Amphiphilic Optimization Enables Polyaspartamides with Effective Kinetic Inhibition of Tetrahydrofuran Hydrate Formation: Structure–Property Relationships

Abstract

Kinetic hydrate inhibitors (KHIs) are polymers that play a vital role in gas energy production, transport, and storage. A series of polyaspartamides based on l-aspartic acid were designed to serve as potential KHIs. Tuning the fine structures of the polyaspartamides can inhibit the tetrahydrofuran hydrate formation more effectively than classical KHIs, i.e., poly(N-vinylcaprolactam) (PVCap) and poly(N-vinylpyrrolidone) (PVP). When the hydrophobic side chain is longer, the polyaspartamide is more effective. For elucidation of the polymer structure–property relationships in the inhibition of the clathrate hydrate, the molecular-level interactions between the polyaspartamides and tetrahydrofuran hydrate were studied. Dynamics of water surrounding the polymers probed by NMR relaxometry demonstrate that the polyaspartamides can bind tightly with water molecules in the hydrate, resulting in faster transverse relaxation times of the nonfreezable water. This phenomenon can be interpreted by quantum chemical simul...