丁香酚/改性聚乙烯醇抗菌复合膜的制备与性能

活性包装可通过释放功能性物质而提高食品的防腐保鲜性能，以延长食品的货架期。聚乙烯醇(PVA)由于其优异的综合性能在包装领域备受关注，但其强亲水性使其存在耐水性差、机械性能弱等问题。据此，本研究选用纤维素纳米纤维(CNF)复合PVA，进而通过柠檬酸(CA)交联，制备PVA-CC成膜基材；再将天然植物精油丁香酚(EUG)作为抗菌模板分子载入到PVA-CC聚合物网络中，制备了具有抗菌活性的复合膜PVA-CCE。通过对复合膜的结构和性能进行一系列的表征与测试发现，该复合膜具有良好的机械性能、耐水性、热稳定性和抗菌性。经过CA交联后的复合膜PVA-CCE在水中的溶胀率可从原来的495.74%降低至72.00%，耐水性得到了显著提升；并且与纯的PVA膜相比，该复合膜的熔融温度降低了11℃，分解温度提高了20℃，这说明经过CA共价交联后PVA的加工性能得到改善。同时，复合膜中存在游离的CA能够降低分子间的作用力而起到增塑作用，并可以与EUG协同抗菌增强复合膜的抗菌效果。这些实验结果表明，复合膜PVA-CCE在活性包装领域具有十分广泛的应用前景。     

钛酸酯络合物对聚乙烯醇的交联作用

合成了水溶性钛酸酯络合物,它能在常温下与聚乙烯醇(PVA)水溶液交联成凝胶体,凝胶时间可据需要控制在几分钟到几小时,凝胶体交联度随PVA水溶液的浓度和交联剂用量增大而增大,交联度越大,凝胶体的耐水性越好。     

18-C-6+mSA/mCS双极膜的制备及表征

18-冠醚-6(18-C-6)和聚乙烯醇(PVA)改性海藻酸钠(SA)制备了阳膜层(18-C-6+m SA),戊二醛(GA)和PVA改性壳聚糖(CS)制备了阴膜液(m CS),将阴膜液流延于上述阳膜层上,制备了18-C-6+m SA/m CS双极膜。红外谱图表明18-C-6与海藻酸钠已成功交联。分别从双极膜的氢离子渗透性能、溶胀度、I-V工作曲线、交流阻抗、热稳定性能等方面表征了双极膜的性能,实验结果表明,经18-C-6改性的双极膜具有较低的溶胀度,较低的工作电压和膜阻抗,较高的氢离子渗透性能和热稳定性,是一种性能优异的双极膜。     

用于直接甲醇燃料电池的侧链型磺化聚芳醚酮/聚乙烯醇交联膜的制备与性能研究

以高磺化度的侧链型磺化聚芳醚酮(S-SPAEK)和聚乙烯醇(PVA)为原料,通过溶液共混的方法在120℃下制备了PVA含量不同的S-SPAEK/PVA交联膜.红外光谱图表明S-SPAEK聚合物中的磺酸基团与PVA中的羟基反应生成酯键而形成共价交联.通过对交联膜的性能测试发现PVA的引入明显降低了膜的甲醇渗透系数,改善了膜的溶胀性,提高了膜的保水能力.S-SPAEK/PVA(85/15)交联膜水的脱附系数从S-SPAEK的3.1×10-8 cm2/s降低到2.9×10-9 cm2/s.在25℃和60℃时S-SPAEK/PVA(85/15)交联膜的甲醇渗透系数分别为2.6×10-7cm2/s和3.9×10-7cm2/s,明显低于相同温度下的纯S-SPAEK膜的8.1×10-7cm2/s与14.5×10-7cm2/s,而其质子传导率虽然有所下降,但是在25℃和80℃时分别达到了0.055 S/cm和0.083 S/cm,能够满足直接甲醇燃料电池(DMFCs)对质子交换膜的要求,有望在DMFCs中得到应用.     

基于静电纺丝技术的PET/PVA复合超滤膜制备条件的探索

采用多喷头静电纺丝技术制备了复合超滤膜,该复合超滤膜是以聚对苯二甲酸乙二酯(PET)无纺布为支撑层,PET/PVA复合纳米纤维膜为分离层,再用丙酮和水的混合溶剂处理得到致密分离层.采用扫描电镜法(SEM)、红外光谱法(FTIR)对复合膜表面进行表征,测试了复合超滤膜的抗水解性能.SEM结果表明,复合膜表面的PET纳米纤维的直径为960 nm,PVA纳米纤维的直径为320 nm,用不同比例的混合溶剂对复合超滤膜进行处理会产生不同的表面形貌,最佳的比例是w(丙酮)/w(水)=30/70.抗水解性能实验结果显示比较适宜的交联剂加入量为2 wt%,用该含量对复合膜进行交联,复合膜具有较好的抗水解性能,其中重量损失率为2.12%,溶胀度为3.62%.红外光谱分析表明,交联处理后,复合膜表面的—OH量大大减少,耐水性能提高,交联前后膜表面在—C O和C—O—C处的吸收峰有很大的区别.     

