Deep eutectic solvents (DESs) represent an emergent class of green designer solvents that find numerous applications in different aspects of chemical synthesis. A particularly appealing aspect of DES systems is their simplicity of preparation, combined with inexpensive, readily available starting materials to yield solvents with appealing properties (negligible volatility, non-flammability and high solvation capacity). In the context of polymer science, DES systems not only offer an appealing route towards replacing hazardous volatile organic solvents (VOCs), but can serve multiple roles including those of solvent, monomer and templating agent—so called “polymerizable eutectics.” In this review, we look at DES systems and polymerizable eutectics and their application in polymer materials synthesis, including various mechanisms of polymer formation, hydrogel design, porous monoliths, and molecularly imprinted polymers. We provide a comparative study of these systems alongside traditional synthetic approaches, highlighting not only the benefit of replacing VOCs from the perspective of environmental sustainability, but also the materials advantage with respect to mechanical and thermal properties of the polymers formed.

We report the preparation of thermoresponsive poly(N-isopropylacrylamide) (polyNIPAM) hydrogels via the free radical polymerization of deep eutectic monomer solvents (DEMs) for the first time, where NIPAM serves as a polymerizable hydrogen bond donor. DEMs were prepared by a simple heating and stirring protocol using NIPAM and either choline chloride (ChCl) or acetylcholine chloride (AcChCl) (as hydrogen bond acceptor) in various ratios to yield low-melting point liquids (as low as 15 °C). 1D and 2D NMR spectroscopy supported the association of the NIPAM and choline salts present within the DEM structure, in addition to the low self-diffusion coefficients of the species present compared to when dissolved in water. Thermogravimetric analysis demonstrated an enhanced thermal stability of the DEMs compared to NIPAM. Hydrogels prepared by free-radical polymerization of the prepared DEMs in the presence of N,N′-methylenebisacrylamide (BIS) as crosslinker showed a significant increase in reaction rate compared to the equivalent reaction in water, which was attributed in part to the high viscosity of the DEMs. These gels exhibited thermoresponsive swelling behaviour when immersed in water. Specifically, gels prepared via DEMs featured reduced swelling capacity and increased mechanical strength relative to those prepared by aqueous polymerization, attributed to a significant increase in cross-linking density.

Functionalized iron oxide nanoparticles (IONPs) have unique physical and chemical properties, which make them potential candidates for biomedical applications. In this study, a facile one-pot method is reported for the preparation of poly(acrylic acid) (PAA) functionalized IONPsthrough in situ free radical solution polymerization of AA and subsequent coprecipitation of Fe³⁺ and Fe²⁺ ions. The FTIR spectroscopic and TGA results indicated the successful formation and surface functionalization of IONPs with PAA. Electron micrographs showed that the prepared particles were of nano-sized and their shape is dependent on the concentration of PAA. pH-dependent variation of average hydrodynamic diameter confirmed the pH-responsivity of PAA-functionalized IONPs. Magnetic measurement suggested that the PAA functionalized IONPs were strongly paramagnetic (53.0 emug⁻¹). Fenton-like catalytic generation is carried out to measure toxicity associated with the nanoparticles. The suppression ability for reactive oxygen species (ROS) generation associated with PAA-functionalized IONPs was studied via methylene blue degradation assay to address their toxicity profile. PAA-functionalized IONPs exhibited better suppression ability than that of the bare IONPs. The adsorption behavior of trypsin was also studied at different pH levels and a maximum adsorption is occurred on PAA-functionalized IONPs at pH 5.0. Catalytic behavior study confirmed higher activity of trypsin immobilized on PAA-functionalized IONPs than that of the reference IONPs. Therefore, the functionalized IONPs can be of high interest for magnetically recyclable biocatalyst carrier.

Solvent‐free photopolymerization of vinyl monomers to produce high modulus materials with applications in 3D printing and photoswitchable materials is demonstrated. Polymerizable eutectic (PE) mixtures are prepared by simply heating and stirring various molar ratios of N‐isopropylacrylamide (NIPAM), acrylamide (AAm) and 2‐hydroxyethyl methacrylate (HEMA). The structural and thermal properties of the resulting mixtures are evaluated by 1D and 2D NMR spectroscopy as well as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). UV photocuring kinetics of the PE mixtures is evaluated via in situ photo‐DSC and photorheology measurements. The PE mixtures cure rapidly and display storage moduli that are orders of magnitude greater than equivalent copolymers cured in an aqueous medium. The versatility of these PE systems is demonstrated through the addition of a photoswitchable spiropyran acrylate monomer, as well as applying the PE formulation as a stereolithography (SLA)‐based 3D printing resin. Due to the hydrogen‐bonding network in PE systems, 3D printing of the eutectic resin is possible in the absence of crosslinkers. The addition of a RAFT agent to reduce average polymer chain length enables 3D printing of materials which retain their shape and can be dissolved on demand in appropriate solvents.