【作者】 刘玉山；

【导师】 苏致兴；

【作者基本信息】 兰州大学 ， 高分子化学与物理， 2008， 博士

【摘要】 论文详细叙述了一维纳米材料凹凸棒土(ATP)的发现、分布、产量以及在聚合物中作为填充材料的应用,作为一种天然的纳米材料,ATP具有强大的吸附能力、良好的耐酸碱性、流变性、填充性,并且具有较好的离子交换、热稳定、抗盐、抗凝胶、造浆和高温相变等功能,目前,在我国ATP的应用还处在较低的水平。论文从ATP作为一种理想的聚合物填料角度出发,主要研究了它的表面改性(有机化)及聚合物包裹,对其形态及分散性作了表征。为凹凸棒土/聚合物复合材料的开发应用提供了有益的数据。取得了如下的成果:一:ATP的提纯的与有机化改性:论文以我省的ATP为原料,利用水化法将其提纯。该方法的特点是:简便、高效、纯度好。将提纯的ATP分散在水中,加入十六烷基三甲基溴化铵(CTAB)作为改性剂,经超声波处理,即可完成其表面有机化改性。改性原理可以认为是阳离子季胺盐与ATP表面的粒子交换,也是不同电荷(ATP表面带负电荷)的静电吸附作用。论文探索了不同洗涤条件对org-ATP亲水性和亲油性的影响,并从表层结构给予了解释。二:核-壳结构的ATP@Polymer复合物颗粒的制备和表征:1.1.凹凸棒土/聚苯乙烯纳米复合材料的制备:Org-ATP用乙醇洗涤三遍,水洗一遍,可以得到外层的CTAB有机链分子除尽的单层结构的有机化凹凸棒土,干燥。将干燥的有机化ATP分散在苯乙烯(St)单体中,可以得到稳定性良好的悬浮液,在家用微波炉中加热引发本体聚合,制备得到了不同凹凸棒土含量的ATP/PS纳米复合材料。采用透射电镜表征,发现在PS中ATP呈现单根分散:热失重表征则显示ATP的加入使聚合物的热性能得到了明显的改善。1.2.ATP@PS核-壳结构复合物颗粒的制备在ATP有机化处理的改性液中直接进行的乳液聚合反应,采用的单体是苯乙烯,苯乙烯单体在超声波的振荡作用下扩散进入ATP棒晶表面的双层有机链结构中。当反应在超声波中加热时,所形成的单体包裹棒晶的结构比较稳定,聚合完成时,就可以得到核-壳结构的ATP@PS颗粒。经TEM分析,短的棒晶包裹比较好,得到的复合物颗粒形状类似枣子或者说类似橄榄;长的棒晶在其表面形成粗大的棒状包裹。当反应在电磁搅拌情况下进行时,单体包裹棒晶的结构则被破坏,聚合后,就会得到珠串结构的ATP@PS复合物颗粒,可以发现在棒晶的表面粘满了聚苯乙烯小球,小球对棒晶形成包裹。加入的苯乙烯越多,包裹在棒晶外面的小球越多。2.ATP@PMMA核-壳结构复合物颗粒的制备和表征:将双层org-ATP分散在水中,可以得到稳定性良好的悬浮液,向体系中加入甲基丙烯酸甲酯(MMA)单体,在超声波振荡作用下,单体扩散到棒晶表面的有机层中,对棒晶形成包裹,在超声波中加热聚合,可以得到核-壳结构的复合物颗粒。当体系中单体加入量比较少时,得到类似于变粗的棒晶核-壳结构的复合物颗粒。当单体加入量逐渐增多时,在体系中既存在PMMA对ATP的整体包裹,也存在PMMA白聚颗粒和未包裹的ATP棒晶共存的现象。3.ATP@DP双层聚合物结构的复合物颗粒的制备和表征:论文将多次离心分离得到粒径较小org-ATP,分散在水中,加入MMA,在超声波作用下,单体扩散进入棒晶表面有机层中,加入引发剂,在超声波中加热聚合1小时,得到ATP@PMMA复合物颗粒,此时的体系依旧有好的稳定性,再向其中加入第二单体St,超声振荡24小时,使St充分的扩散进入PMMA层中,再次引发聚合反应,可以得到外层为PS内层为PMMA的双层聚合物包裹的ATP@DP复合物颗粒。并对分散性和形态作了表征。4.核-壳结构的ATP@PANI导电聚合物颗粒的制备和表征:在ATP棒晶表面存在有负电中心,使得ATP对具有阳离子结构的物质有好的吸附性。苯胺(aniline)与盐酸通过氧化偶联聚合可以制备得到盐酸掺杂的聚苯胺(polyaniline,简写为PANI),有好的导电性。苯胺可以与盐酸反应得到具有季胺盐阳离子结构的苯胺盐酸盐,此季胺盐可以吸附在棒晶的表面,它既是ATP的表面改性剂又是合成PANI的反应物。当加入氧化剂进行氧化偶联反应,可以得到核-壳结构的ATP@PANI导电聚合物颗粒。对其进行透射电镜的观测,发现PANI包裹凹凸棒土棒晶形成枣子形状的核-壳结构的ATP@PANI;对其进行电导的表征,发现具有好的导电性,这是由于PANI包裹棒晶的表面形成一个连续的层。更多还原

【Abstract】 Attapulgite is a kind of rare natural clay minerals with fibrous structure.Owing to its properties,such as special crystal structure and superficial character,attapulgite possesses fine adsorptive,rheologic,catalytic and filling capabilities,which endow it with ion exchange,heat stabilization,salt resistance,coagulation,pulping and phase change（in high temperature）performance.Accordingly,attapulgite has high application value.Attapulgite was found in our country in early 80’s.Our states have made it good application in many fields,such as absorption,decoloration, deodorization,salt-resistant slurry and so on.However,the in-depth processing and more abroad use of attapulgit capability remain in investigative stage,which is the important investigative way presently.The attapulgite nanorods are very good filler of the polymer.We introduce the preparation of ATP/polymer nanocomposites and the preparation of core-shell structure composites particles in this paper.1.Purification and surface-modification of ATP:The ATP was provided by Gansu ATP Co.（Linze Gansu）.The ATP was purified as reported previously and dried in oven for the further experiments.The pure ATP was dispersed in water and cetyltrimethylammonium bromide（CTAB）was added into the mixture.The mixture was irradiated in ultrasonic bath for 8h.Then the residue settling at the bottom of the beaker was thrown away and the stable suspension was used for further experiments.After centrifugation,organo-ATP was got.The organo-ATP was washed by ethanol three times and water once.The CTAB chains of the outer shell were washed away and the