聚DL-乳酸的合成与降解性能研究

以辛酸亚锡为催化剂,采用丙交酯的开环聚合法合成了聚DL-乳酸（PDLLA）,并采用正交试验法分析了反应温度、聚合时间和催化剂用量等因素对聚合产物相对分子质量的影响。探讨了聚DL-乳酸在20～120min、180～210℃及不同环境中的热降解性能,研究了聚合物存体外模拟的生物环境中的降解特性。结果表明,当聚合温度为165℃,聚合时间为46h,催化剂用量为0．03％时聚乳酸的相对分子质量可达到21．4×10^4。在一定温度下,聚DL-乳酸的相对分子质量随热降解时间的延长而下降;聚乳酸在空气中的热降解速率比在真空中的热降解速率快。     

乳酸/聚乙二醇嵌段共聚物的合成与表征

利用直接缩聚法制备了乳酸与聚乙二醇的嵌段共聚物(PLEG)。采用正交试验法考察了乳酸与聚乙二醇质量比、催化剂种类、催化剂含量、反应温度和反应时间对PLEG性能的影响。结果显示优化的反应条件:乳酸与聚乙二醇质量比为8.5∶1.5,采用自制的复合催化剂,催化剂质量分数0.6%,聚合温度160℃,聚合时间5h。另外还考察了扩链剂对PLEG性能的影响,结果表明扩链剂能够显著提高PLEG的相对分子质量。对合成的PLEG通过红外光谱、核磁共振、热分析进行了表征。     

不同投料比对直接熔融聚合法生物降解材料聚乳酸-聚乙二醇的影响

以氧化亚锡为催化剂(mc／mLA=0．005),以外消旋乳酸(D,L-LA)单体为原料,使其与数均相对分子质量为1000的聚乙二醇(PEG)共聚,通过直接熔融共聚法,在1650℃、70Pa下反应15h,合成了生物降解材料聚乳酸-聚乙二醇(PLEG)。发现最佳投料比为mu／mPEG=9时,可顺利地得到共聚产物PLEG,且其特性黏数[η]可达最高(0．4009dL/g),产物的亲水性能也得到改善,有利于PLEG作为药物缓释载体的应用。     

双螺杆反应挤出制备马来酸酐接枝聚乳酸材料的研究

利用双螺杆挤出机制备马来酸酐接枝聚乳酸（MPLA）材料．研究了反应挤出工艺并测试了接枝产物的性能。结果表明：随着引发剂用量的增加或双螺杆转速的提高,产物黏度和熔体质量流动速率的变化总趋势是先降低后增高,而温度对挤出接枝反应的影响不明显;通过双螺杆挤出制备出的MPLA具有良好的亲水性和界面相容性。     

直接熔融聚合法合成生物降解材料PLEG研究Ⅴ反应机理

直接以乳酸（LA）单体和聚乙二醇（PEG）为原料,通过直接熔融共聚法,合成了生物降解材料聚乳酸-聚乙二醇（PLEG）,用特性粘数[η]、GPC、FTIR、1H NMR、DSC和X-射线衍射等手段对其进行了系统的表征,发现许多因素对PLEG存在一定的影响,如不同的预聚方式时PLEG的组成不同、左旋乳酸（L-LA）获得的共聚物相对分子质量不如外消旋乳酸（D,L-LA）等.在此基础上,初步探讨了LA与PEG直接熔融共聚的反应机理.     

聚丙烯固相接枝马来酸酐的研究

采用先降解后固相接枝技术,以马来酸酐（MAH）为单体,在自制的搅拌反应器中制备了马来酸酐接枝聚丙烯接枝物（PP-g-MAH）,并对其结构进行了表征与分析,研究了接枝反应时间、接枝反应温度、引发剂质量分数和单体质量分数对接枝率的影响。结果表明,接枝反应温度为120℃、引发剂质量分数为4%、单体质量分数为14%、接枝反应时间为2.5h时,可得到接枝率为2.85%的PP-g-MAH。     

马来酸酐共聚物对高蜡油品低温流动性能的影响

采用自由基溶液聚合法合成了马来酸酐-α-烯烃共聚物,然后通过十八胺与马来酸酐共聚物分子中的酸酐基团发生酰胺化反应得到侧链胺化的马来酸酐-α-烯烃共聚物,研究了马来酸酐共聚物对高蜡油品低温流动性能的影响.结果表明,马来酸酐共聚物可以明显降低高蜡油品的屈服应力和凝点,有效改善蜡晶形态并提高其在油品中的分散性.     

