The first example of bis(indolyl)methane based hyperbranched polyurethanes: Synthesis, solar cell application and anti-bacterial and anti-oxidant properties

Two new AB₂-type blocked-isocyanate monomers containing bis(indolyl)methane moiety were synthesized via a scalable synthetic routes. Except the “A” functional groups, both of the monomers are structurally identical; one was designed with phenolic [sbnd]OH group (Monomer-1) and the other one was designed with alcoholic [sbnd]OH group (Monomer-2). The first examples of indole based hyperbranched polyurethanes were derived from these monomers in DMF and THF solvents. Blocked-isocyanate end-groups of these polymers were modified with PEG-mono methyl ether. The structures of the AB₂-type monomers and their intermediates were confirmed using FT-IR, ¹H NMR, and ¹³C NMR spectroscopy. The formation of hyperbranched polyurethanes and their end-group modifications were confirmed using ¹H NMR spectra. The absolute molecular weights of the polymers were determined using SEC-MALLS technique and the values were found to be varied from 6.8 × 10³ g/mole to 1.1 × 10⁵ g/mole. The diverse functions of all the synthesised polymers were studied. Dye-sensitized solar cells (DSSC) fabricated with a polymer derived from Monomer-2 (InHBPU-5) yielded an overall energy conversion efficiency of η = 6.59% upon 1 sun illumination with visible light. Also, this polymer showed activity almost equal to tetracycline (control) toward both gram-positive and gram-negative bacterial strains. In addition, this polymer and its monomer, both exhibited good capacity for scavenging DPPH free radical.