Synthesis Of Functional Poly(Aroxycarbonyl-Triazole)s By Metal-free Click Polymerization

The development of new polymerization reactions is a constant theme in current polymer chemistry. Most of the new polymerization reactions, if not all, are derived from the established organic reactions.The Cu(Ⅰ)-catalyzed azide-alkyne cycloaddition, i.e. the click reaction, enjoys such advantageous characteristics as high efficiency, atom economy, regioselectivity, and functionality tolerance as well as mild reaction conditions, fast reaction rates and simple product isolation procedures. The click reaction has been actively utilized to synthesize bioconjugates and dendrimers, to decorate surfaces and nanoparticles, and to post-modify preformed polymers. This reaction has also been developed to a polymerization technique for the preparation of linear and hyperbranched polymers. However. it is very difficult to completely remove metallic catalysts after polymerization. The catalyst residues can cause cytotoxicity and deteriorate the photophysical properties of resulting polymers. The development of the metal-free click polymerization process is thus highly desired.In this paper, an efficient metal-free click polymerization of propiolates and azides was developed. Linear and hyperbrached poly(aroxycarbonyltriazole)s (PACTs) with advanced functional properties were prepared by the metal-free click polymerization.We firstly synthesized four aromatic and aliphatic propiolates. The thermally activated click polymerization of propiolates and azides were carried out. The effect of monomer concentration, reaction time and solvent on the yield, molecular weight and regioregularity of the polymer was studied. An optimal polymerization conditions were obtained. It is worthy noting that this polymerization reaction is insensitive to oxygen and moisture and can be carried out in open atmosphere, which further simplify the polymerization. The resulting PACTs could be rapidly degraded in the presence aqueous solution of potassium hydroxide.The metal-free click polymerization of4,4'-isopropylidenediphenyl dipropiolate and tetraphenylethene (TPE)-containing diazides were carried out in a DMF and toluene mixture at100℃for6h. affording PACTs with high molecular weights and regioregularities in high yields. Thanks to the aggregation-induced emission (AIE) feature of contained TPE units, the PACTs are also AIE-active and can serve as fluorescent chemosensors for superamplified detection of explosives.A series of functional PACTs were prepared by the metal-free click polymerization. The resulting PACTs are photo-sensitive and could generate three-dimensional phtotopattern upon UV irradiation. They also show high refractive indices and low optical dispersion, making them promising for photonic applications.Ferrocene-based PACTs with high molecular weights and low polydispersity indices, were synthesized by the metal-free click polymerization of bipropioiates and ferrocene-containing diazides. The ferrocene-based PACTs showed high resistance to thermolysis and electrochemical activity.We attempted the metal-free click polymerization of tripropiolates and diazide, and studied the effect of monomer concentration, reaction time and temperature on the yield, molecular weight and solubility of the polymers. The produced hyperbranched PACTs showed high resistance to thermolysis, high refractive index values and low optical dispersion, and could generate two-dimensional phtotopattern by UV irradiation. Moreover, the PACTs could be rapidly degraded in the presence of potassium hydroxide aqueous solution, showed AIE characteristics and worked as explosive sensors with high sensitivity.