聚乳酸合成方法研究进展

聚乳酸是一类具有优良生物相容性和可生物降解的高分子材料，被广泛应用于医用领域，受到越来越多的关注。聚乳酸的合成主要有两种方法：丙交酯的开环聚合和乳酸直接缩聚。本文综述了近年来聚乳酸合成研究的最新进展，介绍了聚乳酸聚合的两种高效方法——反应挤出法和直接-固相聚合法，并展望了聚乳酸合成研究的前景。     

异辛酸亚锡催化D,L-丙交酯聚合动力学

以异辛酸亚锡为催化剂,D,L-丙交酯开环聚合合成聚乳酸,研究了D,L-丙交酯聚合动力学,考察了催化剂和反应温度对聚合反应的影响,测定了聚合反应的表观活化能及聚合速率方程,并推测了反应机理。     

L-乳酸和聚乳酸的研究进展

综述了乳酸发酵和提取工艺以及聚乳酸的合成进展,分析了L-乳酸及合成聚乳酸两种产品的市场前景,对进一步的技术开发提出了建议。     

活性聚合化学理论进展

活性聚合是合成特制聚合物的一种十分有效的方法。近十年来,人们除在活性阴离子聚合理论和应用方面不断拓宽和深入外,还发现了活性阳离子聚合,活性配位聚合和基团转移聚合及其它准活性聚合方法,笔者拟对各种活性聚合化学理论成就,分类作一介绍。 高分子化学家在对活性聚合理论的长期研究中得出结论,理想活性聚合应满足以下三项准则(1):     

高吸水性树脂的合成

用硝酸铈铵为引发剂制备了丙烯腈在玉米淀粉上的接枝共聚物。考察了聚合条件和水解条件对接枝共聚物吸水能力的影响,并对两种合成方法进行了比较。结果表明:硝酸铈铵引发剂的引发效率高,聚合速度快,树脂的吸水能力强。     

一步法合成高苯橡胶的研究

介绍了一步直接合成高苯乙烯橡胶的聚合法、主要影响因素,研究结果和所得产品与共凝聚法的比较。     

油田用磺化聚丙烯酰胺研究进展

综述了磺化聚丙烯酰胺(SPAM)的各种合成方法,包括水溶液聚合、胶束聚合、微乳液聚合、反向悬浮聚合、分散聚合、离子液体聚合等,简要评述了这些方法的特点.认为SPAM的发展前景广阔,但目前的合成研究主要集中在水溶液法,其他合成方法还需改进完善.     

星型聚合物的合成方法综述

概述了星型聚合物的特点和应用,较详细地介绍了星型聚合物的3种合成方法：活性阴离子聚合法、活性阳离子聚合法和活性自由基聚合法。     

丙交酯合成工艺影响因素的分析

丙交酯是合成聚乳酸的主要原料,其收率和纯度制约着聚乳酸的成本和质量。介绍了聚乳酸的市场概况,重点综述了两步法丙交酯合成工艺的影响因素,分析了反应温度、压力、催化剂等对乳酸缩聚和解聚的影响以及粗丙交酯精制方法的优劣;分析了国内生产企业存在的问题和发展方向,提出丙交酯合成技术发展的关键在于开发高效手性催化剂、高收率的精制技术以及连续化生产工艺等。     

长春应化所与长江化纤公司联合研发玉米淀粉纺丝技术

由中科院长春应化所与常熟市长江化纤有限公司联合研发，采用玉米淀粉纺出纤维材料技术通过了中国纺织工业协会组织的专家鉴定。该技术名为连续聚合熔体直纺聚乳酸长丝，简称“一步法纺丝”。聚乳酸长丝是以玉米淀粉为原料，用细菌发酵和化学合成方法而得到的新型高分子纤维材料，可完全生物降解。由该技术纺出的聚乳酸长丝，     

