Efficient and selective upcycling of waste polylactic acid into acetate using nickel selenide

The conversion of waste polylactic acid(PLA)plastics into high-value-added chemicals through electrochemical methods is a promising and sustainable approach.However,developing efficient and highly selective catalysts for lactic acid oxidation reaction(LAOR)and understanding the reaction process are challenging.Here,we report the electrooxidation of waste PLA to acetate at a high current density of 100 mA cm-2 with high Faraday efficiency(~95%)and excellent stability(>100 h)over a nickel selenide nanosheet catalyst.In addition,a total Faraday efficiency of up to 190%was achieved for carboxylic acids,including acetic acid and formic acid,by coupling with the cathodic CO_(2) reduction reaction.In situ experimental results and theoretical simulations revealed that the catalytic activity center of LAOR was dynamically formed NiOOH species,and the surface-adsorbed SeO_(x) species accelerated the formation of Ni~(3+)species,thus promoting catalytic activity.The mechanism of lactic acid electrooxidation was further elucidated.Lactic acid was dehydrogenated to produce pyruvate first and then formed CH_3CO due to preferential C-C bond cleavage,resulting in the presence of acetate.This work demonstrated a sustainable method for recycling waste PLA and CO_(2) into high-value-added products.

Studies on the Simultaneous Synthesis of Dimethyl Carbonate and Poly(ethylene terephthalate): I. Catalytic Activity of Metal Acetate in Transesterification of Ethylene Carbonate with Dimethyl Terephthalate

A novel direct method for preparation of dimethyl carbonate and poly（ethylene terephthalate） from ethylene carbonate and dimethyl terephthalate has been demonstrated in the presence of metal acetate catalysts, lithium acetate dihydrate showed highest catalytic activity with 47.9% yield of dimethyl carbonate. This method was a green chemical process.

SYNTHESIS OF POLY(VINYL ACETATE)-INTERCALATED GRAPHITE OXIDE BY AN IN SITU INTERCALATIVE POLYMERIZATION

Graphite oxide, a pseudo-two-dimensional solid in bulk form, was synthesized from natural graphite powder by oxidization with KMnO4 in concentrated H2SO4. The poly(vinyl acetate)-intercalated graphite oxide nano-composite was prepared by an in situ intercalative polymerization reaction, in which n-octanol-graphite oxide intercalation compounds were first obtained, vinyl acetate monomer was then dispersed into the interlayer of modified graphite oxide, followed by thermal polymerization of the monomer. It was experimentally shown that the c-axis space of poly(vinyl acetate)-intercalated graphite oxide was increased to 0.115 nm, which suggested there existed a monolayer of poly(vinyl acetate) chain between the layers of graphite oxide. The nanocomposite was also characterized with thermal analysis and FT-IR spectrometry.

Polyvinyl acetate/poly(amide-12-b-ethylene oxide) blend membranes for carbon dioxide separation

In this paper,blend membranes from polyvinyl acetate(PVAc)and block copolymer poly(amide-12-b-ethylene oxide)(Pebax1074)are prepared by solution casting and solvent evaporation method.Although they are homogeneous on a macro-scale,the observations from DSC and SEM indicate micro-phase separation for PVAc/Pebax1074 blend membranes.With the increase of Pebax1074 content,gas permeabilities of CO2,H2,N2and CH4all increase greatly.PVAc/Pebax1074 blend membranes with high PVAc content are appropriate for CO2/CH4separation.The temperature dependence of gas permeability is divided into rubbery region and glassy region.The activation energies of permeation in rubbery region are smaller than those in glassy region,and they all decrease with increasing Pebax1074 content.For N2,H2and CH4,their gas permeation properties are mainly influenced by the dual-mode sorption and hydrostatic pressure effect.But for CO2,its permeability increases with the increase of pressure due to CO2-induced plasticization effect,which is more obvious for PVAc/Pebax1074 blend membranes with high PVAc content.

