聚甲基丙烯酸甲酯单分子膜的静、动态弹性

通过测量分析两个不同分子量的聚甲基丙烯酸甲酯(PMMA)单分子膜的π-A等温线及其微分曲线,讨论了PMMA单分子膜成膜过程和分子量对膜相变状态的影响,并用动态膜障振动法测量了PMMA单分子膜的动态弹性.结果表明,分子链的相互作用(如扭曲和缠绕)在膜的形成中起着重要的作用,并影响膜的静、动态性质.单分子膜的静、动态弹性都有两相特性,且前者比后者小.随着分子量的增大,膜的凝聚性和稳定性都增强,静、动态弹性都增大.     

含Schiff碱基囊泡双分子膜的聚集结构与相变

研究表面活性剂分子在水溶液中的聚集行为对模拟生物膜功能和研究分子间相互作用具有重要意义"'．用于形成囊泡双分子层的表面活性剂主要是类似天然磷脂的双烷基链两亲分子,单烷基链两亲分子在引人刚性基团时亦可形成双分子膜k'．含SChiff碱基两亲分子在水溶液中的聚集性质及间、尾链长度对SChiff碱基构象的影响已有报道"'．本文报道了这类分子的另一种重要成膜性质,即改变制备条件,可选择性地得到不同聚集结构和相变温度的双分子膜·实验中所用成膜分子为：CH。（CH。）。;OPh-N-CH－PhO（CH;）n;N"（CH。）。Br－（m-4;n-…     

空气/水界面单分子膜的弹性

空气／水界面单分子膜的弹性是与膜应用有关的一个重要力学性质。本文对最近十几年来空气／水界面单分子膜的弹性的研究情况进行了综述,着重介绍X射线衍射法（XRD）、动态振动测量法、表面光散射法（SLS）、电生毛细波衍射法（ECWD）等空气／水界面单分子膜弹性的测量技术。     

液晶冠醚LB膜的制备及其性质研究

本文首次研究了五种新合成的液晶冠醚ＬＢ膜的成膜特性。实验发现，其中的单臂胆甾型液晶冠醚在气－液界面易形成稳定的单分子膜，但不易累积形成ＬＢ膜；芳香酯类的单臂液晶冠醚膜的稳定性与链的长短有关；而双臂芳香酯型二氮杂１８－冠－６易形成稳定的膜，且具有特殊的相变性质。膜的特性与物质的化学结构有关，借助ＣＰＫ分子模型，对成膜后分子构型进行了估算，理论计算与实验一致。对纯组分以及单臂液晶冠醚与硬脂酸的混合膜结构，用表面压－面积曲线以及小角Ｘ衍射等进行了表征，并对其中的双臂液晶冠醚作了离子识别功能研究。     

单氮杂冠醚的合成及性质研究（Ⅱ）：两亲分子的合成及在水…

以酰氯或酸酐与Ｎ－（３＇－氨苯基）氮杂冠醚反应合成了一系列含长脂链基团的单氮杂冠醚两亲分子，电镜观测结果表明：系列两亲分子在稀溶液中均能自组织稳定的以双分子膜为基本结构的囊光，其大小为３０－１５０ｎｍ，泡壁厚度为５－２５ｎｍ，并用ＵＶ－Ｖｉｓ和微量得差示扫描量热研究了双分子膜中分子的聚集态和相变过程。     

Langmuir膜分子动力学模拟中的头基效应

运用分子动力学方法研究了Ｌａｎｇｍｕｉｒ膜的结构和相变特性，比较了不同的头基模型对模拟的影响。发现在压膜过程中，膜分子的结构和排列存在相变，其中，分子脂肪链的倾角随着膜内每分子所占面积的增大而增大，分子链内无序的主要原因是脂肪链两端二面角的扭曲造成的。由不同模型模拟得出，带电模型的分子分布比较紊乱，倾角较小。这说明亚相环境和头基的不同，会影响模拟得的膜分子的排列，选择合理的头基模型非常重要。     

