Investigation of poly[4(5)-vinylimidazole] composites and their potential as proton conductive membranes

In order to demonstrate proton conductivity in an imidazole polymer system, novel composite proton exchange membranes were fabricated by casting films of poly[4(5)-vinylimidazole/vinylimidazolium trifluoromethylsufonylimide] and poly(vinylidene fluoride)], PVdF, from mixed dimethylformamide (DMF) solutions. The phase, composition and morphology of these composites were examined by differential scanning calorimetry (DSC), and hot stage polarized microscopy. Thermal stability was evaluated by thermal gravimetric analysis (TGA). Proton conductivity was in a fuel cell test fixture evaluated at GM Fuel Cell Activities in Honeoye Falls, NY. DSC thermograms were characterized by a crystalline melt for the PVdF component at ∼169°C. All composites displayed a well-form exothermic peak for recrystallization of PVdF at ∼121°C. The melting and recrystallization characteristics of PVdF in the composites were substantially identical to those of pure PVdF. In its homogeneous state, poly[4(5)-vinylimidazole/imidazolium trifluoromethylsulfonylimide] exhibited a glass transition temperature, Tg-mid, of -30°C. A glass transition temperature was not observed for the poly[4(5)-vinylimidazole/imidazolium trifluoromethylsulfonylimide] phase in the blends, because the temperature was not scanned below 0°C in the DSC thermograms of the blends. Incorporation of benzoyl peroxide resulted in a slight increase in crystallinity of the 3/1 and 4/1 compositions and a substantial increase in crystallinity of the 8/1 composite. Crystallinity increased slightly as the volume fraction of PVdF was increased. Classic crystalline spherulites were observed in films cast from DMF and dried at temperatures below the melting point of PVdF. On heating to 200°C on the hot stage microscope, crystals melted to reveal a rather amorphous dark field with thin worm-like inclusions which were presumed to arise from the poly[4(5)-vinylimidazole/imidazolium trifluoromethylsulfonylimide] phase. On cooling to ambient temperature, the background field became progressively brighter, however, no structure that might be associated with the reformation of crystallites was observed. This was presumably a result of submicroscopic size of the crystallites. TGA spectra of the all composite films were characterized by two transitions, one at 300°C corresponding to the decomposition of poly[4(5)-vinylimidazole/imidazolium], and one at 450°C which corresponds to the decomposition of PVdF. Mass loss corresponded well with the mass fractions of the two components of the composite. Proton conductivity was measured as a function of relative humidity at 80°C. Conductivity (0.05 S/cm) approaching that exhibited by Nafion® 112 (0.18 S/cm) was realized in the 4/1, PVdF/poly[4(5)-vinylimidazole/imidazolium] composite film. Substantial conductivity (0.02 S/cm) was also measured in the 3/1 composite films. No measurable proton conductivity was observed in films of the 8/1 composite. We believe that this is the first instance in which such high proton conductivity levels have been realized in a polymer system where a Grotthuss mechanism of proton transport might be invoked. These results are very exciting and may point the way to the preparation of membranes exhibiting high levels of proton conductivity at elevated temperature and low relative humidity

Children-related factors associated with life satisfaction of urban older adults living alone in China

IntroductionThe aim of this study is to investigate the association between the number of children, their gender structure, and the gender of children by birth order with the life satisfaction of urban older adults living alone (UOALA) in five Chinese cities. Traditional reproductive views suggest that having more children, especially sons, is associated with higher life satisfaction for older adults.MethodsThis study utilized a cross-sectional design and included a sample of 2,801 UOALA from five Chinese cities. The life satisfaction of participants was measured using standardized questionnaires. To analyze the data, both OLS and OLogit methods were employed.ResultsEmpirical research shows that the number of children has a positive association with life satisfaction of UOALA, which is greater in male older adults than in female ones. The increase in the number of daughters is significantly associated with higher life satisfaction. In terms of gender structure, UOALA with multiple children, including both sons and daughters, tend to have a higher level of life satisfaction, which partly validates the cohort reproductive preference. In terms of gender of children by birth order, UOALA whose first child is a daughter have higher life satisfaction, which is more pronounced among male UOALA, while the association of gender of children by birth order on female UOALA is relatively weak.DiscussionThis study contributes to the understanding of the factors associated with the life satisfaction of UOALA in China. The findings suggest that having more children, particularly daughters, and a balanced gender structure of children is associated with higher levels of life satisfaction. The study suggests the need for targeted social support for UOALA with varying family structures

Composite Expectile Regression with Gene-environment Interaction

If error distribution has heteroscedasticity, it voliates the assumption of linear regression. Expectile regression is a powerful tool for estimating the conditional expectiles of a response variable in this setting. Since multiple levels of expectile regression modelhas been well studied, we propose composite expectile regression by combining different levels of expectile regression to improve the efficacy. In this paper, we study the sparse composite expectile regression under high dimensional setting. It is realized by implementing a coordinate descent algorithm. We also prove its selection and estimation consistency. Simulations are conducted to demonstrate its performance, which is comparable to or better than the alternatives. We apply the proposed method to analyze Lung adenocarcinoma(LUAD) real data set, investigating the G-E interaction

Morphology of Poly (3,4-Ethylene Dioxythiophene) (PEDOT) Thin Films, Crystals, Cubic Phases, Fibers and Tubes.

Poly(3,4-ethylene dioxythiophene) (PEDOT) is a chemically stable, conjugated polymer that is of considerable interest for a variety of organic electronic devices including microfabricated neural electrodes that interface with living cortical tissue. The properties of conducting polymers are strongly dependent on the morphology and structure of the material in the solid-state. The rigid π-π conjugated conformation of PEDOT facilitates charge transport and favors crystallization that reduces solubility and processability, making detailed studies of PEDOT morphology difficult. This has also made it hard to control the microstructure at a variety of length scales. In this dissertation the morphology of PEDOT has been studied and controlled at several different length scales from nanometers to micrometers. On the nanoscale, the primary intermolecular (100) d-spacing in PEDOT crystals has been controlled from 1.15 nm to 1.52 nm by using different counter-ions as dopants. The surface morphology and crystallinity of electrochemically deposited PEDOT films have been controlled by changing deposition conditions. A highly ordered, crystalline PEDOT-Br phase was formed during electrochemical deposition in the presence of bromine counterions. On the tens of nanometers scale, isotropic PEDOT bicontinuous cubic structures with extremely large surface areas were developed using ternary non-ionic surfactant, water and oil systems. On the micrometer scale, aligned PEDOT fibers and tubes were prepared by electrospinning blends of poly(lactide-co-glycolide) (PLGA) or poly(caprolactone) (PCL) and EDOT monomer onto a rotating wheel or a dielectric gap in a metal substrate. These aligned fibers and tubes were shown to precisely direct neural regeneration in specific directions in vitro. These developments help understand the structure and properties of conjugated polymers for use in organic electronic devices.Ph.D.Macromolecular Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/86361/1/jinghwu_1.pd