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In the present paper, we describe how a robust and fundamental methodology was developed for extraction and determination of a principal natural toxin compound, simplexin, from a series of bulk biocomposites. These complex matrices were fabricated by direct encapsulating either ground plant particles or an ethanolic crude extract of the Australian toxic pasture plant Pimelea trichostachya in the biodegradable polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate). Proton nuclear magnetic resonance spectroscopy was initially employed to examine the chemical compositions of these complicated systems. Then, a more sensitive strategy was developed and validated by combining solid-phase extraction and ultrahigh-performance liquid chromatography hyphenated with a quadrupole Orbitrap mass spectrometer for the quantification of simplexin embedded in different biocomposites. Satisfactory linearity (R2 > 0.99) and recovery ranges (86.8–116%) with precision (relative standard deviations) of between 0.2 and 13% (n = 3) were achieved from seven biocomposites. The established protocol was further shown to be accurate and reliable in confirming the homogeneous distribution of the simplexin in different biocomposite formulations. A limited mass transfer of simplexin (< 3.5%) from one of the biocomposites into a simulated but sterilized in vitro rumen environment after a 10-day incubation was also revealed by utilizing the method. This quantitative analysis of targeted natural product within plant material-integrated polymeric platforms has potential application when controlled release is required in the bovine rumen and other biological systems.

Polycyclic hydrocarbons are known to be efficient hydrogen carriers capable of yielding high purity H2 upon dehydrogenation. Due to their high hydrogen density, high boiling point, and stability, these compounds demonstrate the potential to be used as hydrogen donors under catalytic transfer hydrogenation (CTH) conditions. In this work, the potential of a suite of hydrogen carriers to donate hydrogen, as well as the mechanisms affecting their hydrogen transfer, are assessed through the CTH of guaiacol, on Pd/Al2O3, as a model system. The results indicated the following descending order of transfer hydrogenation rate: bicyclohexyl > tetralin » hydrogenated terphenyl (HTP) > cyclohexylbenzene. Among the products, cyclohexanone and phenol are the most abundant, directly resulting from CTH. Detailed analysis of the hydrogen carrier conversion and selectivity clearly shows that the potential for CTH is highly linked to the molecular structure of the donor, rather than the amount of hydrogen available for transfer. A density functional theory (DFT) study, supported by experimental data, reveals that when unsaturated hydrocarbons are utilized, such as tetralin, cyclohexylbenzene, and HTP, the effective CTH rate to guaiacol is limited, despite dehydrogenation being more favorable for those molecules than from fully saturated donors, such as bicyclohexyl.

A growing common public interest in a more sustainable society drives efforts into the development of bio-based and biodegradable polymers. Such renewable polymers can replace conventional non-degradable polymers as the matrix for wood plastic composites (WPCs). However, despite ongoing advancements towards the implementation of these biocomposites, experience with biocomposite mechanical durability is limited. This comparative study investigated the mechanical stability of biocomposites based on polyhydroxyalkanoate (PHA) and wood flour at 50 wt% wood content in real-life in-service conditions, including indoor, outdoor and in soil environments. Polylactic acid (PLA) and polyethylene (PE) wood composites served as comparative reference materials. Aging studies over a 12-month period showed that PHA composites were mechanically stable under indoor conditions. A reduction in mechanical stability was observed for outdoor exposure but the composite property deterioration was independent of the polymer type. In soil, the biocomposites steadily degraded towards a complete loss in mechanical properties, in contrast to the PLA and PE based composites. Overall, the rate of water absorption and the rate of polymer biodegradation are principal factors controlling mechanical stability over time. These factors promote the formation of cracks and voids which in turn weaken the material performance under mechanical loading. Without such crack formation, the composites retained mechanical properties over the aging time. The results provide a basis for consideration of strategic applications of PHA-based WPCs in cases where sustained or time-constrained mechanical performance is required.