SYNTHESIS OF POLYMERIC β-CYCLODEXTRIN SUPPORTED BY CROSSLINKED POLY(ACRYLAMIDE-co-VINYLAMINE)AND ITS CATALYSIS OF THE HYDROLYSIS OF p-NITROPHENYL ACETATE

Polymeric β-cyclodextrin (β-CD) supported by crosslinked poly(acrylamide-co-vinylamine) was synthesized as anartificial analog of hydrolytic enzyme and its catalysis of the hydrolysis of p-nitrophenyl acetate (p-NPA) was theninvestigated. The result showed that the polymer-supported β-CD could accelerate the hydrolytic reaction of p-NPA morequickly than β-CD itself and crosslinked poly(acrylamide-co-vinylamine) alone. The acceleration rate of the polymer-supported β-CD was about 10 times as fast as that of free β-CD in 0.01 mol/L phosphate buffer (pH 7.4) containing 32%DMSO at 37±0.1℃ when the molar amount of β-CD units in the polymer was equal to that of free β-CD in the experiments.The enhanced acceleration of thc polymer-supported β-CD should be ascribed to the cooperative contribution of theinclusion effect of β-CD ring and the nucleophilic effect of amino groups on the polymeric support.

The Effect of Polyvinyl Acetate Polymer on Reducing Dust in Arid and Semiarid Areas

Because the large areas of Iran are on arid and semiarid belt of the world, it has many problems due to windstorms. Wind storms cause dust and haze due to a mass of fine sand or silt soil elevated in the atmosphere. It makes heart disease-cardiovascular and respiratory and so is detrimental for the children. These have plagued the residents and so lives of them are disrupted every so often. In this research, the subject soil stabilization using adherence of poly vinyl acetate polymer as a way to reduce the production of dust is defined for prone area. In this paper, the effect of poly vinyl acetate polymer on silt soil has been studied. In this study the samples were uncompacted particles of soil with different amount of water-solvated polymer (0, 5, 10, 15, 20, 25, 30 grams per meter squared) poured over them. These samples are kept in experimental environment for 7 days. After ensuring complete dryness, their stabilities are tested against wind flow with 20 m/s speed. Results showed that adding more polymers to soil would considerably increase its particles’ stabilities. This stability is due to positive reaction of polymer with soil particles. The effect of this stability is maintained during sample drying time in the lab and the soil maintains its characteristics during testing. The best results are obtained for 20 grams polymer per meter squared, where caused an increase in stability to about 15 times that of the soil without polymer.

RING-OPENING COPOLYMERIZATION OF DL-LACTIDE AND POLY(ETHYLENE GLYCOL) INITIATED BY LANTHANUM ACETATE AND APPLICATION OF THE COPOLYMER AS MATRIX OF MICROSPHERES CONTAINING VIBRIO CHOLERA ANTIGENS

Poly-dl-lactide-poly(ethylene glycol) (PELA) triblock copolymers were synthesized with lanthanum acetate as the initiator. PELA microspheres with entrapped Vibrio Cholera antigen and outer membrane protein (OMP) were prepared by a double emulsion W/O/W based on solvent extraction methods. The obtained microspheres showed smooth and spherical surface and their size varied between 0.5 and 5.0 mu m, which are suitable for oral targeting delivery system. The distribution tests in rabbits and mice through scanning electronic micrography and fluorescence microscope indicated that microspheres have successfully reached the immunization-related tissues, such as the liver, spleen and intestinal peyer's patches, following oral administration. The PELA microspheres were also evaluated as an efficient antigen delivery system by enhancing a higher protective ratio against live Vibrios Cholera.

Radiation grafting of poly(vinyl acetate) onto wheat straw and properties of the product

Poly(vinyl acetate)(PVAc) was grafted onto wheat straw by γ-irradiation to improve the compatibility between wheat straw and high-density polyethelene(PE).The grafting was proved by Fourier transform infrared(FTIR) spectroscopy. The compact structure of wheat straw was loosened because the chemical bonds and crystalline structure were destructed by the γ-rays. The modified wheat straw needed less energy for thermal transition, as revealed by differential scanning calorimetry(DSC).Thermal analysis revealed that grafted PVAc acted as a protective barrier for the wheat straw and leads to an increase in maximum pyrolysis temperature. The crystallite size of grafted wheat straw decreased to 5.33 nm from 5.63 nm before irradiation. There were holes in melted form appeared on the surface of the grafted wheat straws.Both the grafted PVAc and irradiation are beneficial to lower the torque of wheat straw/PE melts and improve its mechanical properties by 36%. Possible mechanism of irradiation grafting was proposed.

