【作者】 李荣；

【导师】 邱学青；

【作者基本信息】 华南理工大学 ， 化学工程， 2012， 博士

【摘要】 两亲聚合物是指分子中同时存在对水相和油相具有亲和性链段的高分子化合物。因其兼具高分子和两亲分子结构的双重性能，在保护胶体、分散及絮凝作用等方面有独特的优势，被广泛应用于日用化工、涂料工业、医药、纺织印染、建筑业等多个领域。近年来，由于国内外日益重视化学品对环境和人体的危害，原料来自于可再生资源的木质素系两亲聚合物已经逐渐成为研究热点。但相对于结构规整的嵌段共聚物和接枝共聚物而言，针对木质素两亲无规聚合物的研究较为薄弱。目前，木质素两亲聚合物主要来自于两大造纸制浆副产品：一是传统的亚硫酸法制浆废液的木质素磺酸盐，由于在酸法制浆过程中引入了磺酸基，其具有较好的水溶性；二是烧碱法或硫酸盐化学制浆废液回收的碱木质素，因分子中的亲水性基团较少而仅溶于碱性溶液，但可通过磺化反应转化为水溶性良好的木质素磺酸盐。木质素两亲聚合物最大的用途之一是作为分散剂，其对固体颗粒的分散性能主要是依靠在颗粒表面上的吸附来实现的，因此，吸附特性和机理的阐明，尤其是吸附形态和吸附规律的研究，对木质素两亲聚合物的改性及表面物化性能的提高均有重要的指导意义。但由于木质素两亲聚合物分子结构和物理化学性质的不均一性给性能表征带来了很大困难，而且分布不均匀的亲水疏水链段也使得聚合物分子间、聚合物分子与溶剂分子间及聚合物分子与颗粒间的作用力更为复杂，对木质素系两亲无规聚合物的研究仍有大量基本理论问题没有得到解决。本论文以酸法制浆废液中回收的木质素磺酸钠为原料，研究了其在气/液界面上的动态吸附行为，不同pH条件下木质素磺酸钠在氧化铝颗粒上的吸附机理，吸附构型对氧化铝悬浮液体系的分散性能的影响，探索了直链醇对木质素磺酸钠在界面吸附性能的影响规律及对木质素磺酸盐分散的增效作用机理；以竹浆造纸制浆黑液中的碱木质素为原料，制备了高磺化度高分子量的接枝磺化碱木质素，考察了其对氧化铝颗粒在水溶液中的分散效能，揭示其吸附分散作用机理，研究结果可为木质素两亲聚合物的应用提供基础数据和理论指导。论文采用轴对称液滴形状测定法研究了不同浓度木质素磺酸钠溶液在气/液界面上的动态吸附行为。结果表明，木质素磺酸钠在气/液界面上的吸附是一个缓慢的过程，其吸附效率主要依赖于木质素磺酸钠聚集体在溶液中的解聚速率；由Langmuir、Frumkin、modified Frumkin及modified Flory-Huggins方程的模拟结果可知，木质素磺酸钠在界面上的吸附量较少且吸附构型疏松，吸附层中的分子与分子间的相互作用很弱以至于可忽略不计，进一步建立了估算其溶液动态表面张力的数学模型。通过Langmuir-Blodgett膜天平（LB膜天平）研究了木质素磺酸钠在气/液界面上的成膜特性。在合适的条件下（溶液浓度为10g/L，亚相为0.01mol/L CdCl₂，进样量为50μL，划障速率为10mm/min），可以将木质素磺酸钠Langmuir膜成功地转移沉积到亲水性石英基材上；而直链醇对木质素磺酸钠在界面上的吸附具有增效作用，促使更多的木质素磺酸钠分子被吸附于界面，使分子在界面上的排列更加有序。通过流变特性、吸附等温线、zeta电位、XPS等测试技术，研究了不同pH条件下木质素磺酸钠在Al₂O₃颗粒表面上的吸附特性，建立了相应的吸附模型，考察了木质素磺酸钠对高固含量悬浮液的分散降黏性能和作用机理。结果表明：当pH值较低时，随着浓度的增大，木质素磺酸钠以聚集体的形式吸附于Al₂O₃颗粒表面，吸附等温线符合Freundlich方程；而当pH值较高时，木质素磺酸钠趋向于以疏松的单分子吸附于颗粒表面，其吸附等温线符合Langmuir方程；在所研究的pH范围内，氢键对吸附没有贡献；木质素磺酸钠在Al₂O₃颗粒表面的吸附作用力与Al₂O₃颗粒的等电点pHIEP有关，当pH<pHIEP时，两者间的吸附作用机制主要为静电作用和Al3+-π作用；而当pH> pHIEP时，Al3+-π作用是主要的吸附作用力；当pH <pHIEP时，颗粒间主要依靠静电排斥作用和空间位阻分散于悬浮液中；而当pH> pHIEP时，颗粒间的分散主要依靠静电排斥作用。通过zeta电位仪、表面电荷密度仪和TEM研究了直链醇对木质素磺酸钠聚集态的影响，得出直链醇的非极性端可插入到木质素磺酸钠分子的碳氢疏水核内，溶解于其分子中，有助于木质素磺酸钠聚集体在溶液中解聚，使包裹的带电基团裸露出来，提高了木质素磺酸钠分子表面的负电性。吸附等温线、zeta电位和XPS等测试结果表明，直链醇的掺入有效地增强了固体颗粒间的静电排斥作用，当溶液条件为酸性或中性时，直链醇的存在有利于木质素磺酸钠对Al₂O₃悬浮液的分散稳定；但当溶液条件为碱性时，直链醇的影响几乎可以忽略不计。以竹浆造纸黑液中的碱木质素为主要原料，通过磺化和缩聚反应制备了具有高磺化度高分子量的碱木质素改性产物SBAL，采用TEM、1H NMR、IR、GPC和自动电位滴定等测试技术对其结构和官能团的含量进行了表征，并研究了SBAL对Al₂O₃颗粒在水溶液中的分散机理和吸附特性。结果表明：SBAL的重均分子量达到了24880Da，是碱木质素的7.38倍，磺化度为2.70mmol/g；SBAL分子内部为木质素的疏水骨架，表面为带亲水性官能团的长侧链，亲水官能团随pH的增加而逐渐电离，使其在水溶液中由卷曲状态逐渐伸展；其在Al₂O₃颗粒表面的吸附特性与Al₂O₃颗粒的等电点pHIEP有关，当pH <pHIEP时，SBAL在Al₂O₃表面的吸附以静电吸附为主，SBAL的吸附有利于增大颗粒表面的负电性，而当pH> pHIEP时，静电吸附作用减弱，吸附质量减小，吸附层结构疏松，对颗粒表面的负电性影响程度降低；在所研究的pH范围内（pH=3¹2），SBAL对Al₂O₃悬浮液有较好的分散效能，低用量时以静电排斥作用为主，高用量时以空间位阻为主。更多还原

【Abstract】 Amphiphilic polymer refers to the macromolecular compound which has both thehydrophilic and hydrophobic properties in the molecular chain. The better dual performances（polymer and amphiphilic molecular structure） may play an important role in protectingcolloid, dispersing, flocculating and so on, and it has been widely used in various industrialprocesses such as domestic chemicals, coatings technology, medicines, textile and dyeingindustry, architecture, etc. Recently, as the domestic and overseas people increasing value theenvironmental pollution and hazards to human health caused by chemical products, ligninamphiphilic polymer has been attracted a lot of attention and become one of the hot topics inacademic areas for the characteristics of renewable and biodegradability.The lignin amphiphilic polymers are mainly from two kinds of byproducts in thepapermaking industry:（1） lignosulfonates, from the traditional sulphite-pulping method, is awater soluble polyelectrolyte owing to the introduced sulfonic group;（2） alkaline lignin,comes from the soda chemi-pulping or kraft pulping, is only dissolved in the alkaline solutionbut can be modified by the sulfonation reaction to improve the