Studies on biodegradability of copolymers of lactic acid, terephthalic acid and ethylene glycol

The copolymers were synthesized by the condensation of lactic acid, terephthalic acid and ethylene glycol. Synthesized copolymers were characterized for various properties such as acid value, hydroxyl value and number average molecular weight, etc. The copolymers were analyzed by FTIR. Copolymers were biodegraded by different fungal species such as Aspergillus sp., Mucor sp., Alternaria sp. and Rhizopus sp., etc. The extent of biodegradation was examined by weight loss and scanning electron microscopy. Biodegradation of copolymer with greater amount of lactic acid was faster than the biodegradation of copolymer with lesser amount of lactic acid.     

Biodegradable poly(lactic acid)/chitosan-modified montmorillonite nanocomposites: Preparation and characterization

In this study, the biodegradable poly(lactic acid) (PLA)/montmorillonite (MMT) nanocomposites were successfully prepared by the solution mixing process of PLA polymer with organically-modified montmorillonite (m-MMT), which was first treated by n-hexadecyl trimethyl-ammonium bromide (CTAB) cations and then modified by biocompatible/biodegradable chitosan to improve the chemical similarity between the PLA and m-MMT. Both X-ray diffraction data and transmission electron microscopy images of PLA/m-MMT nanocomposites indicate that most of the swellable silicate layers were disorderedly intercalated into the PLA matrix. Mechanical properties and thermal stability of the PLA/m-MMT nanocomposites performed by dynamic mechanical analysis and thermogravimetric analysis have significant improvements in the storage modulus and 50% loss in temperature when compared to that of neat PLA matrix. The degradation rates of PLA/m-MMT nanocomposites are also discussed in this study.     

Curcumin-loaded layer-by-layer folic acid and casein coated carboxymethyl cellulose/casein nanogels for treatment of skin cancer

Targeted drug delivery systems using natural polysaccharide/protein biopolymer for tumor cells are an attractive platform for enriching the therapeutic effects and reducing the side effects of the drug. Carboxymethyl cellulose (CMC) and casein (CA) nanogels (NGs) loaded with curcumin (CUR) were prepared by self-assembly method and fabricated with folic acid (FA) and casein using layer-by-layer (LbL) technique for skin cancer drug delivery. The prepared samples were characterized by techniques like zeta potential, FTIR, XRD, TGA and Cryo-SEM. Both the swelling and in vitro drug release was performed in acidic pH (4.5 and 6.8) and physiological pH 7.4. Hemolysis assays demonstrated that the drug carriers are hemocompatible. Confocal microscope studies indicate facilitated uptake of 2-FA/CA/CUR@CMC-CA NGs in MEL-39 melanoma cancer cell line, which in turn result in a higher potential for apoptosis. Compared to pure CUR and CUR@CMC-CA NGs, the 2-FA/CA/CUR@CMC-CA NGs has lower IC50 value and superior cytotoxicity in MEL-39 cells because of folate-receptor mediated endocytosis evaluated by the cellular viability quantification using MTT assay and optical microscope images. Finally from in vitro skin permeation experiments, 2-FA/CA/CUR@CMC-CA NGs showed 3.47 ± 0.03 to 4.15 ± 0.25 μg/ml CUR concentrations at the stratum corneum, epidermal and dermal layers. Overall, our results put forth 2-FA/CA/CUR@CMC-CA NGs as an aspiring candidate to achieve enhanced anticancer effects against melanoma skin cancer.     

