羟丙基甲基纤维素醋酸酯与丙酸酯的合成

以羟丙基甲基纤维素(HPMC)为原料,醋酸酐、丙酸酐为酯化剂,在吡啶中进行酯化反应制备了羟丙基甲基纤维素醋酸酯和羟丙基甲基纤维素丙酸酯。通过改变体系的溶剂用量,得到了具有较好性状和取代度的产物,采用滴定法测定了取代度,并对产物进行表征和性能测试。结果表明,反应体系在110℃下反应1~2.5 h,反应后选用去离子水为沉淀剂,可得到取代度大于1(理论取代度为2)的粉末状产物,两种产物在乙酸乙酯、丙酮、丙酮/水等多种有机溶剂中溶解性较好。     

三甲基硅基甲基纤维素的合成及膜的富氧性能

引言 在分离膜研究与发展的历史上,天然高分子是最早使用和进行改性的膜材料.纤维素及其衍生物具有原料丰富易得、成本低、无污染、成膜性好等优点,至今仍作为常用的膜分离材料[1].由于纤维素中存在大量的羟基和强的分子间氢键,氧透过性能并不理想,因此很少将纤维素直接用作气体分离尤其是氧氮分离的膜材料.近来,有专利报道对纤维素进行改性修饰,在羟基上连上含硅的基团如三甲基硅基,可以获得好的富氧性能[2].但由于该反应属于非均相反应,这一制备方法的实施和验证有困难.本文选用能够溶于有机溶剂的甲基纤维素(MC)为原料,以六甲基二硅胺烷(HMDS)作为三甲基硅基化试剂,通过均相反应很容易地制备了具有较高的取代度和良好的有机溶剂溶解性能的三甲基硅基甲基纤维素(TMS-MC).经溶液浇铸成膜,对其富氧性能研究后发现,与甲基纤维素膜相比,该膜的透氧系数和氧氮分离系数分别得到显著改善.     

纤维素醚基础知识——（三）非离子型纤维素醚

甲基纤维素（methyl cellulose,MC)是纤维素醚类中带有起支配作用的甲基取代基的最简单的形式。它包括甲基纤维素本身及其混合醚羟乙基甲基纤维素（HEMC）,羟丙基甲基纤维素（HPMC）,羟丁基甲基纤维素（HBMC）,乙基甲基纤维素（EMC）和羧甲基甲基纤维素（CMMC）,混合醚类所具有的性质与MC类似。在100度下水中的热凝胶作用与水溶性MC相同,在有机溶剂中的溶解性与DS＞2．4的高取代度MC相同。     

国外甲基纤维素的应用

甲基纤维素为纤维素醚类中工业化生产较早的一个品种。 在甲基纤维素中,由于甲基取代度的不同而有不同的溶解性能、低取代度的甲基纤维素品种,使溶于烧碱水溶液中,中取代度的能溶于冷水中而不溶于热水,高取代度的能溶于有机溶剂中,其中低取代度的和高取代度的品种应用面较小,而以水溶性中取代度品种的用途为最广,该水溶性品种,美国以“Methocel”牌号、德国以“Tylose”和法国以“Rhomellose”等牌号生产和销售于国际市场,由于它可配     

羟丙基甲基纤维素（HPMC）发展状况和开发前景

一、概况 羟丙基甲基纤维素(HPMC)是纤维素醚工业中产量最低、物化性能最好、用途最广泛的纤维素醚类,属于非离子型高分子化合物。与离子型甲基羧甲基纤维素不同,它与重金属不起反应。根据其成品中甲氧基含量和羟丙基含量的比例不同,可得到在性能上有所差别的各个品种。 HPMC实际上是一种经环氧丙烷改性的甲基纤维素,故它具有与甲基纤维素相类似的冷水溶解和热水不溶的特性。HPMC在有机溶剂中的溶解性优于其水溶性,它能溶于甲醇和乙醇溶     