Coiled-coils with defined assembly properties are attractive materials for the manufacture of peptide-based hybrid nanomaterials. In tailoring such peptide assemblies, the incorporation of aromatic residues is increasingly being investigated due to their potential to deliver controllable functionalities, such as interaction with aromatic porphyrins, carbon nanotubes, or graphene. Aromatic residues have the potential to either destabilise or stabilise the α-helical peptide structure, depending on the quantity, type, combination, and position of these residues in the peptide chain. In this work, we used a known synthetic three heptad repeat peptide containing no aromatic residues as an α-helical template. We then substituted the aliphatic residues with two different types of aromatic residues (phenylalanine and tryptophan), varying their number, position, and combination in the peptide chain as a preliminary assessment of the impact on peptide architecture. Circular dichroism (CD) spectroscopy combined with coarse-grained (CG) and all-atom (AA) molecular dynamics (MD) simulation were used to analyse the peptide structure and assembly. Aromatic residues designed to be within the hydrophobic core were had impact on self-assembly than those placed on the outer face of the coil. Tryptophan was seen to destabilise α-helical structure more than phenylalanine, potentially due to steric hindrance and hydrogen-bonding interactions. Using atomic force microscopy (AFM) and supported by CG-MD simulation, substituting all phenylalanine residues with tryptophan appeared to completely destabilise fibril-formation propensity. Subsituting tryptophan into the first heptad repeat was seen to have a greater impact on fibril formation compared to subtitution into the third heptad repeat, suggesting the importance of sequence design. These results add to the body of knowledge used to inform the design of α-helical peptides when incorporating aromatic residues.

This chapter focuses on the biodegradable subset of bioplastic alternatives, including thermoplastic starch, polylactic acid, and polyhydroxyalkanoate, which offer significant potential for tackling long-term plastic pollution. The majority of plastic ends up in landfills, but a considerable proportion also will escape into the environment, including the oceans. The volume of biodegradable bioplastics produced represents only a very small fraction of global plastics production. The fate of biodegradable bioplastics in natural and engineered environments is poorly understood and potentially problematic. Biodegradable bioplastics, as a “silver bullet” for plastic pollution, are not compatible with this agenda, as they are normally being designed from the outset to be disposed of after one use. A critical question when considering the use of biodegradable bioplastics is what happens to polymers in the environment. Starch-based mulch films have been shown to perform similarly to conventional plastic in terms of agronomic benefit, although control of lifetimes and mechanical properties can be a challenge.

BACKGROUND Various active chemical agents, such as soil microbial inhibitors, are commonly applied to agricultural landscapes to optimise plant yields or minimise unwanted chemical transformations. Dicyandiamide (DCD) is a common nitrification inhibitor. However, it rapidly decomposes under warm and wet conditions, losing effectiveness in the process. Blending DCD with an encapsulating polymer matrix could help overcome this challenge and slow its release. Here, we encapsulated DCD in a biodegradable matrix of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and investigated the effects of DCD crystal size and loading rates on release rates. RESULTS Three DCD crystal size fractions (0–106, 106–250 and 250-44 μm) were blended with PHBV at 200, 400, 600 and 800 g.kg−1 loadings through extrusion processing and release kinetics were studied in water over eight weeks. For loadings ≥600 g.kg−1, more than 95% release was reached within the first seven days. By contrast, at 200 g.kg−1 loading only 10%, 36% and 57% of the DCD was mobilized after eight weeks in water for 0–106 μm, 106–250 μm and 250–420 μm crystal size fractions, respectively. CONCLUSION The lower percolation threshold for this combination of materials lies between 200 and 400 g.kg−1 DCD loading. The grind size fraction of DCD significantly affects the quantity of burst release from the surface of the pellet, particularly below the lower percolation threshold. The results presented here are likely translatable to the encapsulation and release of other crystalline materials from hydrophobic polymer matrixes used in controlled release formulations, such as fertilisers, herbicides and pesticides. This article is protected by copyright. All rights reserved.