薄层法制备聚天冬氨酸及其阻垢性能研究

以马来酸酐和碳酸铵为原料,通过薄层聚合制备了聚天冬氨酸,研究了反应物配比、聚合时间及反应温度等因素对聚合物产率、相对分子质量的影响;考察了聚合物用量及相对分子质量对阻垢性能的影响.结果显示:碳酸铵和马来酸酐的化学计量数为1.2∶1、反应温度185℃、反应时间50～60 min时,产率可达88%,产物对硫酸钙和碳酸钙均具有良好的阻垢性能.     

直接熔融聚合法合成生物降解材料PLEG研究IV预聚方式的影响

直接以乳酸（LA）单体和聚乙二醇（PEG）为原料，通过直接熔融共聚法，合成了生物降解材料聚乳酸-聚乙二醇（PLEG），用特性粘数[η]、GPC、FFIR、^1H NMR、DSC等手段对其进行了系统的表征，发现不同的预聚方式存在一定的影响，LA和PEG直接进行一步预聚时相对分子质量较高，对药物缓释载体PLEG的合成较为有利。     

马来酸双十八酯的合成及宏观动力学

以对甲苯磺酸为催化剂、甲苯为带水剂,以马来酸酐和十八醇为原料合成马来酸双十八酯。考察了原料配比、催化剂用量、带水剂用量和反应时间等因素对反应过程的影响,并测定了动力学数据。通过实验得到了反应工艺条件：n（十八醇）：n（马来酸酐）=2.3：1,对甲苯磺酸用量为马来酸酐和十八醇总质量的0．5％,甲苯用量为马来酸酐和十八醇总质量的96％,反应温度≤130℃、反应时间为4．0h,在该条件下马来酸酐的转化率达到98．76％。合成马来酸单十八酯的反应为二级反应,速率方程中的指前因子为O．655152L／（mol·min）,活化能为17．82kJ／mol。合成马来酸双十八酯的反应为二级反应,速率方程中的指前因子为1．53951×1011L／（mol·min）,活化能为98．05kJ／mol。     

Syntheses of poly(lactic acid)‐poly(ethylene glycol) serial biodegradable polymer materials via direct melt polycondensation and their characterization

Directly starting from lactic acid (LA) and poly(ethylene glycol) (PEG), biodegradable material polylactic acid‐polyethylene glycol (PLEG) was synthesized via melt copolycondensation. The optimal synthetic conditions, including prepolymerization method, catalyst kinds and quantity, copolymerization temperature and time, LA stereochemical configuration, feed weight ratio m_LA/m_PEG and M_n of PEG, were all discussed in detail. When D ,L ‐LA and PEG (M_n = 1000 Da) prepolymerized together as feed weight ratio m_{D ,l‐LA}/m_PEG = 90/10, 15 h copolycondensation under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave D ,L ‐PLEG1000 with the highest [η] of 0.40 dL/g, and the corresponding MW was 41,700 Da. Using L ‐LA instead of D ,L ‐LA, 10 h polymerization under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave L ‐PLEG1000 with the highest [η] of 0.21 dL/g and MW of 15,600 Da. Serial D ,L ‐PLEG with different feed weight ratio and M_n of PEG were synthesized via the simple and practical direct melt copolycondensation, and characterized with FTIR, ¹H NMR, GPC, DSC, XRD, and contact angle testing. D ,L ‐PELG not only had higher MW than PDLLA, PLLA and L ‐PELG, but also better hydrophilicity than PDLLA. The novel one‐step method could be an alternative route to the synthesis of hydrophilic drug delivery carrier PLEG instead of the traditional two‐step method using lactide as intermediate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 577–587, 2006     

