The role of diisocyanate structure on microphase separation of solution polymerized polyureas

被引:62
作者
He, Yong [1 ,2 ]
Zhang, Xinya [2 ]
Runt, James [1 ]
机构
[1] Penn State Univ, Dept Mat Sci & Engn, University Pk, PA 16802 USA
[2] S China Univ Technol, Sch Chem & Chem Engn, Guangzhou 510640, Guangdong, Peoples R China
基金
美国国家科学基金会;
关键词
Polyurea; Phase separation; X-ray scattering; STRUCTURE-PROPERTY RELATIONSHIPS; SEGMENTED COPOLY(ETHER UREA)S; COMPLEX DIELECTRIC SPECTRA; ANGLE X-RAY; PHASE CONNECTIVITY; HARD SEGMENTS; POLYURETHANES; MORPHOLOGY; SOFT; ELASTOMERS;
D O I
10.1016/j.polymer.2014.01.001
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
Three diisocyanates with different symmetry and planarity (2,6-TDI, 2,4-TDI and MDI) were used to synthesize polyureas with the same oligomeric polyetheramine having a molecular weight of similar to 1000 g/mol. The influence of diisocyanate symmetry on the phase separated morphology, hydrogen bonding behavior, and molecular dynamics were investigated. Symmetric diisocyanate structures facilitated self-assembly of hard segments into ribbon-like domains, driven by strong bidentate hydrogen bonding. The hard domains for the 2,6-TDI polymer appear to be continuous in AFM images, while the persistence length of the hard domains in the 2,4-TDI and MDI polymers gradually decrease, and fewer hard domains are apparent with decreasing hard segment symmetry. The extent of hard/soft segment demixing, assessed from small-angle X-ray scattering, was very incomplete for all of the polyureas and is significantly influenced by hard segment structure. For the 2,4- and 2,6-TDI polyureas, two segmental relaxations were observed using dielectric relaxation spectroscopy; one arising from relatively unrestricted motion in the soft segment rich phase, and a slower process associated with segments in the soft phase constrained by their attachment to hard domains. (C) 2014 Elsevier Ltd. All rights reserved.
引用
收藏
页码:906 / 913
页数:8
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