Preparation and burning behaviors of flame retarding biodegradable poly(lactic acid) nanocomposite based on zinc aluminum layered double hydroxide

A flame retarding biodegradable polylactic acid (PLA) nanocomposite based on flame retardant composites (containing ammonium polyphosphate (APP), pentaerythritol (PER) and melamine cyanurate (MC) by controlling the weight ratio was 2:2:1) and organomodified zinc aluminum layered double hydroxide (Zn-Al-LDH) has been prepared by melt-compounding directly. The morphology and burning behaviour of nanocomposite with 2 wt% Zn-Al-LDH loadings were investigated. The extent of dispersion of LDH was quantified by wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM), illuminating the good dispersion state for ZnAl-LDH in the PLA matrix. Significant improvements in fire retardant performance were observed for the nanocomposite from microscale combustion calorimeter (MCC) and cone calorimetry (reducing both the heat release rate and the total heat released). It revealed that incorporation of FR and ZnAl-LDH was very efficient in improving the flame retardance of PLA composite.     

聚乳酸/壳聚糖季铵盐皂石纳米复合材料的原位插层聚合及性能表征

通过两步法将2,3-环氧丙基三甲基氯化铵接枝壳聚糖合成了水溶性壳聚糖季铵盐(HTCC),以其为插层剂对稀有的新疆皂石(Saponite)黏土矿物进行有机改性,制备了壳聚糖季铵盐皂石(HTCC-saponite),并以其为助剂,以丙交酯为单体,通过原位插层聚合法制备了聚乳酸(PLA)/HTCC-saponite纳米复合材料.最优化合成条件:聚合反应温度150℃,辛酸亚锡加量2%(质量分数),HTCC-saponite加量1%(质量分数)、聚合反应时间16 h.微观结构分析表明HTCC-saponite具有插层与剥离共存的结构.采用X射线衍射(XRD)、透射电子显微镜(TEM)、热重分析(TG-DTG)和差示扫描量热仪(DSC)等对PLA/HTCC-saponite纳米复合材料的微观结构、形貌及热稳定性进行了表征和分析.结果表明,HTCC-saponite有效改善了PLA的结晶性能,提高PLA的热稳定性.抗菌测试结果表明,HTCC-saponite具有良好的抗菌性,并赋予PLA/HTCC-saponite复合材料较强的抑菌能力.     

Enhancement of the photocatalytic activity and electrochemical property of graphene-SrWO4 nanocomposite

SrWO₄ is a promising candidate as not only photocatalyst for the removal of organic pollutants from water, but also electrode material for energy storage devices. However, the drawbacks of its poor adsorptive performance, low electrical conductivity, and high recombination rate of photogenerated electron-hole pair impede its practical applications. In this work, we have developed a new graphene/SrWO₄ nanocomposite synthesized via a facile chemical precipitation method. Characterizations show that SrWO₄ nanoparticles with 80 nm or so deposited on the surface of graphene nanosheets. Graphene nanosheets in the graphene-SrWO₄ hybrid could increase adsorptive property, improve the electrical conductivity of hybrid, and reduce the recombination of electron-hole pairs. As a kind of photocatalyst or electrode material for supercapacitor, the binary graphene-SrWO₄ hybrid presents enhanced photocatalytic activity and electrochemical property compared to pure SrWO₄.     

In vitro and in vivo evaluations of nanofibrous nanocomposite based on carboxymethyl cellulose/polycaprolactone/cobalt-doped hydroxyapatite as the wound dressing materials

These days, Ophthalmic wound treatment is a major problem; due to its nature, bio/materials are the best choices as wound dressing materials. The main objective of the current survey is to develop and investigate effective wound dressing materials for skin care applications. In these ways, we combined the good biological properties of Cobalt-doped hydroxyapatite particles (CoHAp) with the structural properties of Polycaprolactone (PCL)/ carboxymethyl cellulose (CMC) nanofibers. Electrospinning and co-precipitation methods were used to synthesize nanofibers and CoHAp particles, respectively. Nanocomposites were synthesized in the absence and different percentages of CoHAp. The PCL/CMC, PCL/CMC/CoHA 5 %, PCL/CMC/CoHA 10 %, and PCL/CMC/CoHA 15 % formulated nanocomposites have the diameter of 383 ± 50, 391 ± 84, 441 ± 65, and 495 ± 99 nm, respectively. The synthesized nanofibrous wound dressing porosity and water absorption capacity were in the range of 40 to 60 % and 32 to 63 %, respectively. Hemo and cytocompatibility of the nanofibrous wound dressing were analyzed by in vitro evaluation, and the results were satisfactory and the structures were fully biocompatible. The PCL/CMC/CoHA 10 % wound dressing, were selected as the best nanocomposites for wound healing based on our animal studies on the healing outcomes. The results showed that the PCL/CMC nanofibers-Cobalt-doped HAp wound dressing is an effective bioactive nano-biomaterials for the wound healing process.     

