Atomistic study of macroscopic analogs to short chain molecules

TL;DR

This study uses chaotic surface waves to simulate thermal behavior in macroscopic chains, revealing universal scaling for long chains and unique stiffness properties for short chains, bridging macroscopic experiments with polymer physics.

Contribution

It introduces a novel macroscopic analog using chaotic waves to mimic thermal polymer behavior and explores the scaling and stiffness properties of short versus long chains.

Findings

Universal scaling in long chains matches theoretical predictions.

Short chains exhibit unexpectedly high compressional stiffness.

Chains soften rapidly as length increases, aligning with expected scalings.

Abstract

We use a bath of chaotic surface waves in water to mechanically and macroscopically mimic the thermal behavior of a short articulated chain with only nearest-neighbor interactions. The chaotic waves provide isotropic and random agitation to which a temperature can be ascribed, allowing the chain to passively explore its degrees of freedom in analogy to thermal motion. We track the chain in real time and infer end-to-end potentials using Boltzmann statistics. We extrapolate our results, by using Monte Carlo simulations of self-avoiding polymers, to lengths not accessible in our system. In the long chain limit we demonstrate universal scaling of the statistical parameters of all chains in agreement with well-known predictions for self-avoiding walks. However, we find that the behavior of chains below a characteristic length scale is fundamentally different. We find that short chains have much greater compressional stiffness than would be expected. However, chains rapidly soften as length increases to meet with expected scalings.