The Study On Poly Alcohol Acetal Derivatives As Low Molar-mass Organic Gelator

In this work, a series of poly alcohol acetal derivatives as gelators weresynthesized. The relation between structure and gelation ability were studied, and theapplication of nano-material were achieved.36 compounds of were prepared by condensation between aromatic aldehyde andploy alcohol such as sorbitol,mannitol,xylitol, then esterification and acylation. Thestructure of the products have been confirmed by NMR and LC-MS. This paperindicated that it was good for condensation reaction when benzene-ring bearingelectron-attaching groups. It also showed that and the 6-hydroxyl group could bereacted with acyl halide, haloid ether and halo alkene, but not with halo alkane. It wasnot only the first time to find that the reaction product of D-mannitol and aromaticaldehyde is tri-condensation derivatives, but also the first time to obtain thep-phthaldehyde-sorbitol derivatives containing eight hydroxyl groups.The gelation ability of the poly alcohol acetal derivatives was evaluated. Itshowed that most compounds possessed the gelation abilities and formed transparentthermo-reversible gels with minimum gelation concertration of < 1w% in a widerange of organic solvents containing oxygen atom such as alcohols, ketones andethers etc. It was noted that alkyl alcohol and anisole had greater gelation ability thanaryl alcohol, cyclic alcohol and ketone. Surprisingly, the gelation ability will begreatly dropped when a little water was added in the solvent. It was found firstly thatthe compounds when benzene-ring bearing amino group would lose their gelationability.The transmission electron microscope revealed that the gels formed had afibrillar structure from about 50 to 100 nm in diameter. The fibres further formed anentangled network that was responsible for the entrapment of solvent moleculesduring gelation. The enthalpy of gel-sol phase transition by hydrogen bonding was55.4 KJ.mol-1 for compound 3 in glycerol(25℃).FT-IR studies revealed that the aggregates and self-assembly of the gelatorsoccurred as a result of cooperating non-covalent interactions such as intermolecularhydrogen-bonding. X-ray diffraction analysis illustrated that dry-gel state could keepthe fibrillar network structure of the gel state.Using organogel fibers formed by the poly alcohol acetel derivaties gelators as atemplate, the SiO2 and TiO2 nanoparticles were prepared the first time. The TiO2particles are anatase crystal form with 10-20 nm in diameter, and the SiO2 particlesare uncrystallized. The TiO2 nanoparticles have good photocatalysis degradationproperties, and the kinetics is the first-order to methylene blue.