棉花纤维中木质素的相对分子量

分子量是聚合物的重要特性之一,木质素的分子量及其分布是研究苯丙烷类结构的反应、物理化学特性和评价其改性产物质量的内容之一。本研究以陆地棉TM-1成熟纤维为材料,分别利用酶解-温和酸解木质素法和二氧六环法提取棉纤维中木质素,结合凝胶渗透色谱法(gel permeation chromatography,GPC)调查和评价2种方法获得的棉纤维中木质素的相对分子量。结果表明,经二氧六环处理提取的棉花纤维中的木质素(dioxane lignin,DL)的重均分子量为2924g mol~(–1)、数均分子量2403 g mol~(–1),略高于由酶解-温和酸解处理提取的木质素(enzymatic hydrolysis-mild acidolysis lignin,EMAL)的重均分子量(2169 g mol~(–1))和数均分子量(1970 g mol~(–1)),EMAL的多分散系数稍低,说明木质素的均一性比DL高。表明EMAL法提取的木质素更适用于分析棉纤维中木质素的相对分子量。利用EMAL法分析棉纤维中木质素相对分子量表明,不同棉花品种的木质素重均分子量分布范围为938~2169 g mol~(–1),数均分子量分布范围为857~1970 g mol~(–1),多分散性系数在1.09~1.74间,均小于2。重均分子量与纤维马克隆值呈显著负相关,数均分子量与纤维长度呈显著负相关,与纤维马克隆值呈极显著负相关。

Relative Molecular Weight of Lignin in Cotton Fiber

Molecular weight is one of the important characteristics of polymers, lignin molecular weight and its distribution is one of the contents for studying responses of phenylpropanoid structure, physicochemical characteristics and evaluation of the modified product quality. In this research, the relative molecular weight of lignin extracted respectively by enzyme hydrolysis mild acidolysis and dioxane from mature cotton fibers was studied combined with gel permeation chromatography (GPC). The dioxane lignin (DL) had an average molecular weight (Mw) of 2924 g mol–1, and a number-average molecular weight (Mn) of 2403 g mol–1, which were slightly higher than the enzymatic hydrolysis-mild acidolysis lignin (EMAL, Mw was 2169 g mol–1 and Mn was 1970 g mol–1). The polydispersity coefficient of EMAL was slightly lower than that of DL, showing the higher uniformity in EMAL than in DL. The method of EMAL was more suitable to analyze the relative molecular weight of lignin in cotton fiber. The relative molecular weights of lignin in different cotton varieties, extracted by EMAL, were analyzed, showing that the MW distribution range of lignin was 938–2169 g mol–1, while Mn was 857–1970 g mol–1 and the polydispersity coefficient was 1.09–1.74 (less than 2). The weight average molecular weight had significantly negative correlation with the micronaire value (P<0.05). The number average molecular weight was negatively correlated with fiber length (P<0.05), and the micronaire value (P<0.01), respectively.