Tuning Mesoporosity in Cross-Linked Nanostructured Thermosets via Polymerization-Induced Microphase Separation

Using the synthetic approach of polymerization-induced microphase separation (PIMS), we prepared cocontinuous and cross-linked nanostructured monoliths from bulk polymerizations of styrene and divinylbenzene (DVB) in the presence of polylactide macro-chain-transfer agents (PLA-CTAs). The resulting monolithic precursors were converted to cross-linked mesoporous materials following hydrolytic degradation of the PLA domain, the morphology and porosity of which were characterized through a combination of small-angle X-ray scattering, scanning electron microscopy, and nitrogen sorption experiments. This report highlights the concept, functionality, and limitations of PIMS for the generation of mesoporous materials through variation of reaction parameters found to strongly influence the porous properties of the matrix: the cross-linker-to-monomer ratio, reaction temperature, molar mass and mass fraction of PLA-CTA, and the reactivity of the DVB isomer. Increases in the cross-linker-to-monomer ratio (≥40 mol % DVB) induced formation of smaller mesopores within the matrix in addition to the principal pore mode largely defined by the molar mass and mass fraction of the PLA-CTA. Higher reaction temperatures and the increased relative reactivity of the <i>p</i>-DVB isomer are shown to influence the matrix integrity, ultimately achieving surface areas as high as 796 m² g^–1 using 8 kg mol^–1 PLA-CTA. In combination, these parameters suggest methods to circumvent limitations of pore collapse associated with concomitant reductions in the molar mass of PLA-CTA