PVA/SiO2-TiO2杂化电纺纤维膜的形态与性能

以正硅酸乙酯(TEOS)、钛酸四丁酯(TBT)和聚乙烯醇(PVA)为原料, 用溶胶凝胶法制备了PVA/(SiO2-TiO2)杂化纺丝液, 将其电纺成纤维膜. 红外光谱结果证实, PVA的羟基与TEOS和TBT水解后的羟基发生了缩合反应, 杂化电纺纤维膜以网络结构形式相结合; X射线衍射分析表明, 杂化电纺纤维膜的结晶度比纯PVA电纺纤维膜小; 扫描电镜表明, 随杂化纤维膜中无机相含量的增加, 纤维的直径不断增加, 纤维出现一定的弯曲和扭曲, 并伴有少量带状结构的纤维; 紫外-可见光谱结果表明, TiO2的引入增加了纤维膜的抗紫外性; TGA热分析结果表明, 杂化纤维膜的耐热性能优于纯PVA电纺纤维膜的; 耐水性和稳定性测试表明, 杂化纤维膜的耐水性和稳定性优于纯PVA和PVA/SiO2电纺纤维膜的.     

聚乙烯醇多孔膜的制备及其对二氧化钛的负载研究

以聚乙烯醇(PVA)为聚合物基体,戊二醛为交联剂,乙酸为催化剂,聚乙二醇6000(PEG-6000)为致孔剂,制备了聚乙烯醇多孔膜(porous PVA films,PPF多孔膜);再将实验室自制的二氧化钛溶胶(TiO_2)负载于PPF多孔膜上,制备得到聚乙烯醇原位负载二氧化钛功能薄膜(PPF-TiO_2)。采用红外光谱、扫描电镜、分光光度计等分别考察了PPF多孔膜的交联条件、负载前后PPF-TiO_2功能薄膜的形貌,PPF-TiO_2功能薄膜对甲基橙的去除率。研究结果表明,为制备适宜交联度及孔径的PPF多孔膜,戊二醛浓度为5%(wt),PEG-6000用量为PVA用量的0.6倍为宜;PPF多孔膜对TiO_2负载的温度为40℃,负载时间为2h能够获得负载量为43%的PPF-TiO_2功能薄膜。此外,PPF-TiO_2功能薄膜比商品化TiO_2对甲基橙的降解率(100mg/L)更快,且具有可循环使用的优势。     

碳纳米管的加入对聚偏氟乙烯/丙烯酸酯共混物形状记忆性能的影响

利用聚偏氟乙烯(PVDF)微小结晶的物理交联点作用,制备了形状记忆性能优异的聚偏氟乙烯/丙烯酸酯聚合物(PVDF/ACM)共混材料。为提高其形状回复应力,又将碳纳米管(CNT)引入该共混体系中,系统研究了PVDF/ACM/CNT三元体系纳米复合材料的制备、结构及性能。结果表明,碳纳米管在PVDF/ACM体系中分散均匀;在基本保持其形状记忆性能的前提下,加入质量分数为4%的CNT,材料在25℃时的储能模量由2000 MPa提高至3130 MPa。     

尿素/乙醇胺复配增塑聚乙烯醇性能的研究

采用尿素/乙醇胺为复合增塑剂,利用流延法制备了增塑改性的PVA膜.通过FTIR法研究了尿素/乙醇胺复合体系与PVA的相互作用,采用XRD、DSC考察了增塑改性PVA膜的结晶性能和热性能.研究结果表明,乙醇胺作为尿素的良溶剂,能有效抑制尿素从PVA基体中析出.由尿素、乙醇胺组成的复合增塑剂能破坏PVA分子中的氢键作用、降低PVA的结晶度和熔点,对PVA的增塑作用显著.增塑改性后的PVA膜在水中的溶胀率(DS)下降,溶失率(S)增加.力学性能测试表明增塑改性后的PVA膜拉伸强度(TS)降低,断裂伸长率(E%)提高.含30phr尿素/乙醇胺的PVA膜的拉伸强度、断裂伸长率分别为23.89MPa和542.88%.     

PVDF亲水复合膜的制备及表征

聚偏氟乙烯(PVDF)膜材料存在强疏水性的缺陷,亲水化改性是解决该问题的主要途径。以PVDF为基膜材料、聚乙烯醇(PVA)为共混材料、N,N-二甲基乙酰胺(DMAc)为溶剂,采用相转化法制备PVDF/PVA复合膜。考察了复合膜的PVDF/PVA共混比、固含量、低分子化合物添加剂、聚合物添加剂等非溶剂添加剂对复合膜接触角的影响。结果表明,当PVDF/PVA共混比为7/3,固含量为13%时,制备的复合膜接触角为22.92°;当添加剂为无水氯化锂、纳米二氧化硅、聚乙烯吡咯烷酮(PVP)时,复合膜接触角分别从53.12°、30.51°和41.89°都降低到了0°,亲水性提高,其中纳米二氧化硅作为添加剂时复合膜亲水性最好;当添加剂为丙三醇、PMMA、PEG时,复合膜接触角都增大,亲水性变差。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.