Catalytic polymerization of a cyclic ester derived from a "cool" natural precursor.
(-)-Menthide, a seven-membered lactone derived from the natural product (-)-menthol, was polymerized using a structurally defined zinc-alkoxide catalyst to form an aliphatic polyester. The polymer was fully characterized by NMR spectroscopy, size exclusion chromatography, and matrix-assisted laser desorption ionization mass spectrometry. The polymerization reaction occurred in a controlled fashion and polymer samples with M(n) values up to 90 kg mol(-1) were obtained by varying the catalyst loading. Monitoring of the rate of polymerization by in situ FT-IR spectroscopy (ReactIR) revealed a first order dependence on (-)-menthide. The temperature dependence of the observed rate constant between 30 and 90 degrees C was well described by the Arrhenius equation and gave E(a) = 38.4 +/- 0.9 kJ mol(-1). Thermodynamic parameters (deltaH(p) degrees = -16.8 +/- 1.6 kJ mol(-1), deltaS(p) degrees = -27.4 +/- 4.6 J mol(-1) K(-1)) for the polymerization of (-)-menthide were also determined by measuring the equilibrium monomer concentration at different temperatures ranging from 40 to 100 degrees C. The equilibrium monomer concentrations at 25 and 100 degrees C were calculated to be 0.031 +/- 0.018 and 0.120 +/- 0.063 M, respectively.
Zhang
Donghui
D
Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431, USA.
Hillmyer
Marc A
MA
Tolman
William B
WB
D002384:Catalysis; D002850:Chromatography, Gel; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D011091:Polyesters / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
D011091:Polyesters