Polymeric dressing formulations containing water-soluble fullerene derivatives

The effect of small additions of water-soluble fullerene C₆₀ derivatives on the strength properties of polyvinyl alcohol films was examined. Solutions of polyvinyl alcohol and fullerenol were tested as polymeric dressing formulations for glass-reinforced plastics based on a thermoplastic polyethylene or polyamide matrix.     

Synthesis of Amphiphilic Fullerene Derivatives and Their Incorporation in Langmuir and Langmuir‐Blodgett Films

Various amphiphilic fullerene derivatives were prepared by functionalization of [5,6]fullerene‐C₆₀‐I_h (C₆₀) with malonate or bis‐malonate derivatives obtained by esterification of the malonic acid mono‐esters 5 – 7 . Cyclopropafullerene 10 was obtained by protection of the carboxylic acid function of 6 as a tert‐butyl ester, followed by Bingel addition to C₆₀ and a deprotection step (Scheme 2). The preparation of 10 was also attempted directly from the malonic acid mono‐ester 6 under Bingel conditions. Surprisingly, the corresponding 3′‐iodo‐3′H‐cyclopropa[1,9][5,6]fullerene‐C₆₀‐I_h‐3′‐carboxylate 11 was formed instead of 10 (Scheme 3). The general character of this new reaction was confirmed by the preparation of 15 and 16 from the malonic acid mono‐esters 13 and 14 , respectively (Scheme 4). All the other amphiphilic fullerene derivatives were prepared by taking advantage of the versatile regioselective reaction developed by Diederich and co‐workers which led to macrocyclic bis‐adducts of C₆₀ by a cyclization reaction at the C‐sphere with bis‐malonate derivatives in a double Bingel cyclopropanation. The bis‐adducts 37 – 39 with a carboxylic acid polar head group and four pendant long alkyl chains of different length were prepared from diol 22 and acids 5 – 7 , respectively (Scheme 9). In addition, the amphiphilic fullerene derivatives 45, 46, 49, 54 , and 55 bearing different polar head groups and compound 19 with no polar head group were synthesized (Schemes 11–13, 15, and 5, resp.). The ability of all these compounds to form Langmuir monolayers at the air‐water interface was investigated in a systematic study. The films at the water surface were characterized by their surface pressure vs. molecular area isotherms, compression and expansion cycles, and Brewster‐angle microscopy. The spreading behavior of compound 10 was not good, the two long alkyl chains in 10 being insufficient to prevent aggregation resulting from the strong fullerene‐fullerene interactions. While no films could be obtained from compound 19 with no polar head group, all the corresponding amphiphilic fullerene bis‐adducts showed good spreading characteristics and reversible behavior upon successive compression/expansion cycles. The encapsulation of the fullerene in a cyclic addend surrounded by four long alkyl chains is, therefore, an efficient strategy to prevent the irreversible aggregation resulting from strong fullerene‐fullerene interactions usually observed for amphiphilic C₆₀ derivatives at the air‐water interface. The balance of hydrophobicity to hydrophilicity was modulated by changing the length of the surrounding alkyl chains or the nature of the polar head group. The best results in terms of film formation and stability were obtained with the compounds having the largest polar head group, i.e. 45 and 46 , and dodecyl chains. Finally, the Langmuir films obtained from the amphiphilic fullerene bis‐adducts were transferred onto solid substrates, yielding high‐quality Langmuir‐Blodgett films.     

Effect of Silk Fibroin Reinforcement on the Properties of Potato Starch-Polyvinyl Alcohol Blend Films

Starch and polyvinyl alcohol composite films, reinforced with raw and methylmethacrylate-grafted silk fibroin particles, were prepared by the solution-casting method on leveled plates. Silk fibroin was used as reinforcement for starch and polyvinyl alcohol (St/PVA) blends in order to improve their mechanical and water-resistance properties. The composites were plasticized with citric acid and cross-linked with gluteraldehyde. The reinforced films showed an increase in tensile strength with decrease in elongation at break. The optimized samples were characterized by scanning electron microscopy and were studied for their antibacterial properties. The biodegradable behavior was studied by the soil burial method.     

