Cyclic polymers possess unique properties compared to their linear counterparts, such as smaller hydrodynamic volumes, lower intrinsic viscosities and higher glass transition temperatures, due to the fact that they have reduced sizes, restricted conformational flexibility and lack of chain ends. Several cyclic versions of commercial polymers were synthesized with our reported tungsten catalyst supported by a tetraanionic pincer ligand. Their cyclic topologies were confirmed by size-exclusion chromatography, viscometry and rheology analysis. Cyclic poly(4-methyl-1-pentyne) (PMPY) was synthesized. Upon hydrogenation cyclic poly(4-methyl-1-pentene) (PMP) was afforded. Linear PMP has high optical transparency, relatively high thermal stability and chemical resistance. The cyclic PMP showed high transparency in the 300 nm to 800 nm region of the visible spectrum. A 10 °C increase in glass transition temperature was observed for cyclic PMP versus linear amorphous PMP. Cyclic poly(1-pentene) was also synthesized on a 10-gram scale by polymerization of 1-pentyne and hydrogenation. Also, cyclic poly(p-methoxylphenylacetylene) was made and converted to cyclic poly (p-hydroxylphenylacetylene) via demethylation using boron tribromide. The resulting polymer was found to be soluble in basic aqueous solution and its solubility was pH responsive. The successful synthesis of these cyclic polymers provides a new opportunity to further study and ultimately utilize cyclic polymers.

Catalytic synthesis and post-polymerization modification of cyclic polyalkynes

256th National Meeting (2018)

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