Date of Award
Doctor of Philosophy (PhD)
Michael B. Sponsler
Bruce S. Hudson
Inclusion compounds, Polyacetylene
Physical Sciences and Mathematics
The creation of isolated, oriented and insulated polyacetylene (PA) chains was assisted by utilizing the favorable features of self assembling inclusion compounds to form inclusion complexes (IC). Calculations suggesting that conducting or even superconducting behavior is anticipated for a one-dimensional, "infinite", isolated PA chain led to the desire to experimentally synthesize this polymer in a manner consistent with the model underlying the theoretical treatment. A two-pronged approach was taken to accomplish this objective. The first method proposed was to isolate a small molecule PA precursor, with terminal end groups that are favorable to cleavage with UV irradiation, in an IC. The small molecule chosen was (E,E)-1,4-diiodo-1,3-butadiene (DIBD) due to the easy cleavage of C-I bonds and stereochemically pure synthesis. Once isolated in an IC, UV-light was used to polymerize the monomer unit. The second method proposed was to simultaneously grow PA while it was encapsulated by an IC. This was attempted by utilizing olefin metathesis with the Grubbs group of catalysts to grow the polymer in a solution containing the desired host molecule. As the polymer forms the host molecule should encapsulate the polymer.
The small molecule inclusion method produced DIBD UICs with three different formation techniques: slow evaporation, slow cooling, and vapor transfer. All crystals formed had the same unit cell, which suggests that the same crystal structure was formed by all methods. These crystals were irradiated with 254 or 532 nm light, and the resulting photoproducts in the UICs were probed by Raman spectroscopy. These results showed that both irradiation wavelengths converted the isolated monomer to PA. This conversion was observed to occur selectively at the surface of the crystal when 254 nm light was used, likely due to strong absorption of the 254 nm radiation by the DIBD monomer in the crystal. The 532 nm sample showed deeper penetration into the DIBD UIC. This deeper penetration resulted in a higher amount of DIBD converted to PA in the UIC versus the use of 254 nm light. This is important because to have complete conversion within the UIC light will need to penetrate completely through the crystal.
The simultaneous inclusion and polymerization method was attempted with both urea and tris(o-phenylenedioxy)cyclotriphosphazene (TPP) to form ICs. Possible PA ICs resulted from the work with TPP and was consistent with PA inclusion. Melting point was the first characterization technique attempted with the possible ICs but the data was very inconclusive. FT-IR was the second characterization technique attempted, the data showed a change in the vibrations associated with PA, suggesting something was different about the material formed in this manner versus the unrestricted bulk polymer. X-ray data was then taken of the material which appeared to indicate a hexagonal host lattice with a possible disordered guest present within it.
The potential uses for this material are mostly in the electronics industry. Conductive polymers are most useful in OLED TVs, Li-polymer batteries, and thin film solar cell application. If these PA ICs show strong conductive behavior the main use for them would be as batteries or in molecular circuits. If superconducting behavior is observed then it could fundamentally shift our understanding of conducting polymers. This would represent a huge leap forward in organic molecular electronics research. This PA research could also lend insight into graphene or carbon nanotubes since these two materials are heavily studied for their desirable properties but face many similar synthetic challenges.
Lashua, Amanda F., "Isolation of polyacetylene: Exploring the properties of isolated, oriented, and insulated polyacetylene utilizing inclusion crystal chemistry" (2014). Dissertations - ALL. 58.