聚甲基丙烯酸甲酯/聚丙烯酸乙酯互穿网络体系相逆转、相态结构与性能的研究

本文研究了聚甲基丙烯酸甲酯/聚丙烯酸乙酯互穿网络体系(PMMA/PEALIPN)相分离和组分配比对其相逆转、相态结构及动态力学性能的影响.同时,对LIPN与其相应的混合乳液体系的结构和阻尼特性进行比较.结果表明,LIPN体系由于存在网络的相互贯穿,与混合体系相比其相分离程度低,出现精细结构,密度较高.当丙烯酸乙酯(EA)含量低时,PEA呈细胞结构分散在PMMA连续相中,随EA量的增加,体系出现相逆转并在EA体积含量为48％至86％范围内呈两相连续,各种性能发生突变和具有高阻尼特性.实数模量的实验点服从用Halpin-Tsai-Nielsen模量上、下限方程和描述两相连续的对数混合律三个方程结合计算的理论曲线.     

多壁碳纳米管对环氧树脂/聚醚酰亚胺体系相分离的影响

通过溶液混合的方法制备了环氧树脂/聚醚酰亚胺(PEI)/多壁碳纳米管(MWCNTs)三元复合物,并使用扫描电镜(SEM)、原位红外分析(FTIR)、流变测试和非等温DSC等手段研究了MWCNTs的存在对体系相分离形貌和固化反应的影响.扫描电镜的结果显示,在固化后的样品中MWCNTs较均匀地分散在两相中.150℃下固化,不含MWCNTs和MWCNTs含量为0.75 pbw的体系相分离形貌呈海岛状结构,而进一步增大MWCNTs含量后相分离形貌呈双连续结构,且相区尺寸随MWCNTs含量的增加而减小.120℃下固化,不含MWCNTs和MWCNTs含量为0.75 pbw的体系相分离形貌呈双连续结构,而进一步增大MWCNTs含量后,体系相分离形貌呈相反转结构.FTIR和DSC的测试结果表明,MWCNTs表面的羟基对环氧树脂的固化反应起到催化作用,使得固化反应速度加快,反应活化能降低.而流变测试的结果表明,随着MWCNTs含量增加,一方面交叉跨越多个相区的碳纳米管使得体系黏度增大,对相分离起到了一定的抑制作用;另一方面使得体系凝胶化时间提前,导致体系相分离形貌被固定在相分离的较早阶段,起到有效调控相分离形貌的作用.     

钙离子诱导的海藻酸钠/黄原胶凝胶化临界行为研究

研究了海藻酸钠/黄原胶混合体系的相行为及其对海藻酸钠-钙离子凝胶化临界行为的影响.当海藻酸钠浓度为0.5 wt%时,随着黄原胶的添加,混合体系出现相容、相分离及液晶3种不同的相行为.与纯黄原胶溶液相比,海藻酸钠/黄原胶混合溶液在更低的黄原胶浓度下开始形成液晶,这是由于混合体系中相分离的发生导致了黄原胶有效浓度升高.利用葡萄糖酸内酯(GDL)在线酸化Ca-EDTA,释放钙离子,研究了不同钙离子引入量时(f=[Ca2+]/[COO-])混合体系的黏弹性.Winter-Chambon分析发现临界凝胶点(f gel)随黄原胶浓度的增加而降低.当相分离发生时,临界凝胶点急剧降低,当液晶结构形成后,临界凝胶点呈现上升趋势.通过对比Winter-Chambon方法和临界凝胶点模量松弛法所测得的松弛临界指数(nw和nr),发现黄原胶的添加使海藻酸钠临界凝胶失去结构自相似性.相分离的发生导致临界凝胶结构排列更加致密,而液晶的出现使临界凝胶结构排列相对疏松.     

溶剂对SEBS/PMMA共混物薄膜形态的影响

采用原子力显微镜研究了聚（苯乙烯嵌-乙烯／丁烯嵌-苯乙烯）（SEBS）和聚甲基丙烯酸甲酯（PMMA）共混物不同溶剂旋转涂膜的表面形态和相分离行为。结果表明,用共混物的氯仿溶液旋转涂膜,可见明显的共混物的宏观相分离和SEBS的微观相分离形态。改变选择性溶剂可使旋涂膜具有不同的均匀度和形态结构,其相区的尺寸和形状相差甚大,有海岛型、网状、双连续状结构。AFM显示用环己烷／丁酮混合溶剂旋转涂膜,共混物的相分离最为彻底;用选择性溶剂氯仿时次之,但有明显的相分离;对SEBS和PMMA均无选择性的单一溶剂或混合溶剂则无明显相分离。     