Effect of fullerene C<Subscript>60</Subscript> on the structure and mechanical characteristics of polyethylene: Technological aspect

On the basis of the literature data, a retrospective analysis of the thermodynamic characteristics of dissolution of fullerene C₆₀ in a series of single-ring aromatic solvents is presented. The effect of the molecular structure of a solvent on its dissolving capacity with respect to fullerene is studied. The parameter of the boiling temperature of the solvent normalized to its molecular mass is introduced. The correlation of this parameter with the dissolving capacity of the solvent is discussed. Special emphasis is placed on the effect of halogen-containing solvents on the dissolution of fullerene and indirectly on the development of the mechanical characteristics of films prepared from common solutions of fullerene and low-density polyethylene. For comparison, the films prepared from PE melts modified with low concentrations of fullerene are considered. The film structure is studied via X-ray analysis, optical microscopy, AFM, small-angle scattering of linearly polarized light, and DSC. The films with the maximum strength are prepared from solutions in halogen-containing solvents at a concentration of fullerene below 1 wt %. In this case, spherulites are 5–10 times smaller than those in the films cast from solutions in other solvents. In the films cast from common solutions of PE and fullerene in bromobenzene, crystal solvates C₆₀ · 2C₆H₅Br are formed. It seems that the formation of the crystal solvates binds the residual solvent and thus affects the mechanical behavior of the films, thereby eliminating the plasticizing effect of residual bromobenzene. Localization of fullerene in various regions of the supramolecular structure of the films is discussed, and the morphology of the separating regions of the crystal solvate fullerene phase is analyzed.     

Synthesis and Characterisation of Polyvinyl alcohol (PVA)/Silica Hybrid Composites Derived Through the Sol-Gel Method in Aqueous Medium: Effect of Acid Content,Silica Content and Viscosity of PVA on the Dispersion Characteristics of Silica and the Physical Properties of the Composites

A cheap and environment friendly route towards the synthesis of Polyvinyl alcohol/silica hybrid composites is presented. Polyvinyl alcohol/silicate hybrid materials were synthesised in aqueous medium by the sol-gel method using dil HCl (0.5 N) as catalyst and a cost-effective silica source sodium silicate. The synthesis method was aimed at enhancing the rate of co-condensation of silica within the polyvinyl alcohol matrix. Transparent and flexible hybrid films of homogenous thickness were obtained after gelation at 45°C for 24 h and extended drying for another 48 h. The hybrid composites were characterised by fourier transform infrared spectroscopy (FTIR), scanning electron microscopoy (SEM), thermogravimeric analysis (TGA), tensile strength, elongation at break and water uptake measurements. SEM micrographs revealed that silica was dispersed in the PVA matrix without the large aggregation of particles for a molar composition of 0.0004 PVA:0.048 Sodium silicate: 0.004 HCl.     

Sol–gel synthesis of calcium hydroxyapatite thin films on quartz substrate using dip-coating and spin-coating techniques

Sol–gel synthesis route was suggested to prepare calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, CHA) thin films on quartz substrates. CHA thin films were obtained using dip-coating and spin-coating techniques by coating the substrates 1, 5, 15 and 30 times. In the sol–gel process, the ethylenediaminetetraacetic acid and 1,2-ethandiol as complexing agents were used. Moreover, triethanolamine and polyvinyl alcohol were used as gel network forming materials. After each coating procedure the films were annealed at 1,000 °C. The results obtained from dip-coating and spin-coating techniques were compared in this study. It was demonstrated, that the formation of calcium hydroxyapatite depends on dipping (or spinning) time and annealing duration.     

Effect of lipophilicity of C60 fullerene derivatives on their ability to inhibit peroxide oxidation of lipids in aqueous medium

The aqueous solutions of C₆₀ fullerene derivatives were studied by means of dynamic light scattering, their effect on the peroxide oxidation of lipids (POL) in aqueous solutions was investigated via chemiluminescence method. It was shown that the colloidal solubility in water, which defines the antioxidant activity of C₆₀ fullerene derivatives during POL, is controlled by the chemical structure of the addend added to C₆₀ fullerene. For the studied derivatives, the direct dependence of the efficiency of POL inhibition on the lipophilicity was established.     

