Kiesewetter, Matthew, K
Ring-opening polymerization; organocatalysis; caprolactone; ROP; monomer; polymer
Polymers are defined as large molecules constructed from small, repeating units (monomers) which make up everyday items, such as: plastic bags and bottles, waterproof coatings, pipes, etc. H-bonding urea (U) or thiourea (TU) catalysts paired with base cocatalysts used for organocatalytic ring-opening polymerization (ROP) of cyclic esters have been shown to exhibit fast rates of polymerization and result in polymers with controlled molecular weights (Mn) and low polydispersity indexes (PDI). Additionally, organocatalytic ring-opening polymerization (ROP) techniques have been shown to be tolerant of the incorporation of functional groups into the monomer feed, which is vital for the catalytic synthesis of biologically active polymers. H-bonding catalysts have seen considerable gains in the field of ROP recently, delivering fast reaction rates to rival that seen in metal-based catalysts but with enhanced control of Mn, PDI and functional group incorporation. Variation of the substituent position on the monomer allows for optimization of the material properties, such as: solubility, polarity, thermal, and mechanical. This research investigated the kinetics of H-bonding organic catalysts for the ROP of the functionalized monomers of interest (5-MeCL, 6-MeCL, and TOSUO). Until this point, these new monomers have only been polymerized to approximately 7% conversion after 8 days with a commonly used guanidine base organocatalyst for ROP. Using the dual H-bonding catalysts, whose electronics can be modified, along with different commercially available bases, provides a more tunable approach for the ROP of functionalized lactones.