聚乳酸的合成、结构及性能

乳酸经减压蒸馏制得单体丙交酯，再以氧化锌为催化剂聚合得到聚乳酸。单体及聚合物均由结构鉴定证实，对产物的分子量、力学性能及降解等重要性质作了研究。     

聚苯硫醚的合成及性能

本文主要讨论了一种重要的热塑性工程塑料─聚苯硫醚的合成方法及物理性能。     

含磺酸甜菜碱聚乳酸的合成及其作为药物载体的研究

以磺酸丙基二乙醇基甲基铵内盐为引发剂开环丙交酯形成了含磺酸甜菜碱的聚乳酸(PLAMPS),在确认了聚合物的分子结构后通过溶剂挥发法制备聚合物胶束。用动态光散射法(DLS)测定胶束的粒径及粒径分布,用荧光分光光度计测聚合物的临界胶束浓度。以疏水性化合物β-胡萝卜素(β-carotene)为模型药物研究胶束的载药性质,用双光束紫外分光光度计法测定载药量与包封率。结果表明,PLA-MPS胶束能够包载疏水性药物,PLA20-MPS胶束的载药量与包封率最大分别为10%和60.3%之间。     

不同相对分子质量PTMG合成聚醚酯的 表征与性能研究

以对苯二甲酸二甲酯（DMT）、1,4-丁二醇（BDO）、聚四氢呋喃醚（PTMG）为原料,采用熔融缩聚方法一步合成了一系列的PBT—co-PTMG,通过红外光谱、核磁共振和凝胶色谱等分析方法对其分子结构和相对分子质量进行了表征,用DSC和TG研究了其耐热性能。结果发现：1）以相对分子质量为2000和1000的PTMG为软段合成的聚醚酯,其相对分子质量稍大;而以相对分子质量为3000的PTMG为软段合成的聚醚酯弹性体,其相对分子质量相对较小。2）相对分子质量为2000和1000的PTMG合成的聚醚酯弹性体的熔点和降解温度差不多,而相对分子质量为3000的PTMG合成聚醚酯弹性体的熔点和降解温度较低。     

聚丙交酯-乙交酯聚合物(PLGA)涂层体外降解行为研究

为了防止心血管支架植入后再狭窄的发生,目前采用将抑制平滑肌细胞生长的药物通过高分子载体涂在支架表面.由于支架植入体内后,涂层受到血液冲刷作用.本工作采用可降解高分子材料PLGA作为载体,将PLGA薄膜置于体外循环冲刷装置中,在37℃、pH7.4的Hank's模拟体液、模拟血流冲刷作用下的体外降解,并与静态降解作为对比.采用SEM、GPC、1H-NMR和DSC技术研究了聚合物在降解过程中形貌、分子量及分子量分布、失重率、组成和热性能的变化,并对降解机理进行探讨.与静态降解相比较,在流动体液中,高分子载体表面形貌、失重率以及分子量变化均较慢.上述结果与表面微环境有关.     

聚丙交酯-乙交酯共混膜与梯度膜的体外降解特性研究

以聚丙交酯-乙交酯(PLGA)50/50与75/25为原料,采用流延法制成薄膜,其中包括PLGA50/50单成分膜、PLGA75/25单成分膜、两者的共混膜以及成分非均匀分布的梯度膜,将4种不同类型的膜浸泡在37℃、PH=7.4的磷酸盐缓冲液中进行体外降解实验.对4种膜降解过程中的分子量、质量损失、吸水率、pH值以及表...     

PHBV/PPC反应共混物的热性能与动态力学性能及形态结构

将甲基丙烯酸缩水甘油酯接枝的聚(β-羟基丁酸酯-co-β-羟基戊酸酯)(PHBV-GMA)与马来酸酐封端的聚碳酸亚丙酯(MA-PPC)反应性共混。采用差示扫描量热仪、动态力学分析仪和偏光显微镜分别研究了共混物的热性能、动态力学性能和形态结构。结果发现,通过反应接枝,MA-PPC降低了PHBV的结晶度,阻碍了PHBV的结晶,PHBV部分扩散进入MA-PPC相区。PHBV球晶尺寸降低,PHBV和MA-PPC共混组分的相容性得以改善。     

正硅酸乙酯封端聚丙撑碳酸酯及其热性能研究

以正硅酸乙酯(TEOS)为封端剂对聚丙撑碳酸酯(PPC)进行封端,得到了正硅酸乙酯封端聚丙撑碳酸酯(TEOS-PPC),采用凝胶渗透色谱法、热重分析法、差示扫描量热分析法和动态热机械分析法对聚合物的性能进行了表征。聚合物分子量的测试表明,封端过程中有扩链反应的发生。热分析结果表明用TEOS对PPC进行封端可以有效地提高PPC的耐热性能和玻璃化转变温度。     

