Lopez-Oliva, A.P., Warren, N.J., Rajkumar, A. et al. (5 more authors) (2015) Polydimethylsiloxane-Based Diblock Copolymer Nano-objects Prepared in Nonpolar Media via RAFT-Mediated Polymerization-Induced Self-Assembly. Macromolecules, 48 (11). pp. 3547-3555. ISSN 0024-9297
Abstract
Monocarbinol-functionalized polydimethylsiloxane (PDMS; mean degree of polymerization = 66) was converted via esterification into a chain transfer agent (CTA) for reversible addition–fragmentation chain transfer (RAFT) polymerization. The degree of esterification was determined to be 94 ± 1% by 1H NMR spectroscopy and 92 ± 1% by UV absorption spectroscopy. This PDMS CTA was then utilized for the dispersion polymerization of benzyl methacrylate (BzMA) in n-heptane at 70 °C. As the PBzMA block grows, it becomes insoluble in the reaction medium, which drives the in situ formation of PDMS–PBzMA diblock copolymer nanoparticles via polymerization-induced self-assembly (PISA). Depending on the precise reaction conditions, the final diblock copolymer chains can self-assemble to form spheres, worms, or vesicles. Systematic variation of the copolymer concentration and the target degree of polymerization (DP) of the PBzMA block enables construction of a phase diagram that allows the reproducible targeting of pure copolymer morphologies, as judged by transmission electron microscopy and dynamic light scattering studies. 1H NMR spectroscopy studies confirm that relatively high BzMA conversions (>90%) can be achieved within 8 h at 70 °C. Gel permeation chromatography studies (THF eluent) indicate high blocking efficiencies and relatively low final polydispersities (Mw/Mn = 1.14–1.34). Small-angle X-ray scattering (SAXS) has been used to characterize selected examples of the spherical nanoparticles in order to obtain volume-average diameters, which increase monotonically when targeting longer DPs for the core-forming PBzMA block. A relatively high copolymer concentration (>25% w/v) is required to obtain a pure worm phase, which occupies an extremely narrow region within the phase diagram. Selected worm and vesicle dispersions were also analyzed by SAXS, which enables determination of the mean worm cross section, mean worm length and vesicle membrane thickness. In addition, the highly anisotropic worms formed free-standing gels in n-heptane, with rheology measurements indicating viscoelastic behavior and a gel storage modulus of around 104 Pa.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 American Chemical Society. This is an author produced version of a paper subsequently published in Macromolecules. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) |
Funding Information: | Funder Grant number ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL (EPSRC) EP/L024160/1 EUROPEAN RESEARCH COUNCIL PISA - 320372 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 18 Feb 2016 09:55 |
Last Modified: | 06 Nov 2017 10:13 |
Published Version: | https://dx.doi.org/10.1021/acs.macromol.5b00576 |
Status: | Published |
Publisher: | American Chemical Society |
Refereed: | Yes |
Identification Number: | 10.1021/acs.macromol.5b00576 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:95174 |