SEC-MALLS-RI体系测定魔芋胶分子结构特性的研究

Study on Molecular Structure Characteristics of Konjac Glucomannan by Using SEC-MALLS-RI System

[目的]用SEC-MALLS-RI系统测定魔芋胶的分子结构。[方法]采用凝胶渗透色谱(SEC)、多角度激光光散射(MALLS)与示差折光检测仪(RI)联用技术系统测定魔芋胶的分子量、分子量分布、分子旋转半径(RMS)及其构象。[结果]魔芋胶的分子结构特性是:重均分子量(Mw)=1.040×106 g/mol,数均分子量(Mn)=9.395×106 g/mol,z-均分子量(Mz)=1.329×106 g/mol;数均旋转半径(Rn)=110.5 nm,重均旋转半径(Rw)=115.9 nm,z-均旋转半径(Rz)=129.6 nm;分散度分别是Mw/Mn=1.107和Mz/Mn=1.414。分子旋转半径RMS与分子摩尔数之间的关系曲线斜率为0.40±0.00,表明魔芋胶是一个高度紧密且具有分支结构的聚合物。[结论]建立了测定聚魔芋胶分子量及其分布的激光光散射法,结合凝胶渗透色谱,能在较大范围内准确测量聚合物的绝对分子量,且试验误差较小,重现性好。

[ Objective] The study aimed to determine the molecular structure characteristics of konjac glucomannan （KGM） by using SECMALLS-RI system. [ Method] The molecular mass, molecular mass distribution, RMS radius and conformation of KGM were systematically determined by using the coupling technique of size-exclusion chromatography （ SEC ） , the equipped with multi-angle laser light scattering （MALLS） and differential refractive index detectors （RI）. [ Result ] The molecular structure characterizations of KGM were determined as follows： Mω = 1. 040 x 10^6 g/mol, Mn = 9. 395 x 10^6 g/mol, Mz= 1. 329 x 10^6 g/mol, and Rn = 110.5 nm, Rw = 115.9 nm, Rz = 129.6 nm, and Mω/Mn = 1. 107 , Mz/Mn = 1. 414. The curve slope of the relationship between RMS and molecular Moore number was 0.00, 0.40, suggesting that KGM was a highly compact and branched polymer. [ Conclusion] The laser light scattering method that could determine the molecular mass and its distribution in KGM Was established. Combined with the gel permeation chromatography, the method could accurately measure the absolute molecular weight of the polymer in a wide range, with a smaller error and good repeatability.