Si-Tethered Bis- and Tris-Malonates for the Regioselective Preparation of Fullerene Multi-Adducts

Bis- and tris-malonates constructed around a silicon atom have been prepared by reaction of malonate derivatives bearing an alcohol function with di-tert-butylsilyl bis(trifluoromethanesulfonate) and tert-butyl(trichloro)silane, respectively. These compounds have been used for the regioselective bis- and tris-functionalization of C₆₀ under Bingel conditions. By changing the nature of the linker between the central Si atom and the reactive malonate groups, the malonate precursors have been optimized to produce specific bis- and tris-adducts with excellent regioselectivity. A complete understanding of the electronic and stereochemical factors governing the regioselectivity has been obtained by combining computational studies with a complete analysis of the by-products formed during the reactions of the Si-tethered tris-malonates with C₆₀. Finally, desilylation reactions of the resulting fullerene bis- and tris-adducts have been carried out to generate the corresponding acyclic fullerene bis- and tris-adducts bearing alcohol functions.     

Antioxidant properties of water-soluble amino acid derivatives of fullerenes and their role in the inhibition of herpes virus infection

The antioxidant properties of water-soluble amino acid derivatives of fullerene C₆₀ (ADF) were studied. It was shown by the change in the concentration of malonic dialdehyde in rat brain mitochondria that the ADF are antioxidants. They were shown by the change in the luminol glow to possess antiradical activity, which is determined by the acceptor properties of the fullerene spheroid and is independent of the structure of the attached addends. Stereoselectivity of the antioxidant properties of the enantiomers of amino acid derivatives of fullerene C₆₀ was found. The L-isomers of ADF inhibit lipid peroxidation, whereas the D-isomers do not inhibit. A reliable correlation between the development of cytomegalovirus (CMV) infection and the process of lipid peroxidation in the cell culture was established. An efficient inhibitor of the CMV infection from the class of amino acid derivatives of fullerene with antioxidant activity was obtained.

     

Irradiation of Crosslinked, Poly(Vinyl Alcohol) Blended Hydrogel for Wound Dressing

In order to obtain a more ideal hydrogel wound dressing, crosslinked hydrogel films blended with polyvinyl alcohol (PVA), polyvinyl pyrrolidone, kappa-carrageenan (KC), and powder silk were prepared by electron beam, and their physiochemical properties were investigated as a combination of function factors. The experimental results showed that the gel fraction of the hydrogel films depended mainly on irradiation dose and the monomer concentration of the polymers, the properties of hydrogel could be greatly extended or improved by blending homopolymers. The rate of gel formation of the hydrogel was raised, and the water evaporation from hydrogel could be retarded after mixing with KC, while the tensile strength of hydrogel films were obviously increased after mixing with silk. Toxicity and healing effect of PVA/PVP/KC/silk blended hydrogel films as wound dressings were evaluated. The irradiated blended hydrogel showed satisfactory properties for wound dressing, the hydrogel did not induceany acute general toxic effects, and it is effective for fast healing of wound.     

Glutaraldehyde crosslinking of arabinoxylan produced from corn ethanol residuals

This study investigated the possibility of substituting petroleum-based polymers with biopolymers for films and paper coatings. Arabinoxylan (AX) was extracted from distillers’ grains, a low-value corn ethanol byproduct, and modified through crosslinking with glutaraldehyde (GA) which was made into films and paper coatings. The effects of degree of substitution (DS) on film and coating properties of GA cross-linked AX, referred to as GAX, were investigated. The GAX films had markedly higher tensile strength, approximately 3 times higher than the unmodified AX films at low DS, with higher DS causing a negative effect on the film tensile strength. Compared to unmodified AX coating, paper coated with GAX also had significantly higher tensile index, presumably due to high adhesion between the coating and paper interface. When used as a coating binder with calcium carbonate pigments, GAX showed comparable performance to polyvinyl alcohol, a common industrial binder, demonstrating the potential to be substituted for the petroleum-based paper coating binder.     

