53 research outputs found
Two-photon-induced birefringence in azo-dye bearing polyimide; the birefringence changes versus the writing power
Ultra-short high-intensity light pulses were utilized
to induce the optical birefringence in a polyimide material
possessing the azo-dye covalently bonded to the main
chain. The obtained results showed that a two-photon absorption
process was involved in a creation of the sample
birefringence which, to the best of our knowledge, was not
previously reported for polyimide materials. The growths
and decays of birefringence were examined as functions of
the pulse intensities. No damage to the material during the
illumination process was detected in a wide range of optical
powers applied. High birefringence level of the order of
0.005 was measured
Azobenzene Functionalized “T-Type” Poly(Amide Imide)s vs. Guest-Host Systems - A Comparative Study of Structure-Property Relations
This paper describes the synthesis and characterization of new “T-type” azo poly(amide
imide)s as well as guest-host systems based on the “T-type” matrices. The matrices possessed
pyridine rings in a main-chain and azobenzene moieties located either between the amide or imide
groups. The non-covalent polymers contained the molecularly dispersed 4-phenylazophenol or
4-[(4-methyl phenyl)diazinyl]phenol chromophores that are capable of forming intermolecular
hydrogen bonds with the pyridine rings. The FTIR spectroscopy and the measurements of the
thermal, optical and photoinduced optical birefringence were employed for the determination of
the influence of H-bonds and the specific elements of polymer architecture on physicochemical
properties. Moreover, the obtained results were compared to those described in our previous works
to formulate structure-property relations that may be considered general for the class of “T-type” azo
poly(amide imide)s
Novel concept of polymers preparation with high photoluminescent quantum yield
A series carbazolyl-containing polymers were synthesized by anionic polymerization of various oxiranes and methyl methacrylate. The polymerization was carried out using as initiator carbazylpotassium activated 18-crown-6 in THF. The polymers were prepared and found using size exclusion chromatography to have a degree of polymerization (DPn) about 20 relatively and low dispersity in the range of 1.07–1.66. Their optical properties were investigated by means of UV–vis and photoluminescence spectroscopies. The obtained polymers emitted light with maximum emission about 370 nm and high quantum yield ranging up to 79 %. Thus, it was confirmed that the utilization of fluorophore initiator for polymerization of non photoresponsive monomers is quite efficient for the preparation of photoluminescent polymers
Thermocapillary marangoni flows in Azopolymers
It is well known that light-induced multiple trans-cis-trans photoisomerizations of
azobenzene derivatives attached to various matrices (polymeric, liquid crystalline polymers) result in
polymer mass movement leading to generation of surface reliefs. The reliefs can be produced at small
as well as at large light intensities. When linearly polarized light is used in the process, directional
photo-induced molecular orientation of the azo molecules occurs, which leads to the generation of
optical anisotropy in the system, providing that thermal effects are negligible. On the other hand,
large reliefs are observed at relatively strong laser intensities when the optofluidization process is
particularly effective. In this article, we describe the competitive thermocapillary Marangoni effect of
polymer mass motion. We experimentally prove that the Marangoni effect occurs simultaneously
with the optofluidization process. It destroys the orientation of the azopolymer molecules and results
in cancelation of the photo-induced birefringence. Our experimental observations of polymer surface
topography with atomic force microscopy are supported by suitable modelings
Examination of the effect of selected factors on the photovoltaic response of dye-sensitized solar cells
The impact of photoanode preparation on the photovoltaic performance of dye-sensitized solar cells was investigated. The effects of titanium dioxide layer thickness, type of solvent and immersion time used for photoanode fabrication, and addition of coadsorbents and a cosensitizer on photon-to-current conversion efficiency and photovoltaic parameters were studied. Commercially available N719 and dyes prepared in our research group, 5,5′-bis(2-cyano-1-acrylic acid)-2,2′-bithiophene and 2-cyano-3-(2,2′:5′,2″-terthiophen-5-yl)acrylic acid, were applied as sensitizers. The effect of studied factors on UV–vis properties and morphology, that is, the root-mean-square roughness of the photoanode, was examined and correlated with the photovoltaic response of the constructed devices. Additionally, the amount of dye molecules adsorbed to the TiO2 was investigated. It was found that all considered factors significantly impacted photovoltaic parameters. Also, the photoanode stability was tested by measuring photovoltaic parameters after 14 months
Investigations of new phenothiazine-based compounds for dye-sensitized solar cells with theoretical insight
New D- -D- -A low-molecular-weight compounds, based on a phenothiazine sca old
linked via an acetylene unit with various donor moiety and cyanoacrylic acid anchoring groups,
respectively, were successfully synthesized. The prepared phenothiazine dyes were entirely
characterized using nuclear magnetic resonance (NMR) spectroscopy and elemental analysis.