Lignin, an inexpensive renewable biopolymer that offers both aliphatic and aromatic hydroxyl ( OH) functional groups, is a potential raw material for the polyurethane industry. Contemporary approaches for incorporating lignin in rigid polyurethane foam (RPUF) involve mechanical mixing of microscale lignin powder under ambient conditions or at high loading levels, resulting in the RPUF with inferior compressive mechanical and thermal conductivity properties compared to petrochemical-based controls. Herein, we demonstrate a significant improvement in the dispersion of an industrial grade kraft lignin in a polyol mixture (96% sucrose/glycerine initiated polyether polyol and 4% glycerol) by dispersing at high-temperature (120 °C, 12 h) resulting in RPUF with enhanced performance. Through this methodology, the polyol/lignin dispersion with 5 wt.% lignin has afforded a simultaneous improvement in thermal insulation (by 5%) and compressive strength (by 4%) of RPUF compared to the control and such a property profile, to the best of our knowledge, has not yet been achieved in lignin substituted RPUF systems.

This paper is an overview of current understanding in the areas of composites made from biodegradable thermoplastics and wood fillers. The review finds that the composite properties depend on the type of wood filler, the choice of polymer matrix, the wood filler content, the compatibilization technique used and the processing parameters. The extent of interfacial adhesion and the filler morphology are identified as the underlying factors that control the composite properties. Future research needs are identified, including establishment of fundamental relationships between quantified interfacial adhesion and end-use properties and advanced modelling of biodegradation processes.

The service lifetime of polymer films is controlled by the chemical reactions leading to chain scission and the mediating environmental factors. For application as agricultural cropping film, controlled accelerated degradation is required. For a photo-sensitive linear low density polyethylene (LLDPE) + 1% nano-titania (as the anatase/rutile mixed phase P25), the environmental factors are not only UV dose and temperature but also soil parameters such as moisture and organic material content. This provides a challenge in predicting the useful lifetime from laboratory accelerated ageing studies. To enhance degradation when the (LLDPE + 1% P25) is buried, UV-C pre-irradiation has been shown to accelerate strength loss but the rate of embrittlement is not sufficient for the application as crop propagation film. Biodegradable poly(butylene adipate-co-terephthalate) or PBAT has a higher rate of degradation when buried outdoors in soil than when buried under laboratory conditions: The elongation at break fell from 900% to 70% in one month in the field while similar changes required 6 months in the laboratory. The small changes in M n ¯ for embrittlement in the field suggests that the loss of mechanical properties was not linked to bulk property changes but rather to surface morphology (cracks and holes) as seen by SEM. This suggests that even in thin films, enzyme-mediated hydrolysis of PBAT is surface controlled. DNA analysis of the soil around the buried films after 35 days ageing outdoors showed fungi play a more dominant role in PBAT biodegradation compared to bacteria. UV degradation of PBAT film is controlled by the photochemistry of the terephthalate moiety in the polymer and the development of fluorescence is a useful indicator of the extent of photo-degradation.

Technology advancements for mixed culture polyhydroxyalkanoate production have been made in recent years at pilot scale, and efforts continue towards implementation of the first commercial scale production facilities. The purpose of the present work was to develop thermogravimetric analysis (TGA) methods for routine monitoring of polymer quantity and quality in PHA-rich activated sludge biomass, and for the recovered polymers. TGA quantification of the biomass PHA content correlated directly with the maximum extractable polymer (+/- 2% gPHA/gTS). Acid pre-treatment of the biomass, prior to sample drying, significantly increased the polymer thermal stability in the biomass. This increase helps to improve the resolution of the PHA fraction of the biomass by TGA. From the TGA results, an extension to common solids analysis from Standard Methods, by including an intermediate volatile solids (IVS) assessment, was developed to quantify biomass PHA content. The IVS method entails sample volatilization and weight loss evaluation at a selected temperature between 200 and 300 degrees C. This intermediate temperature is in between the Standard Method sample drying (103 degrees C), and ashing (550 degrees C) oven incubations, for relative weight loss measurements that are made routinely for solids analysis. Thermogravimetric analyses were applied in isothermal polymer recovery experiments using either acetone or 2-butanol as extraction solvents. Trends in extractability as a function of extraction temperature and time correlated directly to the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) co-polymer composition in the biomass, over a 3-hydroxyvalerate in PHBV content ranging from 0 to 40 average weight percent, and a polymer weight average molecular mass between 200 and 600 kDa. Polymer type can be used to anticipate the extraction behavior, or conversely, as shown in the present work, isothermal polymer extraction trends can be used to infer the type of polymer present in the biomass. (C) 2017 Elsevier Ltd. All rights reserved.

