Polyaniline/multiwalled carbon nanotube composite films have been fabricated. It is shown that the nanotubes affect the free N–H environment and quinoid units along the polymer backbone. A 10‐fold increase in conductivity is observed and elemental analysis indicates that the nanotubes compete with chloride ion during HCl doping (see Figure).
The synthesis and characterization of
siloxane-containing perfluorocyclobutane (PFCB)
aromatic polyethers, a new class of fluorosiloxane polymers possessing
a well-defined linear structure of
alternating disiloxanyl-p-phenylene
(cis/trans)-1,2-disubstituted perfluorocyclobutyl
ether linkages with
known fluoroolefin end groups, is described. The unexpected
formation of an aryl Grignard reagent from
4-[(trifluorovinyl)oxy]bromobenzene (2) allowed
for the high-yield synthesis of
4-[(trifluorovinyl)oxy]phenyldimethylsilane (3) which was dehydrogenatively
hydrolyzed in situ and condensed to
bis[1,3-[4-[(trifluorovinyl)oxy]phenyl]]-1,1,3,3-tetramethyldisiloxane
monomer (4). Thermal cyclopolymerization
in
the bulk produces
poly(1,1,3,3-tetramethyldisiloxanyl-p-phenylene-1-oxaperfluorocyclobutylene-2-oxa-p-phenylene) (5) as a clear, flexible, and thermally stable
elastomeric film. Copolymerization of 4 with
a
trifunctional PFCB monomer gives a toughened thermoset with good
thermal stability. Monomers and
polymers were characterized by 1H, 13C, and
19F NMR and FTIR spectroscopy. Number-average
molecular
weights were determined by gel permeation chromatography and, when
possible, quantitative 19F NMR
end group analysis. Synthesis, characterization, thermal analyses,
and current scope of PFCB polymer
chemistry are discussed.
The copolymerization of aryl bis‐ and tris‐trifluorovinyl ether monomers yields aromatic perfluorocyclobutyl (PFCB) polymers, via thermally initiated step‐growth cycloaddition chemistry. PFCB polymers and their copolymers enjoy a unique combination of attributes well suited for applications in photonic technologies, such as broad tailorability of refractive indices and thermo‐optic coefficients, low transmission losses at 1300 and 1550 nm, high thermal, mechanical, and optical stability, and excellent melt and solution processability. Planar PFCB structures can be processed by direct micro‐transfer molding, which is a first step towards rapid soft‐lithographic fabrication of polymer planar lightwave circuits. Copolymerization chemistry and processing parameters and characterization, including thermal (Tg = 120–350 °C) and optical properties (refractive indices from 1.443 to 1.508 at 1550 nm; thermo‐optic coefficients dn/dT = –7×10–5 K–1 to –1.5 × 10–4 K–1), birefringence (< 0.003), and temporal stability of refractive index, are described.
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