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Issue 18, 2012
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Temperature-responsive inclusion complex of cationic PNIPAAM diblock copolymer and γ-cyclodextrin

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Abstract

Aqueous mixtures of γ-cyclodextrin (γ-CD) and the thermosensitive cationic diblock copolymer poly(N-isopropylacrylamide)-b-poly(3-acrylamidopropyl)trimethylammonium chloride (PNIPAAM24-b-PAMPTAM(+)9) or the PNIPAAM homopolymer PNIPAAM47 have been investigated using various experimental methods. Solid γ-CD–polymer inclusion complexes (pseudopolyrotaxanes) form at ambient temperatures in fairly concentrated CD solutions. The NMR measurements showed that the stoichiometry of the inclusion complexes is close to two NIPAAM units per CD molecule. The cationic block of the copolymer is not incorporated into the CD cavity. Synchrotron radiation X-ray diffraction spectra of the solid inclusion complexes indicate a compact columnar structure of CD molecules threaded onto the PNIPAAM chains. In water, square-shaped cyclodextrin aggregates were found to co-exist with single cyclodextrin molecules. In mixed solutions of γ-CD and PNIPAAM24-b-PAMPTAM(+)9 these aggregates disintegrate with time as inclusion complexes are formed and the kinetics was studied using time-resolved static and dynamic light scattering and cryo-TEM. Steady-state fluorescence spectroscopy measurements reveal that the CD molecules dethread from the PNIPAAM chains upon increasing the temperature to 40 °C, which is above the lower critical solution temperature of PNIPAAM.

Graphical abstract: Temperature-responsive inclusion complex of cationic PNIPAAM diblock copolymer and γ-cyclodextrin

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Supplementary files

Article information


Submitted
25 Nov 2011
Accepted
27 Feb 2012
First published
23 Mar 2012

Soft Matter, 2012,8, 5043-5054
Article type
Paper

Temperature-responsive inclusion complex of cationic PNIPAAM diblock copolymer and γ-cyclodextrin

G. Lazzara, G. Olofsson, V. Alfredsson, K. Zhu, B. Nyström and K. Schillén, Soft Matter, 2012, 8, 5043
DOI: 10.1039/C2SM07252A

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