Related Experiment Video
Updated: May 13, 2026

Optical Tweezers to Study RNA-Protein Interactions in Translation Regulation
Published on: February 12, 2022
Exact solution of the Zwanzig-Lauritzen model of polymer crystallization under tension
Himadri S Samanta1, D Thirumalai
1Biophysics Program, Institute of Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
Abstract:
We solve a two-dimensional model for polymer chain folding in the presence of mechanical pulling force (f) exactly using equilibrium statistical mechanics. Using analytically derived expression for the partition function we determine the phase diagram for the model in the f-temperature (T) plane. A square root singularity in the susceptibility indicates a second order phase transition from a folded to an unfolded state at a critical force (fc) in the thermodynamic limit of infinitely long polymer chain. The temperature dependence of fc shows a reentrant phase transition, which is reflected in an increase in fc as T increases below a threshold value. As a result, for a range of f values, the unfolded state is stable at both low and high temperatures. The high temperature unfolded state is stabilized by entropy whereas the low temperature unfolded state is dominated by favorable energy. The exact calculation could serve as a benchmark for testing approximate theories that are used in analyzing single molecule pulling experiments.
Related Concept Videos
Ziegler–Natta Chain-Growth Polymerization: Overview
Recrystallization: Solid–Solution Equilibria
Polymer Classification: Crystallinity
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Crystal Growth: Principles of Crystallization
Initiating crystallization involves manipulating the concentration of the solute and the temperature of the solution. Since crystal growth occurs when the ratio of concentration and solubility of the solute in the solvent – the...
Step-Growth Polymerization: Overview
Many natural and synthetic polymers are produced by...
Determination of Molar Masses of Polymers II

