Structure–properties investigations in hydrophilic nanocomposites based on polyurethane/poly(2–hydroxyethyl methacrylate) semi‐interpenetrating polymer networks and nanofiller densil for biomedical application

Nanocomposites based on sequential semi–interpenetrating polymer networks (semi–IPNs) of crosslinked polyurethane and linear poly(2‐hydroxyethyl methacrylate) filled with 1–15 wt % of nanofiller densil were prepared and investigated. Nanofiller densil used in an attempt to control the microphase separation of the polymer matrix by polymer–filler interactions. The morphology (SAXS, AFM), mechanical properties (stress–strain), thermal transitions (DSC) and polymer dynamics (DRS, TSDC) of the nanocomposites were investigated. Special attention has been paid to the raising of the hydration properties and the dynamics of water molecules in the nanocomposites in the perspective of biomedical applications. Nanoparticles were found to aggregate partially for higher than 3 and 5 wt % filler loading in semi–IPNs with 17 and 37 wt % PHEMA, respectively. The results show that the good hydration properties of the semi–IPN matrix are preserved in the nanocomposites, which in combination with results of thermal and dielectric techniques revealed also the existence of polymer–polymer and polymer–filler interactions. These interactions results also in the improvement of physical and mechanical properties of the nanocomposites in compare with the neat matrix. The improvement of mechanical properties in combination with hydrophilicity and biocompatibility of nanocomposites are promising for use these materials for biomedical application namely as surgical films for wound treatment and as material for producing the medical devises. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43122.     

Highly Efficient Rapid Annealing of Thin Polar Polymer Film Ferroelectric Devices at Sub‐Glass Transition Temperature

An unexpected rapid anneal of electrically active defects in an ultrathin (15.5 nm) polar polyimide film at and below glass transition temperature (T_g) is reported. The polar polymer is the gate dielectric of a thin‐film‐transistor. Gate leakage current density (J_g) through the polymer initially increases with temperature, as expected, but decreases rapidly at T_g ? 60 °C. After ≈2 min at T_g, the leakage is reduced by nearly three orders of magnitude. A concomitant observation is that the drain current (I_d)–gate voltage (V_g) hysteresis decreases with temperature, reaching zero at nearly the same temperature at which J_g collapses. As J_g drops further, the drain current hysteresis increases again but in the opposite direction. This combination strongly supports the interpretation of rapid defect annealing.     

Ferroelectricity in Polar Polymer‐Based FETs: A Hysteresis Analysis

There is an increasing number of reports on polar polymer‐based ferroelectric field effect transistors (FeFETs), where the hysteresis of the drain current–gate voltage (I_d–V_g) curve is investigated as the result of the ferroelectric polarization effect. However, separating ferroelectric effect from many of the factors (such as charge injection/trapping and the presence of mobile ions in the polymer) that confound interpretation is still confusing and controversial. This work presents a methodology to reliably identify the confounding factors which obscure the polarization effect in FeFETs. Careful observation of the I_d–V_g curves, as well as monitoring the I_d–V_g hysteresis and flat band voltage shift as a function of temperature and sweep frequency, identifies the dominant mechanism. This methodology is demonstrated by using 15 nm thick high glass transition temperature polar polymer‐based FeFETs. In these devices, room temperature hysteresis is largely a consequence of charge trapping and mobile ions, while ferroelectric polarization is observed at elevated temperatures. This methodology can be used to unambiguously prove the effect of ferroelectric polarization in FeFETs.     

Examining the bentonite produced in a biodiesel refinery process as soil amendment in a well-draining soil

Clean Technologies and Environmental Policy - The expansion of biofuels produced from cooking oils and vegetal oils is expected to increase, together with the production of exhausted clay used in...     

