The intensity of this peak decreases (shown in Fig. 4b) due to the isomerization of cis double bonds to trans configuration resulting in oxidation and polymerization reaction [48,49]. In the case of UF microcapsules loaded with LO/MBT (Fig. 4c), the band at 2554 cm−1 indicates the S H stretching vibration of MBT.
The peak at 3453 cm−1 is due to NH stretching mode indicates the presence of thione form of MBT molecules. The strong bands observed in the FTIR spectra at frequencies 1020, 1047 and 1090 cm−1 are ascribed to N C S group vibrations in addition to C C C and C H bending vibrations of MBT thione form. The thiocarbonyl(C S) stretching vibration ofthe MBT ascribed to the band at 1074 cm−1