硫酸/丙醇法制备高取代度纤维素硫酸钠

以浓硫酸和正丙醇的混合溶液为磺化剂,制备高取代度纤维索硫酸钠（NaCS）。考察了反应液配比、反应时间、反应温度以及液固比对NaCS取代度和分子量的影响。随着反应时间的延长,反应温度的提高,浓硫酸在反应液中比例的增加,NaCS取代度呈现上升趋势,但增大到一定程度,由于副反应加剧以及纤维素的降解,NaCS分子量下降。结果表明,在硫酸与正丙醇的物质的量之比为2．1,反应液与纤维素的液固质量比为45和反应温度0℃条件下,反应时间16h,Nacs取代度可接近1。将反应条件调节在适当的范围内,反应时间控制在2～16h,可控制NaCS取代度在0．3～1．0,分子量在100-2000kD。     

高直链淀粉醋酸酯的合成与表征

以高直链玉米淀粉为原料 ,甲磺酸为催化剂 ,制备一系列不同取代度的淀粉醋酸酯 ,研究了不同反应时间、温度、催化剂用量等对取代度的影响。结果表明 :反应时间越长 ,取代度越大 ,特性粘度变小 ;随着反应温度的升高 ,取代度增大 ,但特性粘度却明显降低 ;随着酸与酸酐用量的提高 ,取代度逐渐提高 ,特性粘度下降 ;增加 MSA用量 ,可大大提高取代度。应用 FTIR、XRD、DSC等近代测试手段 ,对淀粉醋酸酯样品进行了结构表征。     

一种新型生物微胶囊制备方法

对多组分新型生物微胶囊———SA/NaCS CaCl2/PMCG微胶囊的制备进行了研究,考察了SA质量分数、NaCS质量分数、PMCG质量分数及成膜时间等主要因素对微胶囊性能的影响。实验结果表明SA和NaCS存在最佳质量分数,分别为1.5%和2.5%;随着PMCG质量分数增加及在PMCG中反应时间的延长,微胶囊膜越厚,机械强度则先增加后降低。最终得到膜层较薄、机械强度高、物化性质稳定的中空微胶囊,为其应用奠定了基础。     

氨基甲酰乙基淀粉的半干法制备

以水为反应介质 ,在氢氧化钠碱催化剂存在下 ,半干法制备了氨基甲酰乙基淀粉。考察了碱用量、反应温度、反应时间、丙烯酰胺浓度对反应效率和取代度的影响。当淀粉为 5 .7g、丙烯酰胺 2 .2g、水 2mL时 ,最佳反应条件为 :氢氧化钠 /葡萄糖剩基的摩尔比为 0 .32、反应温度 60℃、反应时间 2h ,此时取代度可达 0 .64 ,反应效率为 64 %。随着丙烯酰胺浓度的提高 ,取代度逐渐增加 ,反应效率逐渐下降     

不同取代度壳聚糖季铵盐的制备及其热稳定性研究

制备了不同取代度的壳聚糖季铵盐(羟丙基三甲基氯化铵壳聚糖),利用单因素实验分析了制备条件,采用热重分析探讨了壳聚糖季铵盐的热降解温度。结果表明,壳聚糖季铵盐的最佳制备条件为环氧丙基三甲基氯化铵(ETA)与壳聚糖的比为3,水与异丙醇的比为3,反应温度为80℃,反应体系的pH值为6.0。壳聚糖季铵盐与壳聚糖相比,热稳定性下降,随着壳聚糖季铵盐取代度的增加,初始降解温度(T0)、最大降解速率温度(Tp)和终止降解温度(Tf)均逐渐降低。同时,从初始降解温度到最大降解速率温度的时间也随着取代度的增加而减少。     

低分子量双胍基苯甲酰壳聚糖的制备及表征

在简单均相体系下,研究了壳聚糖及双胍基苯甲酰壳聚糖在双氧水中的降解特性。采用高效凝胶渗透色谱法测量了降解过程中壳聚糖及双胍基苯甲酰壳聚糖的分子量变化,讨论了该体系下双胍基苯甲酰低聚壳聚糖及双胍基苯甲酰壳聚糖的胍基化取代度的变化,通过红外光谱分析了低分子量双胍基苯甲酰壳聚糖结构。结果表明,在降解反应温度为65℃、H2O2质量百分浓度为3.0%、盐酸浓度为1.0%时,反应时间的延长会导致低聚壳聚糖或对双胍基苯甲酰壳聚糖低分子化产物相对分子量的逐渐降低,胍基化取代度也随之降低;红外光谱表明,采用该降解体系制备的降解产物主链结构基本没有发生变化。     

