Metal-free phenylpropiolate–azide polycycloaddition: efficient synthesis of functional poly(phenyltriazolylcarboxylate)s

Abstract

Cu(I)-mediated and metal-free click polymerizations of azides and terminal alkynes have been developed into powerful techniques for constructing linear and hyperbranched polytriazoles. However, the 1,3-dipolar cycloaddition of azides with internal alkynes is rarely employed as a synthetic tool to prepare functional polymers. In this work, metal-free phenylpropiolate-azide polycycloaddition was developed for efficient synthesis of poly(phenyltriazolylcarboxylate)s (PPTCs), a kind of polyester. The aromatic and aliphatic diphenylpropiolates could readily react with diazides under heating, affording soluble PPTCs with high molecular weights (M_w up to 28 500) in excellent yields (up to 98%). The polymerization is insensitive towards oxygen and moisture, and can proceed smoothly in an open atmosphere. The obtained PPTCs are thermally stable with 5% weight loss temperatures higher than 318 °C. As the polymers contained ester groups, they exhibited fast degradation under basic conditions. The PPTC containing tetraphenylethene moieties shows a unique phenomenon of aggregation-induced emission, and can be employed as a fluorescent chemosensor to sensitively detect explosives. Its thin film can generate two-dimensional fluorescent photopatterns by UV irradiation.