In the morning of February23^rd, Professor Masao Doi from Institute of Theoretical Physics visited the School of Emergent Soft Matter, and gave a colloquium on “Elastic effect on the diffusion of gels and polymer solutions”. Professor Doi is the Chief Scientist of Interdisciplinary Center for Theoretical Study (under the supports of ITP, Oujiang Laboratory, and Wenzhou Institute). He is a foreign member of National Academy of Engineering (USA). Professor Doi is a leading polymer scientist who has worked on many problems in soft matter and made important contributions. He has developed fundamental theories that explain complex dynamical properties of soft matter (polymers, gels, liquid crystals, colloidal solutions, etc.) from microscopic structure of the material.

In his talk, Professor Doi introduced the coupling effect of the diffusion and viscoelasticity in soft matter systems, using the simple polymer gel as an example. He discussed about the swelling dynamics of polymer networks. For spherical gel, the classical theory can explain the dynamics, but it fails to describe the swelling dynamics of gel with other geometries. Using Onsager variational principle, Professor Doi derived a simple model for the swelling of disk-shape gel. For polymer solutions, the inclusion of long-chain polymers leads to the elastic behavior of the solution, especially under extensional flow. His group is focusing on the understanding of soft matter dynamics based on the Onsager variation principle.