辛烯基琥珀酸淀粉酯的应用性能

研究了辛烯基琥珀酸淀粉酯（SSOS）的表观黏度、表面活性、辐射降解和酶降解特性,以及SSOS的乳化性能,结果表明：随着SSOS取代度的增大,糊液的表观黏度值增加,且糊液的配制方式对其黏度有较大影响,通过稀释方式制得的糊液表观黏度明显高于直接糊化法,而且取代度越高,这种差别越显著;随着SSOS取代度的增加,糊液的表面张力下降;SSOS的酶降解和辐射降解具有完全不同的规律,酶降解速率随取代度的增加而减慢,而辐射降解速率随取代度的增加而加快,且辐射剂量越大,高取代度SSOS所受的影响越大。通过正交实验发现SSOS在很宽的范围内具有良好的乳化稳定性,且这种稳定性受SSOS取代度、油水比、SSOS浓度的影响比较显著。     

NaCS/PDMDAAC聚电解质复合膜的制备及静态接触角测定

以纤维素硫酸钠(NaCS)为聚阴离子,聚二烯丙基二甲基氯化铵( PDMDAAC)为聚阳离子,利用两者的界面反应制备了NaCS/PDMDAAC聚电解质复合膜。测量了复合膜表面静态接触角用以表征膜润湿性变化,研究了聚电解质浓度、分子量、反应时间等对接触角的影响。结果表明,复合膜为亲水膜,静态接触角随NaCS浓度、PDMDAAC分子量增大而减小,随PDMDAAC浓度、反应时间增大而增大。     

氧化降解天然胶乳制备液体天然橡胶的研究

使用正交试验和单因素试验研究了氧化降解法制备液体天然橡胶时的工艺条件。结果表明,影响降解胶乳相对分子质量的因子主次顺序为反应时间、温度、丙醛用量和引发剂用量。最佳降解条件为引发剂,2份;丙醛,30份;反应条件80℃×24h,得到Mn为1.2×104。随引发剂用量的增加,降解胶乳相对分子质量先下降后上升;随丙醛用量的增加或温度的升高或反应时间的延长,降解胶乳相对分子质量都下降。     

聚合物体系渗流过程中分子量变化规律研究

聚合物驱油时,聚合物分子量是影响其驱油能力的重要因素之一。实验考察聚合物在岩芯渗流过程中分子量变化规律,实验结果显示,聚合物在岩心渗流过程中,污水体系的分子量降解率低;相同粘度条件下,低分子量高浓度聚合物体系降解率低;相同浓度的条件下,分子量越低降解率越小;相同分子量条件下,浓度越高降解率越低;随着推进距离的增加,降解率逐渐减小。     

Optimizing preparation of NaCS–chitosan complex to form a potential material for the colon‐specific drug delivery system

A novel polyelectrolyte complex (PEC) formed by sodium cellulose sulfate (NaCS) and chitosan was prepared as a candidate material for colon‐specific drug delivery system. It was found in experiments that the properties of two raw materials and the process parameters, such as the degree of substitution (DS) and concentration of NaCS, the viscosity and concentration of chitosan, were very important factors on the properties of the final product—NaCS–chitosan‐PEC. The preparation of NaCS–chitosan complex was optimized by using response surface methodology to evaluate the effects of these parameters on the degradation properties of NaCS–chitosan in the simulated colonic fluid (SCF). The DS of NaCS was in the range from 0.2 to 0.6, the concentration of NaCS from 2 to 4% (w/v), the viscosity of chitosan from 50 to 550 mPa s, and the concentration of chitosan from 0.5 to 1.5% (w/v). A mathematical model was developed to describe the effect of these parameters and their interactions on the degradation of NaCS–chitosan complex. The optimum operation conditions for preparing NaCS–chitosan complex were determined to DS of NaCS of 0.2, the concentration of NaCS of 4.0% (w/v), chitosan viscosity of 327 mPa s, and the concentration of chitosan 0.5% (w/v), respectively. Validation of experiments with 5 confirmatory runs indicated the high degree of prognostic ability of response surface methodology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Modeling of poly(L‐lactide) thermal degradation: Theoretical prediction of molecular weight and polydispersity index

A mathematical model to describe the molecular weight and polydispersity index (Q) in poly(L ‐lactide) (PLLA) thermal degradation has been developed. Based on the random chain scission mechanism, effects of temperature and time on the molecular weight and polydispersity index are included in this model. It incorporates the degradation and recombination reaction of PLLA thermal degradation, while taking into account the equal probability assumption. The developments of molecular weight and polydispersity index of PLLA polymer in the thermal degradation process were investigated at temperature ranging from 180–220°C, the experimental data show PLLA reaches its thermal degradation equilibrium in 2 h. The simulated results of this model are compared with the measured molecular weight and polydispersity index of the PLLA polymer. The changes of the molecular weight and polydispersity index in the PLLA thermal degradation can be predicted by this model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2557–2562, 2003     

小角激光光散射法测定纤维素硫酸钠的分子量

采用小角激光散射法测定了纤维素硫酸钠(NaCS)的分子量,考察了盐离子及其浓度对分子量测定的影响. 结果表明,取代度分别为0.28, 0.40, 0.73的3个样品的分子量分别为879.8, 593.5和226.9 kDa,盐离子浓度为0.05~0.075 mol/L时测定较准确,盐离子浓度为0~0.05 mol/L时光散射强度精密度较低,不利于分子量测定,粘度变化较大,表明此时NaCS分子处于膨胀伸展状态,不利于光散射法测定分子量.     