organo-ATP can be dispersed into toluene with a good stability.The monolayer organo-ATP could be used for the preparation of the ATP/polymer nanocomposites.If the organo-ATP was not washed by any solvent, it has a double-layer CTAB shell on its surface and the outer of the organo-ATP is the CTAB’s hydrophilic chain tail.So,it can be dispersed into water with a good stability and it can be used for emulsion polymerization or soapless emulsion polymerization.2.Preparation of the ATP/PS nanocomposite and core-shell structure ATP@Polymer naocomposites particles:2.1.Preparation of ATP/PS nanocomposite: CTAB-attapulgite for the polymerization was isolated by centrifugal precipitation and washed by ethanol for twice and distilled water for once,dried in an oven and then ground.A series of different grams styrene with the corresponding amount of CTAB-attapulgite and initiator were added into tubes in N₂ atmosphere,and the mixture was irradiated in ultrasonic bath for 15min.Then the tubes were put into microwave oven.The polymerization was initiated by microwave and the mixture became viscous quickly.The tubes were then put into oven 5h for further polymerization.Destroy the glass of the tube and we got the ATP/PS nanocomposite. TEM photographs show attapulgite is randomly oriented network of packed fibers. Thermal analysis shows that the decomposition temperature of the PS chains was increased a little and the interface properties had been improved by the adding of CTAB-ATP.2.2.Preparation of the core-shell structure ATP@PS naocomposites particles:The emulsion polymerization was carried out in the suspension directly.The org-ATP suspension was added to the reaction flask together with St so that St can be absorbed onto the hydrophobic ATP surface.Small droplets of St containing ATP needle as the core were formed under shear and in the presence of the surfactant.These small droplets containing a few needles might aggregate.Because the length of the ATP needles was different:the short ATP needles having a low length/diameter ratio can form a spherical core-shell structure;however,the long ATP needles that have a big length/diameter ratio cannot form spheres.The St can be absorbed into the needles. The shapes of the composite particles are different with the amount of monomer in the system with ultrasonic irradiation or electromagnetism stirring.With ultrasonic irradiation,the ATP needles were found to be in good dispersion,ATP was found adsorbed on the ball-shaped PS.The PS encapsulated completely the ATP needles with the smaller amount of charged monomer to form core-shell structure particles. Using electromagnetic stirring,with the same polymerizing condition,it was found that the ATP needles are encapsulated by PS.The PS on the needles in the form of spherical balls and free PS balls were also found.The organic phase around the attapulgite needles is not stable and the assembly could be destructed under violent stirring.Then the monomer droplets adsorbed the released CTAB molecules and formed PS balls.Then the PS balls were adsorbed onto the surface of org-ATP to form bead-string structure particles.The more monomer was added,the more PS balls were formed,and bigger composite particles were obtained.2.3.Preparation of the core-shell structure ATP@PMMA naocomposites particles:There are negative charges at the surface of the ATP needles.The CTAB chains can bond onto the surface via static forces.In the proposed method,the CTAB was used in high