title: Gelation behaviour of a bent-core dihydrazide derivative: effect of incubation temperature in chloroform and toluene.
abstract: In this work, a new kind of gelator, 1,3-bis[(3,4-dioctyloxy phenyl) hydrazide]phenylene (BP8-C), containing two dihydrazide units as the rigid bent-core, has been synthesized and investigated. It was demonstrated that BP8-C is an efficient gelator which can gel various organic solvents, such as ethanol, benzene, toluene, chloroform, etc. Both an opaque gel (O-gel) and a transparent gel (T-gel), which is more stable, were obtained with BP8-C in chloroform at different incubation temperatures. Kinetic data based on fluorescence spectra revealed that the T-gels showed a larger Avrami parameter (n = 1.44 at 20 °C) than that of the O-gels (n = 1.21 for gelation at temperatures below 0 °C). While BP8-C did form the opaque gel in toluene, gelation took longer at lower incubation temperatures and even precipitated out below 0 °C. The kinetic Avrami analysis on sols of BP8-C with different concentrations shows a two-phrase mechanism, i.e. the n values are between 0.88 and 1.74 followed by 1.69 and 3.01 throughout the temperature range of 5 °C and 35 °C for 5.34 mg mL(-1) BP8-C in toluene, indicating that the fibers formed first and then bundled to produce compact networks. We propose that supersaturation governs the formation of gel in chloroform and that the diffusion process denominates gelation in toluene. XRD and FT-IR measurements confirmed that the xerogels prepared at different temperatures in different solvents exhibited a Col(h) structure and that there are three molecules in one columnar slice. Our results indicate that the gelation process, morphology of the gels and thus the final properties of the gels depend strongly on the preparation conditions such as temperature, solvent, concentration, etc.
authors.affiliation: Key Laboratory of Automobile Materials, Ministry of Education, Institute of Materials Science and Engineering, Jilin University, Changchun 130012, People's Republic of China. minli@mail.jlu.edu.cn.
authors.forename: Chunxue
authors.initials: C
authors.lastname: Zhang
authors.forename: Tianren
authors.initials: T
authors.lastname: Zhang
authors.forename: Nan
authors.initials: N
authors.lastname: Ji
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Binglian
authors.initials: B
authors.lastname: Bai
authors.forename: Haitao
authors.initials: H
authors.lastname: Wang
authors.forename: Min
authors.initials: M
authors.lastname: Li
mesh_terms: D002725:Chloroform / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D006834:Hydrazines / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D012995:Solubility; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014050:Toluene / Q000737:chemistry*
chemical_list: D005782:Gels; D006834:Hydrazines; C029424:hydrazine; D014050:Toluene; D002725:Chloroform