2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008;
New Orleans, Louisiana
Session G1: 25 Years of Scanning Probe Microscopy
8:00 PM–9:30 PM,
Monday, March 10, 2008
New Orleans Marriott
Room: Carondelet (3rd floor)
Sponsoring
Unit:
APS
Chair: Julia Phillips, Sandia National Laboratories
Abstract ID: BAPS.2008.MAR.G1.3
Abstract: G1.00003 : Understanding Polymer Properties through Imaging of Molecules.*
9:00 PM–9:30 PM
Preview Abstract
Abstract
Author:
Sergei Sheiko
(University of North Carolina at Chapel Hill)
The unique advantage of Scanning Probe Microscopy (SPM) is that it allows
imaging of flexible polymer molecules, whose overall size and local
curvature are below the optical resolution limit. The role of molecular
visualization has grown to be especially profound with the synthesis of
complex macromolecules whose structure is difficult to confirm using
conventional techniques such as NMR and light scattering. This is especially
true for molecules that are branched, heterogeneous, and polydisperse. Here,
SPM images provide unambiguous proof of the molecular architecture along
with accurate analysis of size, conformation, and ordering of molecules on
surfaces. The unique advantage of SPM is that one obtains molecular
dimensions in direct space. This offers more opportunities for statistical
analysis including fractionation of molecules by size, branching topology,
and chemical composition as well as sorting out the irrelevant species.
Unlike molecular characterization of static molecules, it remains
challenging to study molecules as they move and react on surfaces. We will
discuss pioneering AFM studies of flowing monolayers one molecule at a time.
Through use of AFM, the flow process was monitored over a broad range of
length scales from the millimeter long precursor film all the way down to
the movements of individual molecules within the film. Molecular imaging
enabled independent measurements both the driving and frictional forces that
control spreading rate. In these studies, one also discovered a new type of
flow instability in polymer monolayers caused by flow-induced conformational
transitions. Recently, molecular imaging has been successfully used to
monitor adsorption-induced degradation of branched molecules. These
experiments open an entirely new perspective in chemistry wherein the
chemical bonds can be mechanically activated upon the physical contact of a
macromolecule with a substrate. This research directly impacts coatings,
lubrication, heterogeneous catalysis, and biochemical assays, i.e.
technologies that are largely controlled by surface-activated changes in the
molecular structure and properties.
*We gratefully acknowledge funding from the NSF (DMR 0606086 and CBET 0609087) and Petroleum Research Fund
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2008.MAR.G1.3