water solubility, reactiveactivity and dispersing performance.One of the largest applications of the lignin amphiphilic polymers is used as the dispersantin the suspension, and the dispersing performance mainly depends on the adsorptionbehaviors of lignin amphiphilic polymers on the surface of solid particles, thus research andenunciation of the adsorption characteristics and the adsorption mechanisms, especially forthe adsorption configuration and the adsorption law, has important instructive significanceand reference value on the modification of lignin amphiphilic polymers and the improvementof its surface physicochemical property. However, the heterogeneity of molecular structure oflignin amphiphilic polymers not only brings difficulties to characterization of property, butmakes the molecular interactions more complex, including the interaction between polymerand polymer, the interaction between of polymer and solvent molecule, and the interactionbetween polymer and solid surface. Therefore, until now, for the lignin amphiphilic polymers,there are still a lot of basic theoretical problems need to be resolved.In the thesis, sodium lignosulfonate （SL） was used as the material, the dynamic adsorptionbehavior of SL on the air-water interface was studied, and the adsorption driving force of SLon Al₂O₃particles surface at different pH values was explored, and the effect of molecularconfiguration on the dispersing performance of Al₂O₃suspension was analyzed. Based on the results, the influences of straight-chain alcohols on the dispersion performance and adsorptionproperty of SL on the Al₂O₃particles were studied. Moreover, a sulfonated lignin-basedmacromolecule polymer, SBAL, was prepared by chemical reaction using alkali lignin fromthe alkaline pulping spent liquor of bamboo as main material. The adsorption properties andthe dispersion efficiencies of SBAL on the Al₂O₃particles in aqueous solution wereinvestigated, and the research results can provide basic data and theoretical guides for theindustrial application of the lignin amphiphilic polymers.The dynamic adsorption behavior of SL aqueous solutions with different concentration atthe air-water interface was investigated using an axisymmetric drop shape analysis-profilemethod. The result showed that the adsorption of SL at the air-water interface was a slowprocess, and the adsorption efficiency depended largely on the depolymerization rate of SLaggregate in the aqueous solution. The data were analyzed by the Langmuir, Frumkin,modified Frumkin and modified Flory-Huggins equations, and the results indicated that theadsorption amount of SL at the interface was smaller, and the molecular configuration of SLwas looser, and the intermolecular force of SL in the adsorption layer was very weak whichcan be negligible. The expression for estimating the dynamic surface tension of SL aqueoussolution was also presented.The film-forming characteristic of SL at the air-water interface was investigated byLangmuir-Blodgett （LB） technique. The results showed that the Langmuir film of SL can betransferred successfully onto the hydrophilic quartz substrate under the proper experimentalconditions: the concentration of SL was10g/L, the subphase solution was the0.01mol/LCdCl₂, the sample volume was50μL and the compression speed was10mm/min. Besides, itwas confirmed that the straight-chain alcohols can improve the adsorption amount of SL at theair-water interface, the synergistic effect between SL molecules and straight-chain alcoholsmade rearrangement of the SL molecular structure at the interface more ordered.The adsorption behaviors and dispersion efficiencies of SL on Al₂O₃particles at