取代基及分子量对非离子型纤维素醚表面特性的影响

根据Washburn的浸渍理论(Penetration Theory)和van Oss-Good- Chaudhury的组合理论(Combining Theory)及应用柱状灯芯技术(Column Wicking Technique),对几种非离子型纤维素醚,如甲基纤维素、羟丙基纤维素和羟丙基甲基纤维素的表面特性进行了测试。由于这些纤维素醚的取代基、取代度和分子量不同,所以它们的表面能及其组成部分有着明显的差异。数据说明,非离子型纤维素醚Lewis碱大于Lewis酸,表面自由能的主要成分是Lifshitz-van der Waals力。羟丙基的表面能及其成分都大于羟甲基。而在相同取代基和取代度的前提下,羟丙基纤维素的表面自由能正比于分子量;而羟丙基甲基纤维素的表面自由能则正比于取代度,反比于分子量。实验还发现非离子型纤维素醚中的取代基羟丙基和羟丙基甲基的表面能似乎都大于纤维素的表面能,而实验证明所测试得出的纤维素的表面能及其成分的数据是与文献所吻合的。     

金刚烷甲酸纤维素酯的合成与表征

以N,N-二甲基乙酰胺/LiCl为溶剂,以对甲苯磺酰氯为共反应剂原位活化金刚烷甲酸,在均相反应体系中合成了新的纤维素高级脂肪酸酯——金刚烷甲酸纤维素酯。采用红外光谱、核磁共振谱进行了表征。热重分析表明,在纤维素链中引入金刚烷基可提高其热稳定性,取代度越高,热稳定性越好。金刚烷甲酸纤维素酯在有机溶剂中的溶解性随取代度增大而提高。     

三羟甲基丙烷单丙烯酸二己酸酯改性硅油

吉林大学的王秀玲等人将三羟甲基丙烷和苯甲醛在对甲苯磺酸催化下、在二氯甲烷溶剂中反应,得到白色苄基保护的三羟甲基丙烷固体;再与丙烯酰氯在三乙胺催化下、在二氯甲烷溶剂中反应,得到苄基保护的丙烯酸酯;在甲醇/盐酸体系中水解,得到三羟甲基丙烷单丙烯酸酯;然后与己酰氯在三乙胺催化下、在四氢呋喃溶剂中反应,制得三羟甲基丙烷单丙烯酸二己酸酯;最后,与含氢硅油（硅氢基质量分数0.09%,黏度700 mPa·s）在氯铂酸催化下、在甲苯溶剂中进行硅氢加成反应,得到淡黄色、透明的Si—C型长链烷基酯改性硅油——三羟甲基丙烷单丙烯酸二己酸酯改性硅油。     

卤代三甲基硅基苯的合成

以四氢呋喃（THF）为溶剂,由对二溴苯、3,5－二溴甲苯及间二氯苯制得芳基格氏试剂后,与三甲基氯硅烷（TMSCI）反应合成4－溴－三甲基硅基苯、5－甲基－3－溴－三甲基硅基苯和3－氯－三甲基硅基苯,产率分别为92％、85％和63％。     

阳离子化羟乙基纤维素醚的合成与溶液性质

以工业羟乙基纤维素(HEC)和N-(2,3-环氧丙基)三甲基氯化铵(GTA)为原料,在碱催化剂下干法制备不同取代度季铵盐型阳离子羟乙基纤维素醚。用均匀设计法优化合成条件,并通过蒙特卡罗模拟得到优化工艺条件,通过实验验证得到阳离子醚化试剂的反应效率达到85%以上,取代度达到0.49。同时探讨了阳离子羟乙基纤维素醚(QHEC)在不同介质中的黏性行为。结果表明,阳离子羟乙基纤维素醚在纯水中具有典型的聚电解质黏性行为,随着QHEC浓度减小,比浓黏度增大。同一QHEC质量浓度下,NaCl溶液中QHEC的比浓黏度总大于KCl溶液中QHEC的比浓黏度;随着外加盐NaCl溶液浓度的增大,其比浓黏度减小。     

Cellulose peroxides derived from carbonylated cellulose and hydrogen peroxide

Cellulose peroxides derived from hydrogen peroxide and cellulose derivative into which a ketone group is introduced by reaction with methyl vinyl ketone were investigated. The amount of peroxide formed on the cellulose substrate increased linearly with increasing carbonyl content of the sample, and sulfuric acid activated the formation of peroxide. The cellulose peroxide was gradually decomposed at 60°C in aqueous medium, and the decomposition was accelerated by addition of ferrous salt or irradiation with light of λ > 300nm. Grafting was initiated by adding methyl methacrylate to the thermal decomposition system under nitrogen. The formation, stability, thermal decomposition, and structure of the cellulose peroxide were discussed in comparison with one derived from aldehyde cellulose and hydrogen peroxide.     

