纳米纤维素-树脂酸多臂星形共聚物可控制备、结构调控机理与性能研究

Nanocellulose derived from the natural cellulose crystalline phase and generally used as nano-reinforced material, is regarded as one of the most important biomass based feedstock featured with the advantage of cellulose such as environmental friendliness, biodegradability, etc, and as well as with the nano-characters. In our previous work, a serial of well-defined brush copolymers derived from cellulose, resin acid, and vegetable oil were developed via controlled/living "grafted from "polymerization. By tuning the molecular architecture, these copolymers can be employed as elastomer. Inspired by this controlled/living synthetic strategy that resin acid derived monomer and vegetable oil derived monomer were grafted onto the backbone of cellulose, various multi-arm star nanocellulose-resin acid coplolymers were prepared via surface controlled/living "grafted from" polymerization of nanocellulose in this proposed work with the aim to develop the next generation of novel elastomer. The molecular architecture design, fabrication and microphase separation tuning mechanism would be mainly investigated. The application of these grafted nanocellulose copolymers used as a nano-reinforced material by blending or by in-situ would be also evaluated. We aim to reveal some key scientific problems, including elucidation of mechanism of structural design and rearrangement, and establishment of structure-function relationship of novel hierarchical structure of resin acid grafted nanocellulose copolymers. In addition, we will further research the application of resin acid grafted nanocellulose copolymers as thermoplastic and elastic material, and explore the possibility of replacing the petroleum based counterpart by entire biomass (cellulose, resin acid and vegetable oil) based elastomers. The research achievements in this project will establish the theoretical and practical foundation for high efficient and high value added utilization of cellulose and resin acids, and will further pave the road toward the development of the novel thermoplastic elastomers.

纳米纤维素源自天然纤维素的结晶部分，是一种具有纤维素环境友好、可降解等优点和兼具纳米特性的生物质原料，常被用作纳米相增强材料。本项目将根据前期研究中刷状纤维素-树脂酸-油脂三元共聚物的合成、结构设计和弹性材料潜在应用等重要发现，在初步建立纤维素与树脂酸基单体和油脂基单体可控聚合复合技术的基础上，通过表面可控聚合法制备纳米纤维素-树脂酸多臂星型共聚物，研究纳米纤维素-树脂酸多臂星型共聚物的制备、结构设计、微相分离调控等机理，研究纳米纤维素的共混和原位增韧、增强机制，揭示纳米纤维素与树脂酸基聚合物复合和结构设计机理、微观结构和宏观性能的关系等科学问题，并进一步深化纤维素和树脂酸在热塑性弹性体领域的应用，探讨全物质基（纤维素、树脂酸和油脂）热塑性弹性体替代石油基产品的可能性。本项目研究将为高效、高附值利用纤维素和松香树脂酸奠定坚实的理论和应用基础，对开发新型热塑性弹性体材料具有重要的指导作用。

纳米纤维素和松香树脂酸都是重要的可再生资源，利用其特有分子结构及特性开发高性能材料是当前生物质资源利用研究的重要研究方向。本项目以纳米纤维素、松香树脂酸基单体（DAGMA）以及油脂基单体（LMA）为原料，在纳米纤维素表面引发原子转移自由基聚合(SI-ATRP），将纳米纤维素、树脂酸和油脂三者进行共价键复合，构筑了新型纳米纤维素-树脂酸-油脂多臂星型热塑性弹性体材料，并研究了该多臂星型共聚物的制备、结构设计、微相分离调控等机理，研究纳米纤维素的共混和原位增韧、增强机制。研究发现（1）该材料集成了纳米纤维素、松香树脂酸和油脂三种天然生物质资源的特性；（2）通过2-溴代异丁酰溴和纳米纤维素CNCs表面羟基之间的酯化反应可以制备出纳米纤维素基ATRP引发剂(CNCs-Br)，通过调整2-溴代异丁酰溴和CNCs表面羟基之间的比例可以调控CNCs-Br的引发点密度；（3）XRD分析结果表明弹性体中仍保留CNCs本身所具有的结晶结构；（4）研究发现引发剂的引发点密度越高，所对应的聚合物侧链的分子量反而越小；（5）弹性体的力学性能可以由纳米纤维素、树脂酸和油脂的组成比例来调控，增加纳米纤维素和树脂酸组份的含量可以提高弹性体的刚性；（6）当松香树脂酸接枝纳米纤维素用量达到40%时，与天然橡胶混合物膜的最大拉伸强度可达12.1MPa；（7）松香树脂酸分子能赋予该弹性体优异且稳定的紫外吸收性能；（8）该弹性体材料可应用作压敏胶（PSA），随着松香树脂酸含量的增加，压敏胶的初粘逐渐降低，持粘逐渐增加；当DAGMA与LMA比例达到7:3时，持粘已经远大于100 小时。通过本项目的研究，揭示了纳米纤维素与树脂酸基聚合物复合分子微观结构和宏观弹性性能的关系，并发现纳米纤维素基弹性材料可作为一种新型的紫外线阻隔PSA材料的潜力，项目研究所取得的成果将为开发新型纳米纤维素基和松香树脂酸基材料提供理论依据。