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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 oxo-3,8-dioxabicyclo[3.2.1]octane (ODO), a bio-derived 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 90 °C higher Tg 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 polymerizability and the thermomechanical properties of the homopolymer and copolymer materials. 

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 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 dispersity (Đ = 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 accelerated polymerization rates. The stereoselective polymerization of rac-lactide afforded stereoblock poly(lactides) that crystallize as stereocomplexes, as confirmed by wide-angle x-ray scattering. 

Compartmentalization is a viable approach for ensuring the turnover of a solution cascade reaction with ephemeral intermediates, which may otherwise deactivate in the bulk solution. In biochemistry or enzyme-relevant cascade reactions, extensive models have been constructed to quantitatively analyze the efficacy of compartmentalization. Nonetheless, the application of compartmentalization and its quantitative analysis in non-biochemical reactions is seldom performed, leaving much uncertainty about whether compartmentalization remains effective for non-biochemical reactions, such as organometallic, cascade reactions. Here, we report our exemplary efficacy analysis of compartmentalization in our previously reported cascade reaction for ambient CH 4 -to-CH 3 OH conversion, mediated by an O 2 -deactivated Rh II metalloradical with O 2 as the terminal oxidant in a Si nanowire array electrode. We experimentally identified and quantified the key reaction intermediates, including the Rh II metalloradical and reactive oxygen species (ROS) from O 2 . Based on such findings, we experimentally determined that the nanowire array enables about 81% of the generated ephemeral intermediate Rh II metalloradical in air, to be utilized towards CH 3 OH formation, which is 0% in a homogeneous solution. Such an experimentally determined value was satisfactorily consistent with the results from our semi-quantitative kinetic model. The consistency suggests that the reported CH 4 -to-CH 3 OH conversion surprisingly possesses minimal unforeseen side reactions, and is favorably efficient as a compartmentalized cascade reaction. Our quantitative evaluation of the reaction efficacy offers design insights and caveats into application of nanomaterials to achieve spatially controlled organometallic cascade reactions.