The goal of this study is to better understand the thermal characteristics and molecular behavior of two poly(desaminotyrosyl arylates). These two polymers were chosen from a combinatorial library of polymers developed by changing the type and size of the two substitutable chain locations. TGA, DSC and TSC studies were conducted on Poly(12,10) and Poly(2,2) after the samples were exposed to various conditions. The TGA of Poly(12,10) shows low water uptake at 25° C, higher water uptake at 80°C. Water uptake for Poly(2,2) at 25°C is similar to Poly(12,10) at 80°C. The Thermally Stimulated Current analysis (TSC) results indicate a molecular mobile region for Poly(2,2) at 80°C and for Poly(12,10) at 40°C. An additional mobile region at 60°C for Poly(12,10) fibers is observed. DSC and TSC studies suggest that Poly(12,10) has two distinct modes of organization with a transition between these modes at about 60°C. The mode above 60°C has the higher water uptake than the mode below 60°C. Annealing at 70°C for 20 hours favors the high temperature mode. At room temperature, the material will relax to the low temperature mode. Previously published results indicate that these two modes of noncrystalline organization represent two different modes of hydrogen bonding.