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991.
种子乳液聚合物胶粒形态及胶膜结构研究 总被引:5,自引:0,他引:5
以醋酸乙烯酯和丙烯酸丁酯为单体,用乳液聚合方法,以极性小的PBA为种子进行了VA种子聚合,用透射电镜染色及皂液滴定方法对胶粒形态进行了表征,结果,上述聚合反应能形成PBA/PVA核壳结构的胶粒,而以PVA为种子对PBA进行聚合,则不能形成PVA/PBA核壳结构的胶粒,其胶粒亦具有类似PBA/PVA核壳结构或半包囊结构,将胶乳制成胶膜,其耐水性能测试表明成膜后胶粒基本保持了其分散阶段的形态。 相似文献
992.
Matthias Haufe Randolf D. Khn Roman Weimann Guido Seifert Dieter Zeigan 《Journal of organometallic chemistry》1996,520(1-2):121-129
Diethylzinc reacts with hydroperchlorates of N-alkylated 1,3,5-triazacyclohexanes (R3TAC; R = methyl (Me), benzyl (Bz), isopropyl (iPr)) and with the hydrotetrafluoroborate of 1,3,5-tris-(para-fluorobenzyl)-1,3,5-triazacyclohexane (FBz3TAC) to give the corresponding cationic zinc ethyl complexes [(R3TAC)Zn(Et)][X] (X = ClO4−, BF4−). Similar complexes were obtained from diethylzinc treated with [HNMe2Ph][BF4] or [HNMe2Ph][B(C6F5)4](Et2O) in the presence of R3TAC (R = Bz, FBz, s-1-phenylethyl (s-PhMeCH)). A product of decomposition of [(Bz3TAC)Zn(Et)][ClO4] was analyzed by X-ray diffraction. The structures of [({s-PhMeCH}3TAC)Zn(Et)][BF4] an [(FBz3TAC)Zn(Et)][BF4] were estimated using nuclear Overhauser enhancement spectroscopy. Protonolysis of diethylzinc with [HNMe2Ph][BF4] in the presence of 13-benzyl-1,5,9-triazatricyclo[7.3.1.05,13]-tridecane (BzTATC) yielded the complex [(BzTATC)Zn(Et)][BF4]. 相似文献
993.
Mira S. Bjelakovi? Natalija M. Krsti? Milan M. Dabovi? Martin Kessler Vladimir D. Pavlovi? 《Tetrahedron》2007,63(40):9960-9969
We report herein the synthesis of a novel modified steroid with two rigidly positioned amino acids in C- and N-protected forms (Gly-OtBu and N-Fmoc-l-Phe) at the angular positions (C-18 methylamino group and C-19 carboxylic function) of the steroid nucleus via amide bonds, starting from 18-cyanopregnenolone acetate over 10 steps. In an attempt to gain more insight into the structural and conformational features of this novel 18-Phe,19-Gly-containing steroidal compound, we describe the detailed 2D NMR spectral analysis. Despite the large size and the conformational flexibility of the amino acid units in this molecule, conformational analysis by NOESY connectivities showed the existence of mainly one conformation (∼95%) in CDCl3 solution with approximately parallel orientation of the phenylalanine and glycine moieties. 相似文献
994.
Marie E Chevalier Y Eydoux F Germanaud L Flores P 《Journal of colloid and interface science》2005,290(2):406-418
The crystallization of paraffins from their solution at low temperature was investigated in the presence of ethylene-vinyl acetate (EVA) copolymers that allow the control of the size of the crystals. Depending on the type of solvent and distribution of the paraffin lengths, the mechanisms of crystal formation and growth are different. Precipitation of the EVA prior to the paraffins leads to the nucleation of a large number of crystals, whereas the adsorption of EVA on the surface of the growing crystals slows down the crystal growth. EVA can act either as a nucleating agent or as a growth inhibitor. These two mechanisms were identified from the analysis of the temperature of crystallization (cloud point), the chemical composition of the crystals, and the observations of the crystal habit. The EVA was able to co-crystallize with the paraffins in crystals of an orthorhombic structure and the melting enthalpies of the crystalline paraffin did not depend significantly on their neighborhood. The energies of interaction between the different paraffinlike components are close to each other, so that minor changes of the experimental conditions may lead to dramatic effects. This is the basic rationale for the large behavioral diversity observed in these systems. 相似文献
995.
本文介绍了TDX-2大孔吸附树选择性地吸附白酒中的三种高级脂肪酸乙酯,而不吸附或极少吸附其他溶质,将酒用泵打入吸附塔,除浊在瞬间完成,流出的酒根据不同产品需要加水降度,理化指无大变化。经树脂处理后白酒质量明显地得到改善,起到催陈作用,缩短陈化才熟期,该工艺已在较大酒厂用于年产万吨粮食低度白酒生产。 相似文献
996.
K.Laxma Reddy 《Tetrahedron letters》2003,44(7):1453-1455
Aromatic and aliphatic nitriles react with tert-butyl acetate in the presence of a catalytic amount of sulfuric acid to give the corresponding N-tert-butyl amides in excellent yields. 相似文献
997.
Carole ChevrinJean Le Bras Françoise Hénin Jacques Muzart 《Tetrahedron letters》2003,44(44):8099-8102
The treatment of 1-acetoxy-1,3-diphenylpropene (1) by C-, O-, S- and N-nucleophiles in basic aqueous media produced the corresponding substitution products in the absence of a transition-metal catalyst. Mechanistic studies, using (S)-1 and p-MeC6H4CH(OAc)CHCHPh as substrates, led to propose a BAL1 cleavage of the ester function leading to a stabilized allylic carbocation as intermediate. 相似文献
998.
999.
Solvent effects on the manganese (III) initiated oxidative free radical reactions of 2-amino-1,4-naphthoquinones are described. This free radical reaction provides a novel method for the synthesis of benzo[f]indole-4,9-diones, benzo[f]indole-2,4,9-triones, benzo[b]carbazole-6,11-diones and benzo[b]acridine-6,11-diones. High chemoselectivity was observed in different solvents. 相似文献
1000.
As an efficient alcohol protecting group, picolinates (Pic), prepared from the corresponding alcohols using commercial picolinoyl chloride, are readily cleaved by Zn(OAc)2 or Cu(OAc)2, even in the presence of other common alcohol protecting groups. Moreover, the picolinyl group at C-2 position in carbohydrates can be selectively cleaved to give methyl 4,6-O-benzylidene-3-O-picolinyl-α-d-glucopyranoside and 3-O-picolinyl methyl-4,6-O-benzylidene-α-d-galactopyranoside in good yields. 相似文献