Effects of reaction conditions on poly(methyl methacrylate) polymerized by living radical polymerization with iniferter

Living radical polymerization of methyl methacrylate (MMA) through the use of benzyl diethyl dithiocarbamate (BDC) was studied. The aim was to investigate the role of the concentration, BDC‐to‐MMA mol ratio, and reaction time upon the molecular weight, polydispersity, and conversion of the product. It was found that the molecular weight and the conversion increase with increase of the concentration at the expense of low polydispersity. The reaction time also played a significant role, especially at a relatively long reaction time where molecular weight, polydispersity, and conversion increased with increasing reaction time. In terms of the mol ratio effect, it was found that there was a critical mol ratio for maximum conversion. The results indicate that the kinetics of polymerization of MMA through the use of a BDC inifeter is different from that in the presence of a conventional initiator. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 938–944, 2000     

Ultrasonic degradation of poly(methyl methacrylate

Ultrasonic degradation studies on a variety of molecular weights and molecular weight distributions of poly(methyl methacrylate) are reported. The extent of degradation was measured using gel permeation chromatography. Polydispersity decreased as a function of irradiation time for polymers with initial broad distributions. In contrast, polymers with an initial narrow distribution increased in polydispersity, passed through a maximum and then gradually decreased in polydispersity. Results appear to show no limiting degree of polymerization for poly(methyl methacrylate).     

纤维素硫酸钠的批量制备及其NaCS-PDMDAAC微胶囊固定化黄色短杆菌培养过程研究

在非均相反应制备纤维素硫酸钠方法的基础上,通过增加液固比,引入搅拌,使体系的温度分布和浓度分布都得到很大改进,由此可以保证产品质量的均一性。用正交试验进行了500 mL反应器制备条件的摸索,并将其逐步放大到1 L、5 L反应器中进行,确立了5 L规模的生产工艺条件。通过对不同规模下制得的硫酸纤维素钠产品在理化性质、制备微胶囊及在微囊化培养等方面对比较,表明研制过程有利于合成出高质量的硫酸纤维素钠,用于制备微胶囊。用NaCS-PDMDAAC(聚二甲基二烯丙基氯化铵—硫酸纤维素钠)微胶囊固定化黄色短杆菌,考察了葡萄糖浓度、摇床转速对黄色短杆菌生长和代谢谷氨酸的影响,确定了一个较优培养条件。胶囊平均生产能力达15.29 g /(Lh)(对微胶囊)。微胶囊固定化黄色短杆菌连续培养12批后,仍具有良好的代谢谷氨酸性能。     

阳离子纤维素在二合一洗衣液中的柔顺和去污性能研究

将阳离子改性纤维素应用于二合一洗衣液,考察阳离子改性纤维素的分子结构对二合一洗衣液配方的柔顺和去污性能的影响。结果表明,阳离子改性纤维素易于形成透明二合一洗衣液配方,并且具有提高织物柔顺性、蓬松度、同时保持良好吸水性的功效。阳离子取代度对柔顺和去污性能的影响不大;疏水取代度越低,柔顺性能越好,去污性能越差;分子量越高,柔顺性能越好,去污性能越差。     

Molecular weight distribution of the graft copolymer comprising mixtures of styrene and acrylamiae on cellulose acetate film by means of gel permeation chromatography

Styrene portion of the radiation-induced graft copolymer comprising styrene and acrylamide was separated by acid hydrolysis and the effects of various grafting parameters (e.g., reaction time, reaction temperature, solvents, monomer composition, etc.) on molecular weight distribution were evaluated by means of gel permeation chromatography. When a single monomer or mixture of two monomers are grafted, the molecular weights is found to increase, but polymer dispersity decreases with the increase of reaction time or reaction temperature except at a higher reaction time due to the continuous enlargment of the growing chain through increased swelling and molecular motion of the trapped radicals. At higher reaction time the degradation of the graft chains lead to lower molecular weight and higher polymer dispersity. Effects of solvents (e.g., methanol, ethanol, and t-butanol) on the molecular weight and molecular weight distribution were discussed on the basis of swelling property and chain transfer constants of the solvents. Styrene-type graft radical being long lived compared to acrylamide type, gave long-chain styrene graft with the increase of styrene content in the reaction mixture. A comparison of the effect of one-and two-component systems on a molecular weight distribution is also discussed.