excess,and it is possible that the organic CTAB molecules formed a doublelayered structure at the ATP surfaces.And there were also some free CTAB molecules in the dispersion.The organo-ATP with double-layered CTAB molecules has polar groups（carboxyl groups）in the outer layer,so it could be dispersed well in water.It is expected to be used as seeds in the soapless emulsion polymerization.So the superfluous CTAB molecules in the organo-ATP dispersion were removed by washing with water.In the cases of encapsulation of ATP needles by the soapless polymerization,the general purpose of the pretreatment with CTAB is to introduce the organic chains onto the ATP needle surfaces so that they have more affinity for the monomers,facilitating encapsulation.So the MMA monomer was adsorbed onto the hydrophobic layer to form the oil phase in the latex.After the soapless emulsion polymerization of MMA in the organo-ATP suspension,the ATP nanoneedls were encapsulated by the PMMA.It is inclined to form a string-bead structure and only the ATP fibrillar single crystal with a small length/diameter ratio could lead to the core-shell structure.The superfluous monomer formed micelles by capturing the outer CTAB molecules of the organo-ATP with double-layered structures when more monomer was added.So some organo-ATP with monolayered structures were formed and aggregated together because of the hydrophobic surface.Therefore,some free PMMA particles and bare ATP needles coexisted with the ATP/PMMA particles after the soapless emulsion polymerization.2.4.Preparation of the core-shell structure ATP@DP naocomposites particles:Hundred milliliter of org-ATP suspension was centrifugated at 3000 rpm for 2 min at first.The sediment at the bottom was thrown away.And the org-ATP was separated by centrifugation at 13,000 rpm for 15 min from the stable suspension.After the wet org-ATP was dispersed into water with ultrasonic agitation,MMA was added into the flask as first monomer.The mixture was irradiated in ultrasonic was then subjected to electromagnetic stirring in flask at 70℃for 1h and the prepared ATP@ PMMA composite particles were used as a seed for the second stage of the seeded emulsion polymerization.St was added to the flask.Then the solution was maintained at room temperature for 24h under ultrasonic agitation,allowing the monomers to swell the seeds.After the emulsion polymerization again,ATP@DP composite particles were got.2.5.Preparation of the core-Shell ATP@PANI Composite ParticlesThere are negative centers on the ATP needles’ surface.The aniline reacted with HCl and formed the anilinium chloride salts.The anilinium cations absorbed to the surfaces of ATP because of the negative centers introduced by the reaction of ATP with hydrochloric acid.Thus,the ATP surfaces can be more hydrophobic so that they have more affinity for the aniline monomers,facilitating encapsulation.So the anilinium chloride salts acted as both the monomer and the surface modifier in the oxidative polymerization.When the oxidant added,the polymerization occurred and the ATP needles were encapsulated by PANI to form the core-shell composite particles.TEM shows that the ATP nanoneedles were encapsulated very well like Chinese dates and the concentration of HCl had no effect on the morphologies of the ATP@PANI composite particles.Electrical conductivity shows that the ATP@PANI composite particles prepared with the more HCl amounts added exhibited the good electrical conductivities.更多还原