聚合物二元体系动态力学性能的估算

动态热机械分析是多相聚合物体系的一个重要研究手段.分析动态力学性能可以研究共混高聚物的相容性、复合材料的界面特性以及高分子运动机理等.本文综述了聚合物二元体系,即填充、纤维增强、共混体系动态力学性能的估算方法.在填充体系中,分别概述有无界面作用两种情况,当存在界面作用时,界面作用越强,模量越大,阻尼越小.对纤维增强体系,讨论了玻璃纤维有无取向的情况下模量和阻尼的估算.特别对于聚合物二元共混体系,分"海-岛"结构和双连续相两种情况,分别讨论了模量与阻尼的估算.     

聚甲基丙烯酸甲酯/聚(苯乙烯-马来酸酐)共混体系相分离的流变学行为

采用动态流变学方法, 对聚甲基丙烯酸甲酯(PMMA)/聚(苯乙烯-马来酸酐)(PSMA)共混体系的相行为进行了研究. 相分离温度由动态储能模量对温度曲线斜率的转折点确定. 结果表明， 表观相分离温度有很大的频率依赖性, 因此， 动态流变学方法应用于相分离温度测定时要外推到频率为零.     

水溶性高分子分子量对其与电荷稳定的胶体分散体系的混合体系相行为的影响

利用同步辐射小角X射线散射技术,对不同相对分子质量的水溶性高分子聚氧化乙烯(PEO)与电荷稳定的聚甲基丙烯酸甲酯(PMMA)乳胶的混合体系的相行为进行了研究。 PEO与PMMA乳胶混合体系的相行为与体系中乳胶粒子的体积分数和PEO的浓度相关。 在一定乳胶粒子体积分数下,在较低PEO浓度下,混合体系保持均匀分散性。 而当PEO浓度高于某一临界浓度时,混合体系将发生相分离,生成集团相或者形成面心立方(FCC)晶体结构。 PEO相对分子质量的大小也是影响混合体系相行为的重要因素。 当PEO的相对分子质量较高时,混合体系发生相分离所对应的临界PEO浓度较低。 除此,PEO相对分子质量对混合体系的结晶行为也有影响。 在低乳胶粒子体积分数下,较高相对分子质量的PEO容易使乳胶粒子结晶。 相反的,在较高乳胶粒子体积分数下,较低相对分子质量的PEO容易使乳胶粒子堆积形成结晶结构。     

SiO_2纳米粒子对PMMA/PS共混物共连续相结构退火粗化过程的影响

考察了亲水性纳米SiO2粒子的加入对聚甲基丙烯酸甲酯/聚苯乙烯(PMMA/PS)共混体系的共连续相结构在静态高温退火时形态稳定性的影响,发现静态高温退火条件下,填充体系共连续组成范围变窄幅度较小、特征结构尺寸的粗化速率减慢.流变测试表明纳米SiO2粒子加入之后PMMA/PS共混体系的黏弹性显著提高,从而能减缓破坏构成共连续相结构的纤维断裂或回缩等松弛过程的速率,有效地抑制PMMA/PS共混体系的共连续相结构粗化进程,提高相结构的稳定性.根据现有的两种粗化理论的定性分析表明,在高填充量的共混体系中,加入纳米SiO2粒子导致共混体系的黏弹性的显著改变是影响PMMA/PS共混体系在静态高温退火时共连续相结构粗化速率的主要因素,相对而言界面张力的变化对共连续相结构在静态高温退火时的粗化速率影响则应该较小.     

SiO_2粒子对PMMA/SAN共混体系相分离行为的影响

采用小角激光光散射(SALLS)并结合动态流变学方法,考察了气相法二氧化硅(SiO2)粒子的加入对聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物(PMMA/SAN)共混体系相行为的影响,得到了添加SiO2粒子前后的相图,发现SiO2粒子对基体相行为的影响与基体的组成有关.对PMMA/SAN(60/40)体系,加入SiO2粒子后相分离温度上升,但并未改变相分离机理,仍为亚稳单相分解过程(spinodal decomposition,SD);而对于PMMA/SAN(30/70)体系,加入SiO2粒子后却降低了体系的相分离温度.该现象可能是SiO2粒子和基体组分界面间组成与PMMA/SAN共混物基体组成的差异造成的.     

