title: A systematic study of peripherally multiple aromatic ester-functionalized poly(benzyl ether) dendrons for the fabrication of organogels: structure-property relationships and thixotropic property.
abstract: A new class of peripherally multiple aromatic ester-functionalized poly(benzyl ether) dendrons and/or dendrimers with different focal point substituents, surface groups, interior structures, as well as different generations have been synthesized and their structure-property relationships with respect to their gelation ability have been investigated systematically. Most of these dendrons are able to gel organic solvents over a wide polarity range. Evident dendritic effects were observed not only in gelation capability but also in thermotropic, morphological, and rheological characterizations. It was disclosed that subtle changes in peripheral ester functionalities and interior dendritic structures affected the gelation behavior of the dendrons significantly. Among all the dendrons studied, the second- and third-generation dendrons G0G2-Me and G0G3-Me with dimethyl isophthalates (DMIP) as peripheral groups exhibited the best capability in gelation, and stable gels were formed in more than 22 aromatic and polar organic solvents. The lowest critical gelation concentration (CGC) reached 2.0 mg mL(-1), indicating that approximately 1.35×10(4) solvent molecules could be entrapped by one dendritic molecule. Further study on driving forces in gel formation was carried out by using a combination of single-crystal/powder X-ray diffraction (XRD) analysis and concentration-dependent (CD)/temperature-dependent (TD) (1)H NMR spectroscopy. The results obtained from these experiments revealed that the multiple π-π stacking of extended π-systems due to the peripheral DMIP rings, cooperatively assisted by non-conventional hydrogen-bonding, is the key contributor in the formation of the highly ordered supramolecular and fibrillar network. In addition, these dendritic organogels exhibited unexpected thixotropic-responsive properties, which make them promising candidates with potential applications in the field of intelligent soft materials.
authors.affiliation: Beijing National Laboratory for Molecular Sciences and CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry Chinese Academy of Sciences (CAS), Beijing 100190 (P.R. China), Fax: (+86) 10-62554472.
authors.forename: Yu
authors.initials: Y
authors.lastname: Feng
authors.forename: Zhi-Xiong
authors.initials: ZX
authors.lastname: Liu
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
authors.forename: Zhi-Chao
authors.initials: ZC
authors.lastname: Yan
authors.forename: Yan-Mei
authors.initials: YM
authors.lastname: He
authors.forename: Chen-Yang
authors.initials: CY
authors.lastname: Liu
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Fan
keywords: dendrimers; gelators; organogels; self-assembly; structure-property relationships