Prof. Dr. Axel Müller

Web Release Date: September 21, 2004

A New Double-Responsive Block Copolymer Synthesized via RAFT Polymerization: Poly(N-isopropylacrylamide)-block-poly(acrylic acid)

Christine M. Schilli, Mingfu Zhang, Ezio Rizzardo, San H. Thang, (Bill) Y. K. Chong, Katarina Edwards, Göran Karlsson, and Axel H. E. Müller*

Makromolekulare Chemie II, Universität Bayreuth, 95440 Bayreuth, Germany, CSIRO Molecular Science, Bag 10, Clayton South, Victoria 3169, Australia, and Department of Physical Chemistry, Uppsala University, Box 579, 75123 Uppsala, Sweden

Received December 4, 2003

Revised Manuscript Received July 23, 2004

Poly(N-isopropylacrylamide)-block-poly(acrylic acid), PNIPAAm-b-PAA, with low polydispersity was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization in methanol. The block copolymers respond to both temperature and pH stimuli. The behavior of the double-responsive block copolymers in solution was investigated by dynamic light scattering, temperature-sweep NMR, cryogenic transmission electron microscopy, and IR spectroscopy. The block copolymers form micelles in aqueous solutions in dependence of pH and temperature. Cloud point measurements indicated the formation of larger aggregates at pH 4.5 and temperatures above the lower critical solution temperature (LCST) of PNIPAAm. The solution behavior is strongly influenced by hydrogen bonding interactions between the NIPAAm and acrylic acid blocks.