Effect of TMA-MMT interfacial sorbitol concentration on TPS interactions

Determine whether the effectively high sorbitol concentration in the first solvation layer of TMA-MMT tempers slightly attractive TMA-MMT–thermoplastic-starch interactions, thereby limiting reductions in polymer segmental diffusion coefficients and conformational entropy near the TMA-MMT surface.

Background

All-atom simulations compare thermoplastic starch (TPS) near lower-polarity pyrophyllite and higher-polarity tetramethylammonium-montmorillonite (TMA-MMT) surfaces. Replacing pyrophyllite with TMA-MMT decreases normalized diffusion coefficients and conformational entropy for near-surface amylose and amylopectin segments, while producing little change in their radius of gyration.

The paper attributes the modest magnitude of these reductions to a proposed mechanism: sorbitol may accumulate at the TMA-MMT surface and effectively plasticize or screen the attractive interaction between the clay and TPS. This explanation is explicitly presented as a conjecture rather than established by the simulations, leaving its validity unresolved.

References

We conjecture that an effectively high plasticizer (sorbitol) concentration in the first solvation layer of TMA-MMT tempered the effect of slightly attractive TMA-MMT--TPS interactions, leading to only a small decrease in diffusion coefficients and conformational entropy of the polymer chains in the near TMA-MMT region w.r.t. to the melt values.

— Characterization and Quantification of Immiscible Polymer Blend Compatibilization by Phyllosilicate Clays  (2610.01576 - Patidar et al., 1 Oct 2026) in Section 3.1, “Physical Insights from AA Simulation of Composites”