COMPATIBILITY IN POLYMER BLENDS OF POLY (VINYL ACETATE) AND POLY (METHYL METHACRYLATE)STUDIED BY NMR

Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering techniques. The nuclear magnetic relaxation time T_1's were measured as a function of composition in blends of PMMA and PVAc prepared from chloroform solution. The results show that the system is miscible for casting from chloroform solution.

Synthesis of poly (vinyl acetate) oligomersand their phase behavior in supercritical carbon dioxide

Three poly(vinyl acetate)(PVAc)oligomers with controlled molecular weight and narrow molecular distribution are synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The effects of the reaction temperature and the added amount of initiator of the PVAc polymerization are discussed.In addition,the phase behavior of the prepared PVAc in pressured CO2 is determined via the cloud point method.The results indicate that the cloud point of PVAc increases with the increase in the molecular weight,the PVAc concentration,and the temperature.The cloud point pressures for the PVAc mass concentration of 0.12%with the molecular weight of 1 550,2 120,and 2 960 g/mol are 13.48,13.83 and 15.43 MPa,respectively,at the temperature of 35℃.It reveals that the solubility of PVAc in ScCO2 at relatively low pressure is remarkably limited.

Poly(Acrylamide-Co-Acrylic Acid)-Zinc Acetate Polymer Electrolytes: Studies Based on Structural and Morphology and Electrical Spectroscopy

Solid polymer electrolytes (SPEs) of polyacrylamide-co-acrylic acid (PAA) as the polymer host and zinc acetate (ZnA) as an ionic dopant were prepared using a single solvent by the solution casting technique. The amorphous and crystalline structures of film were investigated by X-ray diffraction (XRD). The surface morphology of samples was examined by scanning electron microscopy (SEM). The composition and complex formation of films were characterized by Fourier transform infrared (FTIR) spectroscopy. The conductivity of the PAA-ZnA films was determined by electrochemical impedance spectroscopy. According to the XRD and FTIR analyses, all electrolyte films were in amorphous state and the existence of interaction between Zn2+ cations and the PAA structure confirms that the film was successfully prepared. The SEM observations reveal that the electrolyte films appeared to be rough and flat with irregularly shaped surfaces. The highest ionic conductivity (σ) of 1.82 × 10-5 Scm-1 was achieved at room temperature (303 K) for the sample containing 10 wt % ZnA.

<i>In Situ</i>Preparation of Core Shell-Polypyrrole /Poly (Acrylonitrile-Co-Vinyl Acetate) Nanoparticles and Their Nanofibers

Poly (acrylonitrile-co-vinyl acetate)/polypyrrole composite particles with uniform size and morphology have been synthesized using one-step polymerization that involves swelling and coating of polypyrrole (PPy) into P (AN-co-VAc) latex nanoparticles. As an initial stage, free radical copolymerization of acrylonitrile (AN) and vinyl acetate (VAc) was synthesized by emulsion polymerization using ammonium persulfate (APS) and dodecyl benzene sulfonic acid salt (DBSA) as a surfactant. P (AN-co-VAc)/PPy composites were obtained first time by in situ addition of the pyrrole into the reaction medium. The electrospun P (AN-co-VAc)/PPy nanofibers were obtained from the nanoparticles with better properties and the effect of PPy on the morphology of nanofibers was studied by scanning electron microscopy (SEM). High degree of homogeneity and molecular order induced by molecular dispersion of polypyrrole on copolymer matrix without phase separation improve the transport properties and stability of polypyrrole, which are critical for high-performance organic electronics.

