Synthesis and fractionated crystallization of organic-inorganic hybrid composite materials from an amphiphilic polyethylene-block-poly (ethylene oxide) diblock copolymer

Mesostructurally ordered inorganic–organic hybrid composite materials were successfully synthesized by utilizing a low-molecular-weight amphiphilic polyethylene-block-poly(ethylene oxide) (PE–PEO) diblock copolymer as the directing agent. The hybrid composites were formed via the sol–gel reaction of inorganic precursor tetraethoxysilane (TEOS) in an acidic ethanol/water solution with various amounts of PE–PEO. In these composite materials, the hydrophobic PE block of the PE–PEO copolymer forms separate microphase on the nanoscales within the rigid matrix of silica network. The crystallization of the PE block is strictly restricted within the microphase by the rigid silica matrix and takes place through homogeneous nucleation under the nanoscale confinement environment.

Ion and solvent dynamics in gel electrolytes based on ethylene oxide grafted acrylate polymers

Multinuclear pulsed field gradient NMR measurements and rheological viscosity measurements were performed on three series of polymer gel electrolytes. The gels were based on a lithium salt electrolyte swollen into a copolymer matrix comprising an acrylate backbone and ethylene oxide side chains. In each series the side chains differed in length and number, but the acrylate-to-ethylene oxide ratio was kept constant. It was found that the self-diffusion coefficient of the cations was much lower than that of the anions, and that it decreased rapidly when the side chains got longer. In contrast, the self-diffusion coefficient of the anions was found to be independent of chain length. In the gel electrolytes, the diffusion coefficients of the solvent molecules are relatively constant despite an increased viscosity with increasing length of the side chains. However, in salt-free gels made for comparison, the diffusion coefficients of the solvent molecules decreased with increasing length of the side chains, which is consistent with an increased viscosity.

Microphase separation in double crystalline poly (ethylene oxide)-block-poly (caprolactone)/poly (4-vinyl phenol) blends

We report microphase separation induced by competitive hydrogen bonding interactions in double crystalline diblock copolymer/homopolymer blends of poly(ethylene oxide)-block-poly(ɛ-caprolactone) (PEO-b-PCL) and poly(4-vinyl phenol) (PVPh). The diblock copolymer PEO-b-PCL consists of two immiscible crystallizable blocks wherein both PEO and PCL blocks can form hydrogen bonds with PVPh. In these A-b-B/C diblock copolymer/homopolymer blends, microphase separation takes place due to the disparity in intermolecular interactions; specifically PVPh and PEO block interact strongly whereas PVPh and PCL block interact weakly. The TEM and SAXS results show that the cubic PEO-b-PCL diblock copolymer changes into ordered hexagonal cylindrical morphology upon addition of 20 wt % PVPh followed by disordered bicontinuous phase in the blend with 40 wt % PVPh and then to homogenous phase at 60 wt% PVPh and above. Up to 40 wt % PVPh there is only weak interaction between PVPh and PCL due to the selective hydrogen bonding between PVPh and PEO. However, with higher PVPh concentration, the blends become homogeneous since a sufficient amount of PVPh is available to form hydrogen bonds with both PEO and PCL. A structural model was proposed to explain the self-assembly and morphology of these blends based on the experimental results obtained. The formation of nanostructures and changes in morphologies depend on the relative strength of hydrogen bonding interaction between each block of the block copolymer and the homopolymer (1-3).

Polystyrene-b-poly(oligo(ethylene oxide) monomethyl ether methacrylate)-bpolystyrene triblock copolymers as potential carriers for hydrophobic drugs

A simple and effective method is introduced to synthesize a series of polystyrene-b-poly(oligo(ethylene oxide) monomethyl ether methacrylate)-b- polystyrene (PSt-b-POEOMA-b-PSt) triblock copolymers. The structures of PSt-b-POEOMA-b-PSt copolymers were characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H NMR) spectroscopy. The molecular weight and molecular weight distribution of the copolymer were measured by gel permeation chromatography (GPC). Furthermore£ the self-assembling and drug-loaded behaviours of three different ratios of PSt-b-POEOMA-b-PSt were studied. These copolymers could readily self-assemble into micelles in aqueous solution. The vitamin E-loaded copolymer micelles were produced by the dialysis method. The micelle size and core-shell structure of the block copolymer micelles and the drug-loaded micelles were confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The thermal properties of the copolymer micelles before and after drug-loaded were investigated by different scanning calorimetry (DSC). The results show that the micelle size is slightly increased with increasing the content of hydrophobic segments and the micelles are still core-shell spherical structures after drug-loaded. Moreover, the glass transition temperature (Tg) of polystyrene is reduced after the drug loaded. The drug loading content (DLC) of the copolymer micelles is 70%-80% by ultraviolet (UV) photolithography analysis. These properties indicate the micelles self-assembled from PSt-b- POEOMA-b- PSt copolymers would have potential as carriers for the encapsulation of hydrophobic drugs.

A participatory workplace health and safety training program for ethylene oxide

The Occupational Safety and Health Administration (OSHA) has regulated ethylene oxide (EtO) on the basis of its acute toxicity and its potential carcinogenic and reproductive effects since 1971. OSHA's 1984 EtO standard and its 1988 revisions focused new attention on health and safety training and other preventive measures. An EtO health and safety training program for hospital sterilization workers was developed by the staff of an independent occupational and environmental health clinic. Participatory and empowerment training methods were central to the approach. Also included were hands-on, demonstration, interactive presentation, and other methods. An EtO Health and Safety Training Manual was developed based on the training experiences. This paper presents the challenges, benefits, and limitations of incorporating participatory and empowerment approaches in the design, implementation, and evaluation of EtO health and safety training.

Determinants of the provision of ethylene oxide medical surveillance in Massachusetts hospitals

An in-depth survey of ethylene oxide (EtO) health and safety was conducted in Massachusetts hospitals (n = 92) to investigate the determinants of the provision of medical surveillance for EtO exposure. We have evaluated the relationships between provision of EtO medical surveillance and (1) activating OSHA-specified triggers for providing EtO medical surveillance, (2) worker training on EtO health and safety, and (3) various public policy, organizational, group, and individual characteristics. Among the Occupational Safety and Health Administration's (OSHA) five specified triggers for provision of EtO medical surveillance, only accidental worker exposures were related to provision of surveillance (RR = 2.56, P < 0.001). Exceeding the Action Level for 30 or more days, one of OSHA's EtO triggers that is also used in a number of other standards, was not related to provision of surveillance (RR = 0.84, P = 0.714). Reports of coverage of EtO medical surveillance issues in worker training were also correlated with the provision of EtO medical surveillance (RR = 3.68, P < 0.001), supporting OSHA's premise that worker training plays an important role in medical surveillance implementation. The presence of detailed written EtO medical surveillance policies was positively related to the provision of EtO medical surveillance (RR = 1.81, P < 0.001). The relationships between these potential determinants and provision of medical surveillance were also validated in multivariate analyses. Implications for improvement of OSHA medical surveillance implementation through revised trigger schemes, improved worker training efforts, and other measures are discussed. Findings are relevant to the future development of medical surveillance and exposure monitoring policies and practices in both substance-specific and generic contexts.