Functional Polyacetylenes Carrying Mesogenic and Polynuclear Aromatic Pendants: Polymer Synthesis, Hybridization with Carbon Nanotubes, Liquid Crystallinity, Light Emission, and Electrical Conductivity

Multifunctional polyacetylenes and their nanohybrids with liquid crystallinity, light emission, and electrical conductivity are developed in this work. New acetylene monomers containing biphenyl mesogens and polynuclear chromophores, namely 4-[3-(1-pyrenyl)propylcarbonyloxy]-4'-biphenylyl 11-(4-ethynylphenoxy)undecanoate (1), 4-[3-(1-pyrenyl)propylcarbonyloxy]-4'-biphenylyl 10-undecynoate (2), and (9-fluorenyl)methyl-4-[(9-decynyl)-carbonyloxy]-4'-biphenylyloxycarbonylmethyl carbamate (3), were synthesized and transformed to their corresponding polymers (P1-P3) by the polymerization reactions catalyzed by organorhodium complexes of Rh+(nbd)[C6H5B-(C6H5)(3)] and [Rh(diene)Cl](2). Whereas none of the monomers were mesomorphic, P1 and P2 were liquid crystalline. The pyrene pendants enabled P1 and P2 to function as dispersants for short (s)- and long (l)-multiwalled carbon nanotubes (MWNTs). P1 assisted the dissolution of s- and l-MWNTs in THF, with respective solubilities as high as 723 and 625 mg/L. The resultant P1/l-MWNT hybrid maintained the smectic mesomorphism of P1 and emitted bluish-green light in THF upon photoexcitation. The hybrid solid readily redissolved in common organic solvents and formed solid films upon solution casting. The hybrid films showed high electrical conductivity. This work demonstrates that polyacetylenes with multiple functionalities can be generated by attaching appropriate functional pendants to the conjugated polyene backbones.