Graft copolymerization of methacrylic acid onto carboxymethyl chitosan

Carboxymethyl chitosan (CMCTS) was prepared and characterized by FTIR, ¹H NMR, and elemental analysis. The graft copolymerization of methacrylic acid (MAA) onto CMCTS using ammonium persulfate (APS) as an initiator was carried out in an aqueous solution. Evidence of grafting was obtained by comparison of FTIR spectra of CMCTS and the grafted copolymer as well as solubility characteristics of the products. The effects of APS, MAA, reaction temperature and time on graft copolymerization were studied by determining the grafting parameters such as grafting percentage and grafting efficiency. With keeping other conditions constant, the optimum conditions were shown as following: [APS]=8 mmol/l, [MAA]=2.4 mol/l, reaction temperature=60-70 °C, reaction time=120 min.     

Synthesis of cross-linked carboxymethyl cellulose and poly (2-acrylamido-2-methylpropane sulfonic acid) hydrogel for sustained drug release optimized by Box-Behnken Design

This research aims to fabricate and characterize chemically crosslinked CMC/PVP-co-poly (AMPS) based hydrogel for the sustained release of model drug metoprolol tartrate through the free radical polymerization technique. Box-Behnken Design was used to optimize CMC/PVP-co-poly (AMPS) hydrogel by varying the content of reactants such as; polymers (CMC and PVP), monomer (AMPS), and crosslinker (EGDMA). Carboxymethyl cellulose (CMC) was crosslinked chemically with AMPS with a constant ratio of PVP by the ethylene glycol dimethacrylate as the crosslinker in the presence of sodium hydrogen sulfite (SHS)/ammonium peroxodisulfate (APS) as initiators. After developing CMC-based hydrogels using different polymers, monomer, and crosslinker concentrations, this study encompassed dynamic swelling, sol–gel fraction, drug release and chemical characterizations such as FTIR, XRD, TGA, DSC, and SEM. In vitro drug release and swelling were performed at 1.2 and 6.8 pH to determine the sustained release pattern and pH-responsive behavior. These parameters depended on the crosslinker, polymer, and monomer ratios used in the formulation development. XRD, SEM, and FTIR showed the successful grafting of constituents resulting in the formation of a stable hydrogel. DSC and TGA confirmed the thermodynamic stability of the hydrogel. Hydrogel swelling was increased with an increase in the ratio of monomer; however, an increase in the ratio of polymer and crosslinker decreased the hydrogel swelling. In vitro gel fraction and drug release also depended on polymer, monomer, and crosslinker ratios. The fabricated CMC/PVP-co-poly (AMPS) hydrogels constituted a potential system for sustained drug delivery.     

溶剂诱导的聚乳酸/聚乳酸衍生物共结晶行为

通过溶液浇铸法制备不同组分的左旋聚乳酸(PLLA)和聚(L-2-羟基-3-甲基丁酸)(PL-2H3MB)共混物.运用差示扫描量热仪(DSC)、偏光显微镜(POM)、广角X射线衍射(WAXD)和热重分析仪(TGA)分析共混物的结晶、熔融行为和热稳定性.通过观察到DSC加热曲线中新的熔融峰判断PLLA和PL-2H3MB共晶...     

