Study On Novel Polyurethane Chain Extander Based On Quadruple Hydrogen Bond

The components in supramolecular polymers are linked through non-covalent bonds. These non-covalent bonds can dissociate and rearrange through a revisible process under proper conditions. A lot of functional materials can be designed using this kind of property. In recent years, the development of the ureidopyrimidinone (UPy) functionality, has helped enormously in opening the way for the exploration of all aspects of supramolecular materials. UPy groups can dimerize through a self- complementary quadruple hydrogen bond, which remarkably increases the degree of polymerization in supramolecular polymers. Mechanical properties of polymers with low molecular weight can be changed significantly through dimerizing of UPy end groups. If more than two UPy groups are introduced in one polymer chain, a supramolecular network can be achieved in which UPy dimers work as physical crosslinkers. Compared with traditional chemical crosslinked network, this supramolecular network are much more elastic and processable.In this thesis, we combined the strong dimerizing UPy groups with the low cost, easy synthesis of polyurethane. Two novel diol compounds containing UPy group were synthesized as polyurethane chain extander. UPy groups were introduced into main chain or side chain of the polyurethane through reaction between OH and NCO terminated prepolymer. A series of different UPy contents in polyurethane were synthesized and their properties were studied. Four kinds of polyurethane with UPy groups in the main chain were synthesized using different molecular weight soft segments. Results of TGA testing indicated that UPy groups in the main chain weakened the thermal decomposition resistance of polyurethane. With the molecular weight of soft segments increase, UPy content decreased so that polyurethane had higher thermal decomposition temperature. Endothermic peaks were observed in DSC testing near 60°C because of the melting of urethane group induced aggregation of UPy dimmers. The DMA testing showed the glass transition terperature of these polyurethanes decreased with the increase of molecular weight of soft segments. All the samples showed an typical rubber plateau between 0°C-50°C. The tensile testing showed the breaking strength decreased with the increase of molecular weight of soft segments while breaking elongation increased.A mixture of another synthesized UPy-contained diol and 1,4-butanediol were used to prepare polyurethanes with different UPy side chain contents. Results of TGA testing indicated that earlier decomposition of UPy groups in the side chain to some existent postponed the thermal decomposition of polyurethane main chain. Endothermic peaks were observed in DSC testing near 60°C-70°C because of the melting of ureido group induced aggregation of UPy dimmers. The DMA testing showed the glass transition terperature of these polyurethanes slightly decreased with the increase of UPy side chain contents. The tensile testing showed that with the UPy side chain contents increase, the breaking elongation increased and breaking strength first decreased, then increased after reached a lowest breaking strength.