【作者】 窦文龄；

【导师】 徐桂英；

【作者基本信息】 山东大学 ， 物理化学， 2009， 硕士

【摘要】 聚醚类嵌段共聚物作为一类典型的高分子表面活性剂,其结构有着丰富的可设计性,如合成中可控制各链段的长度、EO/PO的比例以及嵌段共聚物的分子量等。PEO和PPO在水中的溶解度具有温度依赖性,加之溶液体系溶剂选择的多样性,极大地丰富了其在溶液中形成聚集体的形态。由PEO和PPO嵌段组成的高分子表面活性剂早已广泛用作乳化、润湿、增溶剂等。由这两种嵌段组成的线型三嵌段共聚物有两种类型:Pluronic型和Pluronic-R型,前者常表示为(PEO)_n(PPO)_m(PEO)_n,而后者为(PPO)_m(PEO)_n(PPO)_m,其中n和m分别表示氧乙烯(EO)和氧丙烯(PO)单元的数目。PPO嵌段在水溶液中表现出疏水性质,而PEO嵌段与水亲合,从而使整个分子呈现出两亲性。在水溶液体系,其浓度、结构参数(如嵌段共聚物的分子量和嵌段(EO/PO)比)、链构型(PEO-PPO-PEO或PPO-PEO-PPO)以及体系的温度,对其聚集行为和应用效果有着显著的影响。聚醚类高分子表面活性剂因其具有丰富的结构和聚集行为,故成为人们研究的热点。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,本论文通过表面张力、核磁共振、稳态荧光、透射电子显微镜和界面扩张流变等方法对本实验室合成的多枝状嵌段聚醚AE82和AE83的物理化学性质进行了研究,并考察了AE82和AE83的水溶液对碳纳米管(CNTs)的分散效果,在此基础上,研究了水性环氧树脂E570作为清漆涂料时,CNTs/聚醚分散体系对它的影响。论文主要包括以下四部分内容:论文的第一部分概述了嵌段聚醚高分子表面活性剂的聚集行为和应用,介绍了CNTs的结构、性质和应用,并综述了两亲分子对CNTs的分散稳定作用。论文的第二部分通过表面张力、稳态荧光、电镜和界面扩张流变等方法研究了本实验室合成的多枝状嵌段聚醚AE82和AE83的聚集行为,并对比研究了四个支链的嵌段聚醚T1107和T90R4的聚集行为。结果表明,AE82和AE83降低水的表面张力的效率和效能都远高于T1107和T90R4,且在空气/水界面上的饱和吸附量也都高于T1107和T90R4,而占据的分子最小截面积低于二者,说明AE82和AE83分子在空气/水界面上的排列要比T1107和T90R4分子紧密。稳态荧光光谱实验结果表明,微环境的疏水性大小顺序为AE82＞AE83,表面活性为AE82＞AE83,与表面张力法得出的结论都是一致的。TEM结果表明,随着浓度的增大,AE82分子倾向于形成一个大胶束,而AE83分子倾向于形成新的胶束。这主要是因为分子结构和分子量的差异。界面扩张流变的结果证明,扩张频率越大,AE82的扩张模量和弹性模量越高,而相角随频率的增加不断降低。论文的第三部分主要通过UV-vis-NIR吸收光谱、拉曼光谱和高分辨透射电镜等方法研究了多枝状嵌段聚醚AE82,AE83分散CNTs的能力,比较了它们对CNTs分散能力的差异。结果表明,多枝状嵌段聚醚AE82和AE83都具有分散CNTs的能力,而T1107和T90R4不能分散CNTs,这是由于T90R4的是PPO-PEO型聚醚,PO嵌段在外侧不利于分散CNTs,而T1107的PO含量过低,疏水性较差,不足以与CNTs的侧壁发生疏水相互作用。虽然多枝状嵌段聚醚AE82和AE83的分子结构很相似,但是AE82分散CNTs的效果优于AE83,这可能是因为AE82的表面活性、饱和吸附量和疏水性均较高,导致AE82更易于和CNTs的侧壁发生疏水作用,并且AE82的EO含量较高,也有利于阻止CNTs的聚集。从CNTs/AE82分散体系的UV-vis-NIR吸收光谱可得,被分散的CNTs的浓度随着AE82浓度的增加先增大后降低,对于CNTs/AE83分散体系,被分散的CNTs的浓度随着AE83浓度的增加先急剧升高,然后缓慢升高。根据AE82,AE83,T1107和T90R4对CNTs不同的分散效果进一步验证了前人提出的聚醚分散CNTs的机制:聚醚的疏水链PO基团通过疏水作用吸附在CNTs的侧壁上,而亲水链EO基团伸展于水溶液中阻止CNTs的聚集。论文的第四部分主要比较了纯水体系、多枝状嵌段聚醚水溶液体系和CNTs/聚醚分散体系对水性环氧树脂E570作为清漆涂料时的影响。固化时间都是随着固化温度的升高先迅速下降,当温度达到50℃时,固化时间基本不随温度的升高而变化。AE82和AE83的加入大大缩短了E570的固化时间,并且AE83比AE82的固化时间要短,但是加入AE82和AE83的水溶液与加入CNTs/聚醚分散体系的效果相当,说明在缩短E570的固化时间方面主要是AE82和AE83在起作用。CNTs/聚醚分散体系浓度的改变并没有对水溶液环氧树脂E570的固化时间有很大的影响。含有CNTs/聚醚分散体系的漆膜硬度要高于含有单纯的聚醚水溶液的漆膜硬度,也就是漆膜的硬度的提高主要是因为碳纳米管的存在。更多还原

