Effect of Monomer Sequence and Degree of Acetylation on the Self-Assembly and Porosity of Chitosan Networks in Solution

Abstract

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 chitosan networks shows that blocky sequences of GlcNAc monomers lead to larger pores than random and evenly spaced sequences for DAs less than or equal to 30%. The monomer sequence has little impact on pore size distribution when the DA is 40% or higher. Finally, we show that at low DA, chitosan networks allow free diffusion of small molecules through the network but slow the diffusion of large molecules. At high DA, chitosan networks allow free diffusion of both large and small molecules. We conclude that controlling the monomer sequence of chitosan could be effective at controlling the structure of the resulting network.

Structural Relaxation and Vitrification in Dense Cross-Linked Polymer Networks: Simulation, Theory, and Experiment

“…Then, we can define the cross-link density in simulations as Here, n cross‑link and n monomer are the number of moles of cross-links and normal monomers, respectively. To guarantee a network is formed, we calculated the maximum network size, which is defined as the number of chains in the largest network. , Five values of cross-link fraction ( f cross ) are considered: 0 (linear polymer), 0.11, 025, 0.36, and 0.5. For all these networks, the maximum network size equals the total number of chains, so that the networks are percolated.…”

Biobased Dynamic Polymer Networks with Rapid Stress Relaxation

“…With the rapid growth of population and huge use of resources to generate nonrenewable materials, fossil resources face serious depletion. Consequently, numerous sustainable, nontoxic, biobased resources have been used as alternatives to petroleum-based feedstocks, including, for example, epoxidized soybean oil (ESO), natural rubber, lignin, vanillin, and chitosan . As a low-cost, abundant biomass resource, ESO has several advantages and has attracted significant attention in the academic and industrial sectors. − For example, Hu et al prepared a completely biobased DPN by cross-linking ESO with glycyrrhizic acid.…”

The role of disaccharides as a plasticizer in improving the interaction between chitosan chain based solid polymer electrolytes (SPEs)

“…The presence of functional groups such as amines and hydroxyls in chitosan, sucrose, and lactose made them good donors and acceptors of hydrogen bonds. 23 Based on Fig. 2, a chitosan monomer formed five intramolecular hydrogen bonds which were on atoms N18–H19–O21, N18–H20–O23, N30–H35–O13, O34–H40–O39 and O39–H44–O43 and two intermolecular hydrogen bonds which were on atoms O16–H17–O27 and O21–H22–O47.…”