Biobased films prepared from NaOH/thiourea aqueous solution of chitosan and linter cellulose

In the present study, films based on linter cellulose and chitosan were prepared using an aqueous solution of sodium hydroxide (NaOH)/thiourea as the solvent system. The dissolution process of cellulose and chitosan in NaOH/thiourea aqueous solution was followed by the partial chain depolymerization of both biopolymers, which facilitates their solubilization. Biobased films with different chitosan/cellulose ratios were then elaborated by a casting method and subsequent solvent evaporation. They were characterized by X-ray analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis, and tests related to tensile strength and biodegradation properties. The SEM images of the biofilms with 50/50 and 60/40 ratio of chitosan/cellulose showed surfaces more wrinkled than the others. The AFM images indicated that higher the content of chitosan in the biobased composite film, higher is the average roughness value. It was inferred through thermal analysis that the thermal stability was affected by the presence of chitosan in the films; the initial temperature of decomposition was shifted to lower levels in the presence of chitosan. Results from the tests for tensile strength indicated that the blending of cellulose and chitosan improved the mechanical properties of the films and that an increase in chitosan content led to production of films with higher tensile strength and percentage of elongation. The degradation study in a simulated soil showed that the higher the crystallinity, the lower is the biodegradation rate.     

Controlled drug release behavior of metformin hydrogen chloride from biodegradable films based on chitosan/poly(ethylene glycol) methyl ether blend

In this study, novel smart drug release films were prepared by blending chitosan with polyethylene glycol methyl ether (PEGME), also named as methoxy polyethylene glycol (mPEG), for controlled drug release applications. The polymeric films were characterized by Fourier transform infra-red for functional groups analysis, scanning electron microscopy for morphology and X-ray photoelectron spectroscopy for chemical and surface analysis followed by mechanical and thermal analysis. The mechanical properties showed that with the addition of PEGME (40%), the tensile strength and elongation break were increased up to 34.14 MPa and 26.40%, respectively as compared to the controlled sample (without PEGME). The developed biodegradable films were tested for Metformin hydrogen chloride release ability at a particular rate in phosphate buffer saline solution at pH 7.4. The results showed that chitosan/PEGME blends could be employed for controlled drug release and other biomedical applications.     

Chitosan/N-methylol nylon 6 blend membranes for the pervaporation separation of ethanol–water mixtures

Blend membranes of chitosan and N-methylol nylon 6 were prepared by solution blending. Their pervaporation performances for the separation of ethanol–water mixtures were investigated in terms of acid (H₂SO₄) post-treatment, feed concentration, blend ratio and temperature. The pervaporation performance of the blend membranes was significantly improved by ionizing with H₂SO₄. The blend ratio of chitosan and N-methylol nylon 6 plays a different role at feed solutions of low and high water content. At a feed solution having low water content, an increase in chitosan content caused a decrease in permeability and an increase in separation factor. At a feed solution having high water content, the permeability increases with an increase in chitosan content, while the separation factor shows a maximum value around 60 wt% chitosan. It is proposed that extra permeation channels generated from the phase separation boundary between ionized chitosan and N-methylol nylon 6 account for the abnormal temperature dependence of pervaporation performance of the blend membranes.     

Ferroelectric and piezoelectric properties of nylon 11/poly(vinylidene fluoride) bilaminate films

The ferroelectric and piezoelectric properties of a new class of polymer ferroelectric and piezoelectric materials, nylon 11/polyvinylidene fluoride (PVF₂) bilaminate films, prepared by a co-melt-pressing method, is presented. The bilaminate films exhibit typical ferroelectric D-E hysteresis behavior with a remanent polarization, P_r, of about 75 mC/m², which is higher than the value of 52 mC/m² observed for PVF₂ or nylon 11 films measured under the same conditions. The coercive field, E_c, of the bilaminate films is ～ 78 MV/m, which is higher than that of either PVF₂ or nylon 11 films. Measurements of the temperature dependence of the piezoelectric strain coefficient, d₃₁, and the piezoelectric stress coefficient, e₃₁, were also carried out. The bilaminate films exhibit a piezoelectric strain coefficient, d₃₁, of 41 pC/N at room temperature, which is significantly higher than the PVF₂ films (25 pC/N) and the nylon 11 films (3.1 pC/N). When the temperature is increased to 110°C, d₃₁ of the bilaminate films reaches a maximum value of 63 pC/N, more than five times that of PVF₂ (11 pC/N) and more than four times that of nylon 11 (14 pC/N) at the same temperature. The piezoelectric stress coefficient, e₃₁, of the bilaminate films shows a value of 109 mC/m² at room temperature, almost twice that of the PVF₂ films (59 mC/m²) and about 18 times that of the nylon 11 films (6.2 mC/m²). Measurement of the temperature dependence of the hydrostatic piezoelectric coefficient, d_h, of the bilaminate films also shows an enhancement with respect to the individual components, PVF₂ and nylon 11. ©1995 John Wiley & Sons, Inc.     

