Web Release Date: November 7,
Facile Fabrication of Reversible Core Cross-Linked Micelles Possessing Thermosensitive Swellability
and
Department of Polymer Science and Engineering, Joint Laboratory of Polymer Thin Films and Solution, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China, School of Materials and Chemical Engineering, Anhui Institute of Architecture and Industry, Hefei, Anhui 230022, China, and Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S37HF, United Kingdom
Received July 13, 2007
Revised Manuscript Received September 7, 2007
Abstract:
Poly(ethylene oxide)-b-poly(N-isopropylacrylamide-co-N-acryloxysuccinimide), PEO-b-P(NIPAM-co-NAS), was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization in dioxane
at 70 
C employing a poly(ethylene oxide) (PEO)-based macroRAFT agent. The obtained double hydrophilic
block copolymer molecularly dissolves in aqueous solution at room temperature. Above the lower critical solution
temperature (LCST) of P(NIPAM-co-NAS) block, it self-assembles into micelles consisting of thermoresponsive
P(NIPAM-co-NAS) cores and well-solvated PEO coronas. Cross-linking of the P(NIPAM-co-NAS) cores was
facilely achieved via the reaction of NAS residues with cystamine at elevated temperatures in aqueous media,
forming structurally permanent core cross-linked micelles. Most importantly, the disulfide bonds within the cross-linker can be conveniently cleaved in the presence of dithiothreitol and re-formed again upon addition of cystamine
as a thiol/disulfide exchange promoter, leading to the reversible core cross-linking of micelles. The P(NIPAM-co-NAS) cores of the obtained core cross-linked (CCL) micelles exhibit tunable swelling/deswelling behavior
below and above the critical phase transition temperature. Dynamic laser light scattering, optical transmittance,
1H NMR, and transmission electron microscopy were used in combination to investigate the thermoresponsive
micellization of PEO-b-P(NIPAM-co-NAS) and the subsequent reversible core cross-linking.
Download the full text: PDF | HTML