两亲聚合物表面的反相气相色谱分析

采用反相气相色谱探针技术研究了苯乙烯－氧乙烯－苯乙烯三嵌段两亲聚合物的表面物理化学性质。包括表面吸附热力学函数,表面能的色散分量以及表面分子链与探针的分子间相互作用,。探讨了共聚物中亲油性链段聚苯乙烯（PS）和亲水性链段聚氧乙烯（PEO）的组成比例与其表面性质的关系。结果表明共聚物表面组成中随PEO含量的增加,其表面能增大,表面分子链与探针分子的相互作用增强,表面吸附能力也增强。     

单分子膜的动态弹性

综述了单分子膜弹性研究的最新发现，详细介绍了单分子膜弹性的动态测定方法和硬脂酸、亚油酸等单分子膜弹性的研究结果，讨论了分子结构、亚相正离子、ｐＨ值以及聚合反应对单分子膜弹性的影响。     

聚醚类破乳剂的界面扩张流变性质

采用悬挂滴方法研究了不同结构聚醚类破乳剂与煤油间的界面张力及界面扩张流变性质. 结果表明, 4种聚醚类破乳剂均具有较强的降低界面张力能力, 且支链化程度越低分子在界面上排列越紧密, 直线型破乳剂在低浓度条件下界面张力最低. 破乳剂的分子尺寸较大, 慢弛豫过程控制界面膜性质, 吸附膜以弹性为主. 同时, 柔性聚氧乙烯链和聚氧丙烯链对界面膜性质的影响较大, 随着支链化程度增大, 界面分子间相互作用增强, 界面膜弹性增强, 黏性降低.     

化学力显微镜对ω-巯基正十一胺自组装单分子膜的力滴定研究

采用化学力显微术（ＣＦＭ）研究了一种长链氨基自组装单分子膜的力滴定性质,考察了表面基团性质不同的力探针对力滴定的影响,滴定了金包覆的Ｓｉ３Ｎ经－ＯＨ和－ＮＨ２基功能化的金样品之间的粘滞力,得到了作为淀粉 ＰＨ值函数的粘滞力曲线（力滴定曲线）,结果表明,－ＮＨ２和－ＯＨ基功能化的表面ｐＫ１／２分别为８．４和９．０。     

两亲性嵌段聚醚酯在空气-水界面上的Langmuir单分子膜

聚醚酯是一种新型弹性材料,目前已成为工业化产品[1].对这种嵌段聚醚酯的合成和弹性行为[2]、熔体的流变性能[3]、以及纤维在拉伸状态下的聚集态结构和分子运动[4]已有一些报道.     

花生酸与铈β-二酮络合物混合单分子膜的成膜特性

将铈β-二酮络合物(Ce(tmhd)4)的氯仿溶液与花生酸(AA)的氯仿溶液以不同摩尔比混合并铺展在纯水亚相上,得到其与AA的混合单分子膜.对混合单分子膜的成膜特性(π-A等温线和体系超额自由能)进行了探讨,发现混合单分子膜的超额自由能为负值,混合过程为热力学自发过程,且在配比为1∶ 2时其绝对值最大,体系最稳定,并进一步讨论了混合单分子膜可能的凝聚态结构.在配比为1∶ 2时,研究了混合单分子膜的静态弹性和动态弹性.     

Water-AOT-alkylbenzene microemulsions: influence of alkyl chain length on structure and percolation behavior

We study the percolation behavior of the water-in-oil (w/o) droplet phase of AOT (sodium bis[2-ethylhexyl] sulfosuccinate)-based microemulsions with different alkylbenzenes (toluene, ethylbenzene, butylbenzene or octylbenzene) as oil phase. We use microemulsions of varying composition with molar water to surfactant ratios 0≤W≤ 50 and droplet (water plus surfactant) volume fractions 10%≤φ≤50%. Using dielectric spectroscopy, a percolation transition is observed in w/o microemulsions with butylbenzene or octylbenzene. With increasing molecular weight of the alkylbenzene, the percolation temperature T(P) decreases. The structure of the microemulsions is determined by small angle X-ray scattering (SAXS). With increasing molar weight of the alkylbenzene, the stability range of the L(2) droplet phase extends to higher W. The larger amount of solubilizable water can be related to variable oil penetration of the AOT monolayer, which affects the spontaneous curvature of the surfactant shell.     