Field-induced dipole reorientation and piezoelectricity in heavily plasticized nylon 11 films

Nylon 11 films with very low initial crystallinity were made by dissolving the nylon 11 in 2-ethyl-1,3-hexanediol at 150°C. Films were cast from the solution and excessive plasticizer was removed in a vacuum oven. Films were then melt pressed and quenched to yield heavily plasticized nylon 11 films containing ca. 30% by weight of the plasticizer. These films were poled under vacuum to allow the plasticizer to evaporate in the presence of an electric field. A high piezoelectric response (d₃₁ = 7.1 pC/N) was observed for the films subjected to the maximum electric field (E_p = 350 kV/cm) while the sample contained a large fraction of plasticizer. Significant development of crystallinity was observed without apparent indication of orientation of the crystallites. These studies suggest that the observed piezoelectric response originates primarily from oriented hydrogen bonds in the amorphous regions of nylon 11.     

尼龙6/液晶聚合物共混体系中化学反应对体系热行为及形貌的影响

采用漫反射红外光谱法(DRIFT)和示差扫描量热法(DSC)研究了2种不同特性黏数的尼龙6与3种液晶聚合物(Vectra A950、Vectra B950和Rodrun LC5000)之间的酯-酰胺交换反应.DRIFT测试证实了尼龙6与LC5000之间存在化学反应.DSC分析表明,酯-酰胺交换反应使体系中尼龙6的熔点下降、结晶度降低.增加反应时间和增大共混体系中液晶聚合物的含量有利于酯-酰胺交换反应的发生.与Vectra A950和Vectra B950相比,分子链柔性较强的Rodrun LC5000与尼龙6之间的化学反应更容易进行.扫描电子显微镜(SEM)观察表明,随着共混时间的延长,分散相形貌由球状粒子发展为短棒状纤维,乃至最终形成直径更细的微纤结构.     

Biodegradable biocompatible xyloglucan films for various applications

Polysaccharides are known for their film-forming properties which have been intensively investigated for food and non-food applications. Here we have developed a xyloglucan transparent film for various applications especially in controlled release of drugs and cosmetics. The present study evaluated the properties of the composite films of xyloglucan, chitosan and rice starch obtained by the casting/solvent evaporation method. Xyloglucan chitosan blend film shows better mechanical properties. Hydrophobicity and crystallinity of xyloglucan film was increased by blending with chitosan. This was confirmed by X-ray diffraction studies and contact angle measurements. Scanning electron microscopic observations indicated that the xyloglucan chitosan blend films were smooth and homogenous. Thermogravimetric and differential scannining calorimetric analysis showed a high thermal stability and melting temperature of xyloglucan chitosan film compared with others. The swelling properties of the xyloglucan chitosan blend film, studied as a function of pH showed that the sorption ability of the blend film was high at a pH 7.4. This indicates its controlled release property at that pH. Controlled drug release property of the film was studied by using streptomycin as a model drug.     