聚氨酯交联网络材料的合成与降解性能

探讨了以乳酸和甘油直接缩聚合成交联剂的方法 ,合成了一系列乳酸和甘油不同摩尔比的预聚物 ,并通过红外光谱、核磁共振等证实了所得预聚物与开环聚合所得聚合物有相似的结构 ,同时用六次甲基二异氰酸酯对预聚物进行扩链反应 ,得到了聚氨酯交联网络材料。采用不同的试验方法对该聚氨酯交联网络材料的降解性能进行了研究。结果表明 ,此材料是可降解的 ,其降解率与试验方法和试验条件等因素有关。此方法优于开环聚合法 ,反应过程简单 ,成本低。     

Effects of phenyllactic acid as sanitizing agent for inactivation of Listeria monocytogenes biofilms

3-Phenyllactic acid (PLA) has been reported as an antimicrobial compound with broad-spectrum activity, and it can be produced by food-grade microorganisms, including a wide range of lactic acid bacteria species. In this study, the efficacy of PLA to inactivate Listeria monocytogenes planktonic cells and biofilms was determined and compared with the killing effects of lactic acid (LA), and levulinic acid (LVA) with sodium dodecyl sulfate (SDS). L. monocytogenes biofilms of different maturities, i.e., 37 °C for 3 and 7 d and 15 °C for 4 and 7 d, were produced on 24-well flat-bottom polystyrene plates and treated with PLA (0.25%–3%), LA (1% and 3%), and 3% LVA plus 2% SDS for 5, 10, 30, 60 min, respectively. The results of pure culture assays revealed that 1% PLA reduced the population of L. monocytogenes by 7 log CFU/ml within 1 min. The biofilms assays revealed that L. monocytogenes biofilms could be inactivated to different degrees by the sanitizer treatments. The killing effect of PLA treatment was increased as exposure time and PLA concentrations were increased. The sanitizers of 3% PLA and 1% PLA effectively inactivated the early mature biofilm after a 5-min treatment, whereas 3% PLA was better than all the other sanitizers, including 1% PLA, 3% LA, 3% LVA and 2% SDS for inactivation of the late mature biofilm after a 5-min treatment. Confocal laser scanning microscopy analysis revealed that bacterial cell damages in the biofilm were enhanced as the PLA concentrations and exposure times were increased. These results suggested that PLA was effective in inactivating L. monocytogenes and its biofilm, even for the late mature biofilm.     

聚丙烯酰胺微球在油田调剖堵水中的应用研究进展

聚丙烯酰胺微球广泛应用于油田深部调剖堵水,其合成方法主要有:反相悬浮聚合、反相乳液聚合、反相微乳液聚合和分散聚合等.微球的制备方法、水化膨胀程度等因素影响着微粒粒径,而微球粒径的大小及其分布是影响封堵性能的重要因素.综述了这些因素对聚丙烯酰胺微球封堵性能的影响.     

聚合方法和扩链剂对乳酸聚合物相对分子质量的影响

研究了乳酸熔融缩聚和溶剂回流脱水缩聚两种聚合方法及几种扩链剂对乳酸聚合物相对分子质量的影响。结果表明 ,溶剂回流脱水缩聚所得聚合物的相对分子质量是乳酸熔融缩聚的 2～ 3倍 ,而通过加入合适的扩链剂可使乳酸聚合物的相对分子质量提高十几倍。     

四氯化锡催化合成乳酸仲丁酯

本文采用四氯化锡作为催化剂催化合成乳酸仲丁酯。此法"三废"排放少,产率较高,比传统用浓硫酸做催化剂优越很多。通过实验得出四氯化锡催化合成乳酸仲丁酯的最佳反应条件是:酸醇摩尔比为1:3,即取乳酸(化学纯,85%)7.6ml,仲丁醇24.5ml;催化剂用量为2.0g,反应时间2.5h,以甲苯为带水剂,在此条件下可以得到乳酸仲丁酯的产率为75.6%。     

