Disentangling Polymer Network and Hydration Water Dynamics in Polyhydroxyethyl Methacrylate Physical and Chemical Hydrogels

Abstract

The cross-linker nature and water content may impact the microscopic dynamics of hydrogels components and thus their properties in applications such as drug delivery and water confinement. To investigate these aspects, we used quasi-elastic neutron scattering with contrast variation to distinctly study the polymer and water dynamics in polyhydroxyethyl methacrylate (pHEMA) chemical (cg) and physical (pg) hydrogels with various water contents. For the polymer network, a distribution of relaxation processes was observed, mainly related to the side chains. Water dynamics was found to occur as a H-bond governed process with a jump-diffusion mechanism. The interaction with the polymer matrix considerably slows the water dynamics with respect to bulk water and other confined systems and leads to a fraction of water molecules appearing as immobile. With a higher hydration level, the mobility of both the water and the polymer network increases. For the same water content, pg presents slower relaxation processes and a smaller explored space than their cg equivalents as a result of side chains involvement in the formation of the three-dimensional network typical of hydrogels. In the less hydrated gels, water mobility is sensibly reduced in the cg compared with pg, whereas at higher hydration the mobilities are similar but with shorter residence times in cg.

Dynamics of Water and Other Molecular Liquids Confined Within Voids and on Surface of Lignin Aggregates in Aging Bio Crude Oils

“…The time scale of the motions are faster than the ones found in BCO which indicates that the dynamics observed originates mostly from local rearrangements of the chain conformation. The results are consistent with what reported in hydrated polymer systems (Noferini et al, 2019). Please, note that the fact that no significant stretching of the ISF was observed is attributed to the small fraction of mobile hydrogen atoms and the consequent difficulty in obtaining an accurate modeling.…”

Determination of Antimicrobial and Antibiofilm Activity of Combined LVX and AMP Impregnated in p(HEMA) Hydrogel

“…Employing antimicrobial agents to inhibit bacterial growth and biofilm-formation ability is a reasonable approach to both the prevention and treatment of infections [2]. p(HEMA) is a hydrophilic coating polymer with excellent antifouling capability due to the presence of the O-H group in its structure [16]. Both Gram-positive and Gram-negative bacteria carry a negative charge on their surfaces, which led to initiating the repulsion between negatively charged bacteria and the negative charge of the p(HEMA) surface.…”

“…Poly hydroxyethyl-methacrylate p(HEMA) is a pH-sensitive polymer, containing anionic hydrogel with a primary alcohol [16] that has hydrophilic and lipophilic moieties; it is non-toxic, transparent, and insoluble in water [17,18]. Furthermore, p(HEMA) offers stable mechanical properties [19].…”

Biocompatible and Thermoresistant Hydrogels Based on Collagen and Chitosan

“…Hydrogels can be physical or chemical depending on the crosslinking carried out. In this way, physical hydrogels have non-permanent physical bonds, such as Van der Waals interactions or hydrogen bonds, while chemical hydrogels are composed of covalent bonds, which are stronger [3]. For this reason, physical hydrogels are less stable, being dependent on external stimuli such as ionic strength, solvents, pH or temperature; while chemical ones tend to have greater mechanical resistance, being less dependent on external stimuli.…”