The partial oxidation of dodecane and paraffin wax with bromine at relatively low temperatures (≤120 °C) and the dehydrobromination of the subsequent alkyl bromide intermediates at higher temperatures (>175 °C) to form higher alkenes were investigated. Products were analyzed using nuclear magnetic resonance spectroscopy, gas chromatography, and mass spectrometry. Bromination favored the formation of alkyl bromides on internal carbons of the model long chain alkanes over terminal sites. At lower temperatures (∼90 °C), ultraviolet photochemical initiation of bromination was necessary, while above 105 °C, thermally initiated bromination was observed. Photochemical bromination was found to be inhibited by water and oxygen. The formation of alkenes by the dehydrobromination of the alkyl bromides was observed by temperature-programmed reaction to occur at higher temperatures for n-dodecane (∼190 °C) than for the mixed alkanes in paraffin wax (∼175 °C).

The determination of the safe working life of polymer materials is important for their successful use in engineering, medicine and consumer-goods applications. An understanding of the physical and chemical changes to the structure of widely-used polymers such as the polyolefins, when exposed to aggressive environments, has provided a framework for controlling their ultimate service lifetime by either stabilising the polymer or chemically accelerating the degradation reactions. The recent focus on biodegradable polymers as replacements for more bio-inert materials such as the polyolefins in areas as diverse as packaging and as scaffolds for tissue engineering has highlighted the need for a review of the approaches to being able to predict the lifetime of these materials. In many studies the focus has not been on the embrittlement and fracture of the material (as it would be for a polyolefin) but rather the products of degradation, their toxicity and ultimate fate when in the environment, which may be the human body. These differences are primarily due to time-scale. Different approaches to the problem have arisen in biomedicine, such as the kinetic control of drug delivery by the bio-erosion of polymers, but the similarities in mechanism provide real prospects for the prediction of the safe service lifetime of a biodegradable polymer as a structural material. Common mechanistic themes that emerge include the diffusion-controlled process of water sorption and conditions for surface versus bulk degradation, the role of hydrolysis versus oxidative degradation in controlling the rate of polymer chain scission and strength loss and the specificity of enzyme-mediated reactions.

The photo-oxidative degradation of two complementary linear low density polyethylene (LLDPE) films has been studied: a Ziegler-Natta catalysed 1-octene copolymer (ZN-LLDPE) and a 1-octene copolymer produced by a single site constrained catalyst (m-LLDPE). The degradation processes were followed using a range of characterisation techniques including tensile testing, GPC, MAS-NMR, FTIR, WAXS and SAXS. The chemical species formed on degradation were similar for both polymers. Both also showed an increase in crystallinity and modulus with UV ageing time and a decrease in the long spacing of the lamella. However, the m-LLDPE showed a significantly shorter time to embrittlement than the ZN-LLDPE, which correlated in both polymers with the disappearance of the second yield point. The major observed difference in crystalline structure was a significantly higher interfacial thickness between the crystalline lamellae and the amorphous regions for the ZN-LLDPE, which decreased rapidly on UV ageing. This difference in behaviour was attributed to the nature of the branching in the ZN-LLDPE, which was presumed to sit in blocks along the chain and thus to reside in the interfacial regions. Cleavage of the tertiary carbons in these interfacial regions was less damaging to the mechanical properties than for the m-LLDPE, where chain scission broke more of the tie molecules, thus limiting the ability of the polymer to draw. . This work advances our understanding of polymer microstructural evolution during degradation and the implications of initial polymerisation route and molecular structure on the degradation mechanisms.

