PEGDA hydrogel structure from semi-dilute concentrations: insights from experiments and molecular simulations

Area of Science:

• Polymer Science
• Biomaterials Engineering
• Computational Chemistry

Background:

• Hydrogel efficacy in biomedical applications depends on polymer network topology and pore structure.
• Tuning hydrogel microstructure requires adjusting synthesis parameters like macromer molar mass and concentration.
• Mechanically robust hydrogels for tissue engineering and drug delivery necessitate non-dilute conditions.

Purpose of the Study:

• To characterize structural features of poly (ethylene glycol) diacrylate (PEGDA) hydrogels across various semi-dilute concentrations.
• To investigate the relationship between polymer solution interactions, hydrogel structure, and swelling behavior.
• To provide insights into hydrogel network dynamics for improved biomedical applications.

Main Methods:

• Combined experimental (bulk rheology) and molecular dynamics simulations.
• Characterization of 4.8 and 10 kDa PEGDA hydrogels from semi-dilute solutions.
• Analysis of hydrogel structure using swollen polymer network hypothesis and pore size distributions.

Main Results:

• An entanglement concentration around 28 wt% was identified for PEGDA pre-gel solutions.
• A transition in swelling behavior, with reduced water retention, occurred near the entanglement concentration.
• A structural transition concentration at the swelling inflection point correlated with the entanglement concentration.
• Theoretical mesh sizes exceeded computationally determined pore diameters across all concentrations.
• Molecular simulations revealed dynamic pore behavior distinct from time-averaged features.

Conclusions:

• A structural transition in hydrogels occurs at a concentration comparable to the entanglement concentration, impacting swelling and water retention.
• Discrepancies between theoretical mesh sizes and simulated pore diameters highlight the complexity of hydrogel microstructure.
• Understanding hydrogel network dynamics at physiological temperatures is crucial for designing advanced biomedical materials.