Study On Quadruple Hydrogen-Bonding Polytetrahydrofuran Supramolecular Polymer Materials

The growing development of supramolecular chemistry has become an important direction for the development of chemistry in the 21 st century,which has led people to begin to propose new ideas from the development and synthesis of traditional polymers.Since supramolecular systems can form highly ordered functional assemblies,this providing the basis for the preparation of dynamic supramolecular materials.The supramolecular system containing a ureidopyrimidone structure having a quadruple hydrogen bond structure is now a widely used supermolecular system,namely,the well-known UPy system.In this paper,UPy groups were introduced into polytetrahydrofuran(PTMG).Since UPy groups can be dimerized by four hydrogen bonds and polytetrahydrofuran has obvious crystallinity,the purpose of this study was to investigate the effect of UPy groups on the crystallization behavior of PTMG.Polyurethane(PU)with branched UPy groups was synthesized by using PTMG as a soft segment,andits properties were exploredtoo.The main research content of this paper is as follows:1.In this paper,polytetrahydrofuran with different molecular weight was selected to synthesize PTMG supramolecular polymer with UPy group as end group.Through the tensile test,we found that there is no UPy group introduced PTMG having no mechanical properties,and when introduced UPy Group,the sample has better tensile strength and corresponding elongation at break.And as the molecular weight increases,the poorer the mechanical properties.By differential scanning calorimetry(DSC)and X-ray diffraction(XRD)measurements,we found that when introduced UPy groups,the degree of crystallinity of the polytetrahydrofuran segment decreases,It was observed by polarized light microscope that the PTMG was spherulite without the UPy groups,when introduced UPy groups,the morphology of the PTMG was changed to small broken crystals.We obtained a rod-like crystal morphology by melt-crystallization control of polytetrahydrofuran attached to the UPy group.The thermogravimetric analysis(TGA)test showed that the thermal stability of the sample decreased after UPy group was connected.2.We chosed different molecular weights PTMG as the soft segment,and we prepared a diol chain extender containing UPy,which then reacts with thehexamethylene diisocyanate prepolymer of PTMG,so we got a side chain containing UPy polyurethane.DSC test showed that the crystallization temperature of the crystallization increaseswith the increasing of the molecular weight.Through dynamic mechanical analysis(DMA)test TGA test,we discussed the relationship between the molecular weight of the polyurethane containing UPy in the side chain and its glass transition temperature and decomposition temperature.Through the tensile test,the effect of the UPy-containing group in the side chain on the tensile properties of the polyurethane was discussed.