Polyethylene as a polymeric precursor for carbon fibre production has attracted much attention over recent years. Not only is it a low-cost commodity polymer, it has a higher theoretical carbon yield (at 100%) than polyacrylonitrile (at 67%) and is very readily melt processed into fibres. The challenge is to efficiently dehydrogenate and graphitize polyethylene fibres. This paper explores the use of bromine as a novel oxidant to functionalise polyethylene prior to carbonisation, leading to efficient cyclisation and carbonisation on heating. Through a process of low-temperature photo-induced liquid-phase bromination followed by dehydrobromination at moderate temperature and subsequent carbonisation to 800 °C, a carbonaceous product was obtained in high carbon yield (>90%). The effects of a range of process conditions, as well as the use of different types of polyethylene and polyethylene blends, were explored.

The impact of commonly used agrichemicals (Paraquat, Mancozeb, Chlorpyrifos and Sulfur) on the environmental stability of polyethylene films has been evaluated under accelerated photo-oxidative conditions. Paraquat and Mancozeb when applied to unstabilized clear polyethylene film, followed by exposure to UV radiation, resulted in direct attack of the polymer, evident by faster rates of oxidation and shorter times to embrittlement compared to a polyethylene control. Reapplication of these chemicals during exposure, as often occurs in agricultural practice, resulted in even faster degradation. In contrast, Sulfur and Chlorpyrifos did not have a significant effect on the photodegradation of exposed unstabilized polyethylene film. When the polyethylene film was pigmented (white top layer containing rutile titanium dioxide and carbon black in the bottom layer) and stabilized with the addition of hindered amine stabilizers (HAS), differences in oxidation susceptibility were seen with repeated exposure to Paraquat showing the most dramatic effect. This was evident by an increased carbonyl index, decrease in elongation at break and an increase in tensile stress at yield compared to a control film and other agrichemical treatments. These studies enable degradation from accelerated consumption of stabilizers by the agrichemicals (and their degradation products) to be differentiated from enhanced photochemical initiation of the polyethylene degradation.

Polyhydroxyalkanoate (PHA) biopolymer processing is often challenged by low thermal stability, meaning that the temperatures and time for which these polymers can be processed is restrictive. Considering the sensitivity of PHA to processing conditions, there is a demand for in-line monitoring of the material behaviour in the melt. This paper investigates the application of Near-Infrared (NIR) spectroscopy for monitoring the thermal degradation of PHAs during melt-processing. Two types of materials were tested: two mixed culture PHAs extracted from biomass produced in laboratory and pilot scale after an acidic pre-treatment, and two commercially available materials derived from pure culture production systems. Thermal degradation studies were carried out in a laboratory scale extruder with conical twin screws connected to a NIR spectrometer by a fibre optic to allow in situ monitoring. Multivariate data analysis methods were applied for assessing thermal degradation kinetics and predicted the degree of degradation as measured by (1)H NMR (proton nuclear magnetic resonance spectroscopy). The pre-treated mixed culture PHAs were found to be more thermally stable when compared with the commercial pure culture PHAs as demonstrated by NIR, (1)H NMR and GPC (gel permeation chromatography).

Microbially produced polyhydroxyalkanoates (PHAs) are fully biodegradable biopolyesters that have attracted much attention recently as alternative polymeric materials that can be produced from biorenewable and biowaste resources. The properties of these biological polymers are affected by the same fundamental principles as those of fossil-fuel derived polyolefins, with a broad range of compositions available based on the incorporation of different monomers into the PHA polymer structure, and with this broad range tailoring subsequent properties. This review comprehensively covers current understanding with respect to PHA biosynthesis and crystallinity, and the effect of composition, microstructure and supramacromolecular structures on chemomechanical properties. While polymer composition and microstructure are shown to affect these properties, the review also finds that a key driver for determining polymer performance properties is compositional distribution. From this review it follows that PHA–PHA blend compositions are industrially important, and the performance properties of such blends are discussed. A particular need is identified for further research into the effect of chemical compositional distribution on macromolecular structure and end-use properties, advanced modeling of the PHA accumulation process and chain growth kinetics for better process control.