Degradation of poly(D,L‐lactic acid)‐b‐poly(ethylene glycol) copolymer and poly(L‐lactic acid) by electron beam irradiation

This article investigated the effects of electron beam (EB) irradiation on poly(D ,L ‐lactic acid)‐b‐poly(ethylene glycol) copolymer (PLEG) and poly(L ‐lactic acid) (PLLA). The dominant effect of EB irradiation on both PLEG and PLLA was chain scission. With increasing dose, recombination reactions or partial crosslinking of PLEG can occur in addition to chain scission, but there was no obvious crosslinking for PLLA at doses below 200 kGy. The chain scission degree of irradiated PLEG and PLLA was calculated to be 0.213 and 0.403, respectively. The linear relationships were also established between the decrease in molecular weight with increasing dose. Elongation at break of the irradiated PLEG and PLLA decreased significantly, whereas the tensile strength and glass transition temperature of PLLA decreased much more significantly compared with PLEG. The presence of poly(ethylene glycol) (PEG) chain segment in PLEG was the key factor in its greater stability to EB irradiation compared with PLLA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

直接熔融聚合法合成生物降解材料PLEG研究 V反应机理

直接以乳酸(LA)单体和聚乙二醇(PEG)为原料,通过直接熔融共聚法,合成了生物降解材料聚乳酸-聚乙二醇(PLEG),用特性粘数[η]、GPC、FTIR1、H NMR、DSC和X-射线衍射等手段对其进行了系统的表征,发现许多因素对PLEG存在一定的影响,如不同的预聚方式时PLEG的组成不同、左旋乳酸(L-LA)获得的共聚物相对分子质量不如外消旋乳酸(D,L-LA)等。在此基础上,初步探讨了LA与PEG直接熔融共聚的反应机理。     

乙二醇双子琥珀酸2-甲基戊基双酯磺酸钠的合成与性能研究

采用以碳基固体酸为双酯化反应催化剂,中间产物不需提纯分离等环境友好的合成工艺路线,在常压下合成了乙二醇双子琥珀酸2-甲基戊基双酯磺酸钠。对各步反应条件进行了考察,得到的最佳工艺条件为:单酯化反应:n(顺酐)∶n(2-甲基-1-戊醇)=1.05∶1.00,w(对甲苯磺酸)=1%,反应温度80℃,单酯化反应时间1 h,在该条件下得到产率为98.88%的单酯化产物;磺化反应:n(顺酐)∶n(亚硫酸氢钠)=1.00∶1.05,反应温度70℃,磺化反应时间2.0 h,在该条件下得到产率为98.71%的磺化产物;双酯化反应:n(顺酐)∶n(乙二醇)=1.00∶2.20,w(碳基固体酸)=3%,加热介质温度180℃,双酯化反应时间3.5 h,在该条件下得到产率为85.03%的双酯化产物。测定了目标产物的表面张力为27.79 mN/m;临界胶束浓度为2.5×10-3 mol/L。     

船用不饱和聚酯树脂的耐水性研究

采用苯酐、顺酐和二元醇为主要合成原料,通过醋酸酐对不饱和聚酯的端基进行封端反应。探讨了船用不饱和聚酯树脂的配方及反应条件。生产工艺采用全自动系统控制,并配有在线粘度计。实验结果表明,该树脂产品的吸水率为0.0434%,浸水30d其力学性能几乎没有降低,树脂耐水性好。     

Preparation and characterization of maleic anhydride-functionalized syndiotactic polystyrene

The free radical-induced grafting of maleic anhydride (MA) onto syndiotactic polystyrene (sPS) has been accomplished in the solution process by using 1,1,2-trichloroethane as solvent and dicumyl peroxide as free radical initiator. The amount of MA grafted on sPS was evaluated by a titration method. Grafted products separated from the reaction mixture were purified and analyzed. Fourier transform infrared spectroscopy and ¹H NMR studies indicate that MA attaches to the sPS in the form of single succinic anhydride rings as well as short oligomers. The results obtained by GPC analysis suggest that the degradation and chain extension reaction do not occur under the reaction conditions. Moreover, the crystallization behavior of MA-functionalized sPS was also studied by means of differential scanning calorimetry. It was found that the crystallization behavior of the grafted polymer exhibited somewhat differences in comparison to the neat sPS. The MA-functionalized sPS crystallizes at higher rate than the unmodified polymer, on the other hand, the degree of crystallinity (X_c) are lowered by the presence of the MA grafts.     

