Seminar
Dr. Charles L. McCormick
Monday, February 6th, 2006 at 2
PM
Leigh Hall, Room 309
Dr. Charles L. McCormick,
Bennett Distinguished Research Professor from the University of
Southern Mississippi will be presenting his lecture, "Synthesis
of Precisely Controlled Stimuli-Responsive Block Copolymers via
RAFT: Opportunities for Self-Assembly in Aqueous Media."
Reversible
Addition Fragmentation Chain-Transfer (RAFT) polymerization has been
the focus of intensive research over the past few years since this
methodology allows the synthetic tailoring of macromolecules with
complex architectures including block, graft, comb, and star
structures with selected molecular weight, terminal functionality,
and narrow molecular weight distribution. This presentation
highlights significant milestones in achieving controlled free radical
homopolymerization and
block-copolymerization of water soluble and amphiphilic monomers
including nonionic, cationic, anionic, and zwitterionic species.
It is shown that, under aqueous conditions, control of homopolymerization and further
blocking to extend the molecular weight or to produce
precisely-structured block copolymers require not only careful
selection of reagents (initiator, chain transfer agent, and monomer) but also regulation or
elimination of hydrolysis of the w-terminal (thiocarbonylthio)
functionality. The technological potential of such systems is
illustrated for the stimuli (pH) reversible micelle formation of amphiphilic block copolymers and for
stabilization and stimuli responsive aggregation of gold
nanoparticles bearing covalently tethered co(polymers). Given
the advantages of RAFT over other controlled free radical techniques for preparation of
water-soluble architectures, it may be anticipated that this
technology will be at the forefront of nano- and microscale self
assembly in electronics and biotechnology in the near future. |