Self-healing hyperbranched polytriazoles prepared by metal-free click polymerization of propiolate and azide monomers

The last decade has witnessed the quick develop of self-healing materials. As a newborn strategy, the alternative of irreversible covalent bond formation is, however, to be further developed. In this paper, self-healing hyperbranched poly(aroxycarbonyltriazole)based on such mechanism were prepared by our developed metal-free click polymerization of simplified dipropiolate and triazide. Thanks to their excellent processability and film-forming ability, high quality homogeneous films free from defects were obtained by casting. The cut films could be healed by stacking or pressing the halves together at room temperature and elevated temperature. Thus, this design concept for self-healing materials should be generally applicable to other hyperbranched polymers with reactive groups on their peripheries.

Study on Preparation and Properties of Polyether Polytriazole Elastomers

To explore the application of click chemistry in the field of elastomer materials, propargyl-terminated ethylene oxide-tetrahydrofuran copolymer （PTP（E-co-T）） was prepared from hydroxyl-terminated ethylene oxide-tetrahydrofuran copolymer （P（E-co-T）） by end-etherisation modification. FTIR and ^13C-NMR results indicate that P（E-co-T）-terminated hydroxyl was etherified thoroughly, yielding the target product PTP（E-co-T）, and the content of terminated alkynyl of PTP（E-co-T） was evaluated to be 0.428 mmol.g^-l. Using a polyazide compound as a cross-linker, polytriazole elastomers with various functional molar ratio （R） values were prepared from PTP（E-co-T） by virtue of the CuAAC reaction. Mechanical property tests indicate that with the increase in R, the modulus E and stress Orb of the polytriazole elastomers first increase and subsequently decrease, whereas the strain first decreases and later increases. The mechanical properties of the polytriazole elastomers show a parabolic dependence on the R value. Near the stoichiometric ratio, E and Orb show maxima and the strain εb shows a minimum. Swelling tests demonstrate that the apparent molecular weight of polytriazole elastomer strands also first decreases and subsequently increases. At the stoichiometric ratio, the network structure possesses strands with a minimum apparent molecular weight and a maximum apparent density. Dynamic mechanical analysis reveals that the polytriazole elastomers presented damping peaks at approximately -64℃, corresponding to the glass transition of copolyether strands, and the elastomer exhibited the lowest dissipation factor tanδ at the stoichiometric ratio. Thermal analysis suggests that the weight-loss process of the polytriazole elastomer is characteristic of one-step decomposition, and the elastomer begins to decompose from polyether strands, not triazole groups.

AZIDE-ALKYNE CLICK POLYMERIZATION:AN UPDATE

The great achievements of click chemistry have encouraged polymer scientists to use this reaction in their field. This review assembles an update of the advances of using azide-alkyne click polymerization to prepare functional polytriazoles（PTAs） with linear and hyperbranched structures.The Cu（I）-mediated click polymerization furnishes 1,4-regioregular PTAs,whereas,the metal-free click polymerization of propiolates and azides produces PTAs with 1,4-regioisomer contents up to 90%.The PTAs display advanced functions,such as aggregation-induced emission,thermal stability,biocompatibility and optical nonlinearity.

An air-stable supported Cu(?) catalyst for azide-alkyne click polymerization

An air-stable supported Cu(I) catalyst, Cu I@PS-Phen, was designed and synthesized. Cu I@PS-Phen can efficiently catalyze the click polymerization of diynes a and diazides b to produce soluble and thermally stable polytriazoles with high molecular weights(Mw up to 30800), and low copper residue content(down to 190 ppm) in high yields(up to 94.2%) under mild reaction conditions without the exclusion of oxygen.