Ewa Schab-Balcerzak

Synthesis, characterization, and study of photoinduced optical anisotropy in polyimides containing side azobenzene units.

In this paper, novel processable aromatic polymers with imide rings and attached as side-chain azobenzene units are presented. Polymers differ in the chemical structures of chromophores and polymer backbones. Azopolymers were obtained by a two-step synthetic approach. This includes the preparation of a precursor poly(esterimide) and poly(etherimide) with pendant phenolic hydroxyl groups, followed by the covalent bonding of NLO chromophores onto the polyimide backbone by the Mitsunobu reaction. The degree of functionalization of polymers was estimated by UV-vis spectroscopy. Polymers were characterized and evaluated by FT-IR, (1)H NMR, X-ray, UV-vis, DSC, and TGA methods. The synthesized polymers exhibited glass transition temperatures in the range of 167-228 degrees C, thermal stability with decomposition temperatures in the range of 275-446 degrees C, and excellent solubilities in common organic solvents. The light-induced optical anisotropy was studied in obtained azopolymers with the help of a holographic grating recording technique. Two polarization geometries were applied for the grating inscription s-s and p-p. The influence of the polarization geometry on the diffraction efficiency dynamics and on the depth of the surface modulation was not observed, which is different from results reported in the literature. Surface relief gratings, which appeared after the light exposure, were observed by atomic force microscopy. Additionally, the optical anisotropy in poly(esterimide)s was investigated by photoinduced birefringence measurements. For the first time, in polyimide with covalently bonded azobenzene derivatives, the high photoinduced birefringence (Delta n = 0.01) was measured.

Polarization Dependence of Holographic Grating Recording in Azobenzene-Functionalized Polymers Monitored by Visible and Infrared Light

The holographic grating recording process in thin films of amorphous azobenzene-functionalized polymers has been widely reported in the literature. In spite of the many reports, little is known about the mechanisms responsible for different temporal behaviors of the diffraction efficiency during long recording times. Here, we report on experimental studies of the diffraction efficiency changes during the holographic diffraction grating recording process in photochromic polymer. The gratings were inscribed for four different polarization combinations of the recording beams: s-s, p-p, s-p and right to left circular polarization (RCP-LCP) employing the degenerate two-wave mixing technique. The grating recording process was simultaneously monitored by three different wavelengths: 514.5 nm (writing) and 632.8 and 904 nm (reading). The temporal evolution of the diffraction efficiency (for all polarization configurations and for each wavelengths) was precisely fitted within the model, which assumes simultaneous formation of the absorption grating and three coupling phase gratings shifted by 0 or pi with respect to each other. Two of the phase gratings originate from the refractive index grating changes in the bulk (volume) of a material and the third one from the surface relief modulation. The model enabled us to extract relevant parameters for each grating such as the build-up time constant, its final amplitude, and the phase shifts between phase gratings. Performed studies and the discussion of results revealed the main differences in the diffraction grating formation process for s-s, p-p, s-p, and RCP-LCP polarization configurations.

Poly(amide imides) and poly(ether imides) containing 1,3,4-oxadiazole or pyridine rings: characterizations and optical properties.

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.

Synthesis, materials characterization and opto(electrical) properties of unsymmetrical azomethines with benzothiazole core

Optical (UV-vis and photoluminescence) properties of two soluble organic molecules based on azomethines with benzothiazole core (BTA1 and BTA2) were reported. The structures of both compounds are characterized by means FTIR, (1)H NMR, and (13)C NMR spectroscopy and elemental analysis; the results show an agreement with the proposed structure. The investigated compounds emitted blue light. Influence of excitation wavelength and concentration on maximum and intensity of emission of BTA1 and BTA2 was found. Electrochemical properties of the compounds were studied by differential pulse voltammetry. Introduction of fluorine moieties (BTA1) resulted in lower energy band gap (E(g)) of approximately ∼0.5 eV, whereas BTA2 showed E(g) of ∼2.8 eV. The devices comprised of BTA1 with P3HT:PCBM (1:1:1) showed an open circuit voltage (V(OC)) of 0.40 V, a short circuit current (J(SC)) of 1.19 mA/cm(2), and a fill factor (FF) of 0.23, giving a power-conversion efficiency (PCE) of 0.10% under AM1.5 G irradiation (100 mW/cm(2)).

(Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units

New symmetrical arylene bisimide derivatives formed by using electron-donating–electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N′-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (Eg) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and Eg were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm2 were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of Voc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69–0.90%.

Optical properties of new aliphatic–aromatic co-polyimides

Abstract Optical transmission of a series of aliphatic–aromatic co-polyimides have been investigated in the range 200–3000 nm. The short wavelength edge of transmission depends on the ratios of diamines (aliphatic to aromatic) and on the type of aliphatic diamine. To obtain the optical parameters the approach proposed by Tauc for amorphous semiconductors has been used, because of the similarity of the absorption edges. The values of pseudogaps were found from 1.01 to above 4 eV, while the Urbach energy changed in the range 75–800 meV. All determined parameters have been found to be related to the influence of the polymer chain structure.

New Soluble Polyimides Containing Hydroxylic Groups: I. Synthesis and characterization

A series of aromatic polyimides from different diamidedianhydrides and 2,4-diaminophenol dihydrochloride was synthesized using a one-step high-temperature polycondensation. The structural characterization of the prepared polyimides was carried out by using Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. The influence of the monomers’ structures on the polymers’ properties has been investigated.

Synthesis and characterization of organosoluble aliphatic–aromatic copolyimides based on cycloaliphatic dianhydride

Abstract A series of aliphatic–aromatic polyimides have been synthesized. These polyimides were prepared by high-temperature polycondensation of the aliphatic diamines: 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,9-diaminononane, 1,10-diaminodecane, 1,12-diaminododecane and 4,4 ′ -methylenebis(2,6-dimethylaniline) with 1,2,3,4-cyclopentanetetracarboxylic dianhydride. Various ratios of diamines (aromatic:aliphatic) have been applied for preparation of copolyimides. Polycondensation proceeded at 190 °C and produced copolyimides with reduced viscosities up to 0.92 dl/g. The polyimides were soluble in a wide range of organic, common solvents and showed high-thermal stability. In most cases these polymers formed flexible films which presented excellent transparency.

Investigation of polyimides containing naphthalene units. III. Influence of monomers structure on polymers properties

A series of polymers from dinaphthalene dianhydrides and aromatic diamines has been synthesized using one-step high-temperature polycondensation. The influence of the monomers structure on the polymers properties has been investigated.

New semiladder polymers. Part II: Synthesis and properties of new poly(amideimidazopyrrolones)

Abstract A series of polymers from new diamidedianhydrides of arylene-di(benzene-5-amido-1,2-dicarboxylic) anhydride type and aromatic tetraamines (3,3′-diaminobenzidine and 3,3′,4,4′-tetraaminodiphenylether) were synthesized using one step high temperature polycondensation in m -cresol and p -chlorophenol at 180°C and low temperature polycondensation. The polymers had a semiladder structure. The influence of the monomer structure and polycondensation method on the polymer properties has been investigated.