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排序方式: 共有206条查询结果,搜索用时 31 毫秒
1.
P. Guenoun M. Delsanti D. Gazeau J.W. Mays D.C. Cook M. Tirrell M. Tirrell L. Auvray 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(1):77-86
Aqueous micellar solutions of ionic/neutral block copolymers have been studied by light scattering, small angle neutron scattering
and small angle X-ray scattering. We made use of a polymer comprised of a short hydrophobic block (polyethylene-propylene)
PEP and of a long polyelectrolytic block (polystyrene-sulfonate) PSSNa which has been shown previously to micellize in water.
The apparent polydispersity of these micelles is studied in detail, showing the existence of a few large aggregates coexisting
with the population of micelles. Solutions of micelles are found to order above some threshold in polymer concentration. The
order is liquid-like, as demonstrated by the evolution with concentration of the peak observed in the structure factor (), and the degree of order is found to be identical over a large range of concentrations (up to 20 wt%). Consistent values
of the aggregation number of the micelles are found by independent methods. The effect of salt addition on the order is found
to be weak.
Received: 19 June 1997 / Received in final form: 4 September 1997 / Accepted: 9 October 1997 相似文献
2.
An additive procedure (SIBFA) is developed for the rapid computation of conformational energy variations in very large molecules. The macromolecule is built out of constitutive molecular fragments and the intramolecular energy is computed as a sum of interaction energies between the fragments. The electrostatic and the polarization components are calculated using multicenter multipole expansions of theab initio SCF electron density of the fragments. The repulsion component is obtained as a sum of bond and lone pair interactions.Tests of the procedure on a series of model compounds containing ether oxygens and pyridine-like nitrogens are reported and compared with the results of correspondingab initio SCF calculations. The resulting methodology is compatible with the simultaneous computation of intermolecular interactions. 相似文献
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4.
马来酸酐封端聚碳酸亚丙酯的大分子偶联反应 总被引:6,自引:0,他引:6
自从 1 969年井上祥平[1] 发现二氧化碳 (CO2 )可以同环氧化合物直接共聚合成脂肪族聚碳酸酯(APC)以来 ,这一学科领域受到科学家的广泛关注[2~ 8] .这是因为CO2 所产生的温室效应 ,成为使全球变暖的主要因素[9,10 ] .已经确定CO2 使气侯变暖占诸多因素中的 66% .目前大气中CO2 的体积浓度为 345ppmv,由于人类的各类活动每年以 1ppmv的速度递增 .因此 ,降低CO2 排放量已成为全人类共同关注的热点之一 .另一方面 ,CO2 的固定化以及消耗、利用显然是一个应积极鼓励的研究课题 .目前人们已经将CO2 同环氧乙烷 (EO)、环氧丙烷 (PO)、环… 相似文献
5.
Polypropylene-block-poly(vinylpyrrolidone) copolymer was synthesized through the esterification of dicarboxyl-terminated polypropylene with monohydroxyl-terminated poly(vinylpyrrolidone) and used as a macromolecular surface modifier to improve the surface hydrophilicity of PP. The results of ATR-FTIR and contact angles measurements indicated that PP-b-PVP could diffuse preferably onto the surface by the inducement of high energy interface and lower the water contact angle of polypropylene. Lower loading and lower molecular weight of PP and PVP segment would result in higher surface selective enrichment. 相似文献
6.
A novel supramolecular graft copolymer(SGP) composed of viologen-containing copolymer(P(DMA-co-diEV)) as the main chain and Np ended PNIPAM(Np-PN1PAm) as the grafts is prepared(DMA:N,N- dimethylacryamide,diEV:ethylviologen dimer,Np:naphthalene,PNIPAM:poly(N-isopropylacrylamide)). The grafting is based on the triple complexation among a host of cucurbit[8]uril(CB[8])and two guests of diEV and Np,which is characterized by UV-vis spectra and ITC.Temperature sensitive property of PNIPAm moiety allows SGP to self-assemble into non-covalently connected micelle(NCCM) at high temperature. The micelles are sensitive to reducing agents,for example Na2S2O3,which breaks the current inclusion complex pair and induces aggregation. 相似文献
7.
通过带有PEG官能团的双丙烯酸酯大分子单体的RAFT环聚合反应合成含有十一元环重复结构的PEG大分子刷.不同PEG长度的连接1,2,3-三氮唑的双丙烯酸酯大分子单体通过点击化学反应合成.PEG侧链的较大位阻效应影响双丙烯酸酯大分子单体的聚合行为,以致于双丙烯酸酯大分子单体优先进行环化聚合反应而不发生交联反应.核磁数据和凝胶渗透色谱证明高效的环化聚合反应,而且没有副反应发生.PEG大分子刷在紫外光激发下有较强的荧光,而荧光则强烈依赖于聚合物刷的浓度,这归因于环聚合物在水中的聚集.PEG大分子刷的荧光能被DNA淬灭. 相似文献
8.
根据涂料行业发展对人才的需求,提出了高校讲授涂料课程的意义,介绍了涂料课程的特点,提出了高分子材料专业讲授涂料课程的内容,以及应采用的教学方法和学时安排。 相似文献
9.
10.
Higgins AM Sferrazza M Jones RA Jukes PC Sharp JS Dryden LE Webster J 《The European physical journal. E, Soft matter》2002,8(2):137-143
We investigate the dynamics of spinodal dewetting in liquid-liquid polymer systems. Dewetting of poly(methyl-methacrylate)
(PMMA) thin films on polystyrene (PS) “substrates” is followed in situ using neutron reflectivity. By following the development of roughness at the PS/PMMA interface and the PMMA surface we extract
characteristic growth times for the dewetting process. These characteristic growth times are measured as a function of the
molecular weight of the two polymers. By also carrying out experiments in the regime where the dynamics are independent of
the PS molecular weight, we are able to use dewetting to probe the scaling of the PMMA thin film viscosity with temperature
and molecular weight. We find that this scaling reflects bulk behaviour. However, absolute values are low compared to bulk
viscosities, which we suggest may be due in part to slippage at the polymer/polymer interface.
Received 25 June 2001 and Received in final form 5 December 2001 相似文献