聚(DL-丙交酯-co-ε-己内酯)的合成、结构与性能研究

以辛酸镁为催化剂催化DL-丙交酯和ε-己内酯本体开环共聚合,制备了一系列不同单体配比的共聚物.13CNMR分析了共聚物微观结构,计算各单元平均序列长度,表明两类酯交换反应存在使得单元序列结构重新分布,并趋向于无规化分布;共聚物组成显著影响单元序列长度,各序列长度随相应单体加入量增加而增长.DSC和XRD分析了共聚物热性能和结晶性,表明共聚物结晶性与单元序列长度密切相关.共聚物只观察到一个玻璃化转变温度,符合无规共聚物的Fox方程,说明所得共聚物为无规共聚物,或者说包含有相容性嵌段成分的共聚物.     

基于5,5′-双[P-(4-氨基苯氧基)苯氧基]联嘧啶聚酰亚胺的合成及性能

氢碘酸、2-氯-5-溴嘧啶、对苯二酚以及对溴硝基苯等为原料,通过碘代、Ullmann、Williamson以及还原等反应合成了5,5′-双[P-(4-氨基苯氧基)苯氧基]联嘧啶,用元素分析,IR和1H-NMR等手段对化合物的组成和结构进行了表征。这种二胺与联苯四酸二酐(BPDA)通过两步法聚合获得含联嘧啶单元的聚酰亚胺,通过红外、差示扫描量热仪(DSC)和热重分析等实验测试了该类聚合物的结构、热性能、力学性能及结晶性能。新型聚酰亚胺分子结构单元中多个醚键以及联嘧啶单元氮杂原子的极性综合作用,使其玻璃化转变温度达到262℃,具有较好的热稳定性。     

水热法制备不同形貌纳米ZnO阵列及光学性能的研究

采用简单水热法制备得到棒状、铅笔状和塔状不同形貌的纳米ZnO阵列。采用扫描电镜(SEM)、X射线衍射(XRD)、光致发射光谱对样品结构、形貌、光学性能和催化性能进行表征;结果表明,样品晶型比较完整,PL谱图表明样品在380nm左右都出现了强烈的紫外发射峰。同时,以甲基橙为模拟污染物,通过光催化测试表明,产品均具有良好的光催化性能,其中塔状纳米ZnO的光催化性能较高。     

In situ one-step synthesis of CuInS2 thin films with different morphologies and their optical properties

Journal of Materials Science: Materials in Electronics - CuInS2 (CIS) thin films with petal-like nanostructures were synthesized in situ on copper substrates through a facile, one-step solvothermal...     

Benzene-thermal synthesis and optical properties of CdS nanocrystalline

Solvent thermal process has been successfully applied to prepare nanocrystalline CdS via the reaction CdSO₄ with Na₂S₃ in benzene at 80–120 °C. It was found that solvent, temperature, and reactant have significant effect on crystal structure and particle size of CdS nanocrystalline. The results show that increasing of temperature and using of solvent of low dielectric constant are beneficial to prepare CdS nanocrystalline in hexagonal phase. The water content in the system not only induces the presence of cubic phase CdS nanocrystalline, but also leads to a particle size increase. The results demonstrate that both phase and particle size can be well controlled. As-prepared CdS nanocrystalline powders display obvious blue-shift characteristics.     

Hydrothermal synthesis and optical properties of CuS nanoplates

CuS nanoplates have been successfully prepared in the presence of cation surfactant cetyltrimethylammonium bromide (CTAB) by hydrothermally treating the solution of CuCl₂·2H₂O and Na₂S·9H₂O at 180 °C for 24 h. The as-prepared CuS nanoplates are of hexagonal phase and are single crystal. The thickness and edge length of the nanoplates are about 15 nm and 60 nm, respectively. The products was characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence measurements and ultraviolet-visible light spectrophotometer. The influences of synthetic parameters, such as reaction time and CTAB, on the morphologies of the products have been investigated.     

Low-temperature synthesis and optical properties of wurtzite ZnS nanowires

Single-crystal wurtzite ZnS nanowires have been synthesized via a facile solution route with polyethylene glycol-400 as inducing template at low temperature (170 °C). The as-prepared products have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray analysis (EDX). Raman and photoluminescence spectrum (PL) were used to investigate the optical properties of ZnS nanowires. The strong emission peak centered at 322 nm in PL spectrum could be attributed to the band to band transitions.     