Obesity is associated with the future risk of heavy truck crashes among newly recruited commercial drivers

This study estimates the dose–response relationship between body mass index (BMI) and crash risk in operators of heavy commercial motor vehicles. Intake data were collected during the first two weeks of instruction from 744 new truck drivers training for their commercial driver's licenses at a school operated by the cooperating trucking firm. Drivers were then followed prospectively on the job using the firm's operational data for two years, or until employment separation, whichever came first. Multivariate Poisson regression and Cox proportional hazards models were used to estimate the relationship between crash risk and BMI, controlling for demographic characteristics and for variations in the exposure to risks on the road. Results from the Poisson regression, which used cumulative miles driven as an exposure control, indicated that compared to normal BMI (18.5 < BMI < 25) the risk ratio (RR) for all crashes was significantly higher for drivers in the combined obesity Classes II and III: RR = 1.55 (95% CI 1.24–1.94). Similarly, the multivariate Cox proportional hazard model (controlling for miles and job type on a week-by-week basis) showed that crash risk was significantly higher compared to normal BMI for the same combined obesity Classes II and III: RR = 1.54 (95% CI 1.13–2.10). The results of this prospective study establish an association between obesity and crash risk and have important implications for driver health and public safety.     

On the design and fabrication by two-photon polymerization of a readily assembled micro-valve

This paper reports on the conceptual design and fabrication of a complex shape, readily assembled micro check valve using the two-photon polymerization technique. The material used for the fabrication of the valve is a zirconium containing organic–inorganic hybrid photosensitive sol-gel known to exhibit negligible distortion during photopolymerization. A preliminary computational fluid dynamics study has been carried out in order to evaluate the flow performance of the valve under blood pressures exhibited in healthy human veins. The fabricated micro-valves exhibit good dimensional accuracy when compared to the CAD-created valve design and the capability of an internal moving component to perform its intended function.     

Hydrogen Production by Photo-Induced Reforming of Biomass Components and Derivatives at Ambient Conditions

Hydrogen can be produced at ambient conditions via an efficient, technologically simple, ecologically benign, and potentially very low-cost process, with the use of a Pt/TiO₂ photocatalyst and three abundant and renewable sources: biomass, solar light, and water. The method combines photocatalytic splitting of water and light-induced oxidation of biomass compounds into a single process, able to produce hydrogen at room temperature and atmospheric pressure.     

Electrochemical enhancement of solar photocatalysis: degradation of endocrine disruptor bisphenol-A on Ti/TiO2 films

The photoelectrocatalytic oxidation over immobilized Ti/TiO₂ films in the presence of simulated solar light was investigated for the degradation of bisphenol-A (BPA) in water. The catalyst, consisting of 75:25 anatase:rutile, was prepared by a sol-gel method and characterized by cyclic voltammetry, X-ray diffraction and scanning electron microscopy. Experiments were conducted to assess the effect of applied current (0.02-0.32 mA/cm²), TiO₂ loading (1.3-9.2 mg), BPA concentration (120-820 μg/L), initial solution pH (1 and 7.5) and the aqueous matrix (pure water and treated effluent) on BPA photoelectrocatalytic degradation which was monitored by high performance liquid chromatography equipped with a fluorescence detector. The reaction was favored at anodic currents up to 0.04 mA/cm² and lower substrate concentrations, but it was hindered by the presence of residual organic matter and radical scavengers (e.g. bicarbonates) in treated effluents. Moreover, a pseudo-first order kinetic model could fit the experimental data well with the apparent reaction constant taking values between 2.9 and 32.4 10⁻³/min. The degradation of BPA by pure photocatalysis or electrochemical oxidation alone was also studied leading to partial substrate removal. In all cases, the contribution of applied potential to photocatalytic degradation was synergistic with the photocatalytic efficiency increasing between 24% and 97% possibly due to a more efficient separation and utilization of the photogenerated charge carriers. The effect of photoelectrocatalysis on the ecotoxic and estrogenic properties of BPA was also evaluated measuring the bioluminescence inhibition of Vibrio fischeri and performing the yeast estrogen screening assay, respectively.