The compounds were designed to study the relationship between end-capping donor groups’
structure on their optoelectronic and thermal properties as well as the dye-sensitized solar cells’
performance. The e ect of -conjugation enlargement by incorporation of di erent heterocyclic
substituents possessing various electron–donor a nities was systematically experimentally and
theoretically examined. Density functional theory (DFT) and time-dependent density functional
theory (TD-DFT) calculations were implemented to determine the electronic properties of the
novel molecules
Live cell imaging by 3-imino-(2-phenol)-1,8-naphthalimides : the effect of ex vivo hydrolysis
A series of 3-amino-N-substituted-1,8-naphthalimides and their salicylic Schiff base derivatives were synthesized.
The structure of the obtained compounds was confirmed using 1H and 13C NMR, FT-IR spectroscopy and
elemental analysis and COSY and HMQC for the representative molecules. The photophysical (UV–Vis, PL) and
biological properties of all of the prepared compounds were studied. It was found that the amine with the nhexyl
group in EtOH had the highest PL quantumyield (Ф=85%) compared to the others.Moreover, the chelating
properties of the azomethines with the n-hexyl group (1a, 1b, 1c) were tested against various cations (Al3+,
Ba2+, Co2+, Cu2+, Cr3+, Fe2+, Fe3+,Mn2+, Ni2+, Pb2+, Sr2+ and Zn2+) in an acetonitrile, acetone and PBS/AC mixture.
Compounds that contained the electron withdrawing groups (-Br, -I) had the ability to chelate most of the
studied cations, while the unsubstituted derivative chelated only the trivalent cations such as Al3+, Cr3+ and
Fe3+ in acetonitrile. The effect of the environment on the keto-enol tautomeric equilibrium was also demonstrated,
especially in the case of the derivativewith a bromine atom. The biological studies showed that the tested
molecules had no cytotoxicity. Additionally, the ability to image intracellular organelles such as the mitochondria
and endoplasmic reticulum was revealed. The crucial role of the hydrolysis of imines for cellular imaging was
presented
Effect of polythiophene content on thermomechanical properties of electroconductive composites
The thermal, mechanical and electrical properties of polymeric composites combined using polythiophene (PT) dopped by FeCl3 and polyamide 6 (PA), in the aspect of conductive constructive elements for organic solar cells, depend on the molecular structure and morphology of materials as well as the method of preparing the species. This study was focused on disclosing the impact of the polythiophene content on properties of electrospun fibers. The elements for investigation were prepared using electrospinning applying two substrates. The study revealed the impact of the substrate on the conductive properties of composites. In this study composites exhibited good thermal stability, with T5 values in the range of 230–268 °C that increased with increasing PT content. The prepared composites exhibited comparable PA Tg values, which indicates their suitability for processing. Instrumental analysis of polymers and composites was carried out using Fourier Transform Infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM)
Photoinduced properties of "T-type" polyimides with azobenzene or azopyridine moieties
In this work series of “T-type” polyimides with azobenzene or azopyridine moieties were investigated. It is the
first report where the “T-type” polyimides with derivatives of azopyridine were investigated. The cis-trans isomerization
in the dark in the solid-state was showed. Polyimides with azobenzene derivatives exhibited higher
stability of cis-trans recovery than their azobenzene analogues. For the inscription of the surface relief gratings,
two different intensities of light (10 and 45 mJ/cm2) and a number of pulses (10 and 100) were used. Polyimides
showed the modulation of SRGs up to almost 330 nm. Our studies showed, that azopolyimides are able to orient
the nematic liquid crystal molecules in cell-based on effect at the twisted nematic. The obtained maximum value
of tON was 0.9 ms (1 kHz, 1.5 V/μm) for polyimide with azobenzene moieties. Azopolyimides may be successfully
used in many photonic devices based on the alignment of the liquid crystal mixture i.e. LC diffraction gratings,
Fresnel lens, Vortex, in a photo-pattering technology for creating radical and azimuthal orienting layers
Effect of polyaniline content and protonating dopants on electroconductive composites
Elastic constructive elements prepared by electrospinning using polyacrylonitrile/polyaniline (PAN/PANI) electroconductive composites were prepared and investigated in terms of their thermal and mechanical properties. This study was focused on the impact of the type of counterion of polyaniline and the PANI content in composites on the thermal, conductive and morphological properties of electrospun fibers. In this study, composites obtained from PANI doped with sulfuric acid showed the highest conductivity, and composites obtained from PANI doped with hydrochloric acid showed the highest thermal stability. All obtained composites exhibited good thermal stability, with T5 values in the range of 230–268 °C that increased with increasing PANI content. The prepared composites exhibited comparable PAN Tg values, which indicates their suitability for processing. Instrumental analysis of polymers and composites was carried out using UV–visible spectroscopy, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and scanning electron microscopy
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