differentpH values were investigated by UV-Vis spectroscopy, zeta potential, X-ray photoelectronspectroscopy （XPS） and rheological measurements. Results showed that at low pH values, asconcentration increased, SL adsorbed on the Al₂O₃particles in the form of aggregate and theadsorption isotherms belonged to the Freundlich equation; at high pH values, SL adsorbed inthe form of loose single-molecular configuration and the adsorption isotherms belonged to theLangmuir equation. At pH3¹1, the adsorption was not affected through addition of urea,ruling out hydrogen bond as the controlling factor. The adsorption mechanism of SL on theAl₂O₃particles was related to the isoelectric point of Al₂O₃. The main driving force was considered as the synergistic effect of the electrostatic interaction and the Al3+-π interactionwhen pH <pHIEP, while the Al3+-π interaction was the dominant driving forces when pH>pHIEP. The dispersing mechanism was mainly attributed to the steric hindrance （pH <pHIEP）and the electrostatic repulsive force （pH> pHIEP） owing to the differences of adsorbedconfiguration.The effect of straight-chain alcohols on the aggregation of SL in the aqueous solution wasstudied by the zeta potential, surface charge density and transmission electron microscope（TEM）. The results showed that nonpolar end-group of the straight-chain alcohols could insertinto the hydrophobic core of SL molecule or aggregates, the straight-chain alcohols helped theSL aggregation depolymerize in the aqueous solution, made the wrapped hydrophilic groupsexposed and improved the electronegativity of SL molecules. The adsorption isotherms, zetapotential and XPS results showed that the addition of straight-chain alcohols could increaseeffectively the electrostatic repulsive force between Al₂O₃particles. When suspensions werecarried on in the acidity or neutral solution, the straight-chain alcohols were favorable for theAl₂O₃particles dispersion in the aqueous solution, however, the effect of the straight-chainalcohols could be almost negligible when the suspension in the alkaline solution.SBAL, with higher sulfonation degree and higher molecular weight, was prepared by thesulfomethylation, etherification and polycondensation reactions. TEM and1H NMR resultsshowed that the structure of SBAL was loose spherical, the center of which was thehydrophobic skeletons of lignin, the long side chains with sulfonic and carboxyl groups weredistributed on its surface. GPC and potentiometric titration results showed that the MwofSBAL reached24880Da,7.38times of the alkali lignin, and the sulfonic group content was2.70mmol g1. The adsorption properties and the dispersion efficiencies of SBAL wereinvestigated by means of adsorption isotherms, XPS, zeta potential and rheologicalexperiments. At pH3¹2, SBAL as the dispersant can remarkably reduce the viscosity ofAl₂O₃suspension. The sulfonic, carboxyl and phenolic hydroxyl group of SBAL were ionizedgradually as pH increasing, which made the SBAL molecule chain spread well in the alkalicondition. With the increase of pH, the adsorption amount of SBAL on the Al₂O₃particlesdecreased and the adsorption configuration from compact became loose. When pH <pHIEP,the main adsorption force between SBAL and Al₂O₃particle was electrostatic adsorption,however, when pH> pHIEP, non-static specific adsorption dominated the main force. Whenthe dosage of SBAL was less than the critical dosage （0.5%）, SBAL generated an electrostaticrepulsion between particles by monolayer adsorption on Al₂O₃surface, however, when the dosage was more than the critical dosage, SBAL absorbed on Al₂O₃particles in the form ofaggregation to improve the steric hindrance.更多还原