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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 p-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.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation (DMR-1609459). The authors thank Stacey Saba, Dr. Jonathan Hollinger, and Dr. Michael Larsen for helpful input and Dr. Justin Bolton for synthesis of the RAFT agent. Portions of this work were performed at the Advanced Photon Source (APS), Sector 5 (DuPont?Northwestern?Dow Collaborative Access Team, DND-CAT) and Sector 12. DND-CAT is supported by E.I. DuPont de Nemours and Co., The Dow Chemical Company, and Northwestern University. Use of the APS, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. Parts of this work were carried out in the College of Science and Engineering (CSE) Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program. The Hitachi SU8320 SEM of the CSE Characterization Facility was provided by NSF MRI DMR-1229263.
© 2017 American Chemical Society.
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- Period 3