Methyl ketone-photosensitized polymerization of N-methylolacrylamide with cotton

Photoinitiated, free-radical reactions of cotton cellulose with N-methylolacrylamide (NMA) from aqueous solution through direct excitation of cellulose are reported. Also reactions initiated by energy transfer from excited methyl ketone compounds to cellulose are reported. Dimethyl ketone, dimethyl ketoneformaldehyde, dimethyl diketone, dimethyl diketoneformaldehyde, methyl ethyl ketoneformaldehyde, and methyl phenyl ketoneformaldehyde were used in the sensitized reactions. When methyl ketone products were in solution during photoirradiation, they acted as sensitizers to increase the rate and extent of the reaction of NMA with cotton cellulose. When products that contained formaldehyde were covalently reacted with cotton before photoirradiation, the rate and extent of the reaction of NMA with cellulose were generally decreased. These effects can be at least partially explained by intramolecular energy transfer, as determined by chemiluminescence, electron spin resonance, and excitation fluorescence measurements. When methyl phenyl ketoneformaldehyde was covalently linked to cellulose before photoirradiation, energy localization that initiated free-radical polymerization of NMA was minimized. When cellulose that was padded with a monomer solution was dried before photoirradiation, the extent of the reaction of NMA with cellulose was decreased.     

羟丙基壳聚糖/氧化甲基纤维素自愈合水凝胶的制备及其载药性能

采用高碘酸钠对甲基纤维素（MC）进行氧化制备了氧化甲基纤维素（DAMC），通过羟丙基壳聚糖（HPC）的氨基与DAMC的醛基发生希夫碱反应制备了HPC/DAMC自愈合水凝胶。通过调节HPC和DAMC含量探究水凝胶的微观形态、溶胀性能、力学性能、自愈合性能、体外降解以及药物缓释性能。结果表明，HPC/DAMC自愈合水凝胶具有相互连通的孔隙，且孔径处于80～375μm范围内，在室温无刺激条件下能够在20 min内实现自愈合且具有良好的拉伸性能。此外，HPC/DAMC自愈合水凝胶具有良好的保水性，其溶胀比为14.0～17.4。在溶菌酶的作用下，HPC/DAMC自愈合水凝胶在60 h时质量损失率可达84.2%～99.6%。HPC/DAMC自愈合水凝胶对抗肿瘤药物吉西他滨具有缓释效果，缓释作用长达96 h，药物累积释放率达到83.2%～92.7%。     

ESR studies of the photodegradation of cellulose graft copolymers

Ultraviolet light induced free radicals in cellulose and cellulose graft copolymers were studied by means of ESR spectroscopy. At least six kinds of free radicals were formed in cellulose when the polymer was irradiated with ultraviolet light. Polystyrene and poly(methyl methacrylate) are more resistant to ultraviolet light than cellulose; however, the cellulose graft copolymers of polystyrene and poly(methyl methacrylate) were degraded by ultraviolet light. ESR studies revealed that photoinduced free radicals in cellulose graft copolymers were formed at the grafting branches of the copolymers rather than the cellulose backbone. The mechanisms of light stabilization and energy transfer reactions of cellulose and cellulose graft copolymers are discussed.     

Poly(methyl methacrylate)–cellulose nitrate copolymers. I. Preparation

Poly(methyl methacrylate)–cellulose nitrate copolymers were prepared in the form of rods and sheets by bulk polymerization using benzoyl peroxide as initiator. Suspension polymerization did not succeed in preparing poly(methyl methacrylate)–cellulose nitrate copolymers, especially when cellulose nitrate of 11.4% nitrogen content was used. The parameters such as cellulose nitrate concentration, nitrogen content of cellulose nitrate, the amount of initiator and the reaction time, and the temperature are discussed. The prepared copolymers were irradiated for specified periods of up to 11.83 Mrad. It was found that poly(methyl methacrylate)–cellulose nitrate copolymers did not dissolve in any conventional solvent, but they swelled. Swelling decreases with increasing cellulose nitrate concentrations, nitrogen content of cellulose nitrate, and irradiation dose, indicating the crosslinked structure of the prepared copolymers.     

