FUNCTIONALIZED POLY(P-XYLYLENE)S AND CYCLOPENTA-ANNULATED POLYAROMATIC HYDROCARBON MATERIALS

Author

Ain Uddin, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2021

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Plunkett, Kyle

Abstract

A series of donor-acceptor copolymers containing dicyclopenta[cd,jk]pyrene and dicyclopenta[cd,lm]perylene acceptor units were prepared using palladium catalyzed cyclopenta-annulation reactions. Six polymer variants were prepared with diethynyl containing donor groups based on benzo[1,2-b:4,5-b']dithiophene, thieno[3,2-b]thiophene, and 4-octyl-4H-dithieno[3,2-b:2',3'-d]pyrrole. Copolymer with molecular weights (Mn) of 6-14 kDa, having broad light absorption in the visible region with band gaps of 1.38-1.85 eV was successfully synthesized via the cyclopentannulation polymerization strategy. The synthetic methodology to access these copolymers as well as their optoelectronic properties (e.g., thin-film absorption and cyclic voltammetry) are presented.Second, ladder polymers and small molecules based on a s-indaceno[1,2,3-cd:5,6,7-c'd']dipyrene scaffold were prepared using a palladium catalyzed arylation reaction. Three specific small molecules as well as ladder polymers with molecular weight up to 13 kDa were prepared. These rigid, planar polymers possessed energies of -5.39 to -5.23 eV for the highest occupied molecular orbital (HOMO), -2.42 eV to -2.98 eV for the lowest unoccupied molecular orbitals (LUMO) and optical band gaps of 1.68 to 2.03 eV. These polymers were tested in organic field effect transistors with derivatives giving hole mobilities up to 2.5 X 10-5 cm2V-1s-1. Lastly, strategies for the synthesis and post-modification of poly(p-xylylene)s (PPXs) with sidechains containing alkyl bromide functionality is presented. Diimide hydrogenation of poly(p-phenylene vinylene)s (PPVs) (originally synthesized by a Gilch polymerization) was utilized to prepare PPXs. To keep sidechain-containing bromide functionality intact, backbone reduction of the polymer was carried out with hydrazine hydrate in toluene at 80 °C.Using a post-polymer modification, the alkylbromide sidechains of PPX polymers were modified with trimethylamine to form tetraalkylammonium ion functionality and their functionality was evaluated as an anion conducting membrane. The introduction of tetraalkylammonium ions and hydrophobic chains enhanced the film-forming properties and alkaline stability of PPX while PPX homopolymers containing tetralkylammonium ions were completely water-soluble. To remedy these issues, an in situ crosslinking process that used N,N,N',N'-tetramethyl-1,6-hexanediamine during the tetraalkylammonium formation of brominated PPX polymers allowed the formation of films that could be tested for conductivity. Conductivities of ~10 mScm-1 were measured and gradually declined in magnitude over a month of study.