FTIR-ATR studies of drawing and poling in polymer bilaminate films

A large increase in the remnant polarization of drawn and poled poly(vinylidene fluoride) (PVF₂)/nylon 11 bilaminates compared with the individual films observed in other studies provides the motivation for the examination of dipole orientation in variously treated single and bilaminate films with FTIR-ATR spectroscopy. Four ATR spectra are collected from each surface using two sample orientations and two light polarizations for each incident light angle. The incident light angle is varied to obtain information about the change in structure with depth. Computer simulations of the experimental optics using anisotropic optical constants aides in the interpretation of experimental results. As the result of simple one-way drawing in PVF₂ and nylon 11, anisotropy in dipole orientation is observed in the plane transverse to the draw direction. In both single and bilaminate films, the average direction of the amide plane in nylon 11 and the CF₂ dipoles in PVF₂ resides in the plane of the film, perpendicular to the subsequent poling field direction as a result of one-way drawing. The transverse plane orientation is depth dependent in nylon 11 in both single and bilaminate films and is attributed to a surface-induced effect. Poling fields of 1.6 MV/cm produce large differences between the surfaces of single films and the bilaminates. At the interior interface of the drawn and poled bilaminates, the PVF₂ and nylon 11 dipoles important in polarization appear to be random. The structural implications of this as well as other observations from the spectra are interpreted in terms of the large remnant bulk polarization in the poled bilaminate. © 1994 John Wiley & Sons, Inc.     

Mucoadhesive and elastic films based on blends of chitosan and hydroxyethylcellulose

Mucoadhesive polymeric films have been prepared based on blends of chitosan and hydroxyethylcellulose. The blends have been characterized by IR spectroscopy, DSC, WAXD, TGA, SEM, and mechanical testing. It is demonstrated that the mechanical properties of chitosan are improved significantly upon blending with hydroxyethylcellulose. An increase in hydroxyethylcellulose content in the blends makes the materials more elastic. The thermal treatment of the blends at 100 degrees C leads to partial cross-linking of the polymers and formation of water-insoluble but swellable materials. The adhesion of the films towards porcine buccal mucosa decreases with increasing hydroxyethylcellulose content in the blends.     

锌离子对壳聚糖复合膜结构和性能的影响

通过在壳聚糖溶液里加入乙酸锌制备Zn2+/壳聚糖复合膜,并利用FTIR、XRD、DSC、DMA和AFM考察了加入不同量Zn2+对壳聚糖复合膜微观结构、表面形貌、结晶性能以及热行为的影响.结果表明,壳聚糖分子中的—NH2、—OH、—NHCO—活性基团和Zn2+发生了配位反应,且随着Zn2+量的增加,有关复合膜表面的粗糙度明显增大.Zn2+的量增加到一定程度后会导致发生明显的相分离,复合膜的储能模量也随之明显下降.     

Synthesis and Properties of Dendronized Chitosan

Summary: Chitosan films and microspheres were prepared and their surfaces were functionalized with first generation dendritic molecules. The films were modified by Weisocyanate dendron, while Behera's and bis Behera's amine dendrons were used to modify the microspheres. Prior to dendronization films were prepared by blending chitosan with 18% of polyvinyl pyrrolidone (PVP), and casting the resulting mixture. The degree of dendronization reached was 28%. The microspheres were prepared by coacervation/precipitation, after which the surfaces were activated with either epychlorohydrine (ECH) or 1,4-butanediol diglycidyl ether (BDGE). The oxirane groups were utilized to form covalent bonds between chitosan and dendrons. The degree of dendronization yielded with Behera's amine was 60% for both activating agents. When bis Behera's amine was used, the dendronization reached values of 15 and 21% when ECH or BDGE were used, respectively. The dendronized products were characterized through spectroscopic and microscopic studies and by determination of swelling indexes. Only one of the surfaces was dendronized in every film, which therefore presented a hydrophobic and a hydrophilic surface. Since these films maintain the properties of chitosan, they offer interesting potential as dressings for exuding wounds. The different surfaces make the microspheres potentially applicable as carriers for delivery and controlled release of drugs.     

Influence of chitosan and epoxy cross-linking on physical properties of binary blends

In this study, blends of chitosan (Cs) and bisphenol-F-diglycidyl ether (3.80 × 10^?3 to 3.80 × 10^?2 mol) were cast by the solution route. FT-IR results suggested that chitosan was cross-linked at terminal amino groups through diepoxide linkage. The chitosan films became less flexible and stiffer upon reaction with epoxy. Blending improved percentage elongation (31%) and toughness (10 MPa), whereas Young’s modulus (145 MPa) and tensile strength (45 MPa) were decreased. Extent of weight loss in Cs/BPFDGE was lower (15%) than that of original precursors (chitosan 33%). Moreover, blending of chitosan with BPFDGE increased water absorption properties due to generation of hydrophilic ?OH groups.     

