Preparation and properties of poly(vinyl alcohol)/silica nanocomposites derived from copolymerization of vinyl silica nanoparticles and vinyl acetate

Nanocomposites of poly(vinyl alcohol)/silica nanoparticles (PVA-SNs) were prepared by in-situ radical copolymerization of vinyl silica nanoparticles functionalized by vinyltriethoxysilane (VTEOS) and vinyl acetate with benzoyl peroxide (BPO, i.e., initiator), subsequently saponified via direct hydrolysis with NaOH solution. The resulting vinyl silica nanoparticles, PVA-SNs were characterized by means of fourier transformation spectroscopy (FTIR), transmission electron microscopy (TEM) and the elemental analysis method. Effects of silica nanoparticles on viscosity and alcoholysis of PVA-SNs were studied by a ubbelohode capillary viscometer and the back titration method. The morphological structure of PVA-SN films was investigated by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile test were used to determine the thermal and mechanical properties of PVA-SN films. The results indicated that the content of vinyl groups on the surface of the vinyl silica nanoparticles was up to 3.02 mmol/g and vinyl silica nanoparticles had been successfully copolymerized with vinyl acetate. Furthermore, compared to pure PVA, silica nanoparticles bonded with polymer matrix in a low concentration affected the viscosity and alcoholysis of the PVA-SNs materials. At the same time, it resulted in the improvement of the thermal and mechanical properties of the PVA-SN materials due to a strong interaction between silica nanoparticles and the polymer matrix via a covalent bond. It could be found that the optical clarity of the membrane was changed through UV-Vis absorption spectrum due to the introduction of silica nanoparticles.     

On the self-association of the normal alcohols and the glass transition in alcohol-alcohol solutions

The glass-transition temperature (T_g) in mutual binary mixtures of the primary alkanols from methanol throughn-octanol has been measured as a function of composition. For mixtures of the alkanols heavier than ethanol,T _g is found to be a linear function of the number-average molecular length. Methanol and ethanol mixtures show higherT _g values than indicated by this relation. These results are found to be consistent with association of the heavier alkanols into chains of very great length in the supercooled liquid, while ethanol and methanol must form networks with a moderate degree of crosslinking between chains.     

Photophysical characterization of mixed micelles of n-butanol/SDS and n-hexanol/SDS. A study at low alcohol concentrations

 The effect of the addition of n-butanol (BuOH) and n-hexanol (HexOH) on the micellization of sodium dodecylsulfate (SDS) has been investigated using fluorescence quenching methods. The binding constants were calculated using an expression which relates the total concentration of alcohols and the micelle concentration. The values of K were 4.67 and 17.6 M^-1 for BuOH/SDS and HexOH/SDS, similar to values obtained by other methods. The cmc of SDS decreases on addition of alcohols and goes through a minimum for the BuOH/SDS system. Micellar aggregation numbers (N) were determined from linear plots of Ln (I ⁰/I) against [Quencher] at low alcohol concentrations. For 15 mM SDS, in the presence of BuOH the N values decrease on addition of alcohol up to 0.2 M. For HexOH, N can be assumed to be constant up to 4.8 mM, after which N decreases. The polarity of the micellar core containing alcohol was evaluated from the I ₁/I ₃ ratio of monomeric pyrene. The effect of addition of the alcohol causes a decrease in the I ₁/I ₃, which corresponds to a decrease in the polarity of the pyrene solubilization site. Received: 28 October 1996 Accepted: 10 January 1997     

Synthesis ofN-methacryloyl- andN-allyl-substituted derivatives of ethyl 5-oxo-2-pyrrolidinecarboxylate

A method for the preparation of previously unknownN-methacryloyl- andN-allyl-derivatives of ethyl 5-oxo-2-pyrrolidinecarboxylate has been developed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 767–769, March, 1996.     

Blends of starch with ethylene vinyl alcohol copolymers: effect of water,glycerol, and amino acids as plasticizers

Blends of thermoplastic starch with poly(ethylene‐co‐vinyl alcohol) copolymer (EVOH) were melt extruded with water/glycerol as plasticizer and a series of amino acid additives. The biggest factor in end‐use mechanical properties proved to be the relative humidity (RH) during storage. Plasticized starch‐EVOH blends stored at 0 and 50% RH changed significantly over time, with, for example, the tensile strength (TS) of the glycerol‐plasticized blend increasing from 4.7 to 26.3 MPa over 8 weeks when maintained at 0% RH. In contrast, the TS of this same sample stored at 75% RH remained unchanged for 8 weeks. Amino acids provided relatively minor, but significant changes in mechanical properties with time. Based on TS, elongation‐to‐break, and modulus, it may be concluded that β‐alanine, sarcosine, and L ‐proline were more effective than glycerol at maintaining strong flexible blends. Increases in crystallinity and changes in morphology with time, as described by modulated DSC were correlated to these changes in mechanical properties. Published in 2007 by John Wiley & Sons, Ltd.     

