Design, Synthesis And Secondary Structure Of Helical Poly(N-Propargylamides) And Poly(N-Propargylureas)

Helical polymers attract growing interests because of their uniquestructures, properties, and potential applications. Among the synthetic helicalpolymers, polyacetylene derivatives with conjugated main chains andfunctional pendent groups, have gathered much more attention. In thepresent thesis, a series of substituted polyacetylene monomers includingN-propargylamides and N-propargylureas were designed and synthesized. Themonomers' structures were identified by IR and NMR spectroscopies andelement analysis; their melting/boiling points were measured. The monomerswere polymerized in the presence of Rh⁺ catalyst ((nbd)Rh⁺B^-(C₆H₅)₄, (nbd:norbornadiene)). The solubility of the resulting polymers was tested incommon solvent. The secondary structures of the polymers were investigatedby measuring their UV-vis and CD spectra; the polymers' thermal stabilityand cis-structure were studied by TG and ¹H NMR technology, respectively.The different pendent groups in the poly(1-3) side chains placed differenteffects on the stability of the helices adopted by the corresponding polymers.It was concluded that the pendent groups affected largely both the formationof intramolecualr hydrogen bonds formed in the neighboring amide groups form stable helices under the examined conditions. Poly(10) with chiralpendent groups and the copolymers of monomers 9/10 with different ratiosshowed very high optical specific rotation which indicated that they took ahelical structure with a predominantly one handed screw sense. Poly(11-12)could not form helical conformation under the examined condition.