The changes to the polymer microstructure during thermo- and photo-oxidative aging of LLDPE-based films have been investigated by thermal fractionation. During thermo-oxidative aging there was an exponential increase in the rate of the reduction in the fraction of polymer segments with a methylene sequence length (MSL) of approximately 249. All films embrittled only after the fraction of these segments decreased to below 7.5%, suggesting that the thermal fractionation data can be correlated to embrittlement time. In contrast, during photo-oxidative aging there was an initial rapid reduction followed by a gradual increase in the relative fraction of segments with an average MSL of 249. The initial decrease in the fraction of segments with an average MSL of 249 was similar to what was observed during thermo-oxidative aging and was consequently attributed to chain scission and/or oxidation of chains including tie-molecules. The latter increase in the fraction of chains with this average MSL was attributed to alkyl radical recombination which would result in an overall loss of branches and the formation of chain segments with high MSLs.

Polyhydroxyalkanoate (PHA) biopolymers are widely recognised as outstanding candidates to replace conventional petroleum-derived polymers. Their mechanical properties are good and can be tailored through copolymer composition, they are biodegradable, and unlike many alternatives, they do not rely on oil-based feedstocks. Further, they are the only commodity polymer that can be synthesised intracellularly, ensuring stereoregularity and high molecular weight. However, despite offering enormous potential for many years, they are still not making a significant impact. This is broadly because commercial uptake has been limited by variable performance (inconsistent polymer properties) and high production costs of the raw polymer. Additionally, the main type of PHA produced naturally is poly-3-hydroxybutyrate (PHB), which has limited scope due to its brittle nature and low thermal stability, as well as its tendency to embrittle over time. Production cost is strongly impacted by the type of the feedstock used. In this article we consider: the production of PHAs from methanotrophs using methane as a cost-effective substrate; the use of mixed cultures, as opposed to pure strains; and strategies to generate a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer (PHBV), which has more desirable qualities such as toughness and elasticity.

This work investigates the use of polyhydroxyalkanoate (PHA) films as moisture barriers for thermoplastic starch (TPS) films, to produce biodegradable, multi-layer materials with high gas barrier properties. This is a necessary extension to the limited work available on this topic and confirms that PHAs are suitable coating materials for TPS films intended for use in food packaging. Under storage conditions of up to 75% relative humidity (RH) for 2 weeks, a PHA coating maintained the moisture content (MC) of the TPS below the point at which its barrier properties were detrimentally affected. Furthermore, for PHBV coating thicknesses of 91–115 μm, the MC of the TPS remains significantly lower than uncoated TPS for the duration of the experiment (>25 days). The flux of water into the coated TPS fit to a model based on Fick's law. However, when the multi-layered films were stored at 95% RH delamination occurred within 24 h. Preliminary investigation into possible material design improvements showed that the addition of a small amount of PHA to the TPS layer prolonged the time to delamination.

The mechanism of the reaction of allyltrimethylsilanes with electrophiles was investigated using a number of approaches. Firstly, the kinetics of the reaction of the relatively simple allylsilane, allyltrimethylsilane, with dichloroacetic acid were investigated by 1H NMR. Both addition and electrophilic cleavage reactions were observed, with no reversion to starting material occurring. A comparison was made with the reaction of the alkene, 4,4-dimethylpent-l-ene, where a rate enhancement of four orders of magnitude was observed on substituting the s-CMe3 group by a s-SiMe3 group. The second approach involved the synthesis of an optically active siliconcentred allylsilane, based on the relatively uncongested, unstrained silacyclopentane structure. Of the methods of synthesis attempted, the most successful was asymmetric synthesis via dimenth-3-oxysilane derivatives. Using this route, optically active 1-cis-crotyl-2-methyl-1-phenyl-1-silacyclopentane was synthesised. The electrophilic cleavage of this allylsilane with anhydrous hydrogen chloride proceeded with inversion (after the intermediate formation of an addition compound). The reactions of various allylsilanes with trifluoroacetic acid were also investigated. These reactions generally proceeded with y-addition relative to silicon, followed by rearrangement and cleavage in an SE’ fashion. However, for the silane derivatives of s-pinene (E- and Z-1,2-dimethyl-(2,10-pinen-10-yl)methylsilacyclopentane) the stabilisation offered by the formation of a tertiary carbenium ion outweighed that produced by the s-silyl effect. Thus, s-addition of a proton followed by rearrangement of the intermediate carbenium ion and ring opening of the pinene structure before addition of the anion was observed.

