Studies On Synthesis And Properties Of Polymers Containing Pillararenes As The Pendent Groups

Supramolecular polymers, as the perfect products of the combination of polymer science and supramolecular chemistry, not only possess the inherent properties involving optical, electrical, thermal and mechanical properties, but also exhibit dynamic reversibility and stimuli responsiveness to environment, due to their noncovalent bonds. Therefore, they can be used as smart materials with excellent properties. However, researches about supramolecular polymers mainly concerned small molecules, while supramolecular polymers constructed by polymers are rarely reported. As is well known, polymers posses some advantages such as high strength and good stability. Therefore, it is significative to construct supramolecular polymers which exhibit both the advantages of polymers and the properties of supramolecular chemistry. Recently, pillararene has been a new generation of host molecules because of its highly symmetric structure, easy modification and complexation with various guest molecules. However, little researches on supramolecular polymers constructed by pillararene-containing polymers were rarely reported. This dissertation mainly involved the synthesis of copolymers with pillararenes as the pendent groups and the studies of the effect of host-guest complexation on the thermal properties. It was composed of three chapters. In the first chapter, the construction of supramolecular polymers and the host-guest chemistry were introduced.In the second chapter, we have successfully developed a facile method to synthesize pillar[5]arene monomer with polymerizable group, which was further applied to obtain a copolymer with pillar[5]arenes as the pendant groups by free radical polymerization. Moreover, a supramolecular polymer gel based on the pyridinium-pillar[5]arene motif was fabricated by selecting a bifunctionalized guest G, and the mechanism of gel formation was explored. Based on the competition of host-guest interaction, such gel could be transformed to sol by addition of competitive host(ethyoxyl pillar[5]arene EtP5A) or guest molecules (butanedinitrile). NMR spectroscopy, dynamic light scattering and rheology characterizations prove that the interaction between pillararene and bi-functioned guest molecule was destroyed. Meanwhile, upon heating, such supramolecular gel was also transformed into sol as a result of the damage of π-π stacking of pillararenes, which was demonstrated by X-ray diffraction. Therefore, we proposed that the complexation between pillararene and bifunctionalized guest as well as the ordered stacking were indispensable to construct this supramolecular gel.In the third chapter, a series of polymers containing different content of pillararenes were synthesized, of which the composition and molecular weight were confirmed by’H NMR spectrum and gel permeation chromatography. Besides, the interaction between pillararenes on the side chain of polymer and guest molecules was investigated by 1H NMR, and the effects of host-guest complexation on the thermal properties were studied by means of thermogravimetric analysis(TGA), and differential scanning calorimetry (DSC). Introducing pillararenes into the chain of PMMA could decrease the glass transition temperature (Tg) and increase the decomposition temperature (Td). What’s more, the Tg could decrease and Td increase more with more pillararene on the side chain. When mixing guest G with polymers containing P5A, we also found the Tg also increased along with more pillararenes, and Td decreased due to the weak interaction of host-guest complexation. All these phenomenons indicated that the thermal properties of polymer could be tuned by introducing pillararenes and host-guest complexation, which provide reference to expand the application of pillararenes in the field of polymer.