The ability to synthesize polymers with various architectures enables properties to be tailored for numerous product applications. Polymer macrocycles, also known as ring polymers or circular polymers, have been attracting attention due to their possible unique properties because of the lack of chain ends. This feature may ultimately benefit tire technology by reducing rolling resistance and wear, without sacrificing traction. Two important contributions to rolling resistance are the Payne effect (filler interaction) and energy dissipation due to thermal motion of chain ends, which do not exist in ring polymers. However, synthesizing pure rings in large sample sizes has been difficult, which has limited a thorough analysis of polymer properties. A green chemistry method developed by Puskas and Rosenthal-Kim, known as Reversible Radical Recombination Polymerization (R3P), has produced the following high molecular weight, highly pure ring polymers in multigram quantities: poly(3,6-dioxa-1,8-octanedithiol) (poly(DODT)) and polyisobutylene-disulfide (PIB-SS). In further research, dithiothreitol (DTT) degraded the PIB-SS to a mixture of pentamer-to-dimer PIB-dithiols, creating a biodegradable PIB. More recently, the Puskas Lab has developed a technique using Liquid Chromatography at Critical Conditions (LCCC) to determine if the poly(DODT) and PIB-SS samples contain linear polymer contaminants. Collaborators at Texas Tech University are evaluating the rheological properties of poly(DODT) and PIB-SS, and CalTech will evaluate these polymers further using X-ray Photoelectron Spectroscopy. Current results on these unique polymers will be presented.