|
|
|
 |
 National Science
Foundation Award #0513010 |
 |
|
|
Viscoelastic Behavior of Stimuli-Responsive Metallo-Supramolecular Polymers |
| |
| Investigator(s): |
Alexander Jamieson (PI)
|
| Sponsor: |
Case Western Reserve University, OH 44106 2163684510
|
| Start Date/Expiration Date |
2005-09-01 to 2008-08-31 (amended 2005-04-20) |
| Awarded Amount to Date: |
$330,000 |
| Abstract: Stimuli-responsive polymers (SRPs) exhibit a change in properties upon application of an external
stimulus, such as a change in temperature, ionic strength, pH, electric, magnetic or mechanical fields or by
chemical or biological analytes. Examples include liquid crystal polymers (LCPs), polymer solutions and
gels, which undergo a change in phase morphology, electro- and magnetorheological fluids and electroactive
polymers (EAPs). SRPs have potential applications as smart films in sensors, actuators, electro-optic
devices, etc., where the viscoelastic properties become important. A recent advance has been the
development of metallosupramolecular polymers and networks based on metal:ligand binding. This project
requests support to investigate the molecular origin of the viscoelastic behavior of a novel family of
metallosupramolecular polymers, developed by S. J. Rowan and coworkers, which dissolve in various
organic solvents, and which can be conveniently functionalized by incorporation of photonic or ionconducting
moieties. Knowledge of the molecular origin of the viscoelastic and thermodynamic behavior of
these materials is a key step towards rational molecular design, aimed at optimizing their properties, and to
understanding how to process them into functional films. Such studies have not been systematically
pursued to date, and are the subject of this proposal.
Rowan et al. create supramolecular polymers and networks of controlled architectures from a bisligand
functionalized monomer via addition of lanthanide and transition metal ions, which act, respectively,
as crosslinkers and as chain extenders. Thus, the molecular weight and network architecture is determined
by the ionic concentration and composition, and by the ion-binding strength and kinetics. These materials
combine the functionality of the metal ions with the processability and mechanical strength of a dynamic
polymeric network. We propose studies to first investigate the properties of the supramolecular polymers
formed by mixing the monomer with transition metal ions. Viscometric, light scattering and small-angle
neutron scattering studies will be performed as a function of monomer:metal ion ratio, in different solvents,
and as a function of temperature. The role of the coordinating power of the metal ion and solvent will be
explored. The results will be interpreted in terms of apparent chain molecular weight, in the context of
theories of equilibrium chains and/or kinetically frozen chains. These studies will then be extended to study
the effects of adding lanthanide as crosslinker. The onset of gelation and/or phase separation will be probed
by scattering and rheological measurements. The structure and morphology of the gel phase will be
examined by light, x-ray and neutron scattering techniques and by optical and transmission electron
microscopy. These studies will provide the first comprehensive picture of the relationship between
precursor structure and metal ion binding characteristics versus thermodynamic and viscoelastic behavior
for this important new class of stimuli-responsive materials.
The intellectual merit of the proposal derives from the fact that the results obtained will generate
important new fundamental knowledge on an important new class of stimuli-responsive materials. In
addition, they will serve to test existing theories of self-assembling polymers and networks, and more
importantly are expected to identify novel phenomena, which will provide new challenges for theorists.
Moreover, the project will have broader impact, in that it will serve to train two PhD graduate
students, and is expected to provide research opportunities for undergraduate students in a vital area of
polymer research. The results will be disseminated at national and international meetings and will be
published in leading scientific journals. In addition, it is expected that our findings will generate empirical
knowledge, which will be an important step toward practical commercial application of these materials as
functional, stimuli-responsive coatings and films. |
|
| NSF Org: |
DMR - Division of Materials Research |
| Award Number: |
0513010 |
| Award Instrument: |
Standard Grant |
| Program Manager: |
Andrew J. Lovinger
DMR Division of Materials Research
MPS Directorate for Mathematical & Physical Sciences
|
| NSF Program(s): |
POLYMERS |
| Field Application(s): |
Materials Research |
| Program Reference Code(s): |
SINGLE DIVISION/UNIVERSITY, 9161 |
| Program Element Code(s): |
1773 |
|
|
| |
 |
|
|
|
|
|
|
|
