In situ Crosslinking of Nanostructured Block Copolymer Microparticles in Supercritical Carbon Dioxide

He, Guping; Bennett, Thomas M.; Alias, Kartini; Jiang, Long; Schwab, Simon; Alauhdin, Mohammad; Howdle, Steven M.

Abstract

We report a novel and facile approach to “fix” the internal nanostructure of block copolymer (BCP) microparticles via in situ crosslinking copolymerisation in dispersion in supercritical CO2 (scCO2). By delaying the addition of the crosslinker and a portion of the second monomer, polymerisation induced microphase separation (PIMS) within the microparticles is well preserved, while the growing chains of precursor poly(methyl methacrylate)-block-poly(4-vinyl pyridine) (PMMA-b-P4VP) or poly(methyl methacrylate)-block-poly(benzyl methacrylate) (PMMA-b-PBzMA) microparticles are crosslinked. The unique structure of the as-synthesised crosslinked microparticles were fully characterised using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, the swelling and solubility behaviour of the crosslinked PMMA-b-P4VP microparticles was investigated. Notably, the porosity generated by swelling in ethanol can be well controlled by the quantity of crosslinker incorporated. Macropores > 100 nm – ~20 nm, sub-10 nm mesopores, and non-porous microparticles were all achieved by varying the crosslinker incorporation from 0, 0.5, 1, to 4 wt%, respectively. In situ AFM nanomapping of the crosslinked P4VP domains in 80% humidity revealed that microparticles with a high degree of crosslinking (8 wt% divinylbenzene) are highly resistant to swelling in humidity, by contrast to their non-crosslinked counterparts. This versatile approach further expands the available repertoire for fabricating porous BCP microparticles with tunable physico-chemical properties, morphologies and pore sizes, greatly broadening their application potential to more diverse fields.

Citation

He, G., Bennett, T. M., Alias, K., Jiang, L., Schwab, S., Alauhdin, M., & Howdle, S. M. (2019). In situ Crosslinking of Nanostructured Block Copolymer Microparticles in Supercritical Carbon Dioxide. Polymer Chemistry, 10(29), 3960-3972. https://doi.org/10.1039/c9py00556k

• Journal Article Type: Article
• Acceptance Date: Jun 13, 2019
• Online Publication Date: Jun 14, 2019
• Publication Date: Jun 14, 2019
• Deposit Date: Jun 17, 2019
• Publicly Available Date: Jun 15, 2020
• Journal: Polymer Chemistry
• Print ISSN: 1759-9954
• Electronic ISSN: 1759-9962
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 29
• Pages: 3960-3972
• DOI: https://doi.org/10.1039/c9py00556k
• Keywords: In-situ crosslinking, Block copolymer microparticles, RAFT dispersion polymerisation, Polymerisation induced phase separation, Porosity control
• Public URL: https://nottingham-repository.worktribe.com/output/2196260
• Publisher URL: https://pubs.rsc.org/en/Content/ArticleLanding/2019/PY/C9PY00556K#!divAbstract
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Single-blind; : Received 15 April 2019; Accepted 13 June 2019; Accepted Manuscript published 14 June 2019