Hydrogels have gained a lot of attention with their widespread use in different industrial applications. The versatility in the synthesis and the nature of the precursor reactants allow for a varying range of hydrogels with different mechanical and rheological properties. Understanding of the rheological behavior and the relationship between the chemical structure and the resulting properties is crucial, and is the focus of this review. Specifically, we include detailed discussion on the correlation between the rheological characteristics of hydrogels and their possible applications. Different rheological tests such as time, temperature and frequency sweep, among others, are described and the results of those tests are reported. The most prevalent applications of hydrogels are also discussed.

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A biorenewable polymer is synthesized via a green process using the RAFT principle for the first time in supercritical CO2 at 300 bar and 80 °C. α‐Methylene‐γ‐butyrolactone polymers of various chain lengths and molecular weights are obtained. The molecular weights vary from 10 000 up to 20 000 with low polydispersity indexes (PDI <1.5). Furthermore, the monomer conversion in supercritical CO2 is substantially higher, respectively 85% for ScCO2 compared to ≈65% for polymerizations conducted in dimethyl formamide (DMF) solvent. Chain extensions are carried out to confirm the livingness of the formed polymers in ScCO2. This opens up future possibilities of the formation of different polymer architectures in ScCO2. The polymers synthesized in ScCO2 have glass transition temperature (Tg) values ranging from 155 up to 190 °C. However, the presence of residual monomer encapsulated inside the formed polymer matrix affects the glass transition of the polymer that is lowered by increasing monomer concentrations. Hence, additional research is required to eliminate the remaining monomer concentration in the polymer matrix in order to arrive at the optimal Tg.

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Oxidative chemical vapor deposition (oCVD) is an extremely effective method for solvent-free deposition of highly conductive polypyrrole films, where polymer synthesis, doping, and film formation are combined in a single...

Both shape memory and self-healing polymers have received significant attention from the materials science community. The former, for their application as actuators, selfdeployable structures, and medical devices; and the latter, for extending the lifetime of polymeric products. Both effects can be stimulated by heat, which makes resistive heating a practical approach to trigger these effects. Here we show a conductive polyketone polymer and carbon nanotube composite with crosslinks based on the thermo-reversible furan/maleimide Diels−Alder chemistry. This approach resulted in products with efficient electroactive shape memory effect, shape reprogrammability, and self-healing. They exhibit electroactive shape memory behavior with recovery ratios of about 0.9; requiring less than a minute for shape recovery; electroactive self-healing behavior able to repair microcracks and almost fully recover their mechanical properties; requiring a voltage in the order of tens of volts for both shape memory and self-healing effects. To the best of our knowledge, this is the first report of electroactive self-healing shape memory polymer composites that use covalent reversible Diels−Alder linkages, which yield robust solvent-resistant polymer networks without jeopardizing their reprocessability. These responsive polymers may be ideal for soft robotics and actuators. They are also a step toward sustainable materials by allowing an increased lifetime of use and reprocessability.

Diphenolic acid is functionalized with furfuryl amine and subsequently incorporated in a (partly) bio-based polyester through interfacial polycondensation with terepthalic chloride. The furan groups present in the resulting polyester are able to form a thermoreversible covalent network with different bismaleimide moieties via the Diels–Alder (DA) reaction. Our analysis of the polymer network by 1H-NMR clearly shows the formation of both possible stereoisomers (endo and exo) from the Diels–Alder coordination of furan and maleimide. Furthermore, it was found that these isomers can be reversibly interchanged at temperatures below the reported retro Diels–Alder reaction temperature, a phenomenon often claimed but, until present, never directly observed, for thermally reversible polymeric systems. Finally, a proof of principle for reversibility and recyclability is shown.

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