Catalytic Hydrogenation over Palladium Complex of Molecular Complex of Poly(4-vinylpyridine) with Acetic Acid

The palladium complex of the molecular complex of poly(4 vinylpyridine) with acetic acid(PVP/ HAc Pd) was prepared. Its catalytic activity for the hydrogenation of nitrobenzene was found much higher than that of the corresponding palladium complex of poly(4 vinylpyridine). In the presence of a strong inorganic alkali, especially potassium hydroxide, the catalytic activity is greatly improved. The suitable hydrogenation condition for PVP/HAc Pd is to use 0 1 mol/L ethanol solution of potassium hydroxide as the hydrogenation medium and the hydrogenation is carried out at 45 ℃.

Transesterification of Ethylene Carbonate with Dimethyl Terephthalate over Various Metal Acetate Catalysts

The reaction between ethylene carbonate and dimethyl terephthalate was carried out for the simultaneous synthesis of dimethyl carbonate and poly（ethylene terephthalate）, This reaction is an excellent chemical process that is environmentally friendly and produces no poisonous substance. The metal acetate catalysts used for this reaction are discussed in detail. Lithium acetate dihydrate was found to be a novel and efficient catalyst for this reaction. Compared with other metal acetates, lithium acetate dihydrate can attain a maximum catalytic activity at a lower concentration. When the reaction was carried out under the following conditions： the reaction temperature from 230 to 250 ℃, molar ratio of ethylene carbonate（EC） to dimethyl terephthalate（DMT） 3： 1, reaction time 3 h, and a catalyst amount of 0. 4% （molar fraction to DMT）, the yield of dimethyl carbonate（DMC） was 79. 1%.

乙酸氧钛催化酯化缩聚法合成聚丁二酸乙二醇酯及其性能研究

聚丁二酸乙二醇酯(PES)作为一种脂肪族聚酯,具有良好的力学性能和全生物降解特性,在降解塑料领域具有广阔的应用前景。以溶剂热法制备了一种乙酸氧钛化合物,将其作为催化剂用于催化丁二酸(SA)和乙二醇(EG)酯化缩聚合成高分子量PES。系统考察了催化剂用量(催化剂占反应物料的质量分数,下同)、反应温度和反应时间对PES分子量的影响,采用^(1)H-NMR和^(13)C-NMR对PES的结构进行了表征,并对其热性能、热稳定性和力学性能进行了测试。结果表明,当催化剂用量为0.6%,在230℃下聚合8 h时,合成的PES的特性黏度[η]为0.78,数均分子量(Mn)为47500,对应的聚合物分散性指数(PDI)为2.66。合成的PES熔点为102.4℃,最大热分解温度为420.2℃,断裂伸长率为505%±5%,拉伸应力为(48.3±0.6)MPa,拉伸弹性模量高达358.8 MPa。以煤制乙二醇为单体合成PES不但可以实现全生物降解聚合物的低成本制备,而且对煤化工产业的高质量发展有重要的现实意义。

聚醋酸乙烯酯(PVAc)对PHB/PCL共混物理化性能研究

聚醋酸乙烯酯(PVAc)作为非共价键型增容剂加入到聚羟基丁酸酯(PHB)/聚己内酯(PCL)(25∶75,质量分数,下同)二元共混体系中,通过溶液浇铸法制备薄膜,探究不同含量的PVAc(1%、3%、5%)对PHB/PCL共混物体系的力学性能和理化性能的影响。结果表明,PVAc含量为1%时,薄膜的断裂伸长率和拉伸强度分别为未添加PVAc的PHB/PCL薄膜的2.50倍、1.19倍。傅里叶变换红外光谱(ATR‐FTIR)显示,在PVAc的桥联作用下,PHB和PCL的羰基(C=O)基团和甲基(CH_3)基团之间存在分子间氢键的相互作用,羰基峰(C=O)发生移位,并且峰值降低。扫描电子显微镜(SEM)显示,PVAc的加入降低了共混体系中分散相的尺寸,分布更为均匀,共混体系的相容性有所改善。

重质碳酸钙聚合改性及其在聚氯乙烯中的应用研究

以重质碳酸钙为主要原材料,通过水磨、聚合改性得到可用于聚氯乙烯(PVC)管件的改性重质碳酸钙。通过粒度仪、热重分析仪、红外光谱仪、摆锤式冲击试验机、万能拉伸试验机、色差仪和光泽仪分别对重质碳酸钙及重质碳酸钙制备的PVC产品进行了表征和分析。结果表明,需在碳酸钙浆液中进行原位聚合反应,聚醋酸乙烯酯才能对碳酸钙包覆改性;聚醋酸乙烯酯改性的碳酸钙相较于常规硬脂酸改性的碳酸钙,在PVC材料应用中表现出了更好的外观及力学性能,这归因于聚醋酸乙烯酯能更好地解决碳酸钙与PVC之间的相容性问题。