D,L-丙交酯的合成与纯化

以D,L-乳酸为原料,在催化剂存在下通过脱水环化合成D,L-丙交酯,研究了反应过程中催化剂用量、脱水温度及稀释剂等因素对D,L-丙交酯产率的影响。用重结晶法对粗产物进行纯化,制备出高产率、高纯度的D,L-丙交酯。实验结果表明,采用二丁基氧化锡为催化剂,最佳催化剂用量(质量分数)为1 5%,最佳脱水温度为140℃,且在反应中加入稀释剂可以显著提高D,L-丙交酯的粗产率;乙醇是理想的重结晶溶剂,粗产物经多次纯化后,可获得总产率达37 3%的纯D,L-丙交酯。     

Poly(lactic acid) film incorporated with marigold flower extract (Tagetes erecta) intended for fatty-food application

Bilayer functional film made of poly(lactic acid), PLA incorporated with 2 wt.% marigold flower extract containing astaxanthin (PLA2M) was fabricated by using a blown-extrusion process. The release of astaxanthin, a keto-carotenoid antioxidant, from the PLA-based film towards 95% ethanol (ETOH) was investigated at 30 and 40 °C. PLA and PLA2M that had been in contact with 95% ETOH at 30 and 40 °C were also investigated for their optical, thermal, structural, molecular weight and barrier properties. PLA2M showed approximately 21% reduction in its water vapor permeability (WVP) as compared to PLA (control bilayer functional film). No significant differences were observed between both PLA and PLA2M in terms of their thermal properties and O₂ permeability. Molecular weight of PLA2M had a slight decreased than that of PLA after processing. A significant change was observed in the IR spectra of PLA2M especially for the carbonyl stretching (1749 cm⁻¹), and –C–O–C aliphatic ester bending (1132 cm⁻¹), which due to the structure of astaxanthin that consists of polyunsaturated alkenes and carbonyl group. Diffusion of astaxanthin from PLA films into 95% ETOH at 30 and 40 °C were 12.7 and 22.8 × 10⁻¹¹ cm²/s, respectively. New crystal domains were formed for the samples exposed to 95% ETOH at 30 and 40 °C due to solvent induced crystallization, with higher temperature inducing larger crystallization. Pouches made of PLA2M were able to maintain the freshness of soybean oil at 30 °C, under light exposure to less than 5 days per guideline by the Codex Alimentarius (<10 milliequivalent/kg), and could be attributed to the slow release of astaxanthin.     

十二水合硫酸铁铵催化合成乳酸正丁酯

将十二水合硫酸铁铵作催化剂,应用于乳酸和正丁醇的酯化反应中,合成了乳酸正丁酯。例如,将０．１ｍｏｌ乳酸、０．２ｍｏｌ正丁醇和０．００３ｍｏｌ催化剂加热回流分水２ｈ,制得乳酸正丁酯,产品收率达９９％。     

Quantitative determination of lactic and acetic acids in cider by 1H NMR spectrometry

A quantitative determination method of lactic and acetic acids in cider is proposed by means of the proton nuclear magnetic resonance (¹H NMR) technique. Lactic acid gives a doublet signal at 1.42 ppm in the spectrum and acetic acid a singlet signal at 2.09 ppm, whose area is used to determine the concentration of these compounds. 3-(Trimethylsilyl)-2,2,3,3-d⁴-propionic acid sodium salt is added to the cider with a double purpose: as a reference for 0.00 ppm and as an internal standard for ¹H NMR measurement. Enzymatic analysis methods are used to validate the method. Good correlations are found between the lactic and acetic acids concentrations obtained by ¹H NMR and those obtained by enzymatic methods in different commercial ciders. For lactic acid, the 95% confidence interval for the slope is 1.05 ± 0.08 (includes 1) and for the intercept 0.27 ± 0.42 (includes 0). For acetic acid, these intervals are 1.01 ± 0.06 for the slope and 0.03 ± 0.08 for the intercept. The described method is fast and direct.