Byard, S.J., Williams, M., McKenzie, B.E. et al. (2 more authors) (2017) Preparation and Cross-Linking of All-Acrylamide Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly in Aqueous Solution. Macromolecules, 50 (4). pp. 1482-1493. ISSN 0024-9297
Abstract
Various carboxylic acid-functionalized poly( N , N -dimethylacrylamide) (PDMAC) macromolecular chain transfer agents (macro-CTAs) were chain-extended with diacetone acrylamide (DAAM) by reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization at 70 °C and 20% w/w solids to produce a series of PDMAC-PDAAM diblock copolymer nano-objects via polymerization-induced self-assembly (PISA). TEM studies indicate that a PDMAC macro-CTA with a mean degree of polymerization (DP) of 68 or higher results in the formation of well-defined spherical nanoparticles with mean diameters ranging from 40 to 150 nm. In contrast, either highly anisotropic worms or polydisperse vesicles are formed when relatively short macro-CTAs (DP = 40-58) are used. A phase diagram was constructed to enable accurate targeting of pure copolymer morphologies. Dynamic light scattering (DLS) and aqueous electrophoresis studies indicated that in most cases these PDMAC-PDAAM nano-objects are surprisingly resistant to changes in either solution pH or temperature. However, PDMAC40-PDAAM99 worms do undergo partial dissociation to form a mixture of relatively short worms and spheres on adjusting the solution pH from pH 2-3 to around pH 9 at 20 °C. Moreover, a change in copolymer morphology from worms to a mixture of short worms and vesicles was observed by DLS and TEM on heating this worm dispersion to 50 °C. Postpolymerization cross-linking of concentrated aqueous dispersions of PDMAC-PDAAM spheres, worms, or vesicles was performed at ambient temperature using adipic acid dihydrazide (ADH), which reacts with the hydrophobic ketone-functionalized PDAAM chains. The formation of hydrazone groups was monitored by FT-IR spectroscopy and afforded covalently stabilized nano-objects that remained intact on exposure to methanol, which is a good solvent for both blocks. Rheological studies indicated that the cross-linked worms formed a stronger gel compared to linear precursor worms.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017 American Chemical Society. This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. |
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/J007846/1 EUROPEAN RESEARCH COUNCIL PISA - 320372 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 23 Mar 2017 11:52 |
Last Modified: | 23 Mar 2017 11:52 |
Published Version: | https://doi.org/10.1021/acs.macromol.6b02643 |
Status: | Published |
Publisher: | American Chemical Society |
Refereed: | Yes |
Identification Number: | 10.1021/acs.macromol.6b02643 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:113889 |