Simulation Study of Hydrophobically Modified Chitosan as an Oil Dispersant Additive

Abstract

Hydrophobically modified chitosan (HMC) is being considered as a possible oil dispersant additive to reduce the volume of dispersant required in oil spill remediation. We present the results of discontinuous molecular dynamics (DMD) simulations intended to determine how the HMC architecture affects its ability to prevent oil aggregation. The HMCs have a comb copolymer architecture with hydrophobic side chains (modification chains) of various lengths (5-15 spheres) to represent alkane chains that are attached to the chitosan backbone. We calculated the oil's solvent accessible surface area (SASA), aggregate size distribution, and aggregate asymmetry at various values of the HMC modification chain length, modification density, and concentration to determine HMC efficacy. HMCs with long modification chains result in larger oil SASA than HMCs with short modification chains. For long modification chains, there is no increase in oil SASA with increasing modification density above a saturation value. The size distribution of the oil aggregates depends on the modification chain length; systems with long modification chains lead to large aspherical aggregates, while systems with short modification chains lead to small tightly packed aggregates. A parametric analysis reveals that the most important factor in determining the ability of HMCs to prevent oil aggregation is the interaction between the HMC's modification chains and the oil molecules, even when using short modification chains. We conclude that HMCs with long modification chains are likely to be more effective at preventing oil aggregation than HMCs with short modification chains, and that long modification chains impede spherical oil droplet formation.

A multiscale coarse-grained model to predict the molecular architecture and drug transport properties of modified chitosan hydrogels

“…The network morphology of native chitosan hydrogels is determined by the ratio of acetylglucosamine (GlcNAc) and glucosamine (GlcN) monomers, expressed as degree of acetylation (w Ac ), 7,8 the water/chitosan ratio, and pH. 9 Tailored chemical modification of the free amine groups on GlcN monomers provides additional control over the properties of the chitosan hydrogels.…”

“…[30][31][32] Finally, the aggregation of chitosan with different w Ac and different modification patterns has been simulated with a MARTINI-like model. 7,33 In the present study, we implement a novel and promising approach for elucidating the structure-property relationship in chemically modified chitosan hydrogels. Our method employs (1) multi-scale coarse-graining (MS-CG), also known as ''force matching'', 34 to derive non-bonded interactions for solute-solute, solute-solvent, and solvent-solvent interactions that reproduce the forces sampled in the all-atom system; and (2) Boltzmann Inversion 35 to derive the bonded interaction potentials.…”

Carboxymethyl Chitosan and Its Hydrophobically Modified Derivative as pH-Switchable Emulsifiers

“…Native −, and modified chitosans , − have been applied to produce and stabilize conventional and Pickering emulsions. In conventional emulsions, the dissolved native chitosan provides a mainly steric barrier against the coalescence of the oil droplets due to its weak surface activity .…”

Development of a Coarse-Grained Model of Chitosan for Predicting Solution Behavior

“…The design of self-assembled systems based on chitosan has become an active field of research because chitosan is biocompatible, polycationic, and chemically modifiable as a result of its amine functional group. Chitosan has shown promise for use in applications ranging from wound healing 1-3 and drug delivery [4][5][6][7][8] to water purification [9][10][11] and oil spill remediation 12,13 . Chitosan self-assembly in solution depends strongly on the degree of acetylation (DA) and pH [14][15][16][17][18] .…”