ABSTRACT
Electron microscopy evolved over the past eight decades as a revolutionary imaging technique for scientists and engineers and represents today a key technology for the characterization of materials across a wide range of applications. Scanning electron microscopy (SEM) is used in materials science for in-depth characterization, quality control, and failure analysis providing topographical, morphological, and compositional information about the surface of different materials. Hydrogels are cross-linked three-dimensional (3D) networks made from hydrophilic polymeric chains which are capable to absorb large amounts of water or biological fluids. Since water is the greatest component of the human body, hydrogels display an undeniable potential as prime candidates for biomedical purposes, in fields like drug delivery, self-healing materials, and carriers or matrices for tissue engineering. These remarkable materials include several benefits, such as increased biocompatibility, tunable biodegradability, tailorable porous architectures, proper mechanical strength, and a degree of flexibility close to natural tissues.
This chapter highlights the important role of SEM in the study of morphological structure of hydrogels obtained from three of the most abundant biopolymers on earth: cellulose, hemicellulose, and lignin. The construction of the 3D porous network is one of the essential factors which influence the final properties, from swelling and mechanical properties to transport kinetics and release of active principles. While much of the research on hydrogels is centred on identification of advanced pathways to create novel materials of superior quality, there will always be a primary need to obtain detailed and complex information about the porous architecture, supramolecular organization and morphology of these materials. SEM is able to provide solid and realistic information related to the appearance, integrity, organization, quality, and degree of uniformity of hydrogels. The obtained data are multiple and allow the construction on several hierarchical levels of a true image of the porous assembly, in a wide dimensional range.
