【作者】 史晓峰；

【导师】 徐桂英；

【作者基本信息】 山东大学 ， 物理化学， 2008， 硕士

【摘要】 高分子表面活性剂是指分子由亲水基团和疏水基团两部分组成的、具有较高分子量(10~3～10~6)的物质。高分子表面活性剂既属于高分子的研究范畴,又属于胶体与界面化学的一大研究对象。利用高分子表面活性剂作模板模拟生物过程、合成纳米材料、发展药物运输及靶向识别等的研究正在蓬勃发展。PEO-PPO-PEO类高分子表面活性剂因其丰富的结构和聚集行为一直是人们研究的热点。本实验室已合成了多种类型的EO-PO类表面活性剂,并用实验方法和分子模拟等手段对其性质进行了研究。在这些工作的基础上,本论文利用界面扩张流变的方法研究了不同结构两亲嵌段共聚物气液界面的扩张粘弹性,并考察了各种因素的影响;利用光镊这种研究分散体系的新方法研究了不同结构两亲嵌段共聚物对聚苯乙烯分散体系的稳定作用;最后研究了支状Tetronic型嵌段共聚物的界面性质和聚集行为,并考察了几种支状聚醚与环糊精形成的超分子复合物。论文主要包括以下五部分内容:论文的第一部分概述了PEO-PPO-PEO嵌段共聚物的界面性质和聚集行为,并综述了各种添加剂如盐、醇、小分子表面活性剂对其聚集行为的影响。论文的第二部分采用界面扩张流变的方法,研究了在较低的频率范围内(0.005～0.1Hz)几种不同结构的Pluronic嵌段共聚物L64、F68、17R4、17R2的界面扩张粘弹性,同时考察了温度、NaCl以及小分子表面活性剂对其界面粘弹性的影响。对于上述的几种嵌段共聚物,扩张弹性对扩张模量的贡献较大,扩张模量的粘性部分都很小。EO含量的增加使嵌段共聚物的扩张模量都增加。对于组成相似但嵌段顺序不同的17R4、L64,无论是吸附膜还是伸展膜,前者的扩张模量远大于后者,且随体相浓度变化呈现不同的变化趋势。L64界面扩张粘弹性受温度影响较17R4更显著,NaCl的加入使17R4的扩张模量出现最大值。Pluronic共聚物的界面粘弹性与低分子表面活性剂如CTAB的粘弹性有显著的区别。当浓度小于各自cmc时,Pluronic共聚物的扩张模量值通常都远小于CTAB的扩张模量值。这是由两者不同的界面弛豫行为决定的。Pluronic共聚物与CTAB在界面的相互作用从界面粘弹性上得到很好反映。混合膜的扩张模量远小于两者模量值的简单加和,甚至低于纯CTAB的模量值。且随CTAB浓度变化,均出现最大值。当CTAB浓度高于cmc后,混合体系的扩张模量均与单独表面活性剂溶液的数值比较接近,说明界面上的聚合物逐渐被表面活性剂分子取代。论文的第三部分采用光镊、浊度和Zeta电位等方法考察了Pluronic嵌段共聚物L64、17R4、F127对聚苯乙烯分散体系的稳定作用。光镊是利用光与物质相互作用产生的力学效应,来俘获、移动和定位微小粒子的装置。近年来光镊成为研究分散体系的新手段。光镊研究结果表明在一定的浓度范围内,L64、17R4都能显著降低聚苯乙烯小球间的排斥能,PPO嵌段在两端的聚合物(如17R4)降低排斥能的效果较PEO嵌段在两端的更明显;而对于分子量和PEO嵌段都更大的F127,却能显著增加聚苯乙烯小球之间的排斥能,对分散体系产生稳定作用。从混合体系的浊度来看,聚苯乙烯/L64,17R4体系浊度降低的速度比纯聚苯乙烯的更快,这说明这两种共聚物的加入加速了分散体系的聚沉,17R4加速聚沉的效果更显著。而F127加入后混合体系聚沉速度变慢,F127对聚苯乙烯分散体系产生了稳定作用。聚苯乙烯小球的Zeta电位随共聚物浓度的增加而增加,这说明聚合物在聚苯乙烯小球上的吸附层厚度逐渐增加,利用精简的双电层模型,估算了聚合物的吸附层厚度。Pluronic嵌段共聚物能否对聚苯乙烯分散体系产生稳定作用取决于共聚物在聚苯乙烯上的吸附量、吸附层厚度以及吸附构象等因素。论文的第四部分研究了支状Tetronic聚醚的界面性质和聚集行为。对于组成相似的支状T1107和线型聚醚F127,后者降低水表面张力的能力和效率都更强;Tetronic聚醚的表面张力等温线也出现双拐点现象,温度升高能诱导其在水溶液中形成胶束,其胶束化过程为熵驱动。pH值对T1107的界面粘弹性有很大影响。随pH的降低,T1107上的二胺发生质子化,这导致其界面膜由于静电斥力而变的疏松,表面张力升高,界面膜的扩张模量和扩张弹性,粘性部分都降低;T1107水溶液的流变性与浓度和温度密切相关,支状结构的存在导致其凝胶化温度高于线形聚醚F127。不同浓度下T1107的零剪切粘度随温度表现出不同的变化趋势。小分子表面活性剂SDS与T1107能发生疏水相互作用,从而影响T1107的界面性质和聚集行为。当T1107的浓度低于其临界胶束浓度时,混合体系的表面张力随SDS浓度表现出先降低后增加再降低的趋势;混合体系的扩张模量随SDS浓度的增大出现一个最大值。论文的第五部分考察了支状Tetronic嵌段聚醚与环糊精形成的复合物。所考察的几种聚醚T90R4、AP432、SF321均能与β-环糊精形成超分子的内含复合物,复合物形成的时间与聚合物的PPO嵌段长度、分子量以及分子量分布有关。IR和XRD都证明了复合物的形成,且几种复合物中环糊精都形成隧道状结构。1HNMR表明在每条PPO链上,氧丙烯单元与环糊精的摩尔比大于2。TGA结果表明聚醚和环糊精复合后两者的热稳定性都提高,这是由两者之间发生相互作用,产生范德华力以及环糊精以隧道状排列后分子之间的氢键造成的。本论文的主要特点和创新点1、较为系统的研究了不同嵌段顺序、分子量的Pluronic嵌段共聚物气液界面的扩张粘弹性,并考察温度,无机盐以及小分子量表面活性剂的影响。不仅丰富了聚合物界面粘弹性的研究内容,也为认清Pluronic嵌段共聚物的界面动力学性质以及界面弛豫行为提供了较为全面的数据,对探讨此类物质在消泡、破乳应用中的机理研究有一定的理论意义。2、首次利用光镊研究了Pluronic嵌段共聚物对聚苯乙烯分散体系的稳定作用,得出了吸附聚合物前后,聚苯乙烯小球排斥能的大小变化趋势。并结合浊度和Zeta电位法得到了较为一致的结论。3、首次利用一类支状的嵌段聚醚与环糊精分子复合制备了基于环糊精的超分子准聚轮烷,并对其结构进行了表征,丰富了聚轮烷这一超分子物质的种类。更多还原

【Abstract】 Macromolecular surfactant consists of hydrophobic group and hydrophiphilic group, whose molecular weight is about 10~3～10~6g/mol.It belongs to the research objects of macromolecular chemistry and colloid chemistry.Macromolecular surfactant has been widely used in bioinspired morphosynthesis strategy,nonmaterial synthesis,and medicine delivery.Several kinds of amphiphilic polyether copolymers have been synthesized in our laboratory,and the properties such as aggregation