环氧化聚丁二烯-聚苯乙烯嵌段共聚物对聚苯醚/环氧体系反应诱导 相分离行为的影响

采用扫描电镜、光学显微镜和光散射仪研究了环氧化聚丁二烯-聚苯乙烯嵌段共聚物(EBS)对聚苯醚(PPO)/双酚A型环氧树脂(DGEBA)/4,4’-二(2,6-二甲基苯胺基)甲烷(DIM-DDM)体系反应诱导相分离行为的影响. 实验结果表明, EBS的加入对PPO/DGEBA/DIM-DDM体系反应诱导相分离的演化过程有阻滞作用. 随着EBS加入量的增加, 体系形成双连续相结构所需的PPO含量范围变宽, 而对于相同PPO含量、形成双连续相的体系则相结构尺寸减小.     

聚偏氟乙烯共混体系的压电性及其分子运动——聚偏氟乙烯-聚甲基丙烯酸甲酯共混体系

本文研究了PVDF-PMMA共混体系的压电性及其分子运动.其松弛转变过程与PVDF-P(VDF-HFE)及PVDF-P(VDF-TFE)共混体系相似,压电性低于PVDF-P(VDF-TFE)共混体系.当PMMA含量为3％时,其压电性与PVDF的接近,而其退极化温度却高于PVDF以及上述二个含氟共混体系的薄膜,随着PMMA的增加,其压电性也随之减弱,这是由于非晶相中偶极子浓度降低之故.     

聚酯胺改善聚甲基丙烯酸甲酯电纺纤维均匀性研究

研究比较线型聚酯胺和超支化聚酯胺作为添加剂用于静电纺丝时,对低浓度聚甲基丙烯酸甲酯溶液可纺性的改善效果及其机理.结果表明,只需加入1wt%的添加剂,无论是线型的还是超支化聚酯胺均能够提高低浓度聚甲基丙烯酸甲酯溶液的可纺性,得到无"串珠"结构的均匀纤维,其直径比不加添加剂而在高浓度纺丝时得到的均匀纤维细很多.通过溶液性能的测试,发现提高可纺性的原因均是由于溶液电导率的提高.超支化聚酯胺因其多枝的结构而含有较多的极性端基,致使本身电导率较高,因而对可纺性的改善效果好于线型聚酯胺.     

COPU／PMMA AB交联聚合物的性能

AB交联聚合物(ABCP)是由聚合物A链与化学组成不同的聚合物B链交联构成。它的网络结构不同于IPN。IPN是由两个独立的网络构成,而在ABCP中仅存在一个聚合物网络。目前人们对它远不及对IPN了解得多。 本文选用蓖麻油为原料,与甲基丙烯酸甲酯共聚,合成了一种ABCP。研究了它的力学性能,转变与松弛,相容性及形态结构与组成及交联密度的关系。     

聚氨酯环氧树脂乳液互穿聚合物网络结构与性能研究

分别以聚四氢呋喃(PTMG)和聚己二酸丁二酯(PBA)为聚氨酯(PU)软段,制备了高环氧树脂(EP)含量的PU/EP乳液互穿聚合物网络(LIPN).通过红外光谱,动态力学分析,原子力显微镜等研究了不同类型软段对LIPN结构与性能的影响.结果表明,LIPN结构已经形成,PU与EP间无化学键结合.以PBA为PU软段制备的LIPN中PU与EP相容性更好,分相程度相对低,互穿程度高,导致EP对PBA软段运动的限制作用较强,EP含量的变化对LIPN的玻璃化转变温度影响更大.研究样品的力学性能和溶剂溶胀性能发现,PBA为软段制备的LIPN均优于以PTMG为软段制备的LIPN,水溶胀率等有大幅减小,表现出明显的互穿协同效应.     

EFFECT OF DILUENTS ON CRYSTALLIZATION OF POLY(VINYLIDENE FLUORIDE) AND PHASE SEPARATED STRUCTURE IN A TERNARY SYSTEM via THERMALLY INDUCED PHASE SEPARATION

The phase diagram of a ternary system of PVDF,dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was determined in terms of a pseudo binary system with the same polymer concentration and different DBP content in diluent mixture.The experimental results showed that as the DBP content increased in diluent mixture,the phase separation changed from liquid-liquid phase separation to solid-liquid phase separation,and both the cloudy point for L-L phase separation and crystallization temperature shif...     

