New photoinitiators derived from PET waste: Molecular simulations and photocatalytic efficiency

Poly (ethylene terephthalate) has versatile commercial applications and after the use of PET products, a huge amount of waste is created all around. Chemical recycling is one of the emerging fields in PET waste minimization. Herein PET waste has been recycled using ammonolysis and aminolysis methods to obtain 1,4 benzene dicarboxamide, N,N′-dihydroxoethyl 1,4-benzene dicarboxamide and N,N′-diaminoethyl 1,4-benzene dicarboxamide. The molecules have been investigated through FTIR and UV–Visible spectroscopy techniques after recrystallization from DMSO solvent. The geometries of aromatic amide molecules were optimized and the molecules have been analyzed for vibrational frequencies and UV excitations. The calculations have been performed using general gradient approximation (GGA) with BLYP (Becke-Lee–Yang–Parr) D-3 exchange functional with double-ζ (DZ) basis set. Further HOMO and LUMO energy levels have also been reported to insight the excitation properties of the molecules. HOMO–LUMO energy gaps derived from Beer-Lambert’s law and Tauc equation. The molecules have been investigated as photoinitiating systems in acetic acid for UV curing of bisphenol-A glycerolate diacrylate using Differential Photocalorimeter. Maximum curing rates and degree of conversion have been estimated through DPC thermograms. The order of curing rates, enthalpy of polymerization and degree of conversion were found in agreement with the energy band gap values obtained through DFT simulations and Tauc equation. These molecules may find applications in UV cured composites, coatings, adhesives, paints, varnishes etc.