@article{benner_hall_2017, title={Nanoparticle-induced assembly of hydrophobically modified chitosan}, volume={43}, ISSN={["1029-0435"]}, DOI={10.1080/08927022.2017.1290235}, abstractNote={Abstract Hydrophobically modified chitosan (HMC) self-assembles in solution to form gels, making it suitable for applications in oil dispersion, hydrogel design and wound dressing. The self-assembly of HMC is driven by the association of hydrophobic moieties that are attached to chitosan monomers along the polymer chain. We present the results of discontinuous molecular dynamics simulations aimed at understanding how the length and density of the hydrophobic modification chains attached to HMC affect self-assembly and the structure of the resulting network. Long modification chains are required to promote the formation of a stable network in solution at a modification density of 5%; the networks form more readily at a modification density of 10%. The pore size distribution of the resulting HMC network is relatively independent of the modification chain length and density. Insertion of different sized hydrophobic nanoparticles into HMC has a significant impact on network formation, with the particles acting as junction points that promote the association of several HMC chains. The networks form faster in the presence of many small nanoparticles than in the presence of few large nanoparticles. We conclude that HMC could be a viable candidate to form hydrogels in solution.}, number={9}, journal={MOLECULAR SIMULATION}, author={Benner, Steven W. and Hall, Carol K.}, year={2017}, pages={664–674} }
 @article{benner_hall_2016, title={Development of a Coarse-Grained Model of Chitosan for Predicting Solution Behavior}, volume={120}, ISSN={["1520-6106"]}, DOI={10.1021/acs.jpcb.6b03407}, abstractNote={A new coarse-grained (CG) model of chitosan has been developed for predicting solution behavior as a function of degree of acetylation (DA). A multiscale modeling approach was used to derive the energetic and geometric parameters of this implicit-solvent, CG model from all-atom simulations of chitosan and chitin molecules in explicit water. The model includes representations of both protonated d-glucosamine (GlcN(+)) and N-acetyl-d-glucosamine (GlcNAc) monomers, where each monomer consists of three CG sites. Chitosan molecules of any molecular weight, DA, and monomer sequence can be built using this new CG model. Discontinuous molecular dynamics simulations of chitosan solutions show increased self-assembly in solution with increasing DA and chitosan concentration. The chitosan solutions form larger percolated networks earlier in time as DA and concentration increase, indicating "gel-like" behavior, which qualitatively matches experimental studies of chitosan gel formation. Increasing DA also results in a greater number of monomer-monomer associations, which has been predicted experimentally based on an increase in the storage modulus of chitosan gels with increasing DA. Our model also gives insight into how the monomer sequence affects self-assembly and the frequency of interaction between different pairs of monomers.}, number={29}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Benner, Steven W. and Hall, Carol K.}, year={2016}, month={Jul}, pages={7253–7264} }
 @article{benner_hall_2016, title={Effect of Monomer Sequence and Degree of Acetylation on the Self-Assembly and Porosity of Chitosan Networks in Solution}, volume={49}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.6b01063}, abstractNote={Chitosan is a versatile biopolymer that can self-assemble in solution to form hydrogels and nanoparticles. It consists of two types of monomers: glucosamine (GlcN) and N-acetylglucosamine (GlcNAc). Chitosan self-assembly is controlled by a balance of interactions between these two types of monomers: GlcN which gets protonated in solution leading to electrostatic repulsion and GlcNAc which contains an acetyl group, leading to hydrophobic and hydrogen bonding interactions. We present the results of discontinuous molecular dynamics (DMD) simulations aimed at understanding how the degree of acetylation (DA) and monomer sequence affect network formation in solution. Chitosans with DAs ranging from 10% to 50% and three different monomer sequences—random, evenly spaced, and blocky—are studied. We show that chitosans with blocky sequences of GlcNAc monomers form percolated networks earlier in time than random and evenly spaced sequences for all DAs tested. Analysis of the pore size distributions of the resulting ...}, number={14}, journal={MACROMOLECULES}, author={Benner, Steven W. and Hall, Carol K.}, year={2016}, month={Jul}, pages={5281–5290} }
 @article{benner_john_hall_2015, title={Simulation Study of Hydrophobically Modified Chitosan as an Oil Dispersant Additive}, volume={119}, ISSN={["1520-6106"]}, DOI={10.1021/acs.jpcb.5b01092}, abstractNote={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.}, number={23}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Benner, Steven W. and John, Vijay T. and Hall, Carol K.}, year={2015}, month={Jun}, pages={6979–6990} }