Effect of multiscale structure on the gas barrier properties of poly(lactic acid)/Ag nanocomposite films

Poly(lactic acid) (PLA) is the most suitable for biodegradable packaging film because of its excellent integrated property, but the poor gas barrier property is its weakness. In this study, a nanocomposite film based on PLA incorporated with 0‐, 1‐, 3‐, 5‐, 10‐, or 15‐wt% nano‐Ag was developed. Effect of multiscale structure on the barrier properties of PLA/nano‐Ag films was studied. The PLA nanocomposite film with 5‐wt% nano‐Ag had the lowest water vapor permeability (WVP) value. Oxygen transmission rate (OTR) value for PLA nanocomposites with 3‐wt% nano‐Ag was found to be the lowest among all the samples. Multiscale structure was demonstrated by the scanning electron microscopy, Fourier transform‐infrared spectroscopy, X‐ray diffraction measurement, and differential scanning calorimetry results. The crystallinity of the PLA phase increased with the content of nano‐Ag in the PLA composites. The evolution of the PLA phase crystallinity could improve the barrier properties of PLA/nano‐Ag composite films for food packaging applications. From the view of multiscale structure, it is better to achieve a balance among short‐range conformation in the amorphous region, long‐range‐ordered structure, and ordered aggregated structure to improve the barrier properties of PLA/nano‐Ag composite films.     

基于环己烷二甲醇和低聚乳酸制备脂肪/芳香共聚酯

通过对苯二甲酸二甲酯(DMT),1,6-己二醇(HDO),以及1,4-环己烷二甲醇(CHDM)和-羟基--羧基DL-低聚乳酸(OLA)在催化剂钛酸四丁酯下熔融缩聚合成了一系列可生物降解共聚酯PHCTL。通过核磁共振(1H NMR),差示扫描量热法(DSC),热重分析法(TG)和广角X射线衍射(WAXS)技术对共聚酯进行了表征,随着CHDM含量的增加,共聚酯的熔点(Tm),热分解温度(Td)等都有了明显的增加。凝胶渗透色谱(GPC)分析得出共聚酯的分子量在1.7-3.6  x104之间。在37 C下 PHCTL共聚酯发生了明显的降解,降解速率的大小与共聚酯的亲水性有关。     

Synthesis and photocatalytic activity of poly(3-hexylthiophene)/TiO2 composites

An heterogeneous conducting polymer composite, poly(3-hexylthiophene)/TiO₂ (P3HT/TiO₂), was synthesized. The photocatalytic activity of P3HT alone and the composite was investigated for the first time by degrading a common dye under UV exposure. It was shown that the photocatalytic activity of the nanocomposites was higher compared to either the polymer or TiO₂ alone. A simple mechanism was proposed to explain this observed synergetic effect.     

Electrosynthesis of lactic acid and 2,3-dimethyltartaric acid from pyruvic acid on lead cathode in aqueous medium

Lactic and 2,3-dimethyltartaric acids have been synthesized from pyruvic acid by changing the nature of the supporting electrolyte and the electrode potential of lead cathode.     

晶相组成可调的高活性可见光应答型二氧化钛纳米复合光催化材料的制备

采用新的化学溶液法,通过不同体积的钛酸四异丙酯的2-乙二醇单乙醚溶液与一定浓度的H₂O₂水溶液直接反应并对生成的钛过氧化配合物进行焙烧,制备了一系列TiO₂光催化剂. 表征发现,所得TiO₂样品为金红石和锐钛矿的纳米复合晶体,改变2-乙二醇单乙醚的体积可实现金红石相比例在0~96%广范围的调变.与商业二氧化钛P-25相比,所得的TiO₂紫外-可见光吸收谱出现明显红移,间隙能降低, 在可见光照射下,该样品对亚甲基蓝有良好的降解活性. 当2-乙二醇单乙醚的添加量为5 ml时,所得样品体相中金红石相比例接近50%,其光催化活性和吸附性能最好,可分别是P-25的3倍和5倍. 拉曼光谱结合X射线衍射等表征结果表明,该样品的表面仅含少量的金红石相. TiO₂纳米复合晶表面晶相的组成和分布对其光催化降解亚甲基蓝的活性及其吸附能力有直接的影响. 另外,TiO₂纳米复合晶的缺陷浓度也是增强其光吸收能力,提高其可见光光催化活性的原因之一.     

