Liposomal Encapsulation of Carvacrol to Obtain Active Poly (Vinyl Alcohol) Films

Lecithins of different origins and compositions were used for the liposomal encapsulation of carvacrol within the framework of the development of active films for food packaging. Liposomes were incorporated into aqueous polymeric solutions from fully (F) and partially (P) hydrolysed Poly (vinyl alcohol) (PVA) to obtain the films by casting. The particle size distribution and ζ-potential of the liposomal suspensions, as well as their stability over time, were evaluated. Liposomal stability during film formation was analysed through the carvacrol retention in the dried film and the film microstructure. Subtle variations in the size distributions of liposomes from different lecithins were observed. However, the absolute values of the ζ-potential were higher (−52, −57 mV) for soy lecithin (SL) liposomes, followed by those of soy lecithin enriched with phosphatidylcholine (SL-PC) (−43, −50 mV) and sunflower lecithin (SFL) (−33, −38 mV). No significant changes in the liposomal properties were observed during the study period. Lyotropic mesomorphism of lipid associations and carvacrol leakage occurred to differing extents during the film drying step, depending on the membrane lipid composition and surface charge. Liposomes obtained with SL-PC were the most effective at maintaining the stability of carvacrol emulsion during film formation, which led to the greatest carvacrol retention in the films, whereas SFL gave rise to the least stable system and the highest carvacrol losses. P-PVA was less sensitive to the emulsion destabilisation due to its greater bonding capacity with carvacrol. Therefore, P-PVA with carvacrol-loaded SL-PC liposomes has great potential to produce active films for food packaging applications.     

Alcohol Solvates of Lanthanoid(III) Trifluoromethanesulfonates

After vacuum dehydration, a number of hydrated trivalent lanthanoid trifluoromethanesulfonates (“triflate”, “OTf” = F₃CSO₃), when recrystallized from various alcohol (ROH) solutions, yield solvates Ln(OTf)₃ · xROH, x = 3, 5 or 6. The following have been defined crystallographically (R/Ln/x): Me/La/3;Me/Gd/6; Et/Sm/3; Et/Gd/5 iPr/Nd,Sm/3. The Me/Gd/6complex, Gd(OTf)₃ · 6MeOH is a mononuclear/ionic form [(MeOH)₆Gd(O–OTf)₂](OTf), the gadolinium environment being octacoordinate, square‐antiprismatic with the O–OTf donors quasi‐trans on different faces of the coordination polyhedron; the Et/Gd/5 complex is neutral, molecular, mononuclear [(EtOH)₅Gd(O–OTf)₃], also with an octacoordinate, square‐antiprismatic coordination sphere, derivative of that of the methanol solvate. The remainder form one‐dimensional polymeric arrays, successive lanthanoid atoms linked by (μ‐O–OTf–O′)₃ triads, at either end of a tricapped trigonal prismatic array, the ROH molecules contributing the capping atoms. A (“baseline”) (re‐)determination of the “parent” Sm(OTf)₃ · 9H₂O is also recorded.     

Alcohol Dimer is Requisite to Form an Alkyl Oxonium Ion in the Proton Transfer of a Strong (Photo)Acid to Alcohol

Alcohols, the simplest amphiprotic organic compounds, can exhibit either acidic or basic behavior by donating or accepting a proton. In this study, proton dissociation of a model photoacid in solution is explored by using time‐resolved spectroscopy, revealing quantitatively for the first time that alcohol acts as a Brønsted base because of H‐bonded cluster formation to enhance the reactivity. The protonated alcohol cluster, the alkyl oxonium ion, can be regarded as a key reaction intermediate in the well‐established alcohol dehydration reaction. This finding signifies, as in water, the cooperativity of protic solvent molecules to facilitate nonaqueous acid–base reactions.     

