Genesis of an ecofriendly A_n + B₃ hyperbranched polyester from Poly (ethylene glycol) and aconitic acid for application as flocculant

Hyperbranched polyesters with polyionic character and high hydrodynamic sizes were synthesized at four different monomer mole ratios (A_n/B₃ = 1:0.5, 1:1, 1: 3 and 1:5) by melt condensation of ecofriendly Poly (ethylene glycol) or PEG and Aconitic acid or AA via A_n+ B₃ approach. The products were characterized by FTIR, ¹H NMR, FESEM, TEM and DSC techniques to establish the microstructure as well as the hyperbranched architecture. The degree of branching was estimated to be within 89%-33% by ¹H NMR measurements. Polyesters synthesized from 1:3 and 1:5 contained low (12%) to moderately high (40%) crosslinked structure as well. Gelation was effectively avoided at 1:0.5 and 1:3 mol compositions by keeping the AA content at lower values than PEG. The most soluble hyperbranched polyester was spherical having a dense core and a higher shell morphology. Whereas, the more crosslinked molecule was spherical but uniformly dense. Due to of the polyelectrolytic nature, the polyesters were used as flocculant to unsettle highly stable kaolin suspension at low suspension concentration maintained at 0.25% concentration by weight. The highest hydrodynamic size of the sample synthesized from 1:1 mole composition, was able to flocculate at the fastest rate (39 s) at pH 2.0 than at the iso-electric point (pH 4.2) of kaolin as well as reproduced the pure water with highest clarity (turbidity: 4 NTU).