Effect Of ?-? Stacking On The Radical Polymerization Of Vinyl Monomer

Aromatic-aromatic or ?-? interactions are important non-covalent intermolecular forces similar to hydrogen bonding, and ?-? interactions between aromatic-rings play a significant role in determining the structures and properties of molecular assemblies in biology, chemistry and material sciences, including molecular recognition, stereoselective organic reactions, nucleic acid and protein macroscopic structures and crystal packing. In this work, a facile synthetic route to prepare 2,5-Diphenyl-styrenene (DVB) via using 2,5-Dibromotoluene and N-bromosuccinimide (NBS) as raw materials. Firstly, 2,5-dibromo-1(bromomethyl)benzene was synthesized by a-haloalkyl reaction of aromatic,phosphonium salts was prepared phosphorous ylides reaction, 2,5-Dibromostyrene was obtained via aqueous witting reaction, target product DVB was developed using cross-coupling reaction. The chemical structure of monomer and key intermediates was characterized by proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR) and fourier transform infrared spectroscopy (FT-IR). The thermal properties of polymer were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The molecular weight of polymer was studied by gel permeation chromatograph (GPC).The radical homopolymerization of 2,5-Diphenyl-styrenene was carried out in toluene or heptane using benzyol peroxide (BPO) as the initiator. The effect of ?-?stacking on the radical polymerization of vinyl monomer was explored by adding hexafluoro-benzene or octafluoronaphthalene in different solution. The ?-? interaction results show a little effect on the conversion of the vinyl monomer in the polymerization process, and there is little effect on molecular weight distribution and stereochemical differences between the PDVB formed with or without HFB. However,?-? interaction may enhance the flexibility of the polymer chain segments, lower the glass transition temperature of the polymer.The radical copolymerization of 2,3,4,5,6-Pentafluorostyrene and 2,5-Diphenyl-styrenene was carried out in toluene and heptane at 70? using benzyol peroxide as the initiator, in toluene at 25? under redox conditions. The optimum comonomer conversions are limited to 10 mol% and still recover a sufficient amount of copolymer for characterization. The values of monomer reactivity ratios were calculated by linear[Fineman-Ross (F-R) and Kelen- Tudos (K-T) equations] and nonlinear least-squares methods (NLLS). The values of monomer reactivity ratios were carried out rDVBrPFS=0.11(25?, toluene), rDVBrPFS= 0.19 (70?, toluene) and rDvBrPFS=0.37 (70?, heptane),respectively. The reactivity ratios demonstrated that both comonomer pairs tend to alternate, and the alternating tendency of copolymer was increased in toluene. In addition,their alternating tendency increases with decreasing temperature.