Iterative synthesis of monodisperse pendants for making comb-like polyurethanes

Publication date: 16 June 2017
Source:Polymer, Volume 119
Author(s): Chien-Hsin Wu, Yu-Ching Chen, Shenghong A. Dai, Su-Chen Chen, Shih-Huang Tung, Rong-Ho Lee, Wen-Chiung Su, Ru-Jong Jeng
Polyurethanes grafted with well-defined polar pendants were synthesized and investigated. A series of linear and dendritic poly(urea/malonamide)s with uniform chain length were first prepared from an iterative synthesis route, which is based on a dual-functional building block, 4-isocyanate-4´-(3,3-dimethyl-2,4-dioxo-azetidine)diphenyl methane (IDD). Moreover, side chain polyurethanes (SPUs) bearing azetidine-2,4-dione functional groups were prepared from one pot reaction for following post-functionalization of poly(urea/malonamide)s when IDD-diols were added to polyurethane prepolymers as chain extenders. Subsequently, the azetidine-2,4-dione functional groups on the SPUs underwent addition reactions with amino functional group containing dendritic or linear poly(urea/malonamide)s under mild condition, without the need of catalyst and protection/deprotection procedure to achieve polyurethanes grafted with well-defined pendants. Mechanical properties of these comb-like polyurethanes strongly depend on the architecture and the molecular length of poly(urea/malonamide) pendants, which could be adjusted by the grafting fractions of the dendritic or linear poly(urea/malonamide)s with various generations. These poly(urea/malonamide) pendants provided strong hydrogen bonding interactions to achieve physical crosslinking effects in the polyurethanes. Consequently, the polyurethanes with improved mechanical properties and sustained phase transition exhibit shape memory properties.

Graphical abstract

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