Hydrogen bonding exchange and supramolecular dynamics of monohydroxy alcohols

TL;DR

This study reveals how hydrogen bonding dynamics influence supramolecular relaxations in monohydroxy alcohols, demonstrating Rouse-like chain motions and chain-swapping processes through combined rheological, dielectric, and NMR analyses.

Contribution

It provides new insights into the molecular mechanisms of hydrogen bonding exchange and supramolecular dynamics, supporting a living polymer model in monohydroxy alcohols.

Findings

Rheological modulus shows Rouse scaling relaxation transitioning to chain-swapping behavior.

Dielectric spectroscopy detects supramolecular dynamics matching rheological timescales.

Hydrogen bonding exchange time follows an Arrhenius temperature dependence.

Abstract

This Letter unravels hydrogen bonding dynamics and their relationship with supramolecular relaxations of monohydroxy alcohols (MAs) at intermediate times. Rheological modulus of MAs exhibit Rouse scaling relaxation of G(t) ~ t^(-1/2) switching to G(t) ~ t^(-1) at time tau_m before their terminal time. Meanwhile, dielectric spectroscopy reveals clear signatures of new supramolecular dynamics matching with tau_m from rheology. Interestingly, the characteristic time, tau_m, follows an Arrhenius-like temperature dependence over exceptionally wide temperatures and agrees well with the hydrogen bonding exchange time from nuclear magnetic resonance measurements. These observations demonstrate the presence of collective Rouse-like sub-chain motions and the active chain-swapping of MAs at intermediate times. Moreover, detailed theoretical analyses point out explicitly that the hydrogen bonding exchange truncates the Rouse-type supramolecular dynamics and triggers the chain-swapping processes, supporting a recently proposed living polymer model.