45 mirror angle

The degree of conversion of the activated test materials was evaluated using a Fourier transform infrared spectrometer (Model IR-Prestige 21, Shimadzu Corporation, Japan) equipped with an attenuated total reflectance device composed of a horizontal ZnSe crystal with a 45° mirror angle (PIKE Technologies, Madison, WI, USA). A light-emitting diode (LED) light-curing unit (Optilight Max, Gnatus, Sao Paulo, Brazil) was attatched to a support coupled to the spectrometer in order to maintain a distance of 5 mm between the fiber tip and the sample during light activation. The irradiation values (1000 mW/cm^{2 (link)}) were measured using a digital power meter (Bluephase meter, Ivoclar; Schaan, Liechtenstein).
The infrared spectra of the uncured and cured samples were obtained (n=3). Real-time measurements were conducted using attenuated total reflection. The height of the aliphatic C=C absorption peak observed at 1638 cm⁻¹ and the carbonyl C=O absorption peak located at 1717 cm⁻¹ was determined from each spectrum. The aromatic carbonyl C=O was used as an internal reference. Double bond conversion was determined using a previously described method.^{16 (link)}

The degree of conversion of the experimental materials was evaluated using Fourier transform infrared spectroscopy with a spectrometer (Prestige 21, Shimadzu, Ltd., Tokyo, Japan) equipped with an attenuated total reflectance device. The reflectance device was composed of a horizontal ZnSe crystal with a 45° mirror angle (PIKE Technologies, Madison, WI, USA). The IRSolution software package (Shimadzu, Columbia, MD, USA) was used in the monitoring scan mode using Happ–Genzel apodization in the range 1750–1550 cm⁻¹ range, an 8 cm⁻¹ resolution and 2.8 mm/s mirror speed. Using this configuration, one scan was acquired every 1 s during light activation. The degree of conversion was calculated as described in a previous study¹⁹ and based on the intensity of the carbon–carbon double-bond stretching vibrations (peak height) at 1635 cm⁻¹, as well as using the symmetric ring stretching at 1610 m⁻¹ from the polymerized and non-polymerized samples as an internal standard. The analyses were performed in triplicate (n=3). The data were plotted and curve fitting was applied using logistic non-linear regression. In addition, the polymerization rate (Pr^-1) was calculated as the degree of conversion at time t subtracted from the degree of conversion at time t − 1. The coefficient of determination was greater than 0.98 for all curves.