Polymer-Supported N-Sulfonated Amino Alcohol for Titanium(Ⅳ) Catalyzed Diethylzinc Addition to Aldehydes

Homogeneous asymmetric catalysis is one of the most important developments in chemistry in the past several decades. Attachment of chiral ligands to a polymeric support offers important advantages such as facilitated workup procedures, easy recovery and reuse of the catalyst in catalytic reactions. Various chiral ligands supported on polymer have been used as catalysts.     

Poly(Organophosphazenes): Use in the Improvement of Standard Materials. Application to the Modification of Surface Properties of Poly(Vinyl Alcohol)

Abstract

Modification of surface properties of poly(vinyl alcohol) by grafting of poly(organophosphazenes).     

Poly-Sugar: Modification of Poly(vinyl Alcohol)

This paper describes the attachment of sugar (sucrose) onto low molecular weight poly(vinyl alcohols) (etherification) to produce a new class of synthetic sweetener. Because of its regulated molecular weight, the new sweetener would pass through the digestive tract and be excreted in its original molecular form. We have termed the new class of sweeteners poly-sugar. The etherification of sucrose with poly(vinyl alcohol) can be carried out either in dimethyl sulfoxide or water. We have prepared poly-sugars with varying degrees of etherification (3.4–5.4). Highly etherified products were bitter, but a poly-sugar with a 4.23 degree of etherification was sweet without any bitter aftertaste.     

Grafting of Vinyudene Chloride. Model Studies with Poly(Vinyl Alcohol) as Substrate

The modification of coatings resins by graft polymerization of vinylidene chloride should produce a coatings binder with improved barrier properties. For superior color stability, vinylidene chloride must be copolymer-ized with other monomers such as alkyl acrylates and methacrylates. Ceric ion initiation was used to graft vinylidene chloride free-radically onto a model alcohol-containing polymer, polyvinyl alcohol. The effects of various reaction parameters on vinylidene chloride grafting were studied. Graft copolymers were characterized using selective solvent extraction, FTIR, SEM, XES, DSC, and x-ray diffraction.     

Reduction of Ruthenium(IV) to Ruthenium(III) in Aqueous Alcohol Solutions of Hydrochloric Acid under Microwave Radiation

The behavior of a kinetically inert form of ruthenium(IV), the -oxo-bis-[pentachlororuthenate(IV)] ion [Ru₂OCl₁₀]^4–, was studied in aqueous alcohol solutions of hydrochloric acid under microwave radiation and upon the heating of the solutions. The conditions were selected for the quantitative reduction of ruthenium(IV) to ruthenium(III) with alcohols in 0.6–10 M HCl solutions in a microwave field. The maximum time it takes to reduce ruthenium(IV) under microwave radiation (30 min) was an order of magnitude shorter than that for heating the solutions in a boiling water bath. Regardless of the type of alcohol, the most rapid reduction of ruthenium(IV) was observed at the boundaries of the studied range of hydrochloric acid concentrations. It was found that, under microwave radiation, thermal effects were the driving force of the process in a 0.6 M HCl solution at 98°C, whereas, in 8–10 M HCl solutions, the contributions of nonthermal and thermal effects were comparable. It was shown that the reducing ability of saturated monoatomic C₁–C₄ alcohols increases with the number of carbon atoms and is also due to specific features of microwave radiation.     

Cofactor-Bound Cross-Linked Enzyme Crystals (CLEC) of Alcohol Dehydrogenase

Horse liver alcohol dehydrogenase was crystallized in the presence of its cofactor. The cross-linked enzyme crystals (CLECs) produced showed good catalytic activity without the addition of extra cofactor (see scheme). The enantioselectivity and stereochemical preference of the CLEC were the same as with the soluble enzyme, and both cofactor and enzyme were considerably more stable in CLEC form. Cofactor regeneration studies on the reduction of cinnemaldehyde indicate the potential for a high level of catalyst productivity.     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上, 制备了Pt/MIL-101(Cr)催化剂, 并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明, Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0wt%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能, 在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上,制备了Pt/MIL-101(Cr)催化剂,并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明,Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能,在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

固体聚合物电解质在肉桂醇电化学氧化中的应用(I)

研究使用白金-SPE 复合电极, 以二价锰离子为催化剂进行肉桂醇的电化学氧化实验. 电解结果的分析表明, 在电化学氧化中肉桂醇中的双键不被破坏. 该反应为后续化学反应(即EC 反应), 对电解生成物的选择性较高, 肉桂醛生成的电流效率高于80%, 肉桂酸生成的电流效率仪在5%左右.     