Influence of the nature of the porous confining network on the sorption, diffusion and mechanical properties of hydrogel IPNs

Two series of amphiphilic hydrogels of various compositions were prepared by sequentially interpenetrating two polymer networks, a poly(2-hydroxyethyl acrylate) (PHEA) network inside either a macroporous matrix of poly(methyl methacrylate) (PMMA) or a macroporous poly(ethyl acrylate) (PEA) network. In both cases poly(2-hydroxyethyl acrylate) (PHEA) served as network II, and the firstly formed porous network was a hydrophobic homonetwork, PMMA or PEA, that conferred mechanical strength to the hydrogel. In order to obtain hydrogels with high hydrophilic content, the first network was prepared in the presence of a solvent, thus yielding a macroporous network. The two families of IPNs thus obtained were: (net-PMMA)-ipn-(net-PHEA) and (net-PEA)-ipn-(net-PHEA), with a PHEA content ranging from 36% to 87% and from 64% to 94%, respectively. The novelty of the work consisted in comparing the effect of using as the first macroporous network a polymer which is glassy at room temperature (PMMA) and another of the same family (PEA) but which is in the rubber state at room temperature. Swelling studies showed that the specific equilibrium water content of PHEA falls from 1.6 for pure (unconfined) PHEA to values that range from 0.4 to 1, for the (net-PMMA)-ipn-(net-PHEA), whereas in the second IPNs family, the equilibrium water uptake of PHEA phase is, at least, the same as that of the pure PHEA (in some cases it is greater). This means that the expansion of the PHEA phase is not restricted by the confining hydrophobic component when this last is in the rubber state at room temperature. Whereas for the first IPNs the mechanical properties significantly increased (storage modulus at 37 °C from 0.25 to 2.5 GPa) compared with those of pure PHEA (25.12 MPa), little if any reinforcing effect was observed in the second type of IPNs. This is due to the fact that the glass transition of the PEA network takes place at a lower temperature than that of PHEA, so both components are in the rubbery state at room temperature. Both series behave differently also in dynamic water sorption experiments: the rigid PMMA network hinders the diffusion of water, yielding lower values of the apparent diffusion coefficients. By contrast, with the PEA polymer as network I this diffusion is similar to that of the pure PHEA homonetwork.     

Effect of molecular interactions on the miscibility and structure of polymer blends

The effect of polymer-polymer interactions on the miscibility and macroscopic properties of PVC/PMMA, PVC/PS and PMMA/PS blends were studied in the entire composition range. The miscibility of the components was characterized by the Flory-Huggins interaction parameter or by quantities related to it. Thermal analysis, light transmittance measurements, and scanning electron microscopy were carried out on the blends and their mechanical properties were characterized by tensile tests. Interactions were analyzed by infrared spectroscopy and contact angle measurements. All three polymer pairs form heterogeneous blends, but the strength of molecular interactions is different in them, the highest is in PVC/PMMA system resulting in partial miscibility of the components and beneficial mechanical properties. The structure of these blends depends strongly on composition. A phase inversion can be observed between 0.5 and 0.6 PMMA content accompanied with a significant change in structure and properties. The PVC/PS and the PMMA/PS pairs are immiscible, though the results indicate the partial solubility of the components. The analysis of the surface characteristics of the components and the comparison of quantities derived from them with miscibility as well as with the macroscopic properties of blends revealed that blend properties cannot be predicted in this way, since they are affected by several factors.     

热致液晶共聚酯酰胺／PET共混物的流变性能和原位增强特性

采用Ｉｎｓｔｒｏｎ３２１１型毛细管流变仪研究了ＰＥＡ／ＰＥＴ共混物的流变性能，据此探讨共混物熔体的可纺性，讨论了共混物配比与复合纤维力学性能的关系，并且偏光显微镜，扫描电镜研究纤维的结构。结果表明，共混物的表观粘度低于ＰＥＴ的粘度，当ＰＥＡ为１０％，共混物的表观粘度达到最小值；且ＰＥＡ含量低于１０％时，共混物的可纺性即，表现出良好的原位增强效果。     

Preferential solvation of poly(methyl methacrylate) and a bisphenol A diglycidyl ether by size-exclusion chromatography

The preferential adsorption coefficient, lambda, of poly(methyl methacrylate), PMMA, in solutions formed by an epoxy resin in tetrahydrofuran (THF), was studied by size-exclusion chromatography (SEC). Only PMMA of lowest molar mass was preferentially solvated by epoxy but at low concentrations of epoxy in the mixture. At higher epoxy content PMMA was preferentially solvated by THF. A simultaneous and competitive solvation between the specific interactions PMMA-epoxy and the self association of epoxy at high concentrations would be the responsible of this inversion point. The more compacted coil of PMMA of higher molecular weights in solution could explain the lack of interaction of these polymers with epoxy. The results also indicated that lambda decreased with the molar mass. This variation has been attributed to the influence of the coil segment density on preferential adsorption.