Oligoester-Derivatized (Semi-)Interpenetrating Polymer Networks as Nanostructured Precursors to Porous Materials with Tunable Porosity

Abstract

Porous polymeric materials with tunable porosity can be engineered from oligoester-derivatized semi-interpenetrating polymer networks (semi-IPNs) or IPNs, respectively composed of either uncrosslinked or crosslinked aliphatic oligoesters entangled in a stiff subnetwork. In this paper, miscellaneous polyester/poly(methyl methacrylate)-based semi-IPN and IPN systems are first prepared as precursors with varying structural parameters, especially the nature [i.e., poly(d,l-lactide), poly(ε-caprolactone)] and the molar mass (i.e., from 560 to 3700 g mol⁻¹) of the oligoester precursor. (Nano)porous networks with defined porosity are then generated through two complementary routes. This original paper discusses the scope and limitations of both approaches and investigates the correlation between the structure and morphology of the generated networks and the porosity of the resulting porous materials. We demonstrate that the choice of the precursors with defined compatibility is of paramount significance in the length scale of phase separation associated with nanostructured networks as well as in the porosity scale of (nano)porous materials derived therefrom. Indeed, we find that the quantitative extraction of uncrosslinked oligoesters from semi-IPNs allows for the elaboration of nanoporous networks with pore diameters lower than 150 nm, provided that a high miscibility between both partners in semi-IPN precursors is attained, i.e. when using the lower molar mass oligoester. Alternately, the total hydrolysis of the polyester subnetwork associated with IPNs offers more versatility, since nanoporous networks can be obtained with a pore size range of 20–150 nm, regardless of the oligoester nature and molar mass in IPN precursors.