【作者】 魏丹；

【导师】 钟理；

【作者基本信息】 华南理工大学 ， 化学工艺， 2012， 博士

【摘要】 胶体稳定性及失稳团聚是胶体科学的核心，其大量出现在自然界和许多工业过程中。研究胶体颗粒的稳定性、失稳团聚、团聚动力学及所形成团聚体的结构对胶体科学及其应用具有重要意义。本体系选用表面功能化聚合物胶体颗粒及牛血清白蛋白作为研究对象，采用各种光散射技术研究它们在静态条件下的稳定性及团聚行为，旨在定量研究聚合物表面各官能团对胶粒稳定性的贡献和对其团聚与融合行为的影响，丰富胶体科学的理论，为聚合物在实际生产和生活中的应用提供指导。一、采用动态光散射（DLS）和静态光散射（SLS）测试了含有不同种类、不同浓度表面官能团的六种聚合物胶粒在不同pH值、不同电解质类型和浓度下的Fuchs稳定性系数W，分别定量考察各官能团对聚合物胶粒稳定性的贡献。实验结果表明，当聚合物胶粒表面只含有固定电荷-SO₄时，胶粒稳定性最低；引入丙烯酸（AA）和丙烯酰胺（AM）均提高了胶粒的稳定性。引入AM时，如pH<3，引入2%的AM的胶粒稳定性比引入1%的低，这是由于AM在聚合物胶粒表面生成的-NH₂质子化生成正电荷，减少了胶粒表面净电荷的量。如pH>3，质子化作用消失，引入2%AM的胶粒的稳定性比引入1%AM的稳定性高；引入AA时，如pH<3，引入1%AA和引入2%AA的胶粒的稳定性基本相同，当pH5时，两聚合物胶粒稳定性皆大大提高且引入2%AA的胶粒稳定性远大于引入1%胶粒的稳定性，当pH8时，二者稳定性又基本相同，说明AA对胶粒的稳定性的贡献是有上限的。引入AA和AM的胶粒表现出pH响应稳定性。在六种聚合物胶粒中，同时引入1%AA和1%AM的胶粒的稳定性最高。二、引入1%AA在聚合物胶粒表面形成聚丙烯酸刷后，胶粒的稳定性随pH值的增加而显著增加，但是引入2%丙烯酸的胶粒，在达到pH8之后，聚丙烯酸电解质刷的离解对胶粒的稳定性的贡献存在上限，其稳定性与pH5时的稳定性几乎相同。本章引入一个描述胶体体系稳定性行为的通用型胶体稳定性模型来拟合它的Fuchs稳定性系数W和pH值，以证明pH响应稳定性以及分析引入2%AA在pH8时其对胶粒稳定性贡献出现上限的原因。拟合结果发现，氢离子（H⁺）与-COO的结合常数（7.6×10⁶）远远大于普通带单层电荷PAA中与H⁺的结合常数（6.3×10⁴），证明在低pH值下，PAA被质子化处于蜷缩状态而没有参与对胶粒稳定性的贡献；Na⁺与的结合常数在引入2%AA时为7.00，远大于引入1%AA时的值（2.30），证明长PAA刷子内部有更多的-COOH处于未电离状态，越靠近聚合物表面的位置，聚电解质刷内部羧基的电离程度越低，定量证明了LEA现象的存在。三、采用小角光散射（SALS）技术测试聚合过程中所形成的团聚体分形维数Df的大小。研究发现，扩散控制（DLCA）条件下，Df能够同时从团聚体平均结构因子（S（q））的幂指数区域和零角度散射强度对团聚体旋转半径函数曲线的斜率得到，所得到的Df的值为1.75，并且在典型的由硬颗粒于DLCA条件下所形成的团聚体的Df范围内（1.75¹.85）。在反应控制（RLCA）条件下，由于小团聚体和初级颗粒的影响，团聚体平均结构因子（S（q））的幂指数区域无法得到正确的Df值，然而从零角度散射强度对团聚体旋转半径曲线函数的斜率能够得到Df的值，其范围为2.20².70，而典型的硬颗粒在RLCA条件下的Df值的范围为2.00².20，融合颗粒的Df值得范围为2.20³.00（完全融合为3.00），证明这种体系在RLCA的条件下发生了部分融合。发现聚合物胶粒的融合与聚合机理有关。四、采用广角和小角光散射技术研究了变性牛血清白蛋白由CaCl₂诱导团聚和凝胶行为。研究发现在低和高的CaCl₂浓度下都生成透明的纤维丝状凝胶，而在中间浓度时却生成一种浊状凝胶。尽管在低和中CaCl₂浓度下分别生成透明纤维状和浊状凝胶与文献报道一致，在高CaCl₂浓度下又重新生成透明状凝胶却未见报道。在高的CaCl₂浓度下重新生成纤维状凝胶是由于高浓度的Ca2⁺反离子的结合产生表面偶极，这种偶极产生一种超短距离的水合力，而且主要产生在蛋白质表面的带电和极性区域（这样就会保护这些区域免于团聚），而疏水性区域的团聚仍然存在导致产生纤维丝状凝胶。五、合成了一种新型的具有高交联密度和优异涂膜性能的环氧树脂和丙烯酸酯同时改性的紫外光（UV）固化水性聚氨酯（UV-EP-AC-WPUD）。通过环氧基团与异氰酸酯基团（-N=C=O）封端的聚氨酯预聚体之间的反应引入质量百分含量为4%的环氧树脂E-20。同时，通过聚氨酯链的-N=C=O基与二元丙烯酸酯（PEDA）以及季戊四醇三丙烯酸酯（PETA）的羟基之间的反应引入碳碳双键（C=C），C=C的含量达到4.65meq/g。采用质量分数为3%的光引发剂Irgacure2959引发涂膜中C=C的聚合，涂膜的凝胶含量在12s UV辐射之后达到91%，意味着C=C的聚合和交联速度快，同时所得到的涂膜的交联度非常高，不溶于溶剂丙酮，测试表明环氧树脂和两种丙烯酸酯单体已经成功嵌入聚氨酯链中，涂膜具有优异的机械性能和化学性能。更多还原

【Abstract】 Colloid stability is the centerpiece of colloid science, and colloidal destabilization andaggregation phenomena are widely involved in many natural and industrial processes.Understanding the colloidal stability, aggregation, the aggregation kinetics and the structure ofthe resulting of aggregates has great importance not only for fundamental researches, but alsofor their applications. Industrial polymer colloids and bovine serum albumin （BSA） have beenchosen for the studies, all kinds of lighting scattering techniques have been used to monitorand characterize their stability and aggregation behavior, aiming to quantify the contributionof each functional group to colloidal particle stability and its influence on particle aggregationand coalescence behavior, rich the theories of colloid science, and provide supervision for theapplication of polymers in industry and daily life.Dynamic light scattering （DLS） and static light scattering （SLS） have been introduced tocharacterize Fuchs stability ratio W for six