木质素分子结构可控修饰及其ATRP接枝共聚物构效关系研究

For the technical problems of difficult to polymerize, uncontrollable reaction and Irregular polymer structure to produce lignin-based polymer materials which resulted from the highly crosslink density and polydispersity of lignin macromolecular structure, a new method for the synthesis of lignin-based functional materials which lignin fractionation, selective activation of functional groups, and further use of atom transfer radical polymerization (ATRP) was mentioned . Ultrafiltration, gradual sedimentation, Organic solvent purification or a combination system were adopted to fractionate lignin in order to obtain a more uniform composition of different lignin fragments in the chemical structure and molecular weight distribution; By regulating the reaction conditions such as the dosage of the monomer to initiate , solvent systems, etc., the selective activation levels of lignin fragments hydroxyl functional groups to synthesis lignin-based macroinitiator which have different degrees of substitution; Graft-polymerize a variety of functional monomers via an advanced living/controlled polymerization method ATRP to prepare novel lignin-based copolymer of different degrees of polymerization; Reveal the structure-activity relationship between a controlled modification of the molecular structure of lignin and its novel ATRP graft copolymer, Through the study of the structure of the reactants , the polymerization kinetics and modified polymer properties. Implementation of this project will provide theoretical and technical support to the regulation of lignin structure, lignin polymerization ATRP directed to build high-value materials.

针对木质素大分子结构高度的交联密度和多分散性对构建木质素基高分子材料所带来的聚合难、反应不可控、聚合物结构不规整等技术难题，提出对木质素进行分级分离、选择性活化官能团、并进一步利用原子转移自由基聚合（ATRP）方法合成新型木质素基功能材料的构思。采用超滤、逐级沉降、有机溶剂纯化及其组合体系等方法分级分离木质素，获取分子量分布较窄、化学结构均一的不同木质素片段；通过调控单体引发剂用量、溶剂体系等反应条件，选择性活化木质素的羟基官能团，合成具有不同取代度的木质素基大分子引发剂；利用活性/可控聚合方法ATRP接枝聚合上各种功能性单体，制备具有不同聚合度的木质素基高分子共聚物；通过对反应物的结构表征、聚合反应动力学研究、改性高分子聚合物性能分析，揭示木质素分子结构可控修饰与其新型ATRP接枝共聚物的构效关系。本项目的实施将为木质素结构修饰、木质素定向ATRP聚合高值化材料构建提供理论和技术支持。

木质素大分子结构高度的结构异质性、多分散性对构建木质素基接枝共聚高分子材料带来接枝困难、反应可控性低、聚合物结构不规整等技术难题。本研究首先对木质素种类进行筛选，筛选出羟基含量高的木质素，再对高羟基含量的木质素进行分级分离。具体是利用磷谱核磁共振波谱（31P NMR）对碱木素、纤维素酶酶解木质素、酸析木素三种木质素的羟基含量进行测定，结果显示碱木素具有最高的总羟基含量和非缩合型酚羟基含量。接着用四氢呋喃（THF）对筛选出的碱木素进行分子量分级分离，选用完全溶解于THF部分的碱木素进行后续的接枝共聚物反应，通过凝胶渗透色谱（GPC）表明获取的溶解于THF的碱木素的分子量分布较窄，多分散指数为2.45。接着通过改变2-溴异丁酰溴（BiBB）与三乙胺（TEA）的添加量，使用分级得到的碱木素制备了不同溴含量的木素大分子引发剂（Lignin-Br）。本研究选用溴含量为3.5mmol/g的Lignin-Br，以CuBr为催化剂，N,N,N',N,'N''-五甲基二亚乙基三胺（PMDETA）或三(2-二甲氨基乙基)胺（Me6TREN）为配体，利用原子转移自由基聚合（ATRP）或电子转移生成活化剂原子转移自由基聚合（AGET ATRP）从Lignin-Br接枝丙烯酰胺（AM）、丙烯腈（AN）、 丙烯酸丁酯（BA）、醋酸乙烯酯（VAc）、N-异丙基丙烯酰胺（NIPAM）和5-乙酰氨基戊基丙烯酸酯（AA）制备出相应的木素基接枝共聚物。通过1H NMR和FT-IR证明了各单体链已经被引入木素骨架中。且通过改变单体用量和接枝顺序等研究了木素分子可控修饰与新型ATRP接枝共聚物性能之间的构效关系。本研究为木质素的可控结构修饰和木质素的定向ATRP聚合高值化材料的构建提供了理论和技术支持。