Understanding the temperature induced aggregation of silica nanoparticles decorated with temperature-responsive polymers: can a small step in the chemical structure make a giant leap for a phase transition?

Mansfield, E. D. H., Filippov, S. K., de la Rosa, V. R., Cook, M. T., Grillo, I., Hoogenboom, R., Williams, A. C. ORCID: https://orcid.org/0000-0003-3654-7916 and Khutoryanskiy, V. V. ORCID: https://orcid.org/0000-0002-7221-2630 (2021) Understanding the temperature induced aggregation of silica nanoparticles decorated with temperature-responsive polymers: can a small step in the chemical structure make a giant leap for a phase transition? Journal of Colloid and Interface Science, 590. pp. 249-259. ISSN 0021-9797 doi: 10.1016/j.jcis.2021.01.044

Abstract/Summary

Temperature-responsive nanomaterials have gained increasing interest over the past decade due their ability to undergo conformational changes in situ, in response to a change in temperature. One class of temperature-responsive polymers are those with lower critical solution temperature, which phase separate in aqueous solution above a critical temperature. When these temperature-responsive polymers are grafted to a solid nanoparticle, a change in their surface properties occurs above this critical temperature, from hydrophilic to more hydrophobic, giving them a propensity to aggregate. This study explores the temperature induced aggregation of silica nanoparticles functionalised with two isomeric temperature-responsive polymers with lower critical solution temperature (LCST) behavior, namely poly(N-isopropyl acrylamide) (PNIPAM), and poly(2-n-propyl-2-oxazoline) (PNPOZ) with similar molecular weights (5000 Da) and grafting density. These nanoparticles exhibited striking differences in the temperature of aggregation, which is consistent with LCST of each polymer. Using a combination of small-angle neutron scattering (SANS) and dynamic light scattering (DLS), we probed subtle differences in the aggregation mechanism for PNIPAM- and PNPOZ-decorated silica nanoparticles. The nanoparticles decorated with PNIPAM and PNPOZ show similar aggregation mechanism that was independent of polymer structure, whereby aggregation starts by the formation of small aggregates. A further increase in temperature leads to interaction between these aggregates and results in full-scale aggregation and subsequent phase separation.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/96062
Item Type	Article
Refereed	Yes
Divisions	Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) > Optical Spectroscopy (CAF) Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) > Thermal Analysis (CAF) Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) > Electron Microscopy Laboratory (CAF) Life Sciences > School of Chemistry, Food and Pharmacy > School of Pharmacy > Pharmaceutics Research Group
Publisher	Elsevier
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