The Effect of NMR Setting Parameters on Molecular Weight Determination of Polyether Diols  

作　　者：Shu-Jie Huang Xiao-Hong Li Ying-Feng Tu 

机构地区：[1]Jiangsu Engineering Laboratory of Novel Functional Polymeric Materials,State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials,College of Chemistry,Chemical Engineering and Materials Science,Soochow University,Suzhou,215123,China

出　　处：《Chinese Journal of Polymer Science》2024年第11期1730-1737,I0010,共9页高分子科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.22231008 and 22071167);the Natural Science Foundation of Jiangsu Higher Education Institutions of China(No.22KJA150005);a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。

摘　　要：Nuclear magnetic resonance(NMR)is an advanced technique for the molecular weight(MW)determination of polymers at quantitative conditions.In this study,we investigate the effect of liquid^(1)H-NMR instrumental setting parameters on the MW determination of polyether diols,namely poly(ethylene glycol)(PEG)and poly(tetramethylene oxide)(PTMO)diols,using hydroxymethylene groups as chain-ends.Our results show that the protons in chain-ends have larger spin-lattice relaxation time(T_(1))than those in main chains.To let most of the excited protons relax to the equilibrium state,the delay time(d_(1))should be much larger than T_(1)of end-groups.When^(13)C decoupling is inactive,the relative errors can be greater than 60%,due to the^(13)C-coupled proton satellite peaks,which can overlap with chain-end groups or be misassigned as chainends.The optimal quantitative NMR conditions for the MW estimation of polyethers are revealed below:standard pulse with inverted gated^(13)C decoupling pulse sequence,32 scans,2.0 s acquisition time in 90 degree of flip angle and 30 s d_(1).The MWs determined from^(1)H quantitative NMR are all smaller than those from SEC which are relative to polystyrene(PS)standards,since the size of polyether chains is larger than that of PS with the same MW.In addition,the MW obtained from SEC for PTMOs shows larger overestimation than PEGs,suggesting PEG chains are more flexible than PTMO’s.

关 键 词：End-group analysis Molecular weight NMR POLYETHER DECOUPLING 

分 类 号：TQ317[化学工程—高聚物工业]