David Dumas

All Publications

• Toughening Poly(lactic acid) without Compromise - Statistical Copolymerization with a Bioderived Bicyclic Lactone. Journal of the American Chemical Society Sanchez, L. A., Woroch, C. P., Dumas, D. M., Waymouth, R. M., Kanan, M. W. 2025

  Abstract

  Poly(lactic acid) (PLA) offers a renewable and degradable alternative to petroleum-based plastic, but its mechanical properties are not ideal for many applications. Herein, we describe the synthesis and polymerization of 2-oxo-3,8-dioxabicyclo[3.2.1]octane (ODO), a bioderived bicyclic lactone, and show that copolymers of l-lactide (LA) with small amounts of ODO have improved mechanical properties over PLA. Homopolymerization of ODO to poly(oxo-3,8-dioxabicyclo[3.2.1]octane) (PODO) is optimized for both solution-phase, organocatalytic and melt-phase, metal-catalyzed conditions. In comparison to the monocyclic analog, ε-caprolactone (CL), ODO has a lower enthalpy of polymerization and faster rate of polymerization. PODO is an amorphous, elastomeric polyester that has a Tg 90 °C higher than poly(ε-caprolactone) (PCL). Statistical copolymerization of LA with small fractions of ODO yields tough and transparent thermoplastics that have over 12× elongation at break compared to native PLA, while maintaining Tg, Young's modulus (E), and yield strength. Together, these results describe how the incorporation of the tetrahydrofuran ring alters lactone polymerizability and the thermomechanical properties of the homopolymer and copolymer materials.

  View details for DOI 10.1021/jacs.4c15697

  View details for PubMedID 39874214

• Ring-Opening Polymerization of Cyclic Esters and Carbonates with (Thio)urea/Cyclopropenimine Organocatalytic Systems. ACS macro letters Morodo, R., Dumas, D. M., Zhang, J., Lui, K. H., Hurst, P. J., Bosio, R., Campos, L. M., Park, N. H., Waymouth, R. M., Hedrick, J. L. 2024: 181-188

  Abstract

  Organocatalyzed ring-opening polymerization is a powerful tool for the synthesis of a variety of functional, readily degradable polyesters and polycarbonates. We report the use of (thio)ureas in combination with cyclopropenimine bases as a unique catalyst for the polymerization of cyclic esters and carbonates with a large span of reactivities. Methodologies of exceptionally effective and selective cocatalyst combinations were devised to produce polyesters and polycarbonates with narrow dispersities (D = 1.01-1.10). Correlations of the pKa of the various ureas and cyclopropenimine bases revealed the critical importance of matching the pKa of the two cocatalysts to achieve the most efficient polymerization conditions. It was found that promoting strong H-bonding interactions with a noncompetitive organic solvent, such as CH2Cl2, enabled greatly increased polymerization rates. The stereoselective polymerization of rac-lactide afforded stereoblock poly(lactides) that crystallize as stereocomplexes, as confirmed by wide-angle X-ray scattering.

  View details for DOI 10.1021/acsmacrolett.3c00716

  View details for PubMedID 38252690