Study of Related Poly(1,3,4-Oxadiazole-Amide)s Containing Silicon or Hexafluoroisopropylidene Groups in the Main Chain

Abstract

Two series of related poly(oxadiazole-amide)s have been synthesized by solution polycondensation reaction of aromatic diamines containing preformed 1,3,4-oxadiazole rings with diacid chlorides having silicon or hexafluoroisopropylidene groups. All these polymers were soluble in polar amidic solvents, such as N -methylpyrrolidinone and dimethylformamide and gave thin transparent free-standing films on casting their solutions. The polymers exhibited high thermal stability, with the initial decomposition temperature being above 400 • C. Most of these polymers did show a glass transition, being in the temperature range of 238-275 • C. Very thin coatings, in the range of tens of nanometres, which were deposited onto silicon wafers exhibited smooth and pinhole-free surfaces in atomic force microscopy investigations. The study of photoluminescence properties revealed that some of these compounds emit blue light, in the range of 440-475 nm. All these characteristics are discussed and compared with those of conventional aromatic poly(1,3,4-oxadiazole)s.

Photo-optical properties of poly(oxadiazole-imide)s containing naphthalene rings

“…Polyimides Id and Ih presented a red-shift of the main emission maxima compared with polyimide If, probably due to the substitution of m-phenylene rings with oxygen in the dianhydride segment of the repeating unit: in the excited state the oxygen acts as a better bridge for the delocalization of the charge, because the position of the phenylene ring next to the oxygen determines the PL more significantly. 13,33 The PL spectra of the films cast from CHCl 3 solutions showed three maxima in the range of 360-398, 419-421 and 484-485 nm, and one shoulder in the range of 444-446 nm ( Table 4). The red-shift of the main PL maximum in film (398 and 385 nm) compared with solution (381 and 376) of the polymides Id and Ih, which contain oxygen bridges in the dianhydride segment of the structural unit, could be explained by negligible intermolecular interactions of the conjugated parts of the polymer chains.…”

“…Two aromatic diamines containing oxadiazole rings, namely, 2,5-bis[4-(paminophenoxy)-phenylene]-1,3,4-oxadiazole and 2,5-bis[4-(m-aminophenoxy)-phenylene]-1,3,4-oxadiazole, have been prepared by a known procedure, 12,13 starting from 4-fluorobenzoic acid and hydrazine hydrate, which first reacted in polyphosphoric acid to produce 2,5-bis(p-fluorophenyl)-1,3,4-oxadiazole, which further reacted with p-or m-aminophenol.…”

“…The absorption maxima at 305-308 nm of these polymers are mainly determined by the diphenyl-1,3,4-oxadiazole unit because the unsubstituted diphenyl-1,3,4-oxadiazole in hexane shows its absorption maximum at 284 nm. 13,23 The absorption shoulders at 331-332 nm and 355 nm are due to the absorption of bis(ketonaphthimide) segments. The polyimide If shows three strong UV absorption peaks, at 306 nm due to the presence of phenyloxadiazole chromophore, and 360 and 381 nm due to the chain segments containing naphthylimide chromophore.…”

Six-member polyimides incorporating redox chromophores

“…Monomers 2,5-Bis(p-aminophenyl)-1,3,4-oxadiazole, 2,5-bis[4-(p-aminophenoxy)phenylene]-1,3,4-oxadiazole and 2,5-bis[4-(maminophenoxy)phenylene]-1,3,4-oxadiazole were prepared according to published procedures [18][19][20]. 1,3-Bis(4-phthalic anhydride)tetramethyldisiloxane, the dianhydride containing dimethyl-substituted siloxane groups, was prepared by the reaction of trimellitic anhydride acid chloride with 1,2-dichlorotetramethyldisilane, in the presence of a catalyst made from a mixture of bis(benzonitrile)palladium chloride and triphenylphosphine, following a published procedure [21].…”

Silicon-containing polyoxadiazoles—synthesis and perspectives

“…Si y Silicon-containing poly(oxadiazole-amide)s, V, have been prepared by solution polycondensation of aromatic diamines containing preformed oxadiazole rings with diphenylsilylene-bis(benzoyl chloride), in N-methylpyrrolidone, at low temperature [39].…”