Full-Text Search:
Home|Journal Papers|About CNKI|User Service|FAQ|Contact Us|中文
《高分子科学(英文版)》 2018-10
Add to Favorite Get Latest Update

NMR Analysis to Identify Biuret Groups in Common Polyureas

Wei-Guang Qiu;Fei-Long Zhang;Xu-Bao Jiang;Xiang-Zheng Kong;College of Chemistry and Chemical Engineering, University of Jinan;  
Polyureas(PU) are well known as a class of high impact engineering materials, and widely used also in emerging advanced applications. As a general observation, most of them are only soluble in a very limited number of highly protonic solvents, which makes their chemical structure analysis a great challenge. Besides the presence of abundant hydrogen bonding, the poor solubility of PU in common organic solvents is often ascribed to the formation of biuret crosslinking in their molecular chains. To clarify the presence of biuret groups in PU has been of great interest. To this end, two samples, based on hexamethylene diisocyanate(HDI) and toluene diisocyanate(TDI) respectively, were synthesized by precipitation polymerization of each of these diisocyanates in water-acetone at30 °C. Their chemical structures were analyzed by high resolution magic angle spinning(HR-MAS) NMR, and through comparison of their NMR spectra with those of specially prepared biuret-containing polyurea oligomers, it was concluded that biuret group was absent in all the PU prepared at 30 °C. In addition, this NMR analysis was also applied to a PU obtained by copolymerization of TDI with ethylene diamine(EDA) and water at 65 °C in EDA aqueous solution. It was confirmed that biuret unit was also absent in this PU and that EDA was more active than water towards TDI. The presence of EDA was crucial to the formation of uniform PU microspheres. This study provides therefore a reliable method for the analysis of PU chemical structure.
【Fund】: financially supported by the National Natural Science Foundation of China(Nos.21274054 21304038 and51473066);; Research Foundation of University of Jinan(No.XKY1604);; Science&Technology Development Plan of Shandong Province(No.2017GGX202009) China
【CateGory Index】: O657.2;O631
Download(CAJ format) Download(PDF format)
CAJViewer7.0 supports all the CNKI file formats; AdobeReader only supports the PDF format.
©2006 Tsinghua Tongfang Knowledge Network Technology Co., Ltd.(Beijing)(TTKN) All rights reserved