pH-responsive diblock copolymer micelles at the silica/aqueous solution interface: adsorption kinetics and equilibrium studies

Sakai, Kenichi, Smith, Emelyn G., Webber, Grant B., Schatz, Christophe, Wanless, Erica J., Butun, Vural, Armes, Steven P. and Biggs, Simon (2006) pH-responsive diblock copolymer micelles at the silica/aqueous solution interface: adsorption kinetics and equilibrium studies. Journal of Physical Chemistry B, 110 30: 14744-14753. doi:10.1021/jp062830q


Author Sakai, Kenichi
Smith, Emelyn G.
Webber, Grant B.
Schatz, Christophe
Wanless, Erica J.
Butun, Vural
Armes, Steven P.
Biggs, Simon
Title pH-responsive diblock copolymer micelles at the silica/aqueous solution interface: adsorption kinetics and equilibrium studies
Journal name Journal of Physical Chemistry B   Check publisher's open access policy
ISSN 1520-6106
1520-5207
Publication date 2006-08-01
Sub-type Article (original research)
DOI 10.1021/jp062830q
Open Access Status Not yet assessed
Volume 110
Issue 30
Start page 14744
End page 14753
Total pages 10
Place of publication Washington, DC, United States
Publisher American Chemical Society
Language eng
Formatted abstract
The adsorption behavior of two examples of a weakly basic diblock copolymer, poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamirio)ethyl methacrylate) (PDMA-PDEA), at the silica/aqueous solution interface has been investigated using a quartz crystal microbalance with dissipation monitoring and an optical reflectometer. Dynamic and static light scattering measurements have also been carried out to assess aqueous solution properties of such pH-responsive copolymers. In alkaline solution, core-shell micelles are formed above the critical micelle concentration (cmc) by both copolymers, whereas the chains are molecularly dissolved (as unimers) at all concentrations in acidic solution. As a result, the adsorption behavior of PDMA-PDEA diblock copolymers on silica is strongly dependent on both the copolymer concentration and the solution pH. Below the cmc at pH 9, the cationic PDMA-PDEA copolymers adsorb as unimers and the conformation of the adsorbed polymer is essentially flat. At concentrations just above the cmc, the initial adsorption of copolymer onto the silica is dominated by the unimers due to their faster diffusion compared to the much larger micelles. Rearrangement of the adsorbed unimers and/or their subsequent displacement by micelles from solution is then observed during an equilibration period, and the final adsorbed mass is greater than that observed below the cmc. At concentrations well above the cmc, the much higher proportion of micelles in solution facilitates more effective competition for the surface at all stages of the adsorption process and no replacement of initially adsorbed unimers by micelles is evident. However, the adsorbed layer undergoes gradual rearrangement after initial adsorption. This relaxation is believed to result from a combination of further copolymer adsorption and swelling of the adsorbed layer.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Faculty of Engineering, Architecture and Information Technology Publications
 
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