2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session B19: Focus Session: Polymers and Ionic Liquids
11:15 AM–2:03 PM,
Monday, March 16, 2009
Room: 320
Sponsoring
Unit:
DPOLY
Chair: Peggy Cebe, Tufts University
Abstract ID: BAPS.2009.MAR.B19.1
Abstract: B19.00001 : Block Copolymers and Ionic Liquids: A New Class of Functional Nanocomposites*
11:15 AM–11:51 AM
Preview Abstract
Abstract
Author:
Timothy Lodge
(University of Minnesota)
Block copolymers provide a remarkably versatile platform for achieving
desired nanostructures by self-assembly, with lengthscales varying from a
few nanometers up to several hundred nanometers. Ionic liquids are an
emerging class of solvents, with an appealing set of physical attributes.
These include negligible vapor pressure, high chemical and thermal
stability, tunable solvation properties, high ionic conductivity, and wide
electrochemical windows. For various applications it will be necessary to
solidify the ionic liquid into particular spatial arrangements, such as
membranes or gels, or to partition the ionic liquid in coexisting phases,
such as microemulsions and micelles. One example includes formation of
spherical, cylindrical, and vesicular micelles by
poly(butadiene-$b$-ethylene oxide) and poly(styrene-$b$-methylmethacrylate) in the
common hydrophobic ionic liquids [BMI][PF$_{6}$] and [EMI][TFSI]. This work
has been extended to the formation of reversible micelle shuttles between
ionic liquids and water, whereby entire micelles transfer from one phase to
the other, reversibly, depending on temperature and solvent quality.
Formation of ion gels has been achieved by self-assembly of
poly(styrene-$b$-ethylene oxide-$b$-styrene) triblocks in ionic liquids, and by
the thermoreversible system poly(N-isopropylacrylamide-$b$-ethylene
oxide-$b$-N-isopropylacrylamide), using as little as 4{\%} copolymer. Further,
these gels have been shown to be remarkably effective as gate dielectrics in
organic thin film transistors. The remarkably high capacitance of the ion
gels ($>$ 10 $\mu $F/cm$^{2})$ supports a very high carrier density in an
organic semiconductor such as poly(3-hexylthiophene), leading to milliamp
currents for low applied voltages. Furthermore, the rapid mobility of the
ions enables switching speeds approaching 10 kHz, orders of magnitude higher
than achievable with other polymer-based dielectrics such as
PEO/LiClO$_{4}$. Finally, we have shown that ordered nanostructures of block
copolymers plus ionic liquids show the characteristic self-assembly
properties of strongly-segregated systems. Prospects for anisotropic ionic
conductivity are also being explored.
*Supported by the National Science Foundation
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.B19.1