Synthesis of Nano-Structured Conjugated Polymers with Multiple Micro-/Meso-Pores by the Post-Crosslinking of End-Functionalized Hyperbranched Conjugated Polymers.

A nano-structured conjugated polymer with multiple micro-/meso-pores was synthesized by post-crosslinking of an end-functionalized hyperbranched conjugated prepolymer. Firstly, an AB monomer 3-((3,5-dibromo-4-(octyloxy)phenyl)ethynyl)-6-ethynyl-9-octyl-9H-carbazole (PECz) was synthesized and polymerized by Sonogashira reaction to give the -Br end-functionalized hyperbranched conjugated prepolymer -PPECz. The photophysical and electrochemical properties of -PPECz were investigated. The λ of absorption and emission of -PPECz in tetrahydrofuran (THF) solution was 313 and 483 nm, respectively. The optical energy bandgap, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) energy levels of -PPECz were 2.98, -5.81, and -2.83 eV, respectively. Then, the prepolymer -PPECz was post-crosslinked by Heck reaction with divinylbenzene to give the porous conjugated polymer -PPECz. The effects of -PPECz concentration and added dispersant polyvinylpyrrolidone (PVP K-30) on the morphology and porosity of -PPECz were investigated. The resulting -PPECzs showed multiple porous structures mainly constructed by micropores and mesopores. Under a higher -PPECz concentration (4 wt/v%), a bulky gel product was obtained. Under lower -PPECz concentrations (0.6 wt/v%~2 wt/v%), the resulting -PPECzs were mainly composed of nano-sized particles. Nearly spheric nanoparticles (200~300 nm) (-PPECz-5) were obtained under the concentration of 1 wt/v% in the presence of PVP (10 wt% of -PPECz). The Brunauer-Emmett-Teller (BET) surface area, pore volume, average pore size, and percentage of pore size below 10 nm of -PPECz-5 were 10.7781 m·g, 0.0108 cm·g, 4.0081 nm, and 94.47%, respectively.