A series of 19 p-substituted aromatic trifluorovinyl ether compounds were prepared from versatile intermediate p-Br-C(6)H(4)-O-CF=CF(2) and underwent thermal radical mediated cyclodimerization to new difunctional compounds containing the 1,2-disubstituted perfluorocyclobutyl (PFCB) linkage. The synthetic scope demonstrates the functional group transformation tolerance of the fluorovinyl ether, and the dimers are useful as monomers for traditional step-growth polymerization methods. (19)F NMR spectra confirmed that p-substitution affects the trifluorovinyl ether group chemical shifts. The first kinetic studies and substituent effects on thermal cyclodimerization were performed, and the results indicated that electron-withdrawing groups slow the rate of cyclodimerization. The data were further analyzed using the Hammett equation, and reaction constants (rho) of -0.46 at 120 degrees C and -0.59 at 130 degrees C were calculated. This study presents the first liner free energy relationship reported for the cyclodimerization of aromatic trifluorovinyl ethers to PFCB compounds.
Hexa-peri-hexabenzocoronene (HBC) derivatives possess many interesting properties ranging from liquid crystallinity, to hole transport, to variable emission behavior, yet are plagued by insolubility and general accessibility of polymerizable substituents. The first synthesis of trifluorovinyl ether-substituted hexabenzocoronene and its polymerization to perfluorocyclobutyl (PFCB) polymers and copolymers is shown. Unlike hydrocarbon ethers, fluoro vinyl ethers are stable under HBC oxidation conditions. Discrete HBC units in PFCB polymers provide access to potentially processable HBC optical materials.
The synthesis and hyperpolarizabilities of a series of push−pull chromophores containing a bis-(4-methoxyphenyl) amine donor and efficient acceptor bridges with thiophene and ring-locked polyene are presented. The chromophores are readily soluble in common organic solvents and exhibit high thermal decomposition temperatures (highest T
d was 358 °C). Molecular hyperpolarizabilities (β) of the chromophores were measured by hyper-Raleigh scattering at 1604 nm (highest β was 20 000 × 10−30 esu). The electrochemical behavior of the chromophores was studied by cyclic voltammetry and agreed well with the observed intrinsic nonlinearities. In addition, preliminary results of conjugated polyene chromophores containing aryl trifluorovinyl ether monomers were synthesized and copolymerized via thermal cyclodimerization, affording perfluorocyclobutyl aryl ether polymers with high glass transitions (highest T
g was 224 °C) and a good thermal stability (typical T
d was >350 °C). These chromophores can be used to develop electro-optic materials due to their large optical nonlinearities, good absorption characteristics, high thermal stability, and excellent solubility with organic solvents and polymeric materials.
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