polymer latices of different type, differentconcentration functional groups, different electrolyte types and concentration at different pHvalues to quantify the contribution of each functional group to polymer stability. Results showthat the particle stabilized purely by sulfate groups （-SO₄） on the surface has the loweststability. The introduction of both acrylic acid （AA） and acrylamide （AM） increases particlestability. For the AM case, when pH<3, the colloidal stability is higher for1%AM than for2%AM due to the effect of NH₂protonation, leading to positive charges which partlyneutralize the negative charges and thus decreases the net charges, however, for pH>3, suchprotonation is negligible, and the stability is higher with2%AM. For the AA case, both atvery low （pH₃） and very high pH values （pH≈8）, the stability is rather similar between1%and2%AA, but in the intermediate pH （pH≈5）, it is higher with2%AA, indicating upperlimit of the AA contribution to particle stability. The stability of polymer latices modified byboth AA and AM is pH responsive. The best stable latex among all the six cases is the onewith both1%AA and1%AM.After introduction of AA, there generates polyelectrolyte brushes on the surface of thepolymer particles, and the stability increases with increasing pH, however, there exists upperlimit at pH8for the particle with2%AA and the stability is very close to pH5. A generalizedstability model has been introduced to make simulation of Fuchs stability ratio W and pHvalues to confirm pH responsive stability and LEA phenomenon. Results show that theassociation constant of H+with-COO is7.610⁶L/mol which is much higher than the value for monolayer macromolecule PAA, i.e.6.3104L/mol, which is reasonable and thereason is because of the protonation of PAA brushes, part of them is buried inside at low pH,does not take part in the association equilibria. Furthermore, the association constant of Na+with-COO is7.00for the case of2%AA, higher than the value （i.e.2.30） for the case of1%AA, confirming that the inner part of the brush protonated more than the outer part, i.e. morethan surface monolayers of macromolecular chains, on the other hand, it confirms the LEAphenomenon.The fractal dimension （Df） of the clusters formed during the aggregation of colloidalsystems reflects correctly the coalescence extent among the particles. In this work we proposeto use the fast small-angle light scattering （SALS） technique to determine the Dfvalue duringthe aggregation. It is found that in the diffusion-limited aggregation （DLCA） regime, the Dfvalue can be correctly determined from both the power-law regime of the average structurefactor of the clusters and the scaling of the zero angle intensity versus the average radius ofgyration. The obtained Dfvalue is around1.75which is between1.75and1.85typical ofDLCA regime for rigid particle. In the reaction-limited aggregation （RLCA） regime, due tocontamination of small clusters and primary particles, the power-law regime of the averagestructure factor cannot be properly defined for the Dfestimation. However, the scaling of thezero angle intensity versus the average radius of gyration is still well-defined, thus