Effect of the degree of polymerization and water content on the thermal transport phenomena in PEGDA hydrogel: a molecular-dynamics-based study.

A hydrogel is a 3D cross-linked polymer network that can absorb copious amounts of water or biological fluid. Due to their biocompatibility and non-toxicity, hydrogels have a wide range of applications in biomedical engineering. To develop hydrogels with superior thermal dissipation properties, atomistic-level studies are required to quantify the effect of the water content and the degree of polymerization. Classical mechanics-based non-equilibrium molecular dynamics (NEMD) simulations were performed in conjunction with a mathematical formulation developed by Müller-Plathe to explore the thermal conductivity of the poly(ethylene glycol)diacrylate (PEGDA) hydrogel. This work reveals that the thermal conductivity of the PEGDA hydrogel is enhanced with the increase in water content and approaches the value of the thermal conductivity of water at 85% water content in the hydrogel. The PEGDA-9 hydrogel, with a lower level of degree of polymerization, has a superior thermal conductivity than the PEGDA-13 and PEGDA-23 hydrogels. The lower level of degree of polymerization is associated with the higher mesh density of polymer chain network junctions that help to achieve the superior thermal conductivity at higher water contents. Increasing the water content improves the structural stability and compactness of the polymer chains, which can be further associated with the enhanced phonon transfer in PEGDA hydrogels. The work will help in the development of PEGDA-based hydrogels with superior thermal dissipation properties for tissue engineering.