behavior and interfacial properties have been investigated by experimental methods and molecular simulation,such as dissipative particle dynamics(DPD)and mesoscale dynamics (MesoDyn)simulation methods.On the base of these researches,we study the interfacial dilational viscoelastic properties of serval amphiphilic block copolymer, and the influence of temperature and salt.Further more,we study the steric interaction of polystyrene sphere with adsorbed PEO-PPO-PEO copolymer by optical tweezers. The stability of polystyrene dispersion with Pluronic copolymer is determined.Finaly, the interfacial properties and aggregation behavior of the Tetronic copolyether are studied.This thesis is divided into five parts.In the first section,the recent research advances of PEO-PPO-PPO aggregation behavior in water and the influence of additives are summarized.In the second section,the interfacial dilational viscoelastic properties of several Pluronic copolymer(L64,F68,17R4,17R2)at air/water interface are investigated by interfacial dilational rheology method at low frequency.The effects of temperature and NaCl on copolymer solution are also investigated.For the above copolymer,the dialtional elasticity dominates the most in its voscoelastic property,while the dilational viscosity contributes is very low.The dilational modul of the copolymer increases with increasing of EO content.For copolymer 17R4 and L64,with similar composing but different block sequence,17R4 has a bigger dilational modul than L64 for both of the adsorption and spread layer.They show different behavior with the increase of bulk concentration.L64 has a more marked influence with temperature than 17R4.The dilational modul of 17R4 passes through a maximum value with the increase of the NaCl concentration.The dilational property of Pluronic copolymer is different from the low molecular weight surfactant such as CTAB significantly,which is determined by the different relaxation process.The interaction between Pluronic copolymer and CTAB can be reflected from the interfacial viscoelastic property. Dilational modul of the mixed films go through a maximum with the increase of CTAB con.When the concentration of CTAB is beyond its cmc,the dilational modul approach to the value of pure CTAB solution,which means the polymer interface are substituted by CTAB fully.In the third section,the effect of different Pluronic copolymer on the stability of polystyrene dispersion is investigated by the method of optical tweezers,turbidity and Zeta potential.By the method of optical tweezers,we can get the steric repulsive interaction potential between two polystyrene spheres.The results indicate when the copolymers 17R4,L64 were adsorbed onto the surface of polystyrene spheres,the interaction potentials are reduced a little compared with the pure polystyrene system. 