PERVAPORATION SEPARATION OF WATER-ACETIC ACID MIXTURES THROUGH AN-co-AA MEMBRANES TREATED WITH RARE EARTH METAL IONS

Pervaporation separation of water-acetic acid mixtures through Poly(AN-co-AA) membranes and rare earth metal ions treated Poly(AN-co-AA)membranes was investigated for the first time. The results showed that the treatment with rare earth metal ions could greatly improve the characteristics of the separation of water-acetic acid mixtures.

低黏度高固含量聚醋酸乙烯酯乳液胶黏剂的制备及应用

聚醋酸乙烯酯(PVAc)具有固化速度快、初粘性好的优点,可作为胶黏剂或增稠剂应用于人造板工业。研究以醋酸乙烯酯(VAc)为单体、聚乙烯醇(PVA)为保护胶体,采用半连续乳液聚合法制备低黏度、高固含量聚醋酸乙烯酯乳液,并考察了PVA种类及其他聚合工艺因素对乳液性能的影响。结果表明:PVA种类对乳液性能影响较大。采用激光粒度分析仪、差示扫描量热仪(DSC)等对不同种类PVA合成的乳液进行表征表明:粒径随PVA醇解度增加而明显增大;PVA聚合度对乳液的玻璃化转变温度(Tg)影响较大。以PVA0599为保护胶体制备的PVAc乳液作为木材胶黏剂时,其拉伸剪切强度达8.62 MPa。

醋酸亮丙瑞林植入剂体外释药模型的建立及释药动力学行为与热力学特征

背景:目前,中国尚未对皮下给药制剂的体外溶出做出明确指导,且由于以聚乳酸-乙醇酸共聚物为载体的缓控释制剂释放周期一般较长,因此开发一个能较好模拟体内吸收的体外释放方法至关重要。目的:制备醋酸亮丙瑞林皮下植入剂,开发与体内相关性良好的体外释放方法,建立体外加速释放模型,考察药物释放动力学和热力学的相关性,阐述释药机制。方法:以聚乳酸-乙醇酸共聚物为载体,利用热熔挤出技术制备醋酸亮丙瑞林植入剂,对其在成型过程中的物理化学性质进行表征;根据开发的体外释药方法进行体外释药实验,以释放度为指标,筛选释放周期为1个月的处方。以成年雄性SD大鼠为动物模型,皮下植入释放周期为1个月的醋酸亮丙瑞林植入剂,于设定的时间点眼眶取血,采用液相色谱-串联质谱法检测血浆中亮丙瑞林的浓度,分析体内、外药物释放相关性。取释放周期为1个月的醋酸亮丙瑞林植入剂,以温度为单变量进行体外加速实验,拟合释放动力学方程,同时扫描电镜下观察植入剂的微观形态。结果与结论:①实验设置了5种配方的植入剂,体外释药实验显示第5种配方植入剂(醋酸亮丙瑞林的投料比为25%、载体投料比为75%,其中载体中分子质量10 kD与30 kD的聚乳酸-乙醇酸共聚物质量比为1∶1)的释药周期为30 d,符合要求,用于后续实验;②建立的体外释放方法与体内释药性相关性良好(y=0.945x-5.58618,R^(2)=0.9454);③体外累计释放曲线符合S型三相模式:突释期、迟滞期和零级快速释放期;在升温过程中,以312.15 K的零级释药速率为基准,热力学与药物释放动力学速率符合方程,r=7.76825E-30×e(k/4.78745)+0.88303;④结果表明开发的体外释放方法能较好阐述药物在体内的释放动态信息,体外释药呈S型释放曲线,释药机制为扩散与溶蚀相结合,且零级快速释药期药物释放动力学和热力学呈指数关系。