Direct condensation of lactic acid in the presence or absence of supported zirconium sulfate

Direct condensation of l ‐lactic acid was studied, aiming at highly crystalline and enantiopure high molecular weight (MW) products. Catalyst‐free polylactic acid (PLA) with weight average MW of 80,000 g mol^?1, based on PLA standards, and a crystallinity of 75% is synthesized at 140°C in a fixed‐bed reactor under vacuum or nitrogen purging. Supported zirconium sulfate is found to be an efficient and enantioselective catalyst for the melt and solid‐state post‐condensation of short‐chain prepolymers. Small‐molecule monohydroxy alcohols, aldehydes, di‐ and monocarboxylic acids (e.g., acrylic acid [1,700 ppm], propionic acid [1,800 ppm]) are detected in the lactic acid and prepolymers by high performance liquid chromatography, electron spray ionization, and electron impact mass spectroscopy. Thermal degradation of polymer chains, the crystallinity of the prepolymer, and the presence of monofunctional impurities are crucial parameters for the limitation of the MW of the resulting product. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42444.     

The aminolysis of styrene–maleic anhydride copolymers for a new modifier used in urea-formaldehyde resins

Styrene (St) and maleic anhydride (MA) alternating copolymers with different molecular weights (MW) were synthesized via radical copolymerization. The copolymers were subsequently transferred into water-soluble maleic amic acid derivatives (SMAA) via the aminolysis of anhydride groups using (NH₄)₂CO₃ as the ammonia sources. The synthesized polymers were applied as a new kind of macromolecular modifier and added into the reaction system during the synthesis of urea-formaldehyde (UF) resins via the traditional alkaline–acidic–alkaline three-step process. The UF resins modified with SMAA were characterized using Fourier Transform Infrared Spectroscopy (FT-IR), ¹³C nuclear magnetic resonance (¹³C-NMR) spectroscopy, and thermal gravimetric analysis (TGA). All the results confirmed the successful incorporation of SMAA chains into the crosslinking network of the UF resins. The modified UF resins were further employed as wood adhesives and the effect of synthesis parameters on their performance was investigated. Meanwhile, the influence of SMAA molecular weight (MW) on the properties of the modified UF resins was also studied. When the UF resins were synthesized with a low molar ratio of formaldehyde/urea (F/U) and a predetermined amount of SMAA added into the reaction system at the second step, plywood bonded using these modified UF resins showed much improved bonding strength (BS) and depressed formaldehyde emission. Moreover, the as-modified UF resins showed good storage characteristics.     

The kinetics and mechanism of cure of an amino-glycidyl epoxy resin by a co-anhydride as studied by FT-Raman spectroscopy

The thermal curing behavior of tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) and a co-anhydride mixture consisting of maleic anhydride (MA) and hexahydrophthalic anhydride (HHPA) was studied from 55 to 100 °C by real-time FT-Raman spectroscopy. The quantitative changes in concentrations of anhydride, epoxy, and new-formed ester were measured and empirical reaction rate curves were constructed reflecting the kinetics of the curing process. After an induction period a simple kinetic scheme that is first order in both epoxy and anhydride monomer consumption described the reaction profile until the reaction was influenced by chemo-rheological changes due to vitrification transition.FT-Raman analysis revealed that curing propagation mainly occurs by polyesterification between epoxide and anhydride. Possible side reactions including the homopolymerization of MA are considered. The main side reaction is decarboxylation of MA that may produces some autocatalysis, but this is a minor contribution to the kinetics of cure. No conclusive evidence has been found for homopolymerization of MA or initiation of the curing reaction by the reaction product of TGDDM and MA, compared to the polyesterification.