Synthesis and characterization of biodegradable poly(ϵ-caprolactone urethane)s. I. Effect of the polyol molecular weight, catalyst, and chain extender on the molecular and physical characteristics

Biodegradable polyurethanes with potential for applications in medical implants were synthesized in bulk with aliphatic hexamethylene diisocyanate, isophorone diisocyanate, poly(ϵ‐caprolactone) diols of various molecular weights, 1,4‐butane diol, 2‐amino‐1‐butanol, thiodiethylene diol, and 2‐mercaptoethyl ether chain extenders. The catalysts used were stannous octoate, dibutyltin dilaurate, ferric acetyl acetonate, magnesium methoxide, zinc octoate, and manganese 2‐ethyl hexanoate. The synthesis reactions were second‐order. All the materials had narrow, unimodal molecular weight distributions and polydispersity indices of 1.5–1.9. The chemical structures of the polyurethanes, as assessed from 1H NMR and 13C NMR spectra, were in good agreement with the monomer stoichiometric ratios. The glass‐transition temperatures of the materials ranged from −38 to −57 °C and were higher for polymers based on isophorone diisocyanate and with higher hard‐segment contents. For polyurethanes with the same hard‐segment content, there was no effect of the material molecular weight on the thermal properties. The tensile strengths of the materials were 12–63 MPa, and the tensile moduli were 8–107 MPa. These increased with an increasing hard‐segment content. The least effective catalyst was magnesium methoxide, and the most effective was ferric acetyl acetonate. Stannous octoate and manganese 2‐ethyl hexanoate were less effective than dibutyltin dilaurate and zinc octoate. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 156–170, 2002 Biodegradable polyurethanes with potential for applications in medical implants were synthesized with aliphatic hexamethylene and/or isophorone diisocyanate, poly(ϵ‐caprolactone) diols, various chain extenders, and the catalysts stannous octoate, dibutyltin dilaurate, ferric acetyl acetonate, magnesium methoxide, zinc octoate, and manganese 2‐ethyl hexanoate. The materials had the assumed chemical structures, polydispersity indices ranging from 1.5 to 1.9, and glass‐transition temperatures ranging from −38 to −57 °C. The tensile strengths and tensile moduli of the materials were 12–63 and 8–107 MPa, respectively. The least effective catalyst was magnesium methoxide, and the most effective was ferric acetyl acetonate.