allowingone to estimate the Dfvalue, i.e., the coalescence extent. The value of Dfunder RLCAcondition is between2.20².70, which is different from the typical value for rigid particleaggregation. i.e. in the range between2.00and2.10, and the value of Dffor coalescencedaggregates is between2.10³.00（3.00for fully coalescence case）, which means partialcoalescence occurred for the current colloid system under RLCA regime. This is the first timeto find that coalescence is related to aggregation regime.We study, using wide-angle and small-angle light scattering techniques, stability andaggregation/gelation behaviors of denatured filamentous bovine serum albumin preaggregates（BSA-PAs）, induced by CaCl₂. It is observed that transparent filamentous gels can be formednot only at low CaCl₂concentrations but also at high CaCl₂concentrations, while the turbidgels are obtained at intermediate CaCl₂concentrations. Although the filamentous gels at lowCaCl₂concentrations and turbid gels at intermediate CaCl₂concentrations are consistent withthe literature observations, the filamentous gels at high CaCl₂concentrations have to beexplained by different mechanisms. The latter is attributed to the repulsive hydrationinteractions originating from increased surface dipoles generated by counterion binding. Since such surface dipole-induced hydration is very short-range and occurs mainly on charged orpolar patches of proteins （thus protected from aggregation）, aggregation of the filamentousBSA-PAs at hydrophobic patches at the two ends is still possible, leading to the formation offilamentous gels.In order to improve the mechanical and chemical properties, especially the solventresistance of the cast films formed from normal waterborne polyurethane （PU） dispersions, anovel ultraviolet （UV）-curable epoxy and acrylate-modified waterborne polyurethanedispersion （UV-EP-AC-WPUD） and its film with high crosslink density and excellent filmproperties were prepared and studied in this paper.4%epoxy resin E-20was introduced in PUchain by grafting reaction between epoxy resin and polyurethane prepolymer terminated withthe-N=C=O group. The C=C bond was introduced in PU chain by the chain-extendingreaction of-NCO in polyurethane prepolymer with two hydroxyl vinyl monomers PEDA andsingle-hydroxyl vinyl monomers PETA, and the obtained maximum C=C content was up to4.65meq/g.3%photoinitiator Irgacure2959was used to initiate the polymerization of C=Cbond in cast films, and the gel content of the UV-EP-AC-WPUD films could reach up to91%after12.0s UV-radiation, which meant the rate of the polymerization and the crosslinking rateof C＝C bond was high, and the obtained UV-EP-AC-WPUD film was highly-crosslinkedand insoluble in solvent. The water absorption, solvent resistance, gel content, pendulumhardness and tensile strength of the cured film were studied, and Fourier transform infraredspectroscopy （FTIR） analysis and film study results showed that the UV-cured EP-WPUDfilms including epoxy resins and hydroxyl-containing vinyl monomers had excellentmechanical and chemical properties; Thermo gravimetric analysis （TGA） also indicated thatthermal stability of the film was improved significantly.更多还原