Tyrosine-PEG-derived poly(ether carbonate)s as new biomaterials. Part II: study of inverse temperature transitions

Tyrosine-poly(alkylene oxide)-derived poly(ether carbonate)s represent a new group of degradable biomaterials that exhibit inverse temperature transitions. Poly(DTE co 70%PEG,1000 carbonate) was chosen as an example to study this special phase transition behavior of the polymers. The observed transition temperature varied slightly depending on the technique used, e.g. CD always gave a lower temperature than UV/Vis. CD and UV/Vis studies indicated that the transition temperature was both heating rate and concentration dependent. Thermodynamic parameters of the transition (enthalpy, entropy, and free energy) were determined by DSC. The molecularity of the transition was 2.6, as calculated from UV and DSC data. The transition temperature could be varied from 18 to 58 degrees C by changing the polymer structure. The new poly(ether carbonate)s may be used in medical applications such as injectable drug delivery formulations and bioresorbable barriers for the prevention of surgical adhesions.