17R4 has a more notable effect on the reduction of potential function than L64.But for copolymer F127 with bigger molecular weight and more EO content,the interaction potential was increased markedly.In another word,F127 can stabilize the polystyrene dispersion while the other two can not.From the turbidity of the polystyrene/copolymer mixture,17R4 and L64 can accelerate the sedimentation rate of the polystyrene dispersion,while for mixture of polystyrene/F127 solution,the turbidity keep the constant for quite a few hours,which means stabilization effect occurred.From the change of Zeta potential of the polystyrene vs the copolymer concentration,we get the thickness of the adsorption layer by the double electric layer model.In the fourth section,the interfacial property and aggregation behavior of branched Tetronic polyether solution are studied.For T1107 and F127,the latter is more efficient in reduction of water surface tension.The surface tension isotherm of the Tetronic polyether water solution also show two inflexion.The rise of temperature can induce the formation of micelle.The pH value of Tl107 solution has a major effect on the interfacial viscoelastic property.The surface tension of T1107 water solution increase with the decreasing of pH,While the dilational moduls and elasticity decrease.The rheology of T1107 water solution is related with its concentration and temperature.The gelation temperature of the T1107 solution is lower than F127 because of its branched structure.T1107 can interact with SDS by hydrophobic interaction.In the fifth section,the inclusion complexes between several Tetronic polyethers and cyclodextrin are investigated.β-cyclodextrin can form supermolecular pseudopolyrotaxanes with branched polyether T90R4,AP432 and SF321.The formation rate depends on the length of the PPO block length,the molecular weight and molecular weight distribution of the polymer.IR and XRD research results all prove the formation of the inclusion complexes which adopted column structure.The results of the ~1HNMR indicate theβ-cyclodextrin cover on the PPO block.The ratio between the PPO block andβ-cyclodextrin is bigger than 2,which mean someβ-cyclodextrin slide off the polymer chain.TGA results show that the therm-stability of both polyether andβ-cyclodextrin are enhanced.They can interact with each other by Van de wall force and hydrogen bond between the borderβ-cyclodextrin molecules.The chief characteristics of this thesis are as follows:1.The interfacial dilational viscoelastic properties of Pluronic copolymer at air/water interface are studied systemically.The effect of temperature and salt concentration are also included.These studies not only enrich the research of the polymer interracial rheology,but also provide comprehensive data for the interracial dynamic property and relaxation process of the Pluronic copolymer.2.Optical tweezers are used to investigate the effect of the Pluronic copolymer on the stability of polystyrene dispersion.We can get the interact potential between two polystyrene spheres before and after the polymer was adsorbed.Combined with the turbutidy and Zeta potential,we get the consistent conclusions.3.A novel kind of supermoleculars pseudopolyrotaxanes between branched polyether andβ-cyclodextrin were prepared and characterized,which enrich the category of polyrotaxanes.更多还原