Thermosensitive properties of telechelic hydrophobically modified poly(n-isopropylacrylamide) in water

POLY 416

Kayoko Nishizono, nishizono-scc@mbox.nc.kyushu-u.ac.jp1, Taisuke Fujimoto1, Francoise M Winnik, francoise.winnik@umontreal.ca2, and Masahiko Annaka1. (1) Department of Chemistry, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka-shi, Fukuoka, 812-8581, Japan, (2) Faculty of Pharmacy and Department of Chemistry, Universite de Montreal, CP 6128 Succursale Centre Ville, Montreal, QC H3C 3J7, Canada
Among the various families of hydrophobically modified (HM) water-soluble polymers, telechelic derivatives bearing hydrophobic end-groups have attracted attention. Recently Winnik and coworkers investigated temperature-dependent properties of telechelic HM-PNIPAM bearing n-octadecyl groups (C18) on both ends in water, and found that above coil-to-globule transition temperature, individual flower micelles with collapsed loops associate to form mesoglobules comprising a few hundreds chains with more rigid and more polar interior than the hydrophobic core of hydrated flower micelles. In this study, we examined the effect of end group on the properties of aqueous solutions of telechelic HM-PNIPAM. PNIPAM carrying n-tetradecyl end groups exhibits individual flower micelles consisting of ~11-12 polymer chains in cold aqueous solution. In solutions heated below LCST, individual flower micelles associate into larger aggregates with bridge conformation that connects two different flower micelles. Above LCST, PNIPAM loops dehydrate and collapse, and the aggregates change into more rigid and dense aggregates.
 

Synthetic and Biological Macromolecules for Emerging Nanotechnologies
6:00 PM-8:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster

Division of Polymer Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007