Reaction of Grignard Reagents with Diethyl Perfluoroacyl (1-Cyanoethyl)phosphonates. Synthesis of Perfluoroalkylated α,β-Unsaturated Nitriles with Predominant Z-Selectivity

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙｍｕｃｈａｔｔｅｎｔｉｏｎｈａｓｂｅｅｎｄｅｖｏｔｅｄｔｏｔｈｅｓｙｎｔｈｅｓｉｓｏｆα ,β ｕｎｓａｔｕｒａｔｅｄｎｉｔｒｉｌｅｓｓｉｎｃｅｔｈｅｙａｒｅｉｍ ｐｏｒｔａｎｔｓｔｒｕｃｔｕｒａｌｆｅａｔｕｒｅｏｆｓｅｖｅｒａｌｎａｔｕｒａｌｌｙｏｃｃｕｒｒｉｎｇｂｉ ｏｌｏｇｉｃａｌｌｙａｃｔｉｖｅｃｏｍｐｏｕｎｄｓ .1,2 Ｔｈｅｉｎｔｒｏｄｕｃｔｉｏｎｏｆｆｌｕｏ ｒｉｎｅｏｒｔｒｉｆｌｕｏｒｏｍｅｔｈｙｌｇｒｏｕｐｉｎｔｏｂｉｏｌｏｇｉｃａｌｌｙａｃｔｉｖ…     

Manufacturing of pH sensitive PVA/PVP/MWCNT and PVA/PEG/MWCNT nanocomposites: an approach for significant drug release

The purpose of this paper is studying the effect of incorporation of Multiwall Carbon Nanotubes (MWCNT) into two different nanocomposites in poly vinyl alcohol (PVA)/polyvinylpyrrolidone (PVP), and PVA/Polyethylene glycol (PEG). MWCNT were synthesized by chemical vapor deposition (CVD) method using acetylene and Fe/Co/Al₂O₃ as carbon precursor and catalyst, respectively. Nitric acid and sulfuric acid were used for purification and functionalization of MWCNT. Afterward, highly pure and functionalized MWCNT (0, 0.02, and 0.05% w/w) were incorporated in PVA/PVP and PVA/PEG to synthesize PVA/PVP/MWCNT and PVA/PEG/MWCNT nanocomposites hydrogel membranes that cross-linked by freezing–thawing. PEG and PVP were selected in these nanocomposites as dispersion matrix for MWCNT as well as for increasing the elasticity of the nanocomposites membranes. The morphology of the hydrogels was characterized by SEM, FTIR, XRD, TGA, and the mechanical properties of the hydrogel membranes were investigated. The swelling behavior in different pH-buffer solutions was studied as well as studying weight loss percentage and swelling kinetic. The drug releasing process of the hydrogel membranes was investigated using salicylic acid as a model drug. It was found that MWCNT are dispersed well into the polymers and crystallinity, mechanical properties and thermal stability of the hydrogels contain MWCNT are better than that without MWCNT. Maximum degree of swelling was observed at pH 7 and swelling degree increases with increasing the ratio of MWCNT in the hydrogels from 0.02 to 0.05%. All hydrogel membranes followed non-Fickian mechanism and drug releasing were controlled by varying the pH and amount of MWCNT.     

Rh—Mo—K／Al2O3催化剂的CO加氢合成低碳醇性能

本文研究了硫化态和还原态Ｒｈ－Ｍｏ－Ｋ／Ａｌ２Ｏ３催化剂上ＣＯ加氢合成低碳醇的反应性能，考察了不同铑负载量、钾助剂、合成气组成和反应条件（温度、压力和空速）对合成醇性能的影响及催化剂的反应稳定性。发现硫化样品较之还原态样品具有更好的合成醇选择性，催化剂中添加铑后，生成醇活性和选择性大幅度提高。选择合适的反应温度、提高反应压力和空速、适当增加合成气Ｈ２／ＣＯ的比例可以获得较好的合成醇反应性能。     

A Mild Isomerization Reaction for β,γ‐Unsaturated Ketone to α,β‐Unsaturated Ketone

A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions.     

直链醇链长对层状液晶结构与稳定性的影响

作为助表面活性剂,直链醇在层状溶致液晶的制备中是非常重要的。本文以层状液晶的相行为和小角度X射线衍射测量,研究了直链醇链长对层状液晶结构与稳定的影响。