We have investigated the potential of several polymers based on perfluoropolyether (PFPE) macromonomers for use in biomaterial applications. Polymer networks were synthesised from the PFPE macromonomers of increasing chain length and the adhesion and proliferation of corneal, vascular and bone cells was evaluated on these polymers. The polymer surfaces were quite hydrophobic, having sessile air-water contact angles ranging between 96 and 125 degrees. However, these polymers supported the attachment and growth of bovine corneal epithelial and endothelial cells and fibroblasts at 60-100% of the rate of cell growth on the culture substratum, TCPS. Furthermore, the PFPE polymers supported the attachment and growth of vascular endothelial cells (from human umbilical artery) and human bone-derived cells over a 7 day period at an equal level to TCPS. The relationship between the macromonomer chain length (n = 1 to 4) and the ability of the resulting PFPE homopolymer to support the overgrowth of corneal epithelial tissue was also evaluated. The PFPE-containing polymers supported corneal epithelial tissue overgrowth, with the most effective having a performance equivalent to that of TCPS. In addition to these homopolymers, copolymers comprising of PFPE and N,N-dimethylaminoethyl methacrylate (DMAEMA) were also synthesised. Surprisingly, the addition of DMAEMA to the PFPE polymer network lead to a reduction in the growth and attachment of corneal epithelial cells and fibroblasts. These results indicate that PFPE-based materials show a potential for use in the development of biomaterials in the ocular, vascular and orthopaedic areas.

The filamentous peptide-based nanowires produced by some dissimilatory metal-reducing bacteria, such as Geobacter sulfurreducens, display excellent natural conductivity. Their mechanism of conduction is assumed to be a combination of delocalized electrons through closely aligned aromatic amino acids and hopping/charge transfer. The proteins that form these microbial nanowires are structured from a coiled-coil, for which the design rules have been reported in the literature. Furthermore, at least one biomimetic system using related synthetic peptides has shown that the incorporation of aromatic residues can be used to enhance conductivity of peptide fibers. Herein, the de novo design of peptide sequences is used to enhance the conductivity of peptide gels, as inspired by microbial nanowires. A critical factor hampering investigations in both microbiology and materials development is inconsistent reporting of biomaterial conductivity measurements, with consistent methodologies needed for such investigations. We have reported a method herein to analyze non-Ohmic behavior using existing parameters, which is a statistically insightful approach for detecting small changes in biologically based samples. Aromatic residues were found to contribute to peptide gel conductivity, with the importance of the peptide confirmation and fibril assembly demonstrated both experimentally and computationally. This is a small step (in combination with parallel research under way by other researchers) toward developing effective peptide-based conducting nanowires, opening the door to the use of electronics in water and physiological environments for bioelectronic and bioenergy applications.

Direct 2H n.m.r. analysis of the 2H-substituted 3- and 4-methylcycloheptenes produced by acid cleavage (CF3CO2D) of mixtures of 4- and 7-methylcyclohept-2-enyltrimethyl-silanes and -stannanes confirms stereospecific γ-anti attack by the electrophile.

The efficacy of the dimethyl(phenyl)silylcuprate and (to a lesser extent) the methyl-diphenylsilylcuprate reagents in converting cyclohex-2-enyl chlorides into the corresponding allylsilanes has been investigated. The presence of copper(I) greatly suppresses formation of the coupled hydrocarbon, and promotes stereo- and regio-selective carbon-silicon bond formation, in a predominantly anti-SN2′ manner. Spectroscopic characterization of the diastereomeric silanes is presented. Grignard routes to some of these silanes are described.