Surface-induced enantiomorphic crystallization of achiral fullerene derivatives in thin films

The chirality of organic semiconductors is important for various applications in optoelectronics and spintronics. Here, we propose a new strategy to induce structural chirality in achiral organic semiconductors in thin films. Enantiomeric fullerene derivatives (S)-pSi and (R)-pSi, which have oligo(dimethylsiloxane) as a low-surface-energy moiety, were synthesized and used as surface-segregated monolayers (SSMs) in spin-coated films of several achiral fullerene derivatives. Upon thermal annealing, the presence of the chiral SSMs led to the crystallization of the fullerenes in the films as an SSM-induced crystal phase at lower temperatures. The crystallized films showed circular dichroism ascribed to the fullerene absorption, the sign and the intensity of which depended on the handedness of the SSM molecules and the film thickness, respectively. These results indicate that the achiral fullerene derivatives in the films were induced by the SSMs to crystallize into enantiomorphic crystals. Our approach to inducing chirality in organic thin films is compatible with many device applications.

Chiral induction: surface-segregated monolayers of chiral molecules induce the enantiomorphic crystallization of achiral fullerene derivatives in thin films.     

Preparation and properties of VO2 thin films by a novel sol–gel process

Vanadium dioxide (VO₂) thin films were fabricated using a simple and novel sol–gel process in which V₂O₅ was used as the vanadium source; oxalic acid was used as the reducing agent; and polyvinyl alcohol was used as the film former to control the viscosity of the VO₂ precursor solution and bond vanadium ions. The microstructure and surface morphology of VO₂ films were studied by X-ray diffraction and scanning electron microscopy, respectively. The results showed that using polyvinyl alcohol forms porous nanostructure of VO₂ films with a uniform grain size of ~25 nm. The measured optical reflectance shows well-defined phase transition as observed by an increase of reflectance upon heating above the transition temperature from ~11 to ~30 % at 1,100 nm. Upon cooling, the expected hysteresis is observed.     

Feasibility of Polyvinyl Alcohol as a Transdermal Drug Delivery System for Terbutaline Sulphate

A series of terbutaline sulphate drug incorporated polyvinyl alcohol (PVA) matrix films were produced by the solvent evaporation method. The effect of xanthan gum and plasticizers (propylene glycol and dibutyl phthalate) on the rate and amount of drug diffusion from PVA membrane across the hydrated cellophane membrane has been evaluated, using an open glass diffusion‐tube. The obtained films were clear, smooth and flexible having sufficient mechanical strength. The mechanical performance of the dry PVA films with xanthan gum and plasticizers were also ascertained. Polyvinyl alcohol‐xanthan gum blends showed a high rate of drug release compared to that of polyvinyl alcohol film alone. Among the two plasticizers employed, propylene glycol showed better permeability. Among different formulations studied, the formulation PVA/xanthan gum/propylene glycol (F7) was found to be an optimized composition for efficient transdermal delivery of the model drug, terbutaline sulphate. The mechanism of drug diffusion has been evaluated using the Peppas model. Stability studies carried out on polymer‐drug formulations revealed that the drug is stable at 40°C and 75% RH for a period of 6 weeks.     

DSC investigation of the polystyrene films filled with fullerene

Polystyrene composite films with different content of C₆₀?+?C₇₀ fullerene mix have been obtained from o-xylene solutions. The mass fraction of fullerene was varied from 0.01 to 0.1 mass%. The glass transition temperatures and specific heat capacities in range of 293?C423?K have been determined for the films by DSC method. The plasticization of the polymer is observed in thermal properties of the films under influence of small fullerene additions. The values of T _g and C _P decrease and thermal coefficient of heat capacity b increase as fullerene content increases up to 0.02 mass%. The effect of interaction between polymer and fullerene molecules on thermal properties becomes evident at higher fullerene content in range from 0.02 to 0.1 mass%. At this the values of T _g and C _P increase and b coefficient decrease with increasing content of fullerene. Concentration dependence of C _P and b values is less steep for polymer composite films in elastic state at temperatures above T _g. Molecular interactions in the composites are discussed in view of our-self and literature data.     

Spectroscopic and Discharge Studies on Graphene Oxide Doped PVA/PVP Blend Nanocomposite Polymer Films

Graphene oxide (GO) nanoparticles were synthesized by modified Hummers method. The synthesized GO nanoparticles were incorporated in polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) blend polymers for the preparation of nanocomposite polymer films by solution cast technique. Different characterizations such as XRD, UV–Vis and FTIR were carried-out on to the prepared nanocomposite polymer films. The thermal analysis of the films was studied by DSC. The morphology of PVA/PVP:GO polymer films confirms GO was exfoliated within the PVA/PVP matrix and also reveals the heterogeneous phase of nanocomposite polymer electrolyte systems. From the conductivity studies the highest conductivity of PVA/PVP: GO (0.45: 0.3) was found to be 8.05 × 10^–4 S/cm at room temperature. Solid state battery has been fabricated with the configuration of Mg⁺/(PVA/PVP:GO)/(I₂ + C + electrolyte) and its cell parameters were calculated for a constant load of 100 kΩ.     

