Applications and Nonlinear Mechanical Properties of Thermoreversible Triblock Copolymer Gels.

摘要

Thermoreversible triblock copolymer gels display a wide variation in mechanical behavior over a temperature range that is experimentally accessible. At elevated temperatures these gels behave as freely flowing solutions, exhibiting fast relaxation behavior. The relaxation time increases dramatically as temperature is reduced, such that at room temperature the gels become strong elastic materials.;The nonlinear mechanical properties of triblock copolymer gels are ultimately dependent on the structure of the underlying physically associating network of triblock copolymer molecules and how this structure evolves during deformation and aging. The aim of this research is to characterize the structure-property relationships of triblock copolymer gels utilizing shear rheometry over a wide range of temperature and deformation rates. Behavior of the gels in the nonlinear regime -- i.e., the stress response during deformation to large strain or strain rate -- is of particular interest.;Triblock copolymer gels were successfully applied as model systems for a variety of engineering and biophysical applications. The thermoreversible nature and mechanical strength of the gels was found to be advantageous in a low-temperature casting process for titanium foams of complex shape. The gels were also demonstrated to be excellent synthetic model systems for strain-stiffening biological materials. Additionally, evidence of flow inhomogeneities in the triblock copolymer gels coupled with the well-defined structure of the gels and the wide range of accessible relaxation times makes these gels ideal model systems for future studies of deformation-induced failure in physically associating solutions and complex fluids. The foundation is also being laid for the rheological investigation of two-dimensional layers of self-assembled triblock copolymer molecules with the hope of establishing these physically associating networks as synthetic model systems for biological membranes and thin films.