Mechanics and nanovoid nucleation dynamics: effects of polar functionality in glassy polymer networks.

We use molecular simulations and experiments to rationalize the properties of a class of networks based on dicyclopentadiene (DCPD), a polymer with excellent fracture toughness and a high glass transition temperature (Tg), copolymerized with 5-norbornene-2-methanol (NBOH). DCPD is a highly non-polar hydrocarbon, while NBOH contains a hydroxy group, introducing polar functionality and hydrogen bonds (H-bonds). NBOH thus represents a possible route to improve the chemical compatibility of DCPD-based networks with less-hydrophobic materials.

Influence of molecular weight between crosslinks on the mechanical properties of polymers formed via ring-opening metathesis.

The apparent molecular weight between crosslinks (Mc,a) in a polymer network plays a fundamental role in the network mechanical response. We systematically varied Mc,a independent of strong noncovalent bonding by using ring-opening metathesis polymerization (ROMP) to co-polymerize dicyclopentadiene (DCPD) with a chain extender that increases Mc,a or a di-functional crosslinker that decreases Mc,a. We compared the ROMP series quasi-static modulus (E), tensile yield stress (σy), and fracture toughness (KIC and GIC) in the glassy regime with literature data for more polar thermosets.

Long-term release of a thiobenzamide from a backbone functionalized poly(lactic acid).

Hydrogen sulfide is emerging as a critically important molecule in medicine, yet there are few methods for the long-term delivery of molecules that degrade to release HS. In this paper the first long-term release of a thiobenzamide that degrades to release HS is described. A series of polymers were synthesized by the copolymerization of L-lactide and a lactide functionalized with 4-hydroxythiobenzamide.

Retention of palladium and phosphine ligands using nanoporous polydicyclopentadiene thimbles.

Thimbles composed of polydicyclopentadiene retained Pd and phosphines used in Buchwald-Hartwig and Sonogashira coupling reactions but allowed the products to permeate. The products were isolated in high yields on the exteriors of the thimbles with no detectable contamination from phosphine and with Pd loadings as low as < 5.5 ppm.