酶促木质素与酚共聚反应及产物表征

在反相微乳液系统中 ,用辣根过氧化物酶进行了酶促木质素与酚共聚反应 ,并进行了红外光谱分析及差示扫描量热分析。结果表明 ,由于在木质素分子间引入了聚甲酚片段 ,共聚物的热性能有较大改善。聚合物的重均分子量随反应温度的升高而增加     

聚丙烯纤维在聚3-羟基丁酸酯与木质素对甲酚复合膜中的改性作用研究

研究了聚3-羟基丁酸酯/聚丙烯纤维(PHB/PP)复合膜和PHB/PP/木质素对甲酚复合膜的力学和热力学性能的影响,分别探讨了PP纤维和木质素对甲酚的添加量对复合膜性能的影响。结果表明,PP纤维含量为8 %且木质素对甲酚含量为3 %时,PHB/PP/木质素对甲酚复合膜的综合性能最佳,适量的PP纤维改善了PHB的拉伸强度,并且木质素对甲酚一定程度上改善了复合膜的热降解性能。     

酶促木质素与酚聚合反应分子量及分布实验

在反相微乳液系统中 ,进行了过氧化物酶催化木质素与酚共聚反应实验 ,考察了酶浓度、WO(水 /表面活性剂 ,质量比 )、表面活性剂浓度、单体 (酚、木质素 )浓度及醇烃比对聚合物分子量的影响。结果表明 ,聚合物重均分子量可用表面活性剂浓度、酶浓度、单体浓度及油相中醇烃比来调控。用单纯形优化法关联了实验数据 ,得到了聚合物重均分子量的关联式 :M =6 2 7× 10 4 (Y1× 10 7) -0 .3 4Y0 .982 Y0 .83 Y2 .4 64 Y1.0 55。聚合物分子量分布出现双峰 ,是两种反应机理竞争的结果。     

竹材木素酚对牛血清蛋白吸附和解吸特点的研究

通过相分离技术,在竹材木质素的苄基引入不同的酚类化合物(对甲酚、邻苯二酚、间苯二酚、连苯三酚)得到不同结构性质的木质素衍生物——木质素酚(木素对甲酚、木素邻苯二酚、木素间苯二酚、木素连苯三酚),通过GPC分析木质素酚的分子量,同时,用考马司亮蓝法研究不同结构的木质素酚和牛血清蛋白之间的吸附和解吸关系。结果表明,四种木质素酚随羟基增加对蛋白质吸附能力增强,竹材木质素酚表现出与木材木质素酚相当的对蛋白质吸附能力。此外,由于竹材木质素末端含有羧基,当溶液pH变化时,特别是木质素多酚在解吸过程中更容易受电荷影响。     

二维核磁谱对木质素酚与磨木木质素结构的对照解析

采用二维核磁(2D-HSQC NMR)比较针叶材马尾松和阔叶材杨木制成的磨木木质素(MWL)及相分离法制备的木质素对甲酚(LPS)的基本结构单元的组成及连接方式。MWL和LPS相对其Klason木质素的得率分别为Ca.10%和Ca.100%,通过红外光谱(FT-IR)、高效凝胶渗透色谱(GPC)、核磁氢谱(1H-NMR)分别比较了其羟基、甲氧基等特征官能团、分子量、导入对甲酚的量。结果表明,LPS由于在木质素的苄基位置高频度(Ca.0.7 mol/C9)地导入了对甲酚,其羟基含量明显高于碱木素等其他类型的分离木质素。通过2D-HSQC NMR谱图的半定量(无内标)计算方法,计算了马尾松和杨木的MWL和LPS中GSH单元以及β-O-4、β-5、β-β连接方式所占的相对比例。结果表明,相分离法虽然在木质素的苄基位置选择性地有规律地导入了对甲酚,但与MWL木质素的骨架结构及主要连接方式的相对比例基本保持不变。     

杨木木质素酚与聚乳酸复合膜性能研究

四种由相分离法制得的杨木木质素酚(木质素对甲酚、木质素邻苯二酚、木质素间苯二酚、木质素邻苯三酚)分别与聚乳酸(PLA)共混铺膜,本文探究了木质素酚的添加量和种类对复合膜力学性能的影响,并对木质素对甲酚与聚乳酸复合膜的吸水性能、热学性能和结晶结构进行了分析。结果表明,随着木质素对甲酚添加量的增加,复合膜的拉伸强度和断裂伸长率都减小,当木质素对甲酚含量达到15%后,复合膜的力学性能趋于稳定值。在相同添加量下,木质素邻苯二酚-PLA复合膜的力学性能相对较好。木质素酚的添加提高了复合膜的热稳定性,在15%添加量时效果较好。这些结果表明,木质素的侧链特征对其在复合材料中的应用性能有重要影响。     