Microwave-assisted synthesis of Ag nanophases and their optical properties

By microwave-assisted method, silver nanophases were produced with size and morphology control. Silver nanoparticles of controlled size from 10 to 80 nm were obtained. Particle size was controlled by varying reaction conditions, including metal source concentration and molecular weight of protecting agent (PVP). Silver nanowires were produced by releasing the metal source gradually from AgFn(1-n)(n = 1-6) with PVP as the morphology directing agent. UV-Vis spectra showed that Ag nanoparticles have absorption bands around 400 nm and the UV-Vis absorptions slightly blue shifted with decreasing particle size.     

Controlled synthesis and electrochemical properties of vanadium oxides with different nanostructures

Vanadium oxides (V₃O₇·H₂O and VO₂) with different morphologies have been selectively synthesized by a facile hydrothermal approach using glucose as the reducing and structure-directing reagent. The as-obtained V₃O₇·H₂O nanobelts have a length up to several tens of micrometers, width of about 60?C150?nm and thickness of about 5?C10?nm, while the as-prepared VO ₂ (B) nanobelts have a length of about 1·0?C2·7???m, width, 80?C140?nm and thickness, 2?C8?nm. It was found that the quantity of glucose, the reaction temperature and the reaction time had significant influence on the compositions and morphologies of final products. Vanadium oxides with different morphologies were easily synthesized by controlling the concentration of glucose. The formation mechanism was also briefly discussed, indicating that glucose played different roles in synthesizing various vanadium oxides. The phase transition from VO₂(B) to VO₂(M) were investigated and the phase transition temperature of the VO₂(M) appeared at around 68 °C. Furthermore, the electrochemical properties of V₃O₇·H₂O nanobelts, VO₂(B) nanobelts and VO₂(B) nanosheets were investigated and they exhibited a high initial discharge capacity of 296, 247 and 227 mAh/g, respectively.     

High-yield chemical synthesis of hexagonal ZnO nanoparticles and nanorods with excellent optical properties

Large yield and low temperature growth of nanostructures are key requirements for fulfilling the demand of large scale applications of nanomaterials. Here, we report a highly efficient chemical method to synthesize high quality hexagonal ZnO nanoparticle and nanorods utilizing the low temperature oxidation of metallic zinc powder in the presence of an appropriate catalyst. This one-step method has advantages such as low temperature (90 degrees C) and atmospheric pressure synthesis and a high yield (> 90%). Microstructure and optical properties of the as-synthesized ZnO nanoparticles are found to be identical or better than those of the commercial ZnO nanopower (Sigma-Aldrich). In particular, in comparison to the commercial nanopowder the as-grown ZnO nanorods and nanoparticles exhibit stronger UV absorption at 376 nm and intense UV photoluminescence emission at -382 nm, with negligible defect emission band. This method is suitable for large-scale production of nanosized ZnO and could be extended for the synthesis of other metal oxides.     

Template-free hydrothermal synthesis and optical properties of ceria hollow nanospheres with rough surface

The large-scale uniform CeO₂ hollow nanospheres with diameter of about 600 nm and rough surface have been successfully synthesized via a simple template-free hydrothermal technology. The obtained samples were examined by XRD, SEM, TEM, XPS, Raman scattering and UV–Vis spectra. The results show that the samples have a cubic fluorite structure of CeO₂ with no crystalline impurity phase and many Ce³⁺ ions and oxygen vacancies exist in the surface of CeO₂ sample. A red-shifting of the band gap is observed for the CeO₂ hollow nanospheres contrasting with the bulk one, which is mainly attributed to the influences of the Ce³⁺ ions and oxygen vacancies.     

Controlled synthesis and optical properties of Au and Au@PS nanoparticles

In this study, uniform gold (Au) nanoparticles (NPs) were prepared using seed-mediated growth method. The particle size was controlled by tuning the dosage of seed solution. Au@PS core–shell NPs were then synthesized by introducing a polystyrene (PS) shell (2–3 nm thick) around the core of Au NPs (115 nm). Evaluation of the surface plasmon (SP) optical properties indicated that wavelength of SP resonance of Au NPs increased gradually with increase in the particle size. This red shift was about 0.92 nm per 1 nm increase in particle size. The results also indicated that the zeta potential and optical properties of Au NPs could be adjusted by coating PS on the outside. Therefore, surface modifications and surface coating were effective ways to control the optical properties of Au NPs.