Development Of Novel Thiol-Yne Click Polymerization

Thiol-yne click polymerization, which was developed in 2009, is a new type of click polymerization. Due to the advantages of simple operation, mild condition, and high efficiency, thiol-yne click polymerization is drawing more and more attention from polymer chemists. Up to now, it has been widely applied in preparation of polythioethers (PTEs) with different topological structures and functions.For the thiol-yne click polymerization, the UV or heat external stimuli are generally required. However, UV light may cause serious injury to researchers and high temperature is not eco-friendly. On the other hand, transition metal catalyzed thiol-yne click polymerization can be proceeded at room temperature with excellent chemical selectivity. But the inevitable problem of metal residual in the products may limit their applications in optoelectronic and biological fields. Organic base catalyzed thiol-yne click polymerization is a kind of metal-free polymerization, yet has a strong restrict for the monomer varieties. Therefore, it is of vital importance to develop an alternatively facile and powerful thiol-yne click polymerization.In this thesis, a spontaneous thiol-yne click polymerization was developed and linear and hyperbrached poly(vinylene sulfide)s (PVSs) with advanced functions were prepared.Firstly, aromatic diynes were synthesized and polymerized with dithiol monomers under a catalyst-free condition. The results indicate that PVSs with high weight-average molecular weights (Mw up to 85.2 kDa) can be obtained in high yields of 97% by simply mixing the aromatic diynes and dithiols with equivalent molar ratio in THF at room temperature for 2h. Such a spontaneous polymerization not only simplifies the operation, but also is free from expensive metal catalysts. Moreover, the polymerization was confirmed to be a free radical process. Using this spontaneous polymerization technique, a series of PVSs with good solubility, thermal stability, film forming ability, and high refractive index were prepared. By incorporating the tetraphenylethene (TPE) unit, an aggregation-induced emission (AIE) PVS was prepared.Secondly, multi-functional hyperbranched PVSs (hb-PVSs) were synthesized via the spontaneous thiol-yne click polymerization. The polymerization conditions including monomer mole ratio were optimized in order to overcome the notorious gelation. Afterward, hb-PVSs with high absolute Mw and good solubility were obtained. The 10-80 times higher absolute molecular weights of hb-PVSs than that the relative values suggest hb-PVSs possess highly branched structures. By introduction of TPE units,hb-PVS with the aggregation-enhanced emission (AEE) property was obtained, which nanoparticles could be used to superamplified detect explosives. Furthermore, all these hb-PVSs could be facilely post-functionalized by alkyne-based click reactions due to the large amount of unreacted ethynyl groups on their peripheries.Finally, the post-functionalization of a linear PVS was investigated. By oxidation reaction, most of the sulfur atoms in PVS were transformed into sulfone groups. Thanks to the electron withdrawing feature of sulfones, the vinyl groups in newly synthesized poly(vinylene sulfone)s (PVSO) were activated and ready for Michael additions. Thus, a facile and efficient post-functionalization method of linear PVS was established. With this methodology, a polymer with 86% grafting ratio and a water soluble fluorescent polyelectrolyte were prepared. It is noteworthy that the quantum yield of a fluorescent PVS can be remarkably enhanced after the oxidation. Moreover, the refractive index of this PVS decreased gradually with the consecutive oxidation, which provides a feasible strategy for fine-tuning refractive index of PVSs.