Luminescence of polyvinyl alcohol – CdS compounds doped with Cu, Al and Mn
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Polyvinyl alcohol – CdS compounds doped with different concentrations of Cu, Al and Mn were produced. It is expected that these compounds have one-dimensional (polymeric) structure. Their luminescence spectra were investigated with the aim of use of luminescence for the structure characterization through comparison of luminescent properties of compounds and other CdS based materials. It was found that addition of copper leads to luminescence quenching while intensity of luminescence of compound doped with manganese reaches maximum at some concentration of additive and aluminum does not influence noticeably on the luminescence intensity of the compound. Luminescence spectra were not significantly changed at the doping. They are different from spectrum of crystalline CdS and similar to luminescence of CdS dissolved in glass. It was also found that luminescence of compounds is highly polarized, luminescence of glass is less polarized and luminescence of crystal CdS is not polarized.Keywords:
Polyvinyl Alcohol
水溶性部分シアノエチル化ポリビニルアルコールを微アルカリ性下過酸化水素でほとんど完全にカルバモイル化した後,ホルムアルデヒドおよび水酸化ナトリウムを添加して過剰の過酸化水素をギ酸ナトリウムとして除去すると,同時にカルバモイル基をN-メチロール化する合成法について各種条件下の反応速度を追求した。その結果精製部分カルバモイルエチル化ポリビニルアルコールを原料とする既報の場合とほとんど同様に円滑にN-メチロール化が施行できることを認めた。すなわち, カルバモイル化反応が定量的に進行すると仮定しての過剰な過酸化水素の除去に必要なホルムアルデヒド計算量以上に添加されたメチロール化用のホルムアルデヒドと-CN基とのモル比が増加するほど,また反応温度が高いほどN-メチロール化速度は増加する。たとえばCH2O/-CN=5mol比において,40℃では60分,50℃では30分でほとんど完全にN-メチロール化され,これらの時間においてメチロール化度に極大値の存在が認められた。また脱エーテル化速度はCH2O/-CNモル比が小さいほど,また反応温度の高いほどより大きく,-COOH基生成量はいずれの反応条件においてもきわめて微量であった。-COOH基の微量生成を無視すれば, ホルムアルデヒド過剰条件では反応速度論的に次式が導かれ,それが近似的に実験結果に適用されることを認めた。x=a[exp(-k3t)-exp{-(k1+k2)t}]aは-CONH2基の初濃度,xはN-メチロール化反応t時間後に生成された-CONHCH2OH基数,またk1はN-メチロール化反応速度定数,k2およびk3は-CONH2基および-CONHCH2OH基の脱エール化反応速定数を示す。なおk1+k2/k3は40～50程度と推定され,k1＞k2＞k3であることが認められた。
Polyvinyl Alcohol
Polyvinyls
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Polyvinyl alcohol(PVA) was water-soluble polymer with wide applications.The nature and applications of the polyvinyl alcohol were briefly introduced in this paper.The current situation of the production and consumption of PVA at home and abroad were mainly analyzed.Development prospect of polyvinyl alcohol was expected.
Polyvinyl Alcohol
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Foams for biomedical applications were made from polyvinyl alcohol, polyvinyl alcohol / polyvinyl pyrrolidone blend and their nanocomposites with nanoclay by clean processes. Air was entrapped into the aqueous polymer solutions during vigorous mixing and then the solutions were freeze-dried. The foams structure was stabilized by crosslinking via gamma irradiation without using any harmful chemicals. The hydrophilic biocompatible foams possessed interconnected open cell structure with remarkable capacity to absorb and retain water. The foams in wet state were soft and flexible. Desirable pore structure and higher water absorption was obtained at a solution concentration of 5 wt% for both polyvinyl alcohol and polyvinyl alcohol / polyvinyl pyrrolidone foams and also for the nanocomposite foams. The polyvinyl alcohol / polyvinyl pyrrolidone foams at a composition of 80/20 had a uniform porous structure. Addition of 20 wt% polyvinyl pyrrolidone increased the size and interconnectivity of the cell structure and rendered more flexible foams than the neat polyvinyl alcohol. Also the nanoclay, in the nanocomposite foams, elevated pore population through generation of more air bubbles during aqueous polymer solution mixing.
Polyvinyl Alcohol
Polyvinyl acetate
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The relationship between the structure of polyvinyl alcohol and its water solubility as well as the dissolve mechanism and research significance were discussed in detail.The study progress of the water-soluble polyvinyl alcohol at home and abroad were mainly introduced,especially followed the study status of Kuraray water-soluble polyvinyl alcohol,and the prospect of water-soluble polyvinyl alcohol of China was raised.
Polyvinyl Alcohol
Water soluble
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Carbonnanotubes (CNTs) suspended in polyvinyl glycol were synthesized and their thermal or electrical conductivity enhancement rate were investigated. Polyvinyl alcohols/CNT based nan fluids have been synthesized by dispersing nan composites ofPolyvinyl alcohol/CNT in distilled water without any surfactant.The results showed that well-dispersed Polyvinyl alcohols/CNTs nan fluids with varying concentration of Polyvinyl alcohol/CNT can be synthesized using the present method.The effective thermal and electrical conductivity of CNT/water and polyvinyl alcohol is measured with different concentration and temperatures (30–50 °C). Dispersed CNT was found to enhance thermal and electrical conductivities of base liquid. Howeverthe ratios of thermal conductivities for various concentration of CNT were to have marginal difference where electrical conductivity show appreciable variations. Polyvinyl alcohol based coolants were found to show high thermal and electrical conductivity in comparison to coolants without Polyvinyl alcohol based coolants. Variation of electrical and thermal conductivities were explained on the bases of molecular interactions between constituent materials. The proposed explanationagree quite well with the experimental data.
Polyvinyl Alcohol
Distilled water
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This paper sugeests a method for fabrication of polyvinyl alcohol-honey nanofibers by electrospinning. Polyvinyl alcohol and honey are all biocompatible and environmentally friendly materials. This combination will lead to wide potential applications in various engineering fields.
Polyvinyl Alcohol
Electrospinning
Biocompatible material
Environmentally Friendly
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Polyvinyl alcohol was heat-treated in powder form to a degree which will render it soluble in hot water but insoluble in cold water to permit purification with cold water. The heat-treated polyvinyl alcohol was then subjected to a formalization treatment in powder form. It was assumed that the reaction takes place mainly in the amorphous region of the polyvinyl alcohol molecule so that the formalized groups exist as selectively substituted groups and may be considered as a form of block copolymer.This polyvinyl alcohol was employed to study the rate of formalization, the degree of swelling of films and the physical properties of fibers prepared therefrom. Polyvinyl alcohol containing formal groups in the amount not more than 5% appeared to be selectively substituted. Fibers obtained from partially formalized polyvinyl alcohol were found to have improved mecnanical properties, especially improved elastic recovery under low strain.
Polyvinyl Alcohol
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Polyvinyl Alcohol
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Abstract— Quenching of the degradative photobleaching of FMN in anaerobic aqueous solution, and of the flavin‐sensitized photo‐oxidation of EDTA, alcohols, glycols, and glycerol, has been examined using flash techniques. The quenching can be produced by addition of KI, by successive flashes, and by increasing the flavin concentration (self‐quenching). It is concluded that the lowest triplet is the photoreactive species in all systems, that the successive flash effect is due to triplet quenching by a reaction product, and that the concentration quenching may be due to either triplet‐triplet annihilation or to reaction between a ground‐state flavin and a flavin triplet.
Flash photolysis
Photobleaching
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