Thermo-responsive Poly(methyl methacrylate)-block- poly(N-isopropylacrylamide) Block Copolymers Synthesized by RAFT Polymerization: Micellization and Gelation Tian Tang, 1 Valeria Castelletto, 1 Petros Parras, 1 Ian W. Hamley,* 1 Stephen M. King, 2 Debashish Roy, 3 Sebastien Perrier, 3 Richard Hoogenboom, 4 Ulrich S. Schubert 4 1 School of Chemistry, University of Reading, Reading, RG6 6AD, United Kingdom 2 ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom 3 Department of Colour and Polymer Chemistry, The University of Leeds, Leeds LS2 9JT, United Kingdom 4 Laboratory of Macromolecular Chemistry and Nanoscience, Eindhoven University of Technology and Dutch Polymer Institute, PO Box 5600 MB Eindhoven, The Netherlands Received: June 15, 2006; Revised: July 31, 2006; Accepted: August 9, 2006; DOI: 10.1002/macp.200600309 Keywords: diblock copolymer; gels; micelles; RAFT polymerization; thermoresponsive Summary: RAFT polymerization was used to prepare PMMA-b-PNIPAM copolymers. Two different chain transfer agents, tBDB and MCPDB, were used to mediate the sequ- ential polymerizations. Micellar solutions and gels were prepared from the resulting copolymers in aqueous solution. When heated above T c of PNIPAM (about 31 8C), DLS revealed that PNIPAM coronas collapsed, resulting in aggre- gation of the original micelles. The micellar gels underwent syneresis above T c as water was expelled from the ordered gel structure, the lattice periodicity of which was determined by SANS. A large decrease in lattice spacing was observed above T c . The gel became more viscoelastic at high tem- perature, as revealed by shear rheometry which showed a large increase in G 00 . Macromol. Chem. Phys. 2006, 207, 1718–1726 ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1718 DOI: 10.1002/macp.200600309 Full Paper