Conductivity and high-temperature relaxation of tyrosine-derived polyarylates measured with thermal stimulated currents

Abstract

Thermal‐stimulated polarization and depolarization experiments without blocking electrodes are performed on tyrosine‐derived polyarylates with different backbone lengths. The experiments on the different samples are carried out using the same thermal history throughout the entire characterization process. The high‐temperature current rise caused by the conductivity of the samples is studied with a simple model that utilizes an approximation of the Williams–Landel–Ferry (WLF) relaxation time. The conductivity data is well reproduced except for temperatures well below the glass‐transition temperature and for small currents. The glass‐transition peak is modeled with a phenomenological expression valid near Tg, which is able to describe the glass relaxation with a minimum number of parameters. The conduction and the glass‐transition relaxation are studied versus the structural changes for the different samples. It is found that the conductivity and the glass‐transition temperature shift to lower temperatures as the methylene groups in the backbone increase. Furthermore, if the experimental data is presented as a function of the reduced temperature, the shape of the glass‐transition relaxation for the different samples is independent of the polymer backbone length. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3504–3511, 1999

Thin Film Elastic Modulus of Degradable Tyrosine-Derived Polycarbonate Biomaterials and Their Blends

“…Also present in the spectra are the composition dependent broad β-relaxations of the tyrosine derived polycarbonates p(DTR carbonate), where R denotes an alkyl substituent in the ester position. The relaxation behavior of p(DTR carbonates) is well-documented and the molecular relaxation mechanisms of the tyrosine-derived polycarbonates were investigated previously by measuring thermally stimulated depolarization currents (TSDC) as a function of temperature. − These relaxation mechanisms contribute significantly to the mechanical properties of polycarbonates especially in the thin film regime where the polymer chains exhibit strong intersegment interactions coupled with secondary relaxation behavior. The implication of the relaxation behavior will be described further in the discussion section.…”

Synthesis, characterization, and degradation of a novel L‐tyrosine‐derived polycarbonate for potential biomaterial applications

“…Since Kohn and Langer1 presented a new group of potential implant biomaterials, pseudo‐poly(amino acid)s, in which the functional groups on the amino acid were used to link individual amino acids or dipeptides via nonamide bonds in 1984, L ‐tyrosine‐based pseudo‐poly(amino acid)s have been extensively researched 2, 3. Kohn and Bourke developed a library of diphenolic monomers based on L ‐tyrosine and corresponding polyiminocarbonates,4, 5 polycarbonates,1 , 6–9 and polyarylates 10, 11. All of the L ‐tyrosine‐based polymers possess nonamide linkages alternating with amide linkages in the backbone and, hence, are named pseudo‐poly(amino acid)s. The introduction of the nonamide linkages has been found to provide a way for improving the engineering properties of such polymers, such as solubility in common organic solvents, hydrolytic degradability, and thermal mold ability 12.…”