Unique evolution of spatial and dynamic heterogeneities on the glass transition behavior of PVPh/PEO blends

Glass transition behavior of hydrogen bonded polymer blends of poly(vinyl phenol)(PVPh) and poly(ethylene oxide)(PEO) is systematically investigated using normal differential scanning calorimetry(DSC) and recently developed multifrequency temperature-modulated DSC(TOPEM),in combination with Fourier transform infrared spectroscopy(FTIR) and nuclear magnetic resonance(NMR) techniques,focusing on the effect of the PEO molecular weight on the spatial and dynamic heterogeneity.It is found,for the first time,that both the glass transition temperature(T_g) and activity energy(E_a) of the blends strongly depend on PEO molecular weight,and a common turning point,which separates the rapid and slow increasing regions,can be found.The interchain hydrogen bonding interactions,both determined by FTIR measurements and obtained from the Kwei equation,decrease with increasing PEO molecular weight,indicating a decrease of the componential miscibility.A series of parameters related to the microscopic spatial and dynamic heterogeneity,such as the activity energy, fragility,nonexponential factor and the size of cooperatively rearranging regions,are calculated from frequency dependency complex heat capacity measured using TOPEM.It is found that each of these parameters monotonically changes with increasing the PEO molecular weight during the glass transition process,demonstrating that hydrogen bonding interaction is the key factor in controlling the spatial and dynamic heterogeneity,thus the glass transition.NMR relaxation results reveal the existence of obvious phase separation large than 5 nm,implying that the cooperatively rearranging regions should be closely related to the interphase region between the two components.The above obtained origin and evolution of spatial and dynamic heterogeneity provide a new insight into the glass transition behavior of polymer blends.     

The study of the interaction of a model alpha-helical peptide with lipid bilayers and monolayers

We studied the interaction of the alpha-helical peptide acetyl-Lys(2)-Leu(24)-Lys(2)-amide (L(24)) with tethered bilayer lipid membranes (tBLM) and lipid monolayers formed at an air-water interface. The interaction of L(24) with tBLM resulted in adsorption of the peptide to the surface of the bilayer, characterized by a binding constant K(c)=2.4+/-0.6 microM(-1). The peptide L(24) an induced decrease of the elasticity modulus of the tBLM in a direction perpendicular to the membrane surface, E(radial). The decrease of E(radial) with increasing peptide concentration can be connected with a disordering effect of the peptide to the tBLM structure. The pure peptide formed a stable monolayer at the air/water interface. The pressure-area isotherms were characterized by a transition of the peptide monolayer, which probably corresponds of the partial intercalation of the alpha-helixes at higher surface pressure. Interaction of the peptide molecules with lipid monolayers resulted in an increase of the mean molecular area of phospholipids both in the gel and liquid crystalline states. With increasing peptide concentration, the temperature of the phase transition of the monolayer shifted toward lower temperatures. The analysis showed that the peptide-lipid monolayer is not an ideally miscible system and that the peptide molecules form aggregates in the monolayer.     

Surface Dynamic Elasticity of Amphiphilic Block Copolymer Monolayers on a Water Surface

The methods of longitudinal and transverse surface waves and of oscillating barrier were used to measure a surface dynamic elasticity of the monolayers of poly(ethylene oxide) and polystyrene block copolymers spread on water within the frequency range of 0.007–520 Hz. At low surface concentrations, the properties of monolayers are determined by the poly(ethylene oxide) block. Upon further monolayer compression, the transition to the regime of polymer brush occurs when the surface dynamic elasticity increases dramatically. Change in the molecular weight of poly(ethylene oxide) block does not lead to the qualitative change in the dependence of surface properties on the degree of monolayer compression. Surface viscosity in the regime of brush significantly differs from the results of calculations made by Buzzaet al. [26]. Possible reasons for this difference are discussed.     