Role of ionic interactions in the compatibility of polyester ionomers with poly(ethylene terephthalate) and nylon 6

Water absorption and other properties of polyamides can potentially be modified by blending with polyesters. The compatibility of a polyester ionomer melt‐blended with nylon‐6 is studied in this article, examining the effect of blending upon crystallization behaviors, morphology, thermal/mechanical properties, and water absorption. Comparisons of the crystallization behaviors of the ionomer/nylon‐6 blends with poly(ethylene terephthalate)/nylon‐6 blends suggest increased compatibility due to greater interactions between the two phases. The results indicate that the presence of a significant amount of the ionomeric groups is required to improve polyester compatibility with polyamides. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2091–2103, 2006     

Poly(epsilon-caprolactone)/chitin and poly(epsilon-caprolactone)/chitosan blend films with compositional gradients: fabrication and their biodegradability

Poly(epsilon-caprolactone) (PCL)/chitin and PCL/chitosan blend films with compositional gradients were successfully fabricated by a dissolution/diffusion method; that is, repeatedly pouring the PCL/chitin (or PCL/chitosan) blend solutions, with variable composition, onto polysaccharide layers. The compositional gradient structure in the resulting films was characterized by polarized optic microscopy, ATR-FT-IR and trans-FT-IR microscopic spectroscopy. Enzymatic degradability of the PCL/chitin and PCL/chitosan blend films with compositional gradients in the presence of lysozyme was compared with those of homogeneous films and two-layer films. It was found that the degradation rate of PCL/chitin blend films with a compositional gradient was far lower than that of the neat chitin film, whereas the degradation rate of PCL/chitosan blend films with a compositional gradient was close to that of the neat chitosan film. The suppression of the chitosan crystallization, which accelerates the enzymatic degradation, at the surface of PCL/chitosan films with a compositional gradient was much more severe than that for PCL/chitin films with a compositional gradient.     

Chitosan Films Obtained from Brachystola magna (Girard) and Its Evaluation on Quality Attributes in Sausages during Storage

High molecular weight chitosan (≈322 kDa) was obtained from chitin isolated from Brachystola magna (Girard) to produced biodegradable films. Their physicochemical, mechanical and water vapor permeability (WVP) properties were compared against commercial chitosan films with different molecular weights. Brachystola magna chitosan films (CFBM) exhibited similar physicochemical and mechanical characteristics to those of commercial chitosans. The CFBM films presented lower WVP values (10.01 × 10⁻¹¹ g/m s Pa) than commercial chitosans films (from 16.06 × 10⁻¹¹ to 64.30 × 10⁻¹¹ g/m s Pa). Frankfurt-type sausages were covered with chitosan films and stored in refrigerated conditions (4 °C). Their quality attributes (color, weight loss, pH, moisture, texture and lipid oxidation) were evaluated at 0, 5, 10, 15 and 20 days. Sausages covered with CFMB films presented the lowest weight loss (from 1.24% to 2.38%). A higher increase in hardness (from 22.32 N to 30.63 N) was observed in sausages covered with CFMB films. Compared with other films and the control (uncovered sausages), CFMB films delay pH reduction. Moreover, this film presents the lower lipid oxidation level (0.10 malonaldehyde mg/sample kg). Thus, chitosan of B. magna could be a good alternative as packaging material for meat products with high-fat content.     

THE EFFECT OF BLENDING SEQUENCE ON PHASE MORPHOLOGY OF NYLON 6/ABS/SMA BLENDS

The preparation process-dependent phase morphology of blends composed of nylon 6 and acrylonitrile-butadiene- styrene(ABS)over a composition range of 30-70 wt% using a styrene-maleic anhydride(SMA)copolymer as the compatibilizing agent with a constant content(5phr)was investigated.The results of the scanning electron microscope (SEM)observation revealed that compared with the binary blends of nylon 6 and ABS,the existence of SMA caused a composition shift of phase inversion to a higher weight fraction of...     