发泡聚乳酸/热塑性聚氨酯/二氧化硅纳米复合材料的泡孔结构

以超临界二氧化碳作为物理发泡剂,通过快速降压法制备聚乳酸(PLA)/热塑性聚氨酯(TPU)/二氧化硅(SiO2)纳米复合材料发泡样品。发泡样品的泡孔结构使用扫面电子显微镜进行观察。在低频区,SiO2增加PLA/TPU共混物的储能模量和复数黏度。SiO2的加入使PLA/TPU共混物发泡样品的泡孔直径减小、泡孔密度增大。SiO2对PLA/TPU共混物发泡样品泡孔结构的改善归因于SiO2的异相成核作用和对共混物流变性能的改善作用。     

Thermal,mechanical and electroactive shape memory properties of polyurethane (PU)/poly (lactic acid) (PLA)/CNT nanocomposites

Polymer blend nanocomposites based on thermoplastic polyurethane (PU) elastomer, polylactide (PLA) and surface modified carbon nanotubes were prepared via simple melt mixing process and investigated for its mechanical, dynamic mechanical and electroactive shape memory properties. Chemical and structural characterization of the polymer blend nanocomposites were investigated by Fourier Transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD). Loading of the surface modified carbon nanotube in the PU/PLA polymer blends resulted in the significant improvement on the mechanical properties such as tensile strength, when compared to the pure and pristine CNT loaded polymer blends. Dynamic mechanical analysis showed that the glass transition temperature (T_g) of the PU/PLA blend slightly increases on loading of pristine CNT and this effect is more pronounced on loading surface modified CNTs. Thermal and electrical properties of the polymer blend composites increases significantly on loading pristine or surface modified CNTs. Finally, shape memory studies of the PU/PLA/modified CNT composites exhibit a remarkable recoverability of its shape at lower applied dc voltages, when compared to pure or pristine CNT loaded system.     

Thermal properties of poly(lactic acid)/organo-montmorillonite nanocomposites

Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility and toughness of the nanocomposites. The samples were prepared by single screw extrusion followed by compression molding. The effect of OMMT and EPMgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (T _m), glass transition temperature (T _g), crystallization temperature (T _c), degree of crystallinity (χ_c), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properties of PLA were greatly influenced by the addition of OMMT and EPMgMA.     

Fire retardancy and biodegradability of poly(methyl methacrylate)/montmorillonite nanocomposite

The poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposite was prepared by emulsifier-free emulsion technique and its structure and properties were characterized with infra red, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, and cone calorimetry. The highly exfoliated MMT layers with dimension 1-2 nm in thickness were randomly dispersed in the polymer matrix containing MMT lower than 5% w/v, whereas the intercalated structure was predominant with MMT content higher than 5% w/v. Consequently, the fine dispersion of the MMT and the strong interactions between PMMA and MMT created significant improvement of the thermo-stability and fire retardancy of the nanocomposite. The combustion behavior has been evaluated using oxygen consumption cone calorimetry. In addition, a scheme was proposed to describe fire retardancy of PMMA and MMT as well as the correlation between the interaction and structure in polymer/clay systems. The biodegradability of the nanocomposite fire-retardant was tested for its better commercialization.     

聚乳酸/蒙脱土纳米复合材料的结构和热性能

聚乳酸/蒙脱土纳米复合材料的结构和热性能;聚乳酸;蒙脱土;纳米复合材料;插层