Synthesis and characterization of dendronized side chain liquid crystalline Poly(2-oxazoline)s towards biomimetic ion channels

Abstract

The polymerization of dendronized monomers is an attractive option to synthesize liquid crystalline columnar polymers with side chain dendrons. Following this approach, we report for the first time in the present study the synthesis of a family of side chain liquid crystalline (SCLC) poly(2-oxazoline)s, poly(2-(3,4,5-tris(4-dodecyloxybenzyloxy)phenyl)-2-oxazoline) (PTOx) from its oxazoline monomer precursor, 2-(3,4,5-tris(4-dodecyloxybenzyloxy)phenyl)-4,5-dihydro-1,3-oxazole) (TAPOx), by cationic ring-opening polymerization (CROP). The optimisation of the reaction parameters (temperature, type of initiator, terminating agent, solvent and monomer concentration), combined with the nature of the CROP allowed us to obtain high molecular weight SCLC poly(2-oxazoline)s. NMR investigations were consistent with the targeted molecular weights of the synthesized PTOx and the living nature of TAPOx polymerization. Regarding the mesomorphic characterization, all synthesized acyl-substituted poly(ethyleneimine)s exhibited liquid crystalline mesophases in a broad temperature range. XRD studies demonstrated that these dendronized poly(2-oxazoline)s self-assemble into columnar structures. Mesomorphic and thermal properties suggest that these family of poly(2-oxazoline)s could be excellent candidates to build up membranes for proton transport applications.