纤维素无定形区反应位点尺寸的表征及抗皱机理研究

The chemical modification of cotton fibers mainly occurs in the amorphous region, and in order to developing the controllable chemical modification and new dyeing and finishing technologies of cotton fibers, it is very necessary to investigate the reaction site distance of the cellulose amorphous region (RDCA) and its distribution. However, no relevant studies on this issue have been carried out so far. The anti-wrinkle finishing of cotton fabrics by polycarboxylic acid (PCA) is based on the crosslinking between different cellulose macromolecules through PCA molecules in the cellulose amorphous region. According to our previous studies, the RDCA corresponds with the reaction site distance between different carboxyls in a PCA molecule. Therefore, in this research project, PCAs with different chemical structures will be employed as molecular probes. The reaction sites of PCA or cellulose molecules as well as the crosslinking anti-wrinkle mechanism between PCA and cellulose will be thoroughly analyzed. Furthermore, the RDCA and its distribution can be analyzed very well. The main study contents include: investigation on the adjustment of RDCA by alkaline mercerization and on the changing orders of different cellulose hydroxyls during the process; the characterization of reaction sites of different structural PCAs and cellulose according to the two-dimensional infrared correlation spectroscopies; and the establishment of reaction models of cellobiose and PCA according to Gaussian calculation about the frontier molecular orbital of reaction molecules. The objects of this research are that the crosslinking anti-wrinkle mechanism of cotton fabrics treated with PCA can be clarified from the molecular reaction sites, and furthermore the RDCA and its distribution can be brought into light. Above all, the results will provide an important theoretical foundation and a direction for developing a novel anti-wrinkle finishing reagent and exploring the chemical modification of cotton fibers under a quantitative regulating reagent ratio further.

棉纤维的化学改性主要发生在其无定形区，为了探究棉纤维的可控改性和发展新型染整技术，迫切需要研究纤维素无定形区反应位点尺寸（RDCA）及其分布。但是，目前尚未有人在该领域进行研究。多元羧酸（PCA）抗皱整理是对纤维素无定形区大分子进行交联，我们的前期研究发现，RDCA与PCA羧基反应位点尺寸存在对应关系。因此，本项目将以不同结构的PCA作为分子探针，通过深入分析PCA与纤维素的反应位点以及交联抗皱机理，对RDCA及其分布展开研究。主要内容：碱丝光调控RDCA及分析纤维素不同羟基变化的活泼性顺序；二维红外相关光谱表征不同结构PCA与纤维素的反应位点；Gaussian理论计算纤维二糖和PCA的前线分子轨道，建立两者的反应位点模型。本项目旨在从分子反应位点的角度揭示PCA对棉织物的交联抗皱机理，进而阐明RDCA及其分布，为开发新型抗皱整理剂以及探究棉纤维的化学剂比例定量调控改性奠定理论基础和方向。

棉纤维无定形区反应位点尺寸（RDCA）及其分布显著影响其化学改性性能，是实现产品附加值的重要手段。但棉织物无甲醛抗皱整理仍未实现产业化，这主要也是受限于对棉纤维RDCA认识不足。为阐明这一关键科学问题，开发出高效棉织物无甲醛抗皱交联剂，本项目采用多元羧酸（PCA）作分子探针进行了研究。主要研究内容：（1）碱丝光调控棉纤维RDCA及羟基变化机理；（2）PCA分子探针表征棉纤维RDCA及其分布；（3）新型结构PCA分子开发及对棉织物抗皱整理。采用傅里叶变换红外光谱、二维相关光谱分析、Gaussian计算等，对相关机理展开研究。结果表明，棉纤维在碱丝光时，纤维素羟基变化顺序为（“→”代表早于）：ν(O(3)‒H(3)…O(5))(分子内氢键)→ν(O(6)‒H(6)…O(3)')(分子间氢键)→ν(O(2)‒H(2)…O(6))(分子内氢键)。当NaOH为200g/L，丝光时间20s时，1,2,3,4-丁烷四羧酸（BTCA）整理棉织物达到最佳效果，折皱回复角（WRA）为252.0°，纬向撕破强力保留率（TSR）为69.30%。柠檬酸（CA）（或BTCA）与棉纤维反应机理：纤维素6位羟基、2位羟基参与酯化反应活泼性更高，且6位羟基酯化反应早于2位羟基。模型分子纤维二糖与CA（或BTCA）反应研究结果也证实了这一点；且CA（或BTCA）分子末端两个羧基参与酯化交联反应。有利于酯化反应交联的棉纤维RDCA分布中4-6Å占比较大，基于此合成了三种新型结构PCA分子聚(马来酸-丙烯酸)、聚(衣康酸-马来酸)和聚(反式乌头酸-丙烯酸)，满足RDCA要求，尤其是聚(反式乌头酸-丙烯酸)可以同时赋予整理织物较高的WRA和TSR，达到研究预期。本项目研究结果有利于从反应位点深入理解棉纤维碱丝光机理、棉纤维与PCA反应位点交联机理，对开发新型交联剂具有理论和实际意义。