聚甲基丙烯酸甲酯/聚醋酸乙烯酯共混相分离过程的标度行为与逾渗结构

本文用激光光散射和光学显微镜方法研究了聚甲基丙烯酸甲脂/聚醋酸乙烯酯共混体系不稳相分离过程最大散射强度I_m(t,T)和相应波矢q_m(t,T)随时间变化规律及相区的逾渗结构。实验结果表明:I_m(t,T)和q_m(t,T)与时间t满足简单的标度关系I_m(t,T)～t~β,q_m(t,T)～t~(-a)。且标度关系β=3α成立,首次揭示了相态结构的分维特征,给出了计算相态结构分维数的简便方法,其分维数D值约为1.68±0.03,与逾渗模型给出的D值接近。     

高分子混合体系相分离过程相结构的自相似与分形

本工作用激光光散射和光学显微镜手段研究了聚甲基丙烯酸甲醋(PMMA)和聚醋酸乙烯酯[PVAc]共混体系相分离过程。结果表明系统的相态结构呈现较强的自相似,结构函数在大波矢处具有q~(-6)的渐近行为,相结构具有分形特征,其分形维数[Fractal Dimension]D约为1,64,初步认为结构函数的标度[Scaling]行为是由于相结构的分形特征所致。     

混合高聚物分相过程标度、分形与Monte Carlo模拟

基于光散射、Monte Carlo模拟标度理论和分形(Fractal)概念研究和分析了高分子混合体系不稳相分离过程结构函数的标度行为和成因, 结果表明相分离的形态是一种分形结构, 其分形维数不随时间变化. 结构函数的标度行为起源于相态的分形结构. 相态的分形结构是不稳相分离特征之一.     

聚甲基丙烯酸甲酯/(苯乙烯-丙烯腈)共聚物混合体系的早期分离

本文用激光光散射技术研究了高分子混合体系聚甲基丙烯酸甲酯/(苯乙烯-丙烯腈)共聚物(PMMA/PSAN)不稳相分离(Spinodal decomposition)过程,结果指出,相分离前期符合Cahn理论预言的结果;首次用光散射技术在高分子混合体系相分离研究中得到了不稳相分离增长速率最大值R(q_m);只(q)的实验结果与理论值相吻合;证实了界面自由能对相分离增长速率的影响是不可忽略的。     

聚电解质溶液中纳米粒子扩散系数的模耦合理论计算

采用模耦合理论(MCT)建立了研究纳米粒子在聚电解质溶液中长时扩散系数D的介观统计方法,提出了有效的聚合物溶液动态散射函数Γpp(k,t)的约化形式.定量计算了溶液微观密度涨落对扩散系数的贡献,考察了扩散系数D对溶液浓度c及纳米粒子半径R的依赖关系,并定量分析了MCT与经典StokesEinstein(S-E)关系的偏离.结果表明,MCT方法的研究结果与实验数据吻合.当纳米粒子尺寸小于聚电解质特征尺寸时,其扩散系数对S-E关系明显偏离.本文建立的基于微观描述的MCT方法为进一步研究纳米粒子在聚合物溶液中的含时扩散动力学行为奠定了理论基础.     

碳系导电填料混杂填充聚合物共混体系的导电逾渗模型

以排除体积理论为基础,提出了3种碳系导电填料混杂填充聚合物共混体系的导电逾渗模型,并利用三维图和二维图对导电逾渗模型进行了描述.选用炭黑、聚团状碳纳米管和阵列碳纳米管3种导电填料,以聚碳酸酯(PC)/苯乙烯-丙烯腈共聚物(SAN)(70∶30,质量比)和PC/聚苯醚(PPO)(70∶30,质量比)2个共混体系进行研究,通过不同导电填料在单一聚合物及其共混物中逾渗值的测量,对导电逾渗模型公式的各个参数进行计算和修正.导电逾渗模型预测结果与样品实际电阻率基本吻合,证明了模型的普适性和实用价值.对于基体相不变的系列聚合物共混体系,可以通过任意一种导电填料在共混体系中的逾渗值及在基体相聚合物中的逾渗值之比得到模型公式的相关参数,从而极大地方便了模型的推广和应用.     