壳聚糖-纤维素硫酸钠聚电解质复合物膜对药物表观渗透系数的测试

药物渗透系数是考察复合物膜的药物释放性能的重要参数. 本文以溶解性不同的两种药物扑热息痛和5-氨基水杨酸(5-ASA)为模型药物研究了其在壳聚糖-纤维素硫酸钠聚电解质复合物膜中的渗透性能. 结果表明：壳聚糖-纤维素硫酸钠聚电解质复合物膜的渗透性能与其溶胀性能密切相关;复合物膜中壳聚糖和纤维素硫酸钠的配比、相对分子量和pH值对膜的渗透性能和溶胀性能影响显著,以扑热息痛作为模型药物研究了壳聚糖-纤维素硫酸钠聚电解质复合物膜在模拟胃肠液中对药物的渗透性能. 通过调整该复合物膜的配方,可以使该膜分别实现胃、小肠和结肠定位释药的目的.     

Probing chitosan and phospholipid interactions using Langmuir and Langmuir-Blodgett films as cell membrane models

The interaction between chitosan and Langmuir and Langmuir-Blodgett (LB) films of dimyristoyl phosphatidic acid (DMPA) is investigated, with the films serving as simplified cell membrane models. At the air-water interface, chitosan modulates the structural properties of DMPA monolayers, causing expansion and decreasing the monolayer elasticity. As the surface pressure increased, some chitosan molecules remained at the interface, but others were expelled. Chitosan could be transferred onto solid supports alongside DMPA using the LB technique, as confirmed by infrared spectroscopy and quartz crystal microbalance measurements. The analysis of sum-frequency vibration spectroscopy data for the LB films combined with surface potential measurements for the monolayers pointed to chitosan inducing the ordering of the DMPA alkyl chains. Furthermore, the morphology of DMPA LB films, studied with atomic force microscopy, was affected significantly by the incorporation of chitosan, with the mixed chitosan-DMPA films displaying considerably higher thickness and roughness, in addition to chitosan aggregates. Because chitosan affected DMPA films even at pressures characteristic of cell membranes, we believe this study may help elucidate the role of chitosan in biological systems.     

Effect of P(MMA-co-MAA) compatibilizer on the miscibility of nylon 6/PVDF blends

With the ultimate objective of enhancing the impact strength and weatherability of nylon 6 engineering plastic, blending with poly(vinylidene fluoride) (PVDF) was studied. In the absence of a compatibilizer the two polymers phase separate, resulting in a deterioration of the properties. Since poly(methyl methacrylate) is known to be miscible with PVDF, we evaluated poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) of low methacrylic acid content as the compatibilizer. The carboxylic acid groups in the MAA units were expected to react with the end amino groups of nylon 6 forming block or graft copolymers, P(MMA-co-MAA)-g-nylon 6, in situ, which will function as the actual compatibilizer. The amount of P(MMA-co-MAA) added, the MMA/MAA composition and heat treatment time were varied to study their effects on the miscibility, morphology, and mechanical properties of nylon 6/PVDF blends. The enhancement of the compatibility of nylon 6 and PVDF by addition of P(MMA-co-MAA) and the partial miscibility of nylon 6 and PVDF has been confirmed through DSC, dynamic mechanical testing, SEM of fracture surfaces, and tensile testing. The decrease in the crystallization temperatures on addition of compatibilizer in DSC experiments suggests that the compatibilizer enhances the interaction between the two components and retards the crystallization. The dynamic mechanical thermal analysis experiments suggest that the compatibility in the amorphous regions of nylon 6 and PVDF in particular has been enhanced. The increase in the heat treatment time in the molten state resulted in further enhancement of the miscibility. The enhancement of compatibility by addition of a reactive compatibilizer and heat treatment resulted in a significant increase in the energy of rupture in tensile testing.     

Preparation and Characterization of Chitosan-Graphene Transducer Assembled via Vacuum Assisted Self-assembly (VASA) Method for Trimethylamine Sensing

A reduced graphene oxide/chitosan (rGO/Chi) nanocomposite film for chemoresistive trimethylamine sensing was prepared by solution-phase mixing and deposited on nylon membrane via vacuum assisted self-assembly (VASA) method. The film was analysed using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The electrical property of the prepared films were measured by four-point probe measurement. Using 0.40% volume fraction (v.f) it was exposed to trimethylamine vapour and its electrical resistance quickly changed. The composite film sensor exhibited linear range from 23 to 230mg/L (r²= 0.9774) and the calculated limit of detection was 20.56mg/L. It exhibited a repeatable response to trimethylamine gas.