Rheological behavior of precursor PPV monolayers

The rheological behavior of different precursor poly(p-phenylene vinylene) (prec-PPV) monolayers at the air-water interface was investigated using an interfacial stress rheometer (ISR). This device nicely reveals a transition of the precursor poly(2,5-dimethoxy-1,4 phenylene vinylene) (prec-DMePPV) monolayer from Newtonian to elastic behavior with increasing surface pressure. The transition is accompanied by an increase in the modulus. This behavior coincides with the coagulation of different 2D condensed domains as revealed by Brewster angle microscopy (BAM). However, partly converted prec-DMePPV monolayers show elastic behavior even at low surface pressures, although a sudden increase of the moduli does occur. This phenomenon is attributed to enhanced hydrophobic interactions between the conjugated moieties in the partly converted polymers. The latter also explains the stretching behavior of the partly converted prec-DMePPV upon transfer in Langmuir-Blodgett-type vertical dipping. The increase of the moduli which is observed is much more gradual in the precursor poly(2,5-dibutoxy-1,4-phenylene vinylene), prec-DBuPPV, a monolayer which is in agreement with the expected expanded state of the latter monolayer.     

Phase transition of alkylsilane monolayers studied by temperature-dependent grazing incidence X-ray diffraction

The phase transition of organosilane monolayers on Si-wafer substrate surfaces prepared from octadecyltrichlorosilane (OTS) or docosyltrichlorosilane (DOTS) was investigated on the basis of grazing incidence X-ray diffraction (GIXD) at various temperatures. The OTS monolayer was prepared by a chemisorption method. The DOTS monolayer was prepared by a water-cast method (DOTS). The GIXD measurement clarified that the OTS monolayer also changed from hexagonal phase to amorphous state above a melting point of otadecyl groups. The GIXD measurements also clarified that the molecular aggregation state of the DOTS monolayer changes from an anisotropic phase to an isotropic phase with an increase in temperature. An estimated linear thermal expansion coefficient of the lattice lengths of a and b of the DOTS monolayer in the rectangular crystalline state assigned a similar value to those of bulk polyethylene with an orthorhombic crystalline lattice. The setting angle of the ab plane of the rectangular DOTS monolayer also showed similar behavior to that of the ab plane of bulk polyethylene.     

Study of pH-sensitive copolymer/phospholipid complexes using the langmuir balance technique: effect of anchoring sequence and copolymer molecular weight

The behavior of three copolymers of N-isopropylacrylamide (NIPAM), methacrylic acid (MAA), and hydrophobic moiety was studied at phospholipid monolayer/subphase interfaces. The hydrophobic moieties, N-terminal dioctadecylamine (DODA) and random octadecylacrylate (ODA), were used as anchoring groups. The interactions between a 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC) monolayer and the copolymers were studied using the Langmuir balance technique. The effect of subphase pH, distribution of anchors along the copolymer chain, and copolymer molecular weight on the nature of the interactions between the copolymer chains and the DSPC monolayer were investigated. A first-order kinetics model was used to analyze the copolymers adsorption at the DSPC monolayer/subphase interface and allowed the interaction area between the copolymer chains and the DSPC monolayer, A(x), to be determined. The interaction area appears to depend on the subphase pH and the copolymer molecular weight. On decreasing pH, the interaction area of high molecular weight copolymers increases significantly; this is consistent with the copolymer chain phase transition from an extended coil to a collapsed globule while pH is lowered. In the latter conformation, strong hydrophobic attractive interactions between the copolymer chains and the hydrophobic part of the DSPC monolayer favor the copolymer intercalation, which could eventually provoke the phospholipidic layer destabilization or rupture.