LAUSR

Abstract A series of linear segmented poly(urethane acyl- semicarbazides) of different compositions were synthesized from polypropylene glycol (M n  ∼ 1000 and 2000), hexamethylene diisocyanate and cyclohexanedicarboxylic acid 1,4 dihydrazide. The polymers exhibited thermoreversible gelation at a minimum gelation concentration of 25 mg/mL in DMSO in about 25 min. Among the comparisons of varying NCO/OH ratios, PPG 1000 based polyurethanes with NCO/OH ∼ 2.5 and 3 and PPG 2000 based systems with NCO/OH ∼ 3.0 and 3.5 exhibited gelation. IR studies on the solutions and gels (in DMSO) revealed the extensive H-bonding between the chains in gel state. Scanning electron micrographs of the xerogel revealed a 3D-network structure – higher hard segment content (P 1000 -1:3.5) led to a fibrous morphology and lower hard segment content (P 2000 -1:3) led to a microsphere like architecture. The phase separation induced gelation mechanism of self-assembly and effect of the stoichiometry on the morphology were explained based on the correlation between DSC, WAXS and FE-SEM data. The xerogels of the self-assembled polymers described in this work demonstrate a remarkable ability to remove dye molecules selectively, rapidly and efficiently. The gels retain their original structure and performance even after they are recycled 20 times which was quantified by UV–vis studies.