Related Experiment Video
Updated: Jul 11, 2026

Covalent Attachment of Single Molecules for AFM-based Force Spectroscopy
Published on: March 16, 2020
Direct measurement of the intermolecular forces confining a single molecule in an entangled polymer solution
Rae M Robertson1, Douglas E Smith
1Physics Department, University of California, San Diego, 9500 Gilman Dr. La Jolla, California 92093-0379, USA.
Abstract:
We use optical tweezers to directly measure the intermolecular forces acting on a single polymer imposed by surrounding entangled polymers (115 kbp DNA, 1 mg/ml). A tubelike confining field was measured in accord with the key assumption of reptation models. A time-dependent harmonic potential opposed transverse displacement, in accord with recent simulation findings. A tube radius of 0.8 microm was determined, close to the predicted value (0.5 microm). Three relaxation modes (approximately 0.4, 5, and 34 s) were measured following transverse displacement, consistent with predicted relaxation mechanisms.
Related Concept Videos
Determination of Molar Masses of Polymers II
Intermolecular Forces
Intermolecular Forces
Intermolecular Forces in Solutions
When the strengths of the intermolecular forces of attraction between solute and solvent species in a solution are no different than those present in the separated components, the solution is formed with no accompanying energy change. Such a solution is called an ideal solution. A mixture of ideal gases (or gases such as helium and argon,...
Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility
Temporary attractive forces like dispersion are present in all molecules, whether they are polar or nonpolar. They...
Intermolecular Forces and Physical Properties

