Solvophobically-Driven Folding of Non-Biological Oligomers and the Solid Phase Synthesis of Phenylacetylene Oligomers

The ordered sequence of monomers in phenylacetylene oligomers can serve as a repeating motif to produce helical structures in solution which posses a tubular cavity. Calculations with modest size oligomers show stable helical conformations with as few as 8 monomer units. Oligomers with triglyme monomethyl ether benzoate functionalized monomers (R = -COO(CH$\rm\sb2CH\sb2O)\sb3CH\sb3)$ reveal dramatic chain-length-dependent aromatic chemical shifting in CD$\sb3$CN, indicative of aromatic stacking and helical structure. In addition. when chain length reaches 12 monomer units, oligomers begin to strongly aggregate which may be a result of helical oligomers associating like their corresponding macrocycles in a face-to-face parallel fashion. Chain length dependence of UV/Vis and $\sp1$H NMR spectra provide strong evidence of the ordering of monomers and intramolecular aromatic stacking which is consistent with the formation of helical structures. Using UV/Vis absorption at 303 nm as an indication of helical structure, reversible thermal helix-coil transitions were measured in 4/6, $\rm CH\sb3CN/CHCl\sb3.$ In agreement with the calculations, the octadecamer possesses the largest shift in \rmδ\sb{A}, the best resolved $\sp1$H NMR spectra of the oligomers longer than 12 monomers, and the largest hypochromic shift at 303 nm which is attributed to intramolecular aromatic stacking.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Nelson, James Curtis

Contributors dc:contributor

• Moore, Jeffrey S.

• Chemistry, Polymer

Language dc:language

eng

Identifier

(MiAaPQ)AAI9812719

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/84387