Photodestruction of Polyvinylpyrrolidone in Aqueous Solutions of Metal Nitrates
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Polyvinylpyrrolidone
ポリピニルピロリドン(PVP)水溶液に脱水剤である電解質や有機液体を加えるとPVFは沈殿する。PVPの沈殿の起こる脱水剤濃度は脱水剤の化学種,系の温度および高分子濃度に依存する。有機液体では相分離を起こすに必要な沈殿剤の濃度は30～50mol%であり沈殿剤が多量に必要であるが,電解質の場合には0.2～1.3mol%と少なくてよい。離液順列において塩析能の強いとされる電解質,すなわちクエン酸ナトリウム,硫酸ナトリウム,炭酸ナトリウムおよび酒石酸ナトリウムでは薗の順に低い濃度で二相分離を起こすが,酢酸ナトリウムやチオシアソ酸ナトリウムは二相分離を起こさない。またこれらの塩析能の強い電解質の場合には高温では二相分離するが低温にすると一相の透明な溶液にもどる。一方,有機液体の場合には温度の効果は電解質の場合とは逆になり低温では二相分離していてもこれらの溶液を高温にすると透明になり0相の溶液になる。二相分離した状態で両相の各成分を定量して相平衡図を得た。 この相平衡図のタイ・ラインによれば水と沈殿剤の比はPVPの濃厚相と希薄相とで異なり,水の割合は濃厚相の方が大きいことがわかった。この差はPVPに水和した水分に基づくものであり,この水分は沈殿剤を溶かし得ないものと仮定してPVPの結合水を求めると, 電解質を添加した系ではPVP残基あたり4～8分子,有機液体を添加した系では2～4分子の水が結合していることがわかった。またこれらの沈殿剤を加えた水溶液を溶媒としてPVPの固有粘度[η]を求めると水や電解質水溶液の場合には[η]は温度とともに低下し,これはPVPの脱水和のためにPVPの糸まりの収縮が起こるためであるが,有機液体を混合した系でに結合水の量が少なく,かつ温度とともに減少する傾向があるにもかかわらず温度とともに[η]は上昇する結果が得られた。これはPVPの結合水は減少するが,有機液体が溶媒和し,このために糸まりの膨潤が起こり[η]は上昇するものと結論した。
Polyvinylpyrrolidone
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Nano-silver/polyvinylpyrrolidone (PVP) composite materials were synthesized in the silver nitrate solution containing PVP by microwave. The mechanism of catalytic reduction of sliver ion by atom N in PVP was discussed. UV-Vis and XRD results indicate the presence of nano silver with face-centered cubic structure. TEM result shows that nano silver particles with 15～25 nm size were homogeneously dispersed in the PVP matrix. XPS results suggest that there is an interaction between PVP and nano Ag.
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The regularities of obtaining silver nanoparticles in the presence of polyvinylpyrrolidone, which was both a reductant and a stabilizer of nanoparticle dispersion, have been studied. The influence of such factors as temperature, polyvinylpyrrolidone amount, concentration and nature of silver salts on the shape and size of nanoparticles has been established. The chemistry of the silver salts and polyvinylpyrrolidone reaction with the formation of vinylsuccinimide units in the structure of macromolecules has been proposed, which is confirmed by the results of IR spectroscopy. It has been established that the shape and size of silver nanoparticles are influenced by the silver salt nature. If silver nitrate is used for the reduction reaction, silver nanoparticles are formed mainly in the form of triangular prisms and polyhedra. When using silver acetate, nanoparticles of spherical shape are predominantly formed. High-quality nanoparticles are formed if the mass ratio of polyvinylpyrrolidone : silver salt is more than 20. The decrease in this ratio deteriorates the stabilization of the formed nanoparticles and increases the particle size of silver until the formation of nanocrystals several hundred nanometers in size. The kinetics of silver salts and polyvinylpyrrolidone reaction has been studied in a solution. The reaction was found to occur faster with increasing temperature and the polyvinylpyrrolidone amount. Silver reduction reaction by polyvinylpyrrolidone was used to provide fungibactericidal properties of hydroxyapatite-filled osteoplastic porous composites based on polyvinylpyrrolidone copolymers with methacrylic esters.
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The article describes the results of the investigations of optical and luminescent properties of PbS suspensions and composite coatings stabilized by high-molecular polyvinylpyrrolidone. Experiments show strong dependence of optical properties and stability of the materials on the concentration ratio between PbS nanoparticles and polymer. Copyright © 2015 John Wiley & Sons, Ltd.
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