A novel nanoencapsulation of n-hexadecane in high molecular weight polystyrene nanoparticles for thermal energy storage was carried out by miniemulsion polymerization using an iron-containing imidazolium-based ionic liquid (IL) as catalyst. The particle size, morphology, molecular weight, and thermal performance of nanoparticles containing the phase change material (PCM) were measured by dynamic light scattering, transmission electron microscopy, gel permeation chromatography, and differential scanning calorimetry, respectively. The nanoparticles were regular spherical, with narrow size distribution and particle size ranged from 138 nm to 158 nm. The enthalpy of melting for the nanoencapsulated PCM increased from 19 J/g to 72 J/g, as the content of n-hexadecane used increased from 20 wt% to 50 wt%. In addition, the nanoparticles showed thermal reversibility after 100 thermal cycles. The high molecular weights of the polymer, up to 1800 kDa, that could be reached with this IL may have contributed positively to this thermal behavior.

The iron‐containing imidazolium‐based ionic liquids (ILs) 1‐n‐butyl‐3‐methylimidazolium heptachlorodiferrate (BMI.Fe2Cl7) and 1‐n‐butyl‐3‐methylimidazolium tetrachloroferrate (BMI.FeCl4) are applied as catalysts in the homogeneous polymerization of n‐butyl vinyl ether. Both solventless conditions as well as using different organic solvents, catalyst concentrations, temperatures, and reaction times are tested to assess the polymerization conditions that lead to the highest molecular weights of poly(n‐butyl vinyl ether). The Lewis acidic IL BMI.Fe2Cl7 proves to be highly efficient, even at low catalyst concentrations. In bulk polymerization, polymers with 142 kg mol−1 are obtained using a 1:10000 molar ratio of catalyst to monomer. In solution polymerization, the monomer consumption is also rapid and the molecular weight of the polymer is related to the catalyst concentration used. These results indicate the potential of this catalyst for industrial applications. In contrast with the acidic IL, the neutral iron‐containing imidazolium‐based IL BMI.FeCl4 does not show any catalytic activity.