【Abstract】 Polyether block copolymer as a typical macromolecular surfactant,is rich in its structure can be designed.Synthesis can be controlled,such as the length of each segment,the ratio of EO/PO and molecular weight of block copolymer,etc.The solubility of PEO and PPO in water with a temperature-dependent,in addition to the diversity of solvent system,greatly enriched in the solution of this type of block copolymer self-assembly in the formation of supramolecular aggregates of the study. PEO and PPO block polymer composed of surfactants have been widely used as emulsifying,wetting,solubilization and so on.There are two types of the linear triblock copolymers:Pluronic and Pluronic-R type,the former often is expressed as （PEO）_n（PPO）_m（PEO）_n,while the latter is（PPO）_m（PEO）_n（PPO）_m,in which n and m, respectively,ethylene oxide（EO） and propylene oxide（PO） number of units.PPO block is hydrophobic and PEO is hydrophilic.It may affect their aggregation in aqueous solution and application that the concentration of the aqueous system or temperature,structural parameters（such as block copolymer molecular weight and the ratio of EO/PO）,chain conformation（PEO-PPO-PEO or PPO-PEO-PPO）,etc..Polyether macromolecular surfactant has been an interesting research because of its various structure and aggregation behavior.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,the physical and chemical properties of branched polyethers（denoted as AE82 and AE83,which were synthesized via anionic polymerization in our lab） are studied by surface tension,steady-state fluorescence measurements and transmission electron microscopy（TEM）,etc.Moreover,the dispersion of carbon nanotubes（CNTs） by branched polyether in aqueous solution is investigated.On the basis,the impact of CNTs/polyether dispersion system is studied when waterborne epoxy resin（E570） is applied as varnish coating.This thesis includes four topics.In the first section,the aggregation behavior in solution and application of block copolymer are summarized.The properties and applications of carbon nanotubes are also presented.And the dispersion of carbon nanotubes by amphiphilic molecules is expatiated.In the second section,the aggregation behaviors of AE82 and AE83,in aqueous solutions were investigated by surface tension,steady-state fluorescence,TEM and the surface dilational viscoelasticity.For comparison,a commercially available block copolymer,Tetronic 1107（T1107） and Tetronic 90R4（T90R4）,were also studied.It is found that both the efficiency and the effectiveness of AE82 and AE83 to lower the surface tension of water are higher than those of T1107 and T90R4.The T_max values of them are higher and the A_min values of them are lower than that of T1107 and T90R4.From fluorescence measurement,it can be conclude that the order of micro-environment hydrophobicity（AE82＞AE83） and the order of ability to lower the surface tension of water（AE82＞AE83）.This is consistent to the conclusions of surface tension measurement.TEM observations reveal that,with increasing concentration,AE82 molecules tend to form a large micelle,while AE83 tend to form a new micelle.In the third section,the ability of dispersing carbon nanotubes（CNTs） in aqueous solutions by branched polyether（AE82 and AE83） was investigated by UV-vis-NIR, Raman spectra and HRTEM observations.For comparison,T1107 and T90R4 were also studied.From the experiments,it was found that AE82 and AE83 can get stable CNTs dispersions for three months while they were not the case for T1107 and T90R4. It is difficult to disperse CNTs by T90R4 because of PPO-PEO type.T1107 is PEO-PPO type,but its low PO%and poor hydrophobicity are not enough to have hydrophobic interaction with the sidewall of CNTs.Although AE82 and AE83 have similar molecular structure,the dispersion by AE82 is better than by AE83.Because AE82 has higher T_max value,stronger hydrophobic and better ability to lower the surface tension of water.It is easier to inteact with the sidewall of CNTs by absorption. Its higher EO%also can stop from the aggregation of CNTs.The absorbance of UV-vis-NIR absorption spectra of CNTs/AE82 system shows that with the increased concentration of AE82 aqueous solution,the concentration of dispersed CNTs increased,and then decrease.But to CNTs/AE83 system,with the increased concentration of AE83 aqueous solution,the concentration of dispersed CNTs increased sharply,and then rose up slowly.The mechanism of dispersing CNTs by different copolymers can be rationalized,that is,when mixed with CNTs,the PO groups would interact with the sidewall of CNTs while the EO groups extend into water and hence create steric repulsion.In the forth section,we compared with the different affection of water system, multi-branched polyether aqueous solution system and CNTs/polyether system when waterborne epoxy resin（E570） is applied as varnish coating.Multi-branched polyether（AE82 and AE83） can shorten the curing time of E570,and CNTs can improve the rigidity of E570 as varnish coating.Curing time is increased with the curing temperature to drop rapidly when the temperature reaches 50℃,the curing time has no change with temperature.更多还原