Ring polymers are one of the model polymers to understand their physical properties because they have no chain ends in their structures.  Due to the difficulty in preparing pure ring polymers, the properties of ring polymers have not been understood well until quite recently.  Dr. Doi has investigated various properties of pure ring polymers such as chain conformation, miscibility and viscoelasticity, by using small-angle neutron and X-ray scattering (SANS and SAXS) and rheological measurements.  He has also investigated viscoelastic properties of ring polymer derivatives such as tadpole-shaped and dumbbell-shaped polymers, which exhibited unique rheological behavior.

References

 Doi, Y.; Takano, A.; Matsushita, Y. et al. Macromolecules 2015, 48, 3140-3147 & 8667-8674.; 2018, 51, 1539-1548, 1885-1893 & 6836-6847.; Rheol. Acta 2017, 56, 567-581.