Ene Click Chemistry Research Articles

A Simple Route to Functional Highly Branched Structures: RAFT Homopolymerization of Divinylbenzene

This work reports on a facile approach to the synthesis of highly branched polymers by the homopolymerization of commercially available divinyl benzene (DVB) via reversible addition−fragmentation chain transfer (RAFT) polymerization. The presence of RAFT agents allows conversions as high as 68% before cross-linking, instead of 15% for conventional free radical polymerization (FRP). The study extends this new approach by synthesizing starlike block copolymers of methyl acrylate (MA) and DVB by exploiting the living characteristic offered by RAFT polymerization. The resulting highly branched DVB polymers are used to produce in situ cross-linked polymeric particles following thermal stimuli. In addition, we exploit the large number of residual double bonds in the highly branched p(DVB) to further functionalize the polymer via thiol−ene click chemistry.

Hairy Hollow Microspheres of Fluorescent Shell and Temperature-Responsive Brushes via Combined Distillation-Precipitation Polymerization and Thiol−ene Click Chemistry

Nearly monodispersed silica core−poly(N-vinylcarbazole) shell (SiO2@PVK) microspheres of 226, 235, and 244 nm in average diameters were first synthesized by surface-initiated distillation-precipitation polymerization of N-vinylcarbazole, in the presence of divinylbenzene, from the 197 nm silica template microspheres prepared by the sol−gel reaction of tetraethyl orthosilicate (TEOS) and 3-(trimethoxysilyl)propyl methacrylate (MPS). The SiO2@PVK−PNIPAM core−shell hairy microspheres (PNIPAM = poly(N-isopropylacrylamide)) were subsequently prepared by grafting the PNIPAM chains (Mn = 11 600 g/mol, polydispersity index =1.32), prepared a priori by reversible addition−fragmentation chain transfer (RAFT) polymerization, to the SiO2@PVK microspheres via the thiol−ene click chemistry. The grafting density of PNIPAM brushes on the SiO2@PVK microspheres was about 0.1 chains/nm2. Hairy hollow microspheres with a fluorescent and cross-linked PVK shell and temperature-responsive PNIPAM brushes were finally obtained, after selective removal of the inorganic silica core from the SiO2@PVK−PNIPAM microspheres by HF etching. The air@PVK−PNIPAM hairy hollow microspheres were characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), fluorescence spectroscopy, and dynamic laser scattering (DLS).