Redox-Initiated Grafting of Acrylic Monomers onto Poly(vinyl Alcohol)

Loss of capacity of magnetic micro ion-exchange resins has been suggested to be caused by cleavage of unstable linkages formed during the graft polymerization reaction. The nature of the grafting process was investigated by using a series of model compounds having the same structural features as the glutaraldehyde-crosslinked poly(vinyl alcohol) core matrix. These compounds were then subjected to hydrogen peroxide oxidation, followed by the addition of monomer in the presence of iron(II). The identity and extent of peroxidation of the intermediate compounds was determined. In each of the peroxidation reactions the tertiary acetal hydrogen was oxidized to a hydroperoxy derivative. Some of these derivatives were able to dimerize to form peroxy compounds. The reactions occurred rapidly at room temperature when an acetal compound was shaken with hydrogen peroxide. Good yields could be obtained by precipitation of the sodium salts of the hydroperoxides. The hydroperoxy derivatives were shown to initiate polymerization of methyl acrylate, acrylic acid, and acrylamide when in the presence of iron(II).     

氟改变了醇在镍(100)表面上的氧化机理

利用程序热脱附(TPD)实验研究了2-丙醇和三氟-2-丙醇在Ni(100)表面的吸附和热反应过程. 实验结果表明, 电负性大的氟原子取代丙醇中γ-位氢原子后, 使丙醇从脱氢反应转化为脱水反应. 在这两种化合物的TPD 实验产物中发现, 有以脱水反应生成的烯烃(丙烯, 三氟丙烯), 脱氢反应产生的酮类(丙酮, 三氟丙酮)等分子析出. 实验结果表明, 氟原子取代γ-H后阻止了产生中间产物醇盐的β-H 脱氢反应, 打开了γ-H脱氢反应的通道, 导致烯烃的产生. 在2-丙醇吸附于镍表面的TPD实验中观察到了消去β-H产生丙酮的脱氢反应, 而1,1,1-三氟-2-丙醇在镍表面上经过脱水反应则产生了3,3,3-三氟丙烯.     

Ceric Ion Initiated Graft Polymerization onto Poly(vinyl Alcohol)

This paper describes the kinetics of the ceric ion-initiated graft co-polymerization of vinyl acetate-acrylonitrile to poly(vinyl alcohol). The graft copolymerization rate R_p was found to be first order with respect to the total concentration of the comonomer mixture [M], the concentration of vinyl alcohol repeating units [PVA], and the mole fraction of vinyl acetate in the comonomer feed mixture. R_p was independent of cerous ion. The grafting rate was independent of ceric ion above a ceric concentration of 0.0020 M but first order in ceric ion below that concentration. Rp initially increased rapidly with [H⁺] to a maximum and then decreased and levelled off at hgher [H⁺]. The rate of ceric ion disappearance was first order in [PVA], independent of [MI, and increased with increasing [H⁺] with a leveling off at high [H⁺]. A reaction mechanism.     