Formation of peroxide on aldehyde cellulose and its ability to initiate graft copolymerization

Cellulose peroxide formed by the treatment of aldehyde cellulose with hydrogen peroxide (H₂O₂) was investigated with respect to formation and decomposition conditions and with respect to graft initiation. Periodic acid-oxidized cellulose was proved to produce the peroxide group on the substrate by subsequent treatment with H₂O₂, whereas no peroxide was produced with unoxidized cellulose. Since the peroxide content of oxidized cellulose increased with increasing carbonyl content of the sample, the peroxide was presumed to be introduced at the site of the aldehyde group of the sample. The peroxide groups formed were proved to revert to aldehyde groups by decomposition upon heating with water to nearly the same level as the original. The structure of the peroxide group was believed therefore to be an α-hydroxy hydroperoxide type. The cellulose peroxide was found to initiate graft copolymerization of methyl methacrylate very easily in thermal initiation and photoinitiation systems.     

Graft copolymers prepared by atom transfer radical polymerization (ATRP) from cellulose

A cellulose-based macro-initiator, cellulose 2-bromoisobutyrylate, for atom transfer radical polymerization (ATRP) was successfully synthesized by direct homogeneous acylation of cellulose in a room temperature ionic liquid, 1-allyl-3-methylimidazolium chloride, without using any catalysts and protecting group chemistry. ATRP of methyl methacrylate and styrene from the macro-initiator was then carried out. The synthesized cellulose graft copolymers were characterized by FTIR, ¹H NMR and ¹³C NMR spectroscopies. The grafted PMMA and PS chains were obtained by the hydrolysis of the cellulose backbone and analyzed by GPC. The results obtained from these analytical techniques confirm that the graft polymerization occurred from the cellulose backbone and the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity. Through static and dynamic laser light scattering and TEM measurements, it was found that the cellulose graft copolymer in solution could aggregate and self-assembly into sphere-like polymeric structure.     

Graft copolymerization of vinyl monomers on modified cottons XV. Initiation by decomposition of aryl diazonium groups

Cellulose bearing aromatic amino groups was prepared by reacting cellulose with 2,4-dichloro-6-(p-nitroaniline)-s-triazine in presence of alkali followed by subsequent reduction of the nitro groups to amino groups. The latter were diazotized and grafting was achieved without homopolymer contamination through decomposition of the cellulose diazonium salt under the effect of metal ions. The dependence of grafting on the nature of the monomers was governed by the pH of the polymerization medium, reaction temperature and concentration of emulsifier. Using a large liquor ratio decreased the graft yield. The cellulose macroradical formed via decomposition of the diazo group was found very effective in inducting methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, isopentyl methacrylate, acrylamide and 2-methyl-5-vinyl pyridine.     

The adsorption mechanism of poly-methyl methacrylate microparticles onto paper cellulose fiber surfaces without crosslinking agents

In this work, poly- (methyl methacrylate) microparticles were effectively adsorbed onto the paper cellulose fiber surfaces during impregnation without crosslinking agents. The adsorption behavior and mechanism of microparticles onto paper cellulose fibers were further examined by physical and chemical property characterization in combination with adsorption kinetic model. We reported that the kinetic adsorption process included three phases: rapid adsorption, saturated adsorption, and equilibrium adsorption. Intermolecular hydrogen bonds which increased gradually with the increase of the mass concentration of PMMA microparticles occurred between the carboxyl group of PMMA microparticles and the hydroxyl group of paper cellulose fibers. Due to the increase of the interaction, the crystallinity-index of the paper cellulose decreased. Furthermore, the hydrophobic interaction also occurred between PMMA microparticles and the paper fibers, leading to preferential adsorption of the microparticles on the surfaces of the hydrophobic (2 0 0) crystal cellulose.