Poly(amide imides) and Poly(ether imides) Containing 1,3,4-Oxadiazole or Pyridine Rings: Characterizations and Optical Properties

Abstract

Two series of new aromatic polyimides were synthesized from 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and 2,5-diamino-pyridine and various diamidedianhydrides and dietherdianhydride via high-temperature polycondensation in N-methyl-2-pyrrolidinone. The structures of polymers were characterized by means of FTIR, (1)H NMR spectroscopy, and elemental analysis; the results showed an agreement with the proposed structure. The polymers exhibited high glass-transition temperatures (T(g) = 199-290 degrees C) and high thermal stability with decomposition temperatures (T(d)) in the range of 437-510 degrees C. The optical properties, that is, absorption and photoluminescence (PL) of synthesized polymers, were investigated in solution and in solid state as a blend with inert poly(methyl methacrylate) (PMMA). The polymers in solution emitted violet-blue light in the range of 417-453 nm depending on the polymer structure. The polymers containing pyridine rings in the backbone emitted light at a longer wavelength than polymers with oxadiazole units. The effect of solvent polarity on polymer emission was found. Additionally, the photoluminescence properties of the polymers before and after protonation with HCl were tested.

Thermal, optical, electrochemical, and electrochromic characteristics of novel polyimides bearing the Acridine Yellow moiety

“…The Stokes shift value was found to be higher for the polymers in protonated solution than in undoped ones except for copolyimides. Protonation caused an increase of PL intensity (except for PI-1); similar results were observed for polyimides with pyridine, triphenylamine and oxadiazole groups [5,21,33]. Significantly high increase of PL intensity after protonation was detected for copolyimides.…”

“…5. In our previous works well-defined spectral changes after protonation of the polyimides with oxadiazole and pyridine rings were observed [5,21]. Taking into account the absorption properties after protonation the changes in UVevis spectra are observed.…”

“…The unique combination of properties makes PI ideal for a variety of applications in microelectronics, microelectromechanical systems, aerospace, photoelectronics, alignment layers in liquid crystal displays, and as membranes for gas separation [1e4]. Significant effort has been made to further improve their properties by chemical modification of the chain backbones and higher-order structure control [5]. Additionally, polyimides have been proposed as a new class of redox-active and electrochromic polymers [6e13].…”

“…protonation. The protonation is one of the important, non-covalent interactions that play a fundamental role in modifying polymer properties as well as in designing of new polymer architectures [5]. Such interaction is possible due to the presence of a heteroatom with a free electron pair, in this case, the nitrogen atom in acridine units.…”

“…A protonation concept for tuning the polymer properties is often used for pi-conjugated polymers such as polyketaniles, polyazomethines and polyaniline [31,32]. Up to date only two studies on protonation of polyimides with HCl acid was done [33,34] except of our works [5,21].…”