基于原位显微光谱的木材细胞壁微区化学成分和基团水分吸附分子机制研究

Moisture adsorption is the fundamental cause of wood dimensional instability and degradation, and molecular mechanism of chemical components and groups in micro-areas of wood cell wall on moisture adsorption is the basis for improving the dimensional stability of wood effectively. The aim of this project is to study the mechanism of chemical components and groups in micro-areas of wood cell wall on moisture adsorption from the molecular level. Using the in situ micro-spectroscopy and humidity control system, one strategy for the quantitative analysis of moisture adsorption of wood cell wall had been introduced. This new approach can be used to investigate moisture adsorption of wood cell wall. Combining with targeted modification methods, this new approach can be used to reveal the effect of chemical components on moisture adsorption of wood cell wall. In future, technique of the spectrum measuring of hydroxyl, combined with difference spectrum and spectral fitting, can be used to clarify the molecular mechanism of hydroxyl and carbonyl groups on moisture adsorption. The molecular mechanism of chemical components and groups on moisture adsorption can improve wood moisture adsorption mechanism, understand the interactions between water and wood and provide theoretical guidance to improve technology of keeping dimensional stability and wood drying.

吸湿性是导致木材尺寸变形、材质降等的本质原因，探明木材化学成分和基团对吸湿性的影响机制是有效改善木材尺寸稳定性的必要前提。本项目拟从分子水平上原位解析木材细胞壁微区化学成分和基团对水分吸附的影响机制。利用原位显微光谱和湿度调控系统，原位测量木材细胞壁微区水分吸附，揭示木材微观水分吸附规律；结合化学成分选择性脱除技术，探明木材细胞壁微区化学成分对水分吸附的影响机制；采用光谱测量羟基技术和谱图数据处理手段，揭示木材细胞壁化学成分中羟基和羰基水分吸附分子机理，进而阐明木材细胞壁微区化学成分和基团对水分吸附的影响机制，从细胞水平完善木材吸湿机理，从分子水平深化木材与水分子相互作用机制，为木材尺寸稳定处理、木材干燥工艺优化和技术开发提供理论指导。

吸湿性是导致木材尺寸变形、材质降等的本质原因，探明木材化学成分和基团对吸湿性的影响机制是有效改善木材尺寸稳定性的必要前提。本项目从分子水平上原位解析木材细胞壁化学成分和基团对水分吸附的影响机制。主要研究结果为：1) 构建和完善木材细胞壁微区平衡含水率和动态水分吸附光谱测量方法，形成光谱测量木材吸湿性的“专利群”；2）证实木材细胞壁水分吸附有效活性位点是C=O、C-O和OH；3）发现木材、热处理木材细胞壁以及细胞壁主要化学组分的吸附水均可分为三类：强氢键结合水，中等强度氢键结合水和弱氢键结合水。吸湿过程包括三个阶段：第一阶段，吸附的水分子直接接触亲水基团形成强氢键；第二阶段间接吸附水分子；第三阶段，吸附水分子形成团簇结构；4）通过谱图对比，发现热处理导致木材中乙酰基含量降低、羟基含量降低；5) 定点测量木材细胞壁S2区域和CC区域水分吸附，证实木材细胞壁不同形态区水分吸附的不均匀性；6）证实显微光谱可用于水分空间分布研究。综上所述，本项目构建了木材细胞壁微区水分吸附测量新方法，可用于后续木材水分关系的深入研究；揭示了木材水分短程分子相互作用力，在分子水平上深化木材与水分子相互作用机制，将为木材尺寸稳定处理、木材干燥工艺优化和技术开发提供理论指导。