聚己内酯-环糊精包合物对聚己内酯结晶行为的影响

采用溶液共混的方法制备了α-环糊精(α-CD)和聚己内酯(PCL)的包合物PCLIC,用X射线衍射和红外光谱对其结构进行了表征,并研究了α-CD、β-CD和PCLC对PCL结晶行为的影响,结果表明线性PCL穿入α-环糊精分子内腔形成了隧道状晶体结构,而且PCLIC对PCL具有明显的异相成核作用,其成核效率比α-CD和β-CD高.     

MWCNTs与疏水纳米SiO_2填充PMMA/PS共混物的导电与动态流变行为

以多壁碳纳米管(MWCNTs)为导电填料、疏水纳米二氧化硅(SiO2)为非导电填料,填充不相容聚甲基丙烯酸甲酯(PMMA)/聚苯乙烯(PS)(1/1,V/V)共混物,制备(PMMA/SiO2)/(PS/MWCNTs)四元导电高分子复合材料(CPC),研究其导电逾渗与动态流变行为,并与PMMA/(PS/MWCNTs)三元CPC进行对比.发现三元、四元CPC具有类似的导电逾渗行为,且逾渗阈值显著低于PS/MWCNTs二元CPC.在四元CPC中,SiO2粒子可细化相区尺寸,提高熔体模量,但不影响熔体热处理过程中的依时性动态导电逾渗行为.MWCNTs与SiO2均显著影响熔体热处理中的依时性模量逾渗行为,分别缩短、延长四元CPC相粗化起始时间,但均延长相粗化时间区间.     

超支化聚(β-环糊精)的合成与表征

通过硅氢加成反应, 以ABx型功能化β-环糊精大单体为原料, 采用一步法合成出新型超支化聚(β-环糊精)高分子. ABx大单体由单取代对甲苯磺酰化β-CD依次与烯丙基胺、1,1,3,3-四甲基二硅氧烷(含氢双封头)及丙烯酰氯反应得到. 采用1H NMR, 13C NMR, 29Si NMR和飞行时间质谱对ABx大单体及其聚合物的结构进行了表征. 利用凝胶渗透色谱/多角度激光光散射(SEC/MALLS)联用仪得到了超支化聚(β-环糊精)的分子量、分子量分布及本体黏度.     

聚甲基丙烯酸胆甾醇酯共聚物的合成、结构与性能研究 Ⅳ.PMACE的相态转变及光学性质

Finkelmann和等人对侧链胆甾型高分子液晶的研究表明,将具有液晶功能的低分子基团,经过一个软段连接到柔性高分子主链上的梳型高分子在一定的温度下可以形成液晶态,调节侧链高分子液晶的分子结构、软段长度,可以改变其相态转变温度及微区形态。前已报导具有不同侧链结构的聚甲基丙烯酸胆甾醇酯共聚物的合成、相态转变及光学性质,本文通过对聚甲基丙烯酸胆甾醇乙烯酯共聚物(PMACE)的液晶态及结晶态的微细结构及相态转变与胆甾侧链含量关系的研究,给出了液晶态的形成条件及结构特征。     

Application of Brewster angle microscopy and fractal analysis in investigations of compressibility of Langmuir monolayers

The aim of this study was to investigate the connection between the lipid/amphiphile monolayer structure at the interface and its macroscopic/rheological properties, in particular, to establish the link between the fractality of the monolayer structure and its compressibility modulus. To that purpose we have used fractal analysis of images obtained by Brewster angle microscopy to infer the fractal dimension of the monolayer structure and relate its change to the corresponding changes in compressibility derived from a simultaneously measured π-A isotherm. The results of the study confirmed the starting assumption based on theoretical considerations that the fractal dimension of an amphiphilic monolayer and its compressibility should be correlated. We have shown that there exists a strong correlation between the fractal dimension and the corresponding compressibility modulus of different amphiphilic materials. Thus, confirming the link between the short ordered structure on the molecular level and the macroscopic property-compressibility of the monolayer. The established correlation between the fractal dynamics and compressibility modulus of the monolayer enabled identification of onset of percolation-a second-order phase transition that is otherwise not easy and unambiguously detectable. We have found that the signature of percolation in a monolayer, regardless of its composition, is the occurrence of a sharp increase (a jump) of compressibility modulus (at macroscopic level) at the characteristic value of the corresponding fractal dimension D = 1.89. This is the result of the abrupt establishment of a connected structure on the molecular level, consequently involving a change in the elastic properties of the monolayer on a macroscopic scale. The results of this investigation provide means for unambiguous identification of the onset of percolation in the Langmuir layer and should facilitate a more efficient application of the percolation theory in further study of processes and structures at the interface during the monolayer compression.     