玉米芯酶解残渣酚化改性工艺及产物结构表征

以玉米芯纤维素酶水解残渣为原料,利用对甲酚和硫酸对其木质素进行酚化改性。采用单因素和正交试验的方法探讨了硫酸浓度、反应温度、反应时间和硫酸用量对酚化改性产物的得率、酚―羟基含量的影响。利用FTIR、1H-NMR和GPC等手段对酚化木质素的结构进行表征。研究结果表明,酚化改性可以有效地提高木质素的酚羟基含量,降低木质素大分子的分子量。正交实验结果表明,反应温度对酚化改性的影响最大,其次是硫酸浓度,酚化改性的最佳工艺条件为:温度40℃,硫酸质量分数60%,时间60 min,硫酸用量20 mL/g(残渣),此条件下木素酚得率达53.85%,酚羟基含量为1.23 mol/C9,相对分子质量(w M)为3388。     

玉米秸秆木质素的漆酶/介体活化处理

采用漆酶配以不同的介体对玉米秸秆木质素进行活化处理,利用红外光谱(FTIR)、紫外光谱、凝胶渗透色谱(GPC)、热失重(TG)、示差扫描量热(DSC)等分析方法研究了介体对漆酶活化降解木质素的影响。结果表明,漆酶会使木质素发生脱甲基作用,降低木质素的相对分子质量,增加酚羟基的含量,但在解聚木质素的同时也伴随着再聚合作用。在漆酶活化木质素的过程中,介体作为传递电子的中间体,能够促进木质素的氧化降解,降低木质素的相对分子质量,提升羟基的反应活性。不同的介体,活化效果不同,HBT、香草醛和紫丁香醛三种介体中,HBT介体的活化效果最佳。     

酶解木质素的制备及其在聚氯乙烯改性中的应用

介绍了采用无机碱性水溶液和有机溶剂分离、提取酶解木质素的方法,研究了热塑性酶解木质素(FTPL10)对聚氯乙烯材料的力学性能、热稳定性的影响。结果表明:当FTPL10用量为5份时,改性聚氯乙烯材料的拉伸强度为30.66MPa,冲击强度为5.91kJ/m2,热稳定时间为2 091s,与未经酶解木质素改性的聚氯乙烯材料相比,拉伸强度略微下降,冲击强度提高了60%,热稳定时间延长了74%。     

三聚氰胺改性木质素的制备及银离子吸附性能

以酶解木质素、三聚氰胺和甲醛为原料,通过接枝反应制备三聚氰胺改性酶解木质素(MEHL),并研究MEHL对银离子的吸附性能。接枝反应的研究结果表明,三聚氰胺和甲醛的添加量对产率有很大影响。酶解木质素、三聚氰胺、甲醛质量比为10:6:6,于90℃下反应4 h,所制得的MEHL的产率可达83.7%。红外光谱、热重和元素分析的结果表明,三聚氰胺成功接枝到酶解木质素分子上。MEHL的含氮量由酶解木质素的0.81%提高到18.55%。银离子的吸附研究表明,MEHL对银离子表现出很好的吸附性能。在银离子初始浓度为0.16 mol·L^-1,在MEHL用量为50 mg,吸附温度为30℃时吸附36 h,MEHL对银离子的吸附容量为944.1 mg·g^-1。     

球形木质素珠体接枝丙烯腈的影响因素研究

利用反相悬浮聚合技术制备球形木质素珠体,再以Fe2＋/H202为引发体系,采用正交实验综合研究了球形木质素珠体与丙烯腈的接枝共聚反应的各种影响因素对珠体的接枝率和接枝效率的影响。结果表明：当m（单体）／m（基体）=10：1,反应时间为90min,反应温度55℃,Fe2＋浓度为0．03mmol／L,H202浓度为2．97mmol／L时,可以得到最佳的接枝率和较高的接枝效率,木质素一丙烯腈接枝共聚物的接枝率为780％,接枝效率可达76．0％。     

Molecular weight and distribution of copolymer of lignin‐phenol in copolymerization catalyzed by peroxidase

The molecular weight and distribution of lignin‐cresol polymer in peroxidase‐catalyzed copolymerization of lignin with cresol in the reversed micellar system can be controlled by adjusting the surfactant concentration and other factors. The maximal mean molecular weight of copolymer obtained is 1890 kDa. The surfactant sustains chain growth. The cresol and/or polycresol is incorporated into the copolymer, and the thermal property of the copolymer is improved. A correlation for copolymer mean molecular weight is developed. The synthesized copolymer drops out of solution and can be easily recovered. The materials appear to act as thermosets and may have applications as replacements of conventional phenolic resins. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2408–2418, 2001     

Blends of vinylic copolymer with plasticized lignin: Thermal and mechanical properties