Etude de la cristallinite de derives n-octadecyliques de l'alcool polyvinylique obtenus par greffage chimique

Differential scanning calorimetry has been used to study the heats of fusion and melting transitions of n-octadecyl derivatives of polyvinyl alcohol. These derivatives were obtained by grafting paraffinic chains on polyvinyl alcohol, at various proportions. The melting transitions are independent of the degree of substitution; the heats of fusion are proportional to the fraction of crystallizable units. Using Flory's equilibrium crystallization theory, it is possible to interpret these results assuming, as demonstrated previously, that the chemical grafting is sequential with two unreacted hydroxyl groups between two adjacent paraffinic side-chains.     

Preparation and properties of water‐soluble chitosan and polyvinyl alcohol blend films as potential bone tissue engineering matrix

The blend film was prepared by casting solutions of water‐soluble hydroxyethyacryl‐chitosan (HEA‐CS) and polyvinyl alcohol (PVA) and cross‐linked by glutaraldehyde. The structure and properties of the blend films were estimated by wide‐angle X‐ray diffraction (WXRD), contact angle measurements with water, and scanning electron microscopy (SEM). The tensile properties of the blend films were investigated and the tensile strength (TS) and the elongation increased with the increased amount of PVA. The thermal stability (thermogravimetric (TG) and derivative thermogravimetric (DTG)) was evaluated and HEA‐CS was more thermally‐stable than that of PVA. The water swelling properties analysis indicated that HEA‐CS in the blends promoted the water absorption owing to its porous structure and the antimicrobial ability of the blend films was retained. Indirect cytotoxicity assessment of the blend films with human bone sarcoma cell (SW1353) indicated that the biomaterials were non‐toxic and did not release substances harmful to living cells. Copyright © 2009 John Wiley & Sons, Ltd.     

An effect of surfactants of different nature on stabilization of foaming systems containing polyvinyl alcohol

The laws of the foam stabilization by mixtures of surfactant of different nature: sodium dodecyl sulfate C₁₂H₂₅OSO₃Na and cetyltrimethylammonium bromide C₁₆H₃₃N(CH₃)₃Br with a nonionic polymer, polyvinyl alcohol were established. High stability of foams from mixtures of surfactant-polyvinyl alcohol compared with the individual components can be related to the formation of mixed structured layers of surface active associates of polyvinyl alcohol with surfactant contributing to thickening of foam films.     

Fullerenes,Nanotubes, and Graphite as Matrices for Collision Mechanism in Secondary Ion Mass Spectrometry: Determination of Cyclodextrin

A technique for improving the sensitivity of high mass molecular analysis is described. Three carbon species, fullerenes, single walled carbon nanotubes, and highly ordered pyrolytic graphite are introduced as matrices for the secondary ion mass spectrometry analysis of cyclodextrin (C₄₂H₇₀O₃₅, 1134 u). The fullerene and nanotubes are deposited as single deposition, and 10, 20, or 30 deposition films and cyclodextrin is deposited on top. The cyclodextrin parent-like ions and two fragments were analyzed. A 30 deposition fullerene film enhanced the intensity of cationized cyclodextrin with Na by a factor of 37. While the C₆H₁₁O₅ fragment, corresponding to one glucopyranose unit, increased by a factor of 16. Although fragmentation on fullerene is not suppressed, the intensity is twice as low as the parent-like ion. Deprotonated cyclodextrin increases by 100× and its C₈H₇O fragment by 10×. While the fullerene matrix enhances secondary ion emission, the nanotubes matrix film generates a basically constant yield. Graphite gives rise to lower intensity peaks than either fullerene or nanotubes. Scanning electron microscopy and atomic force microscopy provide images of the fullerene and nanotubes deposition films revealing flat and web structured surfaces, respectively. A “colliding ball” model is presented to provide a plausible physical mechanism of parent-like ion enhancement using the fullerene matrix.