclusions: The methodology allows for the first time silver impregnation (as opposed to coating) of medical polymers and promises to lead to an antimicrobial biomaterial whose activity is not restricted by increasing antibiotic resistance.
Reversible addition–fragmentation chain transfer (RAFT)-controlled block copolymer synthesis using dispersion polymerization in supercritical carbon dioxide (scCO2) shows unprecedented control over ...blocking efficiency. For PMMA-b-PBzMA and PMMA-b-PSt the blocking efficiency was quantified by measuring homopolymer contaminants using the techniques of GPC deconvolution, gradient polymer elution chromatography (GPEC), and GPC dual RI/UV detection. A new, promising method was also developed which combined GPC deconvolution and GPEC. All techniques showed that blocking efficiency was significantly improved by reducing the radical concentration and target molecular weight. Estimated values agreed well with (and occasionally exceeded) theory for PMMA-b-PBzMA. The heterogeneous process in scCO2 appeared to cause little or no further hindrance to the block copolymerization procedure when reaction conditions were optimized. High blocking efficiencies were achieved (up to 82%) even at high conversion of MMA (>95%) and high molecular weight. These data compare favorably to numerous published reports of heterogeneous syntheses of block copolymers.
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Dispersion polymerization is a well‐established method of producing polymer particles that are easily handled and processed. With careful choice of reaction conditions this technique can yield well ...defined, spherical particles for a wide range of applications. The use of supercritical carbon dioxide (scCO2) as a reaction medium offers a route to performing these syntheses without excessive use of volatile organic solvents and minimizes work‐up and disposal steps. However a significant drawback has been the fact that up till now the control of particle size and morphology from CO2 have been limited. This study presents control of particle size and morphology over an unprecedented range for a single stabilizer in scCO2 by coordinating a few simple parameters to tailor the conditions toward different sizes. Further, this study introduces the novel approach in scCO2 of using delayed monomer addition which allows considerable reduction of the batch‐to‐batch variability as well as reduced agglomeration between particles.
This study presents control of PMMA particle size over an unprecedented range (0.3–5.3 μm) using only a single stabilizer by free radical dispersion polymerization in scCO2. This study explores also delayed monomer addition to considerably reduce batch‐to‐batch variability and reduced agglomeration between particles.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The Oseberg Viking ship burial is one of the most extensive collections of Viking wooden artefacts ever excavated in Norway. In the early twentieth century, many of these artefacts were treated with ...alum in order to preserve them, inadvertently leading to their current degraded state. It is therefore crucial to develop new bioinspired polymers which could be used to conserve these artefacts and prevent further disintegration. Two hydroxylated polymers were synthesised (TPA6 and TPA7), using α-pinene- and oleic acid-derived monomers functionalised with an acrylate moiety. Characterisation using biomolecular hydrodynamics (analytical ultracentrifugation and high precision viscometry) has shown that these polymers have properties which would potentially make them good wood consolidants. Conformation analyses with the viscosity increment (ν) universal hydrodynamic parameter and ELLIPS1 software showed that both polymers had extended conformations, facilitating in situ networking when applied to wood. SEDFIT-MSTAR analyses of sedimentation equilibrium data indicates a weight average molar mass M
of (3.9 ± 0.8) kDa and (4.2 ± 0.2) kDa for TPA6 and TPA7 respectively. Analyses with SEDFIT (sedimentation velocity) and MultiSig however revealed that TPA7 had a much greater homogeneity and a lower proportion of aggregation. These studies suggest that both these polymers-particularly TPA7-have characteristics suitable for wood consolidation, such as an optimal molar mass, conformation and a hydroxylated nature, making them interesting leads for further research.
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There is currently a pressing need for the development of novel bioinspired consolidants for waterlogged, archaeological wood. Bioinspired materials possess many advantages, such as biocompatibility ...and sustainability, which makes them ideal to use in this capacity. Based on this, a polyhydroxylated monomer was synthesised from α-pinene, a sustainable terpene feedstock derived from pine trees, and used to prepare a low molar mass polymer TPA5 through free radical polymerisation. This polymer was extensively characterised by NMR spectroscopy (chemical composition) and molecular hydrodynamics, primarily using analytical ultracentrifugation reinforced by gel filtration chromatography and viscometry, in order to investigate whether it would be suitable for wood consolidation purposes. Sedimentation equilibrium indicated a weight average molar mass M
of (4.3 ± 0.2) kDa, with minimal concentration dependence. Further analysis with MULTISIG revealed a broad distribution of molar masses and this heterogeneity was further confirmed by sedimentation velocity. Conformation analyses with the Perrin P and viscosity increment ν universal hydrodynamic parameters indicated that the polymer had an elongated shape, with both factors giving consistent results and a consensus axial ratio of ~ 4.5. These collective properties-hydrogen bonding potential enhanced by an elongated shape, together with a small injectable molar mass-suggest this polymer is worthy of further consideration as a potential consolidant.
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•Engineered amylose and waste CNF generate good bioplastics.•CNF enhanced crystallinity, mechanics and permeability.•Cellulose nanofibers and amylose showed domain phase separation.
Thermoplastic, ...polysaccharide-based plastics are environmentally friendly. However, typical shortcomings include lack of water resistance and poor mechanical properties. Nanocomposite manufacturing using pure, highly linear, polysaccharides can overcome such limitations. Cast nanocomposites were fabricated with plant engineered pure amylose (AM), produced in bulk quantity in transgenic barley grain, and cellulose nanofibers (CNF), extracted from agrowaste sugar beet pulp. Morphology, crystallinity, chemical heterogeneity, mechanics, dynamic mechanical, gas and water permeability, and contact angle of the films were investigated. Blending CNF into the AM matrix significantly enhanced the crystallinity, mechanical properties and permeability, whereas glycerol increased elongation at break, mainly by plasticizing the AM. There was significant phase separation between AM and CNF. Dynamic plasticizing and anti-plasticizing effects of both CNF and glycerol were demonstrated by NMR demonstrating high molecular order, but also non-crystalline, and evenly distributed 20 nm-sized glycerol domains. This study demonstrates a new lead in functional polysaccharide-based bioplastic systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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