Correction to: Synthesis and characterization of a biopolymer of glycerol and macadamia oil
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Correction to: Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-018-7922-3
The correct versions are given below [Figs. 6–10 with their respective figure captions and the correct text of vibrational spectroscopy in the infrared region, density, solvent resistance, and dye adsorption and fluorescence, scanning electronic microscopy (SEM) and solid UV–Vis analysis section].
Vibrational spectrometry in the infrared region
The infrared spectra of the pre-polymer, macadamia oil, and macadamia polymer are shown in Fig. 6a–c, respectively.
After the reaction between glycerol and maleic anhydride, the formation of pre-polymer occurs and its infrared spectrum can be seen in Fig. 6a. The reaction occurs through the consumption of OH and loss of H of C–H groups of glycerol (peaks 3346, 1040, and 1115 cm−1 for OH; 2935 and 2880 cm−1 for C–H) and the consumption of anhydride carbonyls (1778 and 1852 cm−1). Thus, the pre-polymer has a structure of a conjugated ester, presenting the peaks 1708 (carbonyl stretching) and 1204 and 1156 cm−1 [ester conjugation, C–C(C=O)–O] and maintaining the unsaturation of anhydride (C=C stretching at 1638 cm−1 and C–H binding out of plane at 815 cm−1) [13, 14, 38].
In the macadamia oil spectrum (Fig. 6b), the characteristic peaks are 1743 cm−1 that correspond to C=O stretching of ester groups. The sequence of three peaks at 2853, 2922, and 3009 cm−1 indicates the C–H bond stretching of CH2 groups. The peaks at 1649 and 720 cm−1 are due to unsaturations in the oil (C=C stretching and C–H binding out of plane, respectively) [13, 14, 38].
Finally, in Fig. 6c, note the disappearance or the decrease in some pre-polymer peaks, especially at 1638 cm−1 (C=C of anhydride), suggesting “ene” type reactions during polymerization and the arising of the same major peaks of macadamia oil (1743, 2853, 2922, and 3009 cm−1). The rearrangement of double bonds in the ene reaction leads to a reduction in the intensity of the peaks related to the unsaturations remaining of the macadamia oil (1649 and 720 cm−1) [13, 14, 38].
Density, solvent resistance, and dye adsorption
Using Archimedes principle, the polymer density was determined in triplicate . The found density was 1.32 ± 0.01 g cm−3.
In solvent resistance tests, the polymer presents the results in Table 2.
Water and toluene solubilized a small part of the material, followed by ethyl acetate and finally by ethanol, which is the only one capable of attacking a considerable part of the polymer. Briefly, the sequence of resistance is: water > toluene > ethyl acetate > ethanol. These results show that the macadamia polymer can be used in aqueous and nonpolar mediums.
The solutions adsorbed all dyes well, which indicates a strong interaction of the polymer surface and the particles in solution. That result does not explain the interactions presenting between polymer surface and molecules of dye in solution, but demonstrates that it is possible to incorporate organic molecules into the polymer surface. Since macadamia oil and glycerol are edible substances, a promising application for the macadamia polymer is the incorporation of molecules with pharmacological and nutritional interests that are unstable in the isolated form such as anthocyanin and others antioxidants.
Fluorescence, scanning electronic microscopy (SEM) and solid UV–Vis analysis
Figure 9 illustrated that the macadamia polymer surface is very irregular and rough. This surface profile tends to lead to high superficial areas and a substantial interaction with molecules in solution as demonstrated in the dye adsorption tests.
The oil spectrum (Fig. 10a) presents absorption from 250 nm, and at 310 nm, it begins to fall to zero, with a small increment at 410 nm. In the case of the (Fig. 10b) polymer, the pattern is the same until 330 nm, where a pronounced peak appears with maximum at 363 nm, which is the absorption responsible for the fluorescence of the material.