學生姓名:
陳佳琳
指導教授:
方銘志
學 號:
00539006
學期:
108上
摘 要:
Sodium carboxymethyl cellulose (CMC) is a water-soluble polymeric ether, whichis industrially produced by partially replacing the OH groups on the anhydroglucose units(AGUs) of starting cellulose with carboxymethyl groups (CM groups). Methods used todetermine the degree of substitution (DS) of CMC includes calculating expected value,ASH method, HPLC method, titration method, and NMR method. Magic angle spinning(HR-MAS) 13C NMR analysis calculated the ratio of the integral values of COO−groups and the anomeric C1 signals through well resolved spectra to be the degree of substitution.The method validation results obtained from the comparison of DS(HR-MAS) and DS(ASH) indicated that CMC with low DS (DS≤0.6) representing higher DS(HR-MAS)due to the effective DS(EDS) obtained from solvent-exposed fractions of CMC. Two-dimensional NMR spectroscopic analyses provided complete assignment of the 1H and13C chemical shifts of the eight AGUs comprising the CMC chains. DS(c=o) was determined by the total integral values of COO−groups (substituted groups) in thequantitative 13C NMR spectra of the CMC when that of C1 signals was set to 1. DS(cal)was calculated from the mole fractions (χi) of the AGUs with different substitutionswhich presented a series of signals within 90-60 ppm region in the quantitative 13C NMRspectra. The DS(c=o) and DS(cal) values of CMC samples prepared by multistepcarboxymethylations were compared to the values of titration method. The resultsshowed that quantitative 13C NMR was able to determine the DS of CMC and analyzethe substituent distribution of AUG at the 2-, 3-, and 6-positions of cellulose, whichenable the estimation of the reactivity of the hydroxyl groups toward carboxymethylation.
碩士班專題討論_20191211_陳佳琳.pdf