2.2. Determination of Kinetics of Photopolymerization of Pristine Acrylate Monomers by Real-Time Fourier Transforms Infrared Spectroscopy (RT-FTIR)

The reactivity of the pristine monomers used to prepare the polyHIPEs was determined using the RT-FTIR technique. This time-resolved methodology measured the decrease in the absorbance of the double bonds of the acrylate groups at 1636 cm⁻¹ in a determined time when the photocurable formulation was irradiated with a UV-Vis lamp. The photocurable formulations were prepared by mixing the trifunctional monomer T with the monofunctional monomers I and E, separately and in mixture, in stoichiometric ratios. Table 1 displays the amounts in grams and moles of each component of the formulations. 5 μL of each photocurable mixture was placed between two 3 cm × 3 cm corona-treated PP films. The obtained sandwich was then set in a metal sample holder (held by magnetic strips), that in turn, was vertically positioned within the sample compartment of a Thermofisher Nicolet 6700 FTIR equipment (Thermo Fisher Scientific, Franklin, MA, USA). A Dymax Blue Wave 200 UV-Vis lamp (Dymax, Torrington, CT, USA) was used to perform the experiments. This lamp emits energy in the UVA and visible portion of the spectrum (300–450 nm) (see Figure S1 for emission spectrum of this lamp). The tip of the guide light of the lamp was placed at 45° with respect to the horizontal infrared beam. The distance between the sample and the tip of the UV-Vis lamp was varied between 15 to 20 cm to modulate the intensity of UV light reaching the sample. The data collection rate was 1 spectrum/second. Tests were repeated a minimum of five times for all monomers and the average of these runs is reported. The acrylate conversions were determined by following the band located at 1636 cm⁻¹ corresponding to acrylate double bond vibrations, taking the band of the carbonyl group at 1736 cm⁻¹ as reference.

Composition of the formulations for each studied photocurable HIPE.

* These values correspond to 1% molar with respect to the total amount of double bonds.