Spinodal decomposition of a polystyrene/poly(cyclohexyl acrylate-stat-butyl methacrylate) blend

Summary The dynamics of spinodal decomposition (SD) after a temperature jump from a kinetically formed single phase state into the unstable part of the two-phase region has been studied with a blend of polystyrene and poly(cyclohexyl acrylate-statbutyl methacrylate). The time evolution of the structure factor has been examined by small-angle neutron and light-scattering techniques. The combination of the different techniques gave access to a wide wave vector and time range covering a large range of length scales. The activation energy of the diffusion process during spinodal decomposition was determined by a scaling analysis of the later stages of SD, because early stages of SD could not be resolved.     

Morphological analysis of the effects of ions and ultraviolet light on colloidal monolayers at the air-water interface

The formation of fractal aggregates under the external influence of ions or ultraviolet light has been observed in colloidal monolayers trapped at the air-water interface. A morphological analysis of this is reported in this paper. These fractals have many characteristics similar to those observed in other experiments where electrolyte was added to the bulk. However, they exhibit behavior, such as restructuring, particular to the external influence. In most cases the aggregating system displayed scaling analogous to spinodal decomposition, but with the measured fractal dimension (which depends slightly on the external influence) entering in place of the usual spatial dimension.     

大孔交联聚苯乙烯分形结构的图像分析法研究

采用图像分析法测定大孔交联聚苯乙烯树脂的 现大孔交联聚苯乙烯的外表面具有分形结构,分形维数在２和３之间,将图像分析法测定的分形维数与小角Ｘ－射线散射法测得的结果对照。发现两种方法测定结果虽然不同,但在不同树脂之间的变化趋势是一致的,因此,可用图像分析法比较不同大孔树脂分形结构的差别。     

高分子共混相分离动力学

本文综述了相容高分子共混体系相分离动力学的研究进展.介绍了 Cahn 理论,标度律和分形(Fractal)概念,在研究相分离动力学中的应用。     

Polymer adsorption on a fractal substrate: numerical study

We study the adsorption of flexible polymer macromolecules on a percolation cluster, formed by a regular two-dimensional disordered lattice at critical concentration p(c) of attractive sites. The percolation cluster is characterized by a fractal dimension d(s) (p(c))=91/49. The conformational properties of polymer chains grafted to such a fractal substrate are studied by means of the pruned-enriched Rosenbluth method. We find estimates for the surface crossover exponent governing the scaling of the adsorption energy in the vicinity of transition point, φ(s)(p(c))=0.425±0.009, and for adsorption transition temperature, T(A)(p(c))=2.64±0.02. As expected, the adsorption is diminished when the fractal dimension of the substrate is smaller than that of a plain Euclidean surface. The universal size and shape characteristics of a typical spatial conformation which attains a polymer chain in the adsorbed state are analyzed as well.     

二次电子衬度曲线法研究PVC/MBS共混物断面的分形特征

利用二次电子衬度曲线法测定了聚氯乙烯甲基丙烯酸甲酯丁二烯苯乙烯共聚物(PVCMBS)共混物冲击断面的形貌特征及对应的分形维数值.结果表明,材料的断口或微观结构并不是严格的分形结构,这种自相似性仅存在于一定尺码范围内,不同断面形貌特征所对应的分形维数测量值不同,随着MBS用量增加,PVCMBS共混物缺口冲击强度随满足自相似原理的形貌特征所对应的分形维数值增大而增大.本文从理论上讨论了材料断裂韧性与分形维数的关系.     

大孔交联聚苯乙烯的分形结构研究

采用小角Ｘ－射线散法测定大孔交联聚苯乙烯树脂的结构,发现大多数大孔交联聚苯乙烯在数纳米至数十纳米的标度尺寸范围内具有分形结构,分形维数介于２和３之间。本研究还进一步探讨了交联度、致孔剂,功能基化反应及后处理对大孔交联聚苯乙烯分形结构的影响。