Dynamical mechanical measurements in dry PHEMA and its hydrogels

Abstract

The elastic modulus and tg ~ of poly(2-hydroxyethyl methacrylate) (PHEMA) and its hydrogels have been measured over the frequency range 0.3-30 Hz and the temperature range 120-450 K. The mechanical spectra reveal the presence of a low-temperature ],-relaxation plus a shoulder (E-relaxation) that merges into the a-relaxation. The absorbed water lowers the temperature and rises the height of the lowest temperature peak (the ],-peak for dry PHEMA) while lowering both temperature and height of the a-peak. This behaviour is interpreted in terms of hydrogen-bonding effects between water and polymer which weaken the intra-and/or interchain interactions. Furthermore, the calorimetric analysis in dry polymer is consistent with the mechanical behaviour in the higher-temperature region.

Improving the Loading and Release of NSAIDs from pHEMA Hydrogels by Copolymerization with Functionalized Monomers

“…2A). The T g , which is visualized as a peak in the plots of delta against temperature at around 125°C, was similar to the values found in the literature for other pHEMA‐based systems 29. The shoulder near 90°C can be attributed to rotational isomerism of the ester side chain or other group motions requiring the breaking and reformation of hydrogen bonds.…”

“…Therefore, only the two lowest proportions (25 and 50 mM) could be evaluated for this monomer. After polymerization, all gels had the high rigidity and fragility characteristics of the glassy state of a dry pHEMA system 29. The hydrogel sheets needed to be boiled in water to provide enough flexibility to cut them into small discs.…”

Hydrogels porosity and bacteria penetration: Where is the pore size threshold?

“…Hydrogels obtained in the absence of water (0% mol) showed a glass-to-rubber transition at 109 • C, which is in agreement with the value previously reported for polyHEMA networks [30,31]. Increasing the proportion of water in the monomer solution, the T g of the hydrogels raised from up to 124 • C (Fig.…”

Dynamic molecular mobility of polyurethane by a broad range dielectric and mechanical analysis

“…The aim of this work is to study the molecular dynamics of PHPMA by dielectric and mechanical relaxation spectroscopy. The effects of hydration and crosslinking of PHPMA on the relaxation modes are shown and compared with the abundant literature on the water influence on the poly(hydroxylalkyl methacrylate)s relaxations by differential scanning calorimetry [33][34][35][36][37][38][39][40], dynamic dielectric spectroscopy [26,29,[42][43][44] and dynamic mechanical analysis [45,46].…”