Phase Behavior and Microscopic Dynamics of a Thermosensitive Gel-Forming Polymer

Soft adaptive networks like polymer gels are almost ideal candidates as surrogates for the extracellular matrix, more so when their rheo-mechanical properties can be carefully tuned by temperature. Using both dynamic light scattering and photon correlation imaging, we have investigated the phase behavior and the microscopic dynamics of a thermoresponsive network, Mebiol Gel, extensively and effectively used as a three-dimensional scaffold for cell growth. In the dilute limit, Mebiol displays a temperature-driven association process characterized by a significant increase of the molecular weight, which is not accompanied, however, by a concurrent increase of the aggregate size. This peculiar behavior is consistent with numerical simulations of a simpler but structurally homologous block-copolymer system. By increasing concentration and approaching gelation, the polymer solution progressively attains the structure of a percolating network, as witnessed by the logarithmic decay of the intensity correlation functions extending over many time decades, a relaxation behavior that is found well within the gel phase too. No evidence of a discontinuous transition to a fully arrested gel phase is, however, detectable in the microscopic dynamics.