Characterisation of porous silicon/poly(L-lactide) composites prepared using surface initiated ring opening polymerisation

Bellingham, US

Novel rhodanine based molecular acceptor for organic solar cells

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.A dirhodanine-substituted benzothiadiazole compound has been synthesised using Knoevenagel condensation of a dialdehyde-substituted benzothiadiazole and rhodanine. The resulting compound was deep orange red in colour and shows a HOMO and LUMO levels of −5.61 and −3.85 eV respectively, which makes it suitable for applications such as acceptor for organic solar cells

Designing superhydrophobic surfaces using fluorosilsesquioxane-urethane hybrid and porous silicon gradients

Bellingham, Washingto

In situ modification of Nafion(R) membranes with phospho-silicate for improved water retention and proton conduction

Proton-conducting hybrids from Nafion® and phospho-silicate networks were prepared by solvent-directed infiltration and copolymerization of 2-(methacryloyloxy)ethyl phosphate (EGMP) and 3-[(methacryloyloxy)propyl]trimethoxysilane (MEMO) at different ratios in Nafion®. Fourier transform infrared (FTIR) spectroscopy and 29Si and 31P nuclear magnetic resonance (NMR) spectroscopy confirm the presence of hydrophilic –POH groups and Si–O–P and Si–O–Si bond formation. The hybrid membrane samples show phase-separated morphology. Scanning electron microscopic (SEM) images confirm uniform distribution of 40–60 nm sized phospho-silicate nanoparticles in the membranes. The use of ethanol as solvent, directed the deposition of nanoparticles to the hydrophilic ionic cluster of Nafion®. The water uptake of all the hybridized membranes is higher than that of the unmodified Nafion® membrane due to the presence of strong hydrogen-bonded water molecules within the phospho-silicate inorganics. In general, the proton conductivity of hybridized membranes below 100 °C is lower than that of the unmodified membrane due to restricted mobility as a result of decrease in free volume and disruption of arrangement of hydrophilic domain thereby disrupting the proton movement path. However, above 100 °C and in anhydrous conditions, the hybrid membranes show increased proton conductivity and thermal stability than the blank Nafion®. Among the hybrid membranes, the sample with higher phosphate content exhibits higher water uptake and better proton conductivity

Fluoro-silsesquioxane-urethane hybrid for thin film applications

New fluoropolyurethane hybrids containing fluorinated polyhedral oligomeric silsesquioxane were synthesized for thin film applications using fluoro(13) disilanol isobutyl-POSS (FluoroPOSS) and a short chain fluorodiol and diisocyanate. The kinetics of the urethane reaction was monitored using Fourier transform infrared spectroscopy (FTIR) and the formation of urethane was confirmed using 29Si Nuclear magnetic resonance spectroscopy (NMR). The effect of addition of FluoroPOSS either in the I step or II step of the two step polymerization reaction is evaluated using various spectroscopic, thermal, microscopic, and diffraction techniques. In general, the major shortcoming of the lack of flexibility of fluoropolyurethane from short chain diol and diisocyanate has been overcome by the use of tethered FluoroPOSS. X-ray photoelectron spectroscopy (XPS), atomic force microscpopy (AFM), and contact angle measurements on the hybrid thin films on silicon wafer demonstrate the migration of FluoroPOSS segment to the air-thin film interface when FluoroPOSS is used in I stage reaction, and it resides at the interface when used as a chain extender. However, in both cases, the formed thin film exhibits ultrahydrophobicity with water contact angle of approximately 107° and low contact angle hysteresis and solvent resistance, which are preferable for protective thin film applications

Electrochemical performance of sol-gel derived phospho-silicate-methacrylate hybrid coatings

The sol–gel derived hybrid coatings containing three different compositions of methacrylate-phospho-silicate on mild steel substrates were characterized using potentiodynamic polarization, Electrochemical Impedance Spectroscopy (EIS) and Scanning Kelvin Probe (SKP). The corrosion current and potential along with the polarization resistance were determined using potentiodynamic measurements. The surface work function measured using SKP is correlated to the corrosion potential through a linear equation. The protection of the substrate is rendered by the strong interfacial interaction through acid–base interaction of P–O− group from phosphate with Mn+ from metallic substrate. Also, the coatings are intact and form a highly barrier layer, which restricts the permeation of electrolyte to the substrate surface. Among the studied hybrid coatings, M:E – 3:7 coated samples show better protection through strong interfacial interaction in combination with the defect-free, intact coating

Biomimetic protein-based elastomeric hydrogels for biomedical applications

In recent years, protein-based elastomeric hydrogels have gained increased research interest in biomedical applications for their remarkable self-assembly behaviour, tunable 3D porous structure, high resilience (elasticity), fatigue lifetime (durability), water uptake, excellent biocompatibility and biological activity. The proteins and polypeptides can be derived naturally (animal or insect sources) or by recombinant (bacterial expression) routes and can be crosslinked via physical or chemical approaches to obtain elastomeric hydrogels. Here we review and present the recent accomplishments in the synthesis, fabrication and biomedical applications of protein-based elastomeric hydrogels such as elastin, resilin, flagelliform spider silk and their derivatives. © 2013 Society of Chemical Industry

Induced insolubility of electrospun poly(N-vinylcaprolactam) fibres through hydrogen bonding with Tannic acid

Available online 29 January 2016Water-insoluble poly(N-vinylcaprolactam) (PVCL) electrospun nanofibres have been prepared for the first time by direct electrospinning with Tannic acid (TA) in apolar protic solvents. The PVCL/TA nanofiber mats have been fabricated through a facile one-step procedure which will increase their potential applications in the biomedical field where material stability in an aqueous environment is crucial. Hydrogen bonding between TA and PVCL resulted in nanofibers that are non-water soluble after drying, and the TA/PVCL interactions were confirmed through rheological and infrared spectroscopy measurements. In addition, the optimal ratio of TA and PVCL essential for the production of uniform, insoluble fibres in the range of hundreds of nanometres was established. The contact angle measurements confirmed that the roughness induced by the fibrous morphology of the TA/PVCL mats resulted in hydrophobic surfaces (CA>120°) from materials that otherwise exhibited hydrophilic behaviour (CA<90°) on flat surfaces. This method of using TA as a crosslinker for direct electrospinning of PVCL fibres requires no chemical modification or complex post-synthesis steps, thus facilitating the potential use of these novel PVCL nanofibers for applications as biomedical scaffolds in aqueous environments.Jasmin L. Whittaker, Surya Subianto, Naba K. Dutta, Namita Roy Choudhur

Inorganic-organic hybrid polymers from the polymerisation of methacrylate-substituted oxotantalum clusters with methylmethacrylate: A thermomechanical and spectroscopic study

New inorganic-organic hybrid materials were prepared by free-radical polymerization of methyl methacrylate (MMA) with methacrylate-substituted oxotantalum cluster [Ta4O4(OEt)8(OMc)4] and their properties evaluated. The cluster was prepared by the reaction of the parent alkoxide with methacrylic acid. Samples of the hybrid materials were produced with Ta-cluster to methyl methacrylate in the ratios of 1:50 and 1:100 and were characterized by thermal and spectroscopic techniques. The glass transition temperatures of the hybrid materials are shifted to higher temperatures than pure PMMA as a result of cross-linking of the polymer by the oxotantalum clusters. The increase in T g is also observed from the dynamic mechanical analysis (DMA). Evidence of crosslinking between the Ta-cluster and PMMA is obtained from infrared spectroscopic study. Surface studies performed by X-ray photoelectron spectroscopy (XPS) provide information about the atomic concentrations of the surface and indicate tantalum bonded to oxygen