Synthesis Of A Series Of Bisamides And Phase Behavior Of Their Aqueous Solutions

Thermosensitive polymer has been studied for decades, which have obtainedsufficient attention and exploration in basic science and applications. However,thermosensitivity of aqueous solutions of low molecular weight compounds wasrarely reported. In this dissertation, we tried to synthesize and find severalthermosensitive molecules with simple structure from the perspective of basicresearch.In this dissertation, the design of the bisamides was inspired by the structure ofpoly(2-alkyl-2-oxazoline) which has cloud point. Six bisamides we initiallysynthesized are not thermosensitive. N,N’-(ethane-1,2-diyl)bis(N-methylbutyramide)and N,N’-(propane-1,3-diyl)bis(N-methylbutyramide) are soluble in water. N,N’-(ethane-1,2-diyl)bis(N-methylpentanamide), N,N’-(propane-1,3-diyl)bis(N-methyl--pentanamide), N,N’-(ethane-1,2-diyl)bis(N-methylhexanamide) and N,N’-(propane--1,3-diyl)bis(N-methylhexanamide) are insoluble in water.Based on the solubility in water of six bisamides we mentioned above, weanalyzed the effect of the molecular structure on the solubility. Then we adjusted thealkyl groups of bisamides and carried out the subsequent synthesis. Eventually wesuccessfully obtained seven bisamides which have thermosensitivity, and recorded thetransmittance-temperature curves of bisamide solution. We obtained cloud points ofbisamide solutions at different mass fraction, and plotted the phase diagrams ofbisamide-water system and get their lower critical solution temperatures (LCST). TheLCST of N,N’-(ethane-1,2-diyl)bis(N-ethylbutyramide) is29oC. The LCST of N,N’-(propane-1,3-diyl)bis(N-ethylbutyramide) is28.1oC. Based on the fact that theinteraction between branched alkyl groups is smaller than that between “normal”alkyl groups, we successfully obtained N,N’-(propane-1,3-diyl)bis(N,3-dimethyl-butanamide) with thermosensitivity through replacing the n-pentyl group by isopentyl group, its LCST is16.6oC. In addition, we synthesized an asymmetrical bisamideN-ethyl-N-(3-(N-methylbutyramido)propyl)butyramide, its LCST is42.2oC.