Polymer Networks and Gels

Crosslinked polymers are three-dimensional networks produced by either chemical crosslinking (when the crosslinks are formed by covalent chemical bonds) or physical gelation (when the crosslinks are formed by physical interaction and strong entanglement) between the linear chains of one or more polymers. A special category of networks are those obtained by participating in the crosslinking of at least two polymers, i.e., an interpenetrated polymeric network or semi-interpenetrated polymeric network (when only one of the polymers forms the network, the linear chains of the second crossing the meshes of the network formed by the first).

Their properties, which are both varied and interesting, render polymer networks very attractive materials. Depending on the chemical structure and the crosslinking density, polymer networks can show an elastic or rigid behavior with good mechanical properties. Thermosetting polymers and crosslinked elastomers behave completely differently. Elastomers, whose glass transition temperature is usually below –50 °C, are soft and flexible at ambient temperature, while thermosets show a high stiffness even above the glass transition temperature. The properties of both categories of polymer networks depend on the degree of crosslinking and the crosslinking density of the network. An important feature of these networks is their ability to swell by taking up solvents. When crosslinked polymers have a pronounced hydrophilic character, i.e., water solubility, the obtained networks will have the capacity to include significant amounts of this solvent—swelling behavior—a situation in which we speak about hydrogels.

The applications of polymer networks and gels are extremely varied in different fields of technology, for example, in the biomedical or environmental fields, with these materials obviously contributing to an improvement in the quality of our lives. The Section “Polymer Networks and Gels” deals with all branches of science, biology, medicine, and technology connected to emerging new research in the field of hydrogels, including but not limited to natural and synthetic chemical hydrogels, physical hydrogels, vitrigels, cryogels, hydrogel characterization techniques, interpenetrating and interconnecting networks with hydrogel characteristics, hydrogels as smart polymers and biomaterials, hydrophilic–hydrophobic interpenetrating polymer networks, homopolymers, copolymers and multipolymer hydrogels, nanogels, composite hydrogels, superadsorbent hydrogels, fast responsive hydrogels, smart hydrogels (stimuli responsive hydrogels), micro/nanoparticulate hydrogels, hydrogel films, hydrogel foams and sponges, biodegradation of hydrogels, hydrogels for drug delivery, enzymes immobilized on hydrogels, medical applications of hydrogels (e.g., medical technology, restorative medicine, diagnostic systems, cancer therapy, controlled drug release, gene vectors, biosensors, contact lenses, membranes, medical implants, and inserts), applications of hydrogels in veterinary medicine, cosmetics, tissue engineering, cell culture, biotechnology, artificial muscles and organs, soft robotics, energy storage, environmental remediation, computational and theoretical aspects, molecular simulations of hydrogel structures, and much more.

The Section “Polymer Networks and Gels” of Polymers aims to rapidly publish contributions on the aspects of the synthesis, characterization, and applications of crosslinked polymers, and achievements in the field. Our aim is to offer a platform not only for dissemination but also for debates on new, interesting results in this field with large application potential.

The scope of the section includes but is not limited to the following topics:

• Covalent networks
• Dynamic covalent networks
• Ionic networks (ionic gelation)
• Double crosslinked networks
• Interpenetrating networks (IPN)
• Semi-interpenetrating networks (semi-IPN)
• Interpolymer complexes
• Supramolecular polymer systems
• Thermosetting polymers
• Vitrimers
• Rubber polymers
• Elastomers
• Soft robotics
• Hydrogels
• Functional and smart gels
• 3D/4D printing of gels
• Biomedical applications of gels
• Pharmaceutical applications of gels
• Gels in cosmetics and personal care
• Food gels and edible gels
• Biodegradable and bio-based gels
• Hydrogels for sustainable agriculture
• Energy and environmental applications of gels
• Recycling and reprocessing of polymer network materials
• Life cycle assessment of polymer network products