Raman spectroscopy study on influence of network architecture on hydration of poly(2‐(2‐methoxyethoxy)ethyl methacrylate) hydrogels

Abstract

Thermo‐responsive polymer hydrogels attract a great attention because of their unique behavior in response to changes in the thermal environment. It is related to metastable intermolecular interactions resulting in volume phase transitions (VPT). The hydration of poly(2‐(2‐methoxyethoxy)ethyl methacrylate) (PMEO2MA)‐based materials was studied by Raman spectroscopy and further supported by density functional theory calculations. Hydrogels based on random networks prepared via radiation‐induced free radical polymerization and cross‐linking were compared with hydrogels with more regular structure formed by atom transfer radical polymerization. Two types of regular networks were studied: bare one and decorated by linear dangling chains. It was found that both, the total bound water surrounding the polymer chains (~11 H2O per polymer unit) and accessibility of CO groups for water molecules, are independent of topology of PMEO2MA network. Contrarily, network architecture strongly influences CO–water complex stability, which decreases in a following order: regular bare network, irregular bare network, regular decorated network. It was also shown that the stability of CO–water complex is correlated with VPT temperature in PMEO2MA hydrogels. These studies prove a key role of polymer hydration in its thermo‐responsive properties. Copyright © 2016 John Wiley & Sons, Ltd.

Architecture of Hydrated Multilayer Poly(methacrylic acid) Hydrogels: The Effect of Solution pH

“…Multimembrane polysaccharide hydrogels with an “onion-like” structure were fabricated by multistep gelation of chitosan and alginate and used as scaffolds in biomedical applications for cell transplantation and drug delivery . Changing the architecture of poly­(2-(2-methoxyethoxy)­ethyl methacrylate) networks from random to more regular structures was shown to influence hydrogel hydration . Still, compared to traditional hydrogel parameters, such as composition, cross-link density, and size, network architecture has been much less investigated, and these studies have been mostly limited to bulk materials. − There are even fewer studies on the internal structure of thin hydrogels due to the technical challenges of regulating network assembly and resolving architecture at the nanoscale.…”

Closed-Loop Controlled Photopolymerization of Hydrogels

“…Raman spectroscopy has been utilized for the compositional analysis of hydrogels . In addition, the Raman spectra of hydrogels have also been utilized to characterize the structure of hydrogels. , For example, the sharpness of peaks in the Raman spectra as characterized by the full width at half maximum (FWHM) has been associated with the extent of network structure heterogeneity. As shown in Figure a, we found that the amplitude of the peak at 1409 cm –1 associated with CC bonds differed among the various controllers, suggesting that more CC bonds were consumed from the rate-based bang-bang controlled photopolymerization process ( K D ), which exhibited the lowest curing rate among the closed-loop controlled processes.…”

Nanoscale Observation of Dehydration Process in PHEMA Hydrogel Structure

“…Such an effect may be interpreted in the basis of three state model of water structure. According to the three state model, water molecules can exist in three kinds of states in the hydrogel structure, namely bounded (hydration) state characterized by presence of hydrogen bonds between water and hydrophilic as well as hydrophobic groups in polymer network, interstitial state, where water molecules are surrounded by polymer network and free state also called as bulk water [ 27 – 29 ]. Band shift existing up to 100 min probably reflects in desorption of bulk water and is connected with appearance of high amount of non-bonded water molecules what can be presented by increase of integral intensity of 3600 cm −1 band in Fig.…”