The article presents an investigation into the use of plasticizers for reducing the degree of association existing within lignin molecules, in order to overcome adverse effects on the mechanical properties of its blends with a vinyl chloride–vinyl acetate (VC–VAc) copolymer. Infrared spectroscopy and differential scanning calorimetry were performed to examine the effect of the plasticizer type and concentration in plasticizing Alcell, an organosolv lignin. The results show that the compatibility and efficiency of a plasticizer are strongly influenced by the solubility parameter, which should be close to that of the lignin. Polyblends prepared with several plasticizers, Alcell lignin, and the VC–VAc copolymer were also investigated by thermal analysis and mechanical testing. Variations in the mechanical properties of these blends were found to correlate with the lignin dispersion quality and with the plasticizer efficiency in Alcell lignin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 861–874, 2001     

Kinetics of lipase catalyzedenantioselective esterification of racemic ibuprofen in isooctane

The kinetics of Candida rugosa lipase catalyzed esteritlcation of racemic ibuprofen with n-butanol in isooctane was studied. The kinetic study was carried out with the addition of 0.1% and 2% (by volume) of water for enzyme activation respectively when celite was added into isooctane for enzyme dispersion. The specific initial rate for S-ibuprofen can be fitted with the Ping Pong Bi Bi mechanism with dead-end competitive inhibition by the alcohol. The time courses of the enantioselective esteriflcation of the two ibuprofen enantiomers with different initial substrate concentrations and water contents were simulated with a model in which both effects of enzyme inactivation by long term reaction and reversed hydrolytic reaction under high water content were taken into consideration.     

Modification of oxidized lignins with styrene

The effect of original and ozonized lignins upon the polymerization of styrene was investigated. It was found that the unoxidized lignin prepared by hydrolysis of spruce wood meals with 42% HCl retards the thermal polymerization of styrene. The ozonization of HCl-lignin leads to its chemical transformation during which two types of functional groups are formed: those inhibiting and those initiating the polymerization of styrene. Moreover, the polymerization of styrene in the presence of oxidized HCl-lignin affords both homopolymer and grafted copolymer. The amount of the grafted copolymer depends upon the concentration of active oxygen in lignin formed during oxidation, upon the temperature of polymerization, and, finally, upon the kind and concentration of the solvent used in the polymerization system.     

Multiphase materials with lignin. XII. Blends of poly(vinyl chloride) with lignin–caprolactone copolymers

A previously described starlike copolymer consisting of a lignin derivative (hydroxypropyl lignin) and caprolactone has been blended with poly(vinyl chloride) (PVC) over a composition range of 0–100%. Solvent-cast films of the blends were examined with regard to thermal, mechanical, crystallinity, and morphological characteristics. In addition, the blends were examined with regard to aging effects. The results suggest that the lignin/caprolactone copolymer forms either a miscible (by thermal analysis) or a nearly miscible (with phase dimensions in the order of 10–30 nm) system in which physical properties are modified over a wide range of modulus and elongation. Blends with copolymer content exceeding 50% reveal partial caprolactone crystallinity that increases with age. Lignin derivative not copolymerized with caprolactone, by contrast, produces macrophase-separated structures with exceedingly poor properties. Lignin caprolactone starlike copolymers are materials ideally suited as plasticizers for PVC. © 1994 John Wiley & Sons, Inc.     

Characteristic properties of organosolv lignin/polylactide copolymers

A polylactide (PLA)/switchgrass organosolv lignin graft copolymer was synthesized via ring-opening polymerization. The resulting copolymer was characterized by size exclusion chromatography (SEC), differential scanning calorimetry, tensile testing, and hydrogen nuclear magnetic resonance spectroscopy. Phenolic hydroxyl content, percent lignin retained, and ultraviolet (UV) light transmission were investigated by UV light spectroscopy. Hydrolytic degradation and water vapor transmission rates were also investigated.It was found that the addition of organosolv switchgrass lignin to the polymer slowed the rate of degradation and water vapor transmission rate of the copolymer compared to the PLA homopolymer at varying temperatures. UV light transmission was also reduced with the addition of lignin.     

高沸醇木质素辐射接枝苯乙烯

利用辐射接枝共聚操作简单易行的优点,研究高沸醇木质素在γ-射线辐射下与苯乙烯的辐射接枝反应,并用红外光谱对接枝产物进行表征。结果表明,γ-射线辐射下高沸醇木质素易与苯乙烯发生辐射接枝反应,其最佳接枝条件是:辐射剂量30 kGy,苯乙烯单体与木质素质量比为3∶10,所用木质素为芒秆高沸醇木质素。     

Some water-soluble copolymers from lignin

The utilization of lignin materials would be enhanced if lignin properties could be altered through chemical modification. Towards this end, lignosulfonate, recovered from spent pulping liquors, was grafted with acrylamide or acrylic acid, using redox initiation. Study was made of the effects of some reaction variables (such as reaction medium, lignin/monomer ratio, and initiator concentration) on the copolymerization efficiency and on the copolymer characteristics. Lignosulfonate having bivalent counterions yielded better copolymerization results than that having univalent cations. Aqueous solutions of graft copolymers displayed high viscosities, and exhibited promising stability during storage and against shearing, suggesting the potential use of copolymers as water-thickening agents.