Cellulose Nanocrystals (CNCs) Induced Crystallization of Polyvinyl Alcohol (PVA) Super Performing Nanocomposite Films

This study is aimed to explore the properties of cellulose nanocrystals (CNC)/polyvinyl alcohol (PVA) composite films with and without 1,2,3,4‐butane tetracarboxylic acid (BTCA), a nontoxic crosslinker. CNC and CNC‐PVA nanocomposite films are prepared using solution‐casting technique. Differential scanning calorimetry (DSC) analyses show that crosslinking increased the glass transition temperature but reduced the melting temperature and crystallinity. Furthermore, high CNC concentrations in the PVA matrix interfere with PVA crystallinity, whereas in specific ratio between CNC and PVA, two different crystalline structures are observed within the PVA matrix. Film surfaces and fracture topographies characterized using scanning electron microscope indicate that at certain CNC‐PVA ratios, micron‐sized needle‐like crystals have formed. These crystalline structures correlate with the remarkable improvement in mechanical properties of the CNC‐PVA nanocomposite films, that is, enhanced tensile strain and toughness to 570% and 202 MJ m^?3, respectively, as compared to pristine PVA. BTCA enhances the tensile strain, ultimate tensile stress, toughness, and modulus of CNC films compared to pristine CNC films. Water absorption of crosslinked CNC and CNC‐PVA nanocomposite films is significantly reduced, while film transparency is significantly improved as a function of PVA and crosslinker content. The presented results indicate that CNC‐PVA nanocomposite films may find applications in packaging, and though materials applications.     

Semicontinuous Emulsion Polymerization of Vinyl Acetate. Part I. Homopolymerization with Poly-(Vinyl Alcohol) and Nonionic Coemulsifier

The semicontinuous emulsion polymerization of vinyl acetate has been studied. Poly(vinyl alcohol) as a protective colloid and ethoxylated cetyl alcohol as a coemulsifier were used. The conversion and particle diameter were affected by the stirring speed and the coemulsifier distribution between initial reactor charge and continuously introduced monomer. The amount of unreacted monomer oscillates with time.     

Ultrasonic Degradation and Copolymerization of Poly (Vinyl Alcohol) with Acrylonitrile

The ultrasonic degradation of poly(vinyl alcohol) (PVA) in aqueous solution and copolymerization of PVA with acrylonitrile (AN) were studied. It is confirmed that the rate of degradation of PVA follows the kinetic equation suggested by Baramboim. Both water-soluble and water-insoluble copolymer can be obtained by changing the irradiation time or the amount of AN added to the aqueous solution of PVA. The structure of the copolymer was identified by IR, MS, PGC, and x-ray diffraction. The copolymer prepared is mainly a block one. By irradiating 2% PVA/AN (1/1.6, w/w) at 20 ± 1°C and 21. 5 kHz with 490 W for 28 min, the yield of water-soluble copolymer is 25.49%, the AN content in which is 13.98%. After 100 min, with the weight ratio between PVA and AN 1/4, the yield of the water-insoluble copolymer amounted to 296.01%, the AN content in which is 75.56%.     

Characterisation of Redox Initiators for Producing Poly(Vinyl Alcohol) Hydrogels

Summary: This work focuses on the characterisation of ascorbic acid/persulphate initiating system. Three different persulphates were used (ammonium, potassium and sodium), and a range of initiator concentrations were tested. Gel time, gel quality, initiator toxicity, and cell survival upon encapsulation were measured. No significant differences were observed between the three types of persulphates. Higher concentrations of the initiators resulted in faster gel times (5min for 0.05wt% initiator) and higher quality gels (less than 20% sol fraction), although the lower initiator concentrations were better in terms of cell growth inhibition and survival upon encapsulation. Overall, this system shows great promise for use in biomedical applications, however there is a need to minimise the initiator concentration to increase cell compatibility while maintaining a high enough concentration for adequate gel formation.     

Synthesis and Immunosuppressive Activity of New Amino Alcohol Derivatives(Ⅰ)

A series of new amino alcohol derivatives was synthesized and evaluated for their immunosuppressive activity on mouse peripheral blood lymphocytes.The structures were confirmed by means of 1H NMR,13C NMR,IR and MS.Most of the compounds display moderate to potent inhibitory activity.Compound 9d shows the most activity among them that are expected as a powerful candidate for safer immunosuppressant for organ transplantations and the treatment of autoimmune diseases.