ABSTRACT:An approximately 100% branched hyperbranched polymer was successfully prepared using 2-(4-phenoxyphenoxy)fluorenone as a monomer in an acidic medium. The kinetics of the model reaction between 9-fluorenone and anisole was investigated. The reaction obeyed the second-order kinetics, indicating that the first reaction, i.e., the formation of the intermediate from 9-fluorenone and anisole, is considerably slower than the second one, i.e., the reaction of the intermediate with anisole. Based on this finding, a new monomer expected to produce a 100% branched hyperbranched polymer, 2-(4-phenoxyphenoxy)fluorenone, was designed and prepared. Hyperbranched polymers have attracted considerable attention owing to their unique properties such as an intrinsic globular structure, low viscosity, high solubility, and a large number of terminal functional groups. There are many reports on the synthesis and characterization of hyperbranched polymers and their various applications such as those in blended components, photosensitive materials, nonlinear optics, and catalysts. [1][2][3][4][5][6][7][8] Hyperbranched polymers are generally characterized by a degree of branching (DB) that is theoretically approximately 50% for a polymer derived from an AB 2 monomer; this value is assumed on the basis of the equal reactivity of the B functional groups of the AB 2 monomer. 9 The approaches reported to enhance the DB include slow addition, 10 polymerization in the presence of polyfunctional core molecules, 11 use of polyfunctional AB x monomers, 12 and post-synthetic modification. 13 Although these methods improve the DB, they do not result in a 100% DB. To obtain hyperbranched polymers with a 100% DB, the first reaction step of an AB 2 monomer should activate the second reaction.14 Voit et al. have reported the synthesis of a hyperbranched polymer with a 100% DB by the polymerization of an AB 2 -type monomer in ''criss-cross'' cycloaddition with the maleimide group as the A functional group and azine groups as the two B groups. 15 Recently, Smets et al. have reported that the acid-catalyzed polycondensation of isatins or acenaphthenones with aromatic compounds yielded hyperbranched polymers with a 100% DB. 16,17 These reports prompted us to synthesize a hyperbranched polymer with an approximately 100% DB from a common ketone compound.Ordinary ketones such as fluorenone show a poor ability to undergo diarylation; HCl catalyzes the condensation of fluorenone with phenol to afford the corresponding diarylated compound in a 46% yield in 2 d.18 Yamada et al. demonstrated that the diarylation of fluorenone effectively proceeds when 3-mercaptopropionic acid (MPA) is added to the reaction mixture at 65 C. 19Therefore, we expected that the diarylation utilizing an acid with MPA could apply to the synthesis of 100% branched hyperbranched polymer.In this paper, we present the synthesis of a hyperbranched polymer with an approximately 100% DB by the polycondensation of an AB 2 monomer, 2-(4-phenoxyphenoxy)fluorenone. The model reaction of 9...
On the basis of 1 H NMR analysis of the model complexes formed from ortho-, meta-, and para-phthalic acid with 2-amino-3-hydroxy pyridine (AHP), it was found that the two carboxyl groups located at the ortho position of the benzene ring more easily interact with AHP than those at meta-and para positions. A series of gelators (defined at G1-G5) were prepared from 1,2,4,5-benzene tetracarboxylic acid (BTCA) and AHP at different molar ratios, and their structures were analyzed by 1 H NMR and FT-IR. The gelation performances of the gelators were investigated in details, which indicated that G3 formed at the BTCA/AHP molar ratio of 1.0/2.3 possessed the shortest gelation time, the lowest minimal gelation concentration (MGC), and the highest maximal gel-to-sol dissociation temperature (T gel ). The xerogels were analyzed by SEM and powder X-ray diffraction, especially, the single crystal of G1 obtained directly from the gelling solvent showed complicated hydrogen bonded networks which were a direct evidence to explain the connecting network of the molecules. Based on this, the gelation properties were discussed. The relationship between the structures and properties of the gels is helpful for understanding the gelating mechanism and designing new gelators.Scheme 1. Synthesis of the model compounds.Scheme 2.
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