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151.
152.
Maurício P. Oliveira 《European Polymer Journal》2006,42(5):1196-1205
The effect of itaconic (IA) and fumaric (FA) acids, in the emulsion copolymerization of methyl methacrylate (MMA) with n-butyl acrylate (BA) is presented in this work. The effect of functional monomers on the overall conversion, on the colloidal properties of the latexes as well as on the distribution of the carboxylic groups (buried, particle surface and serum) was examined. The effect of the pH on the partitioning of IA and FA on the copolymerizations was also examined in order to better understand the role of these functional monomers. The carboxylic groups present in the cleaned latexes were analyzed using conductimetry and manual titration with a solution of sodium hydroxide in methanol. The results of these analyses showed that it was possible to determine the distribution profile of the carboxylic groups in the latexes (buried, particle surface and serum). It was demonstrated that IA and FA were distributed differently throughout the three phases of the emulsion, with these differences depending on the solubility of the corresponding monomer. 相似文献
153.
改性聚丙烯酸高级酯的合成及其降凝效果的考察 总被引:4,自引:2,他引:4
用酯化和热聚合同时进行的方法合成了聚丙烯酸高级醇酯(PAE),并对其进行改性,得到改性聚丙烯酸高级酯(MPAE),在实验室评价了MPAE对几种0#柴油的低温流动性能的改进效果。结果表明,该工艺路线产品的收率几乎达到100%,成本低。并且,改性后的聚丙烯酸高级酯在较宽的分子量范围内具有较好的降凝效果;相比之下,改性之前聚丙烯酯高级酯只在很窄的分子量范围内具有降凝效果。与其它柴油降凝剂相比,MPAE对柴油具有良好的感受性,一般能降低柴油冷滤点3℃-6℃,凝固点降幅在10℃-12℃左右,具备了工业化价值。 相似文献
154.
155.
The spectroluminescent and photochemical properties of Eu3+ complexes with copolymers of acrylic acid and alkyl methacrylates were studied. It was found that the photochemical behavior of the macromolecular complexes differs significantly from that of the lowmolecular analogs: in the course of photodecomposition the luminescence intensity of Eu3+ noticeably increases rather than diminishes. The efficiency of the luminescence build up of Eu3+ depends on the composition and the structure of the initial macromolecular complexes. A low concentration of the metal, low content of acrylic acid, and increase in the length of the alkyl radical of methacrylate favor the enhancement of the efficiency of luminescence build up of the rare-earth ion.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1559–1562, September, 1993. 相似文献
156.
Mayo-Pedrosa M. Alvarez-Lorenzo C. Concheiro A. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):681-693
The miscibility of poly(N-isopropylacrylamide) (PNIPA) with poly(vinyl pyrrolidone) (PVP) and a cross-linked poly(acrylic acid) (Carbopol® 971P) was evaluated from the rheological data of aqueous dispersions and the temperature of glass transitions of films made of binary mixtures. PNIPA has a low critical solubility temperature (LCST) of about 33°C, below which 1% dispersion behaves as a viscous system. At temperatures above LCST, the hydrophobic interactions among the isopropyl groups initially provide transient networks of greater elasticity. The LCST of PNIPA as well as its T g (144°C, estimated by DSC and MTDSC of films) were not modified by the presence of PVP. The immiscibility of PNIPA and PVP was confirmed by the absence of interaction between both polymers as shown by FTIR analysis of the films. In contrast, PNIPA and carbopol were miscible and the behaviour of their mixtures differed significantly from that of the parent polymers; i.e. a strong synergistic effect on the viscoelasticity of the dispersions was observed below the LCST. As temperature increased, the blends showed a decrease in the loss and storage moduli, especially those with greater PNIPA proportions. The fall was smoother as the PNIPA proportion decreased. This behaviour may be explained as the result of the balance between PNIPA/carbopol hydrogen bonding interactions (as shown in the shift of C=O stretch in FTIR spectra) and PNIPA/PNIPA hydrophobic interactions. The T g values of the films of the blends showed a positive deviation from the additivity rule; the mixtures containing more than 1:1 amide:carboxylic acid groups have a notably high Tg (up to 181°C). This increase is related to the stiffness induced in the films by the PNIPA/carbopol interactions. 相似文献
157.
End-stage renal diseases are affecting many patients and as a result, demand to receive dialysis service is growing annually. Morbidity and mortality rates are reported to be higher in comparison with healthy humans. The reason is reported to be the hemoincompatiblity of blood purification membranes, which hinders patients’ lives. Activation of different immune systems in the body, in case of blood-membrane interaction, results in several side effects, of which cardiovascular shocks have been mentioned to be a major one. Efforts to solve this issue have resulted in different generations of dialysis membranes. Zwitterionic immobilized membranes are the latest (third) generation, which owns a higher degree of hemocompatiblity with more stability of immobilized structures. This critical review intends to cover recent efforts conducted over the zwitterionization of polymeric membrane surfaces with the goal of improving hemocompatibility. Different aspects of third-generation membranes are discussed for a better understanding of the current gap and gathering the knowledge to further develop the field. Accordingly, this critical survey provides an in-depth understanding of blood purification membranes zwitterionization for paving the way for the optimum enhancement of hemodialysis membrane hemocompatibility. 相似文献
158.
The influence of the composition and structure of a macromolecular ligand on the efficiency of energy transfer in complexes of EuIII and TbIII with ligands based on acrylic acid has been studied. It has been found that a decrease in the size of an alkyl group of methacrylic esters and a low content of acrylic moieties of EuIII complexes with copolymers increase the efficiency of EuIII concentration quenching. Insertion of noncoordinative alkyl methacrylate into the polymeric chain results in an increase in the efficiency of energy transfer from Tb3+ to Eu3+.Translated fromIzvestiya Akademii Nauk. Seriya Klrimicheskaya, No. 6, pp. 1425–1428, June, 1996. 相似文献
159.
Some features of the electrocopolymerization of acrylic acid and acrylamide in aqueous ammonium persulfate have been studied. UV spectroscopic and polarographic data attest to the intermolecular interaction of acrylic acid with acrylamide with the formation of 31, 32, and 11 complexes; the former complex is the strongest. Electrochemical initiation of polymerization of monomers whose 1/2 differ by 0.3 V can result in a copoiymer. The composition of the cathode polymeric coating has been determined by IR-spectroscopy and elemental analysis data. The molar ratios of acrylic acid to acrylamide in this coating and in the complex of the monomers are identical. The role of these complexes as elementary units in copolymerization is noted.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 250–254, February, 1994. 相似文献
160.