Photophysical Properties Of Poly Research Articles

Influence of ZnO/TiO2 nanocomposite on optical and structural properties of OC1C10–PPV–DMP thin film

The photophysical properties of poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene]—End capped with dimethylphenyl (DMP), OC1C10–PPV–DMP, were modified by incorporation various contents of the nanocomposites of both anatase TiO2 and wurtzite ZnO (ZTNCs). The solution blending method was employed to prepare the nanocomposite hybrids of OC1C10–PPV–DMP with ZTNCs before depositing them onto glass substrates. The optical parameters of the hybrid nanocomposite thin films were extracted from both absorption and photoluminescence spectra. XRD, FTIR, and FE-SEM revealed the good incorporation of ZTNC into the polymer matrix with the formation of a nanocomposite structure. By increasing the content of ZTNCs in the polymer matrix, the optical parameters of OC1C10–PPV–DMP such as energy band gap, energy tail, steepness parameter, and CIE chromatic coordinates were tuned. The incorporation of ZTNCs resulted in broadened and improved absorption and emission peaks of the polymer with a systematic shift for its corresponding maximum peaks. These unique findings are crucial for improving the performance of optoelectronic devices based on OC1C10–PPV–DMP/ZTNCs.

Detailed Photophysical Studies of Poly(9,9-di-(2-ethylhexyl)-9-H-fluorene-2,7-vinylene) in Liquid Media and Thin Films

For the present work, solvent (toluene, o-xylene, chloroform, chlorobenzene, and 1,2-dichloroethane) and concentration-dependent (∼10-6-10-3 gml-1) photophysical properties of poly(9,9-di-(2-ethylhexyl)-9-H-fluorene-2,7-vinylene) (PEFV) were investigated in detail in liquid media as well as thin films. Also, temperature-dependent (3-60oC) fluorescence emission measurements of PEFV were conducted in liquid media. The steady-state and time-resolved data indicate the existence of weak interchain interaction in liquid media at high concentration. However, both ground-state aggregation and interchain interaction are present for PEFV in thin film. The interchain interaction plays a dominant role on the fluorescence emission of PEFV in thin film on the red side of the spectra.

Effect of Ag2 S nanoparticles on optical, photophysical, and electrical properties of P3HT thin films.

In the present work, optical, electrical, and photophysical properties of poly(3-hexylthiophen)/silver sulphide (P3HT/Ag2 S) nanocomposites thin films were investigated. New amorphous dispersion formula was used to fit the experimental ellipsometer data and it was observed that the both refractive index (n) and absorption index (k) increased for hybrid films compared with pure P3HT film. The photophysical properties of fabricated films were examined by recording the photoluminescence (PL) and time resolved fluorescence spectra. The PL quenching in hybrid films signalled the formation of a charge transfer complex between host (P3HT) and guest (Ag2 S). The fluorescence average life time was noted to drop to 94 ps for hybrid P3HT:Ag2 S 1:2 film compared with 126 ps for pristine P3HT. Finally, the electrical properties of fabricated films were measured using the Hall effect systems. The surface resistivity (ρ) of pure P3HT thin films was found to be 9.70 × 104 Ω.cm, which decreased slightly for Ag2 S/P3HT hybrid films.

Photophysical properties of poly(phenylene-co-fluorene) synthesized via solid-state oxidative coupling polymerization

A series of benzene-co-fluorene copolymers were synthesized via solid-state oxidative coupling polymerization using FeCl3 as the oxidation catalyst. The structural characterization results confirm that the products are random copolymers composed of 1,4-linked phenylene units and 2,7-linked fluorene units. All the copolymers exhibited good thermal stability. The DSC and XRD results showed that the crystallization of copolymers increased with the increasing fluorene units in the backbones. The relationships among molecular structure, condensed-state structure, and photophysical properties of these polymers were investigated by UV–vis absorption spectroscopy and photoluminescence spectroscopy. The optical properties could be adjusted by using different ratios of fluorene and dibutoxybenzene. Moreover, the polymer concentrations and states affected the emission properties of copolymers. This can be attributed to the change in the effective conjugation length of single polymer and the formation of polymer aggregates and excimers. These unique properties endow the benzene-co-fluorene copolymers with potential applications in optoelectronics.

Influence of Luminol Doping of Poly(o-phenylenediamine) on the Spectral, Morphological, and Fluorescent properties: A Potential Fluorescent Marker for Early detection and Diagnosis of Leishmania donovani.

There has been a steady progress in the development of doped conjugated polymers to remarkably improve their photo physical properties for their application as biomarkers. With a view to enhance the spectral, morphological, and photo physical properties of poly(o-phenylenediamine) (POPD), the present work reports the synthesis of poly(o-phenylenediamine) and doping of this polymer using luminol. The formation of luminol-doped POPD was confirmed by infrared and ultraviolet-visible spectroscopies and X-ray diffraction studies. The energy band gap values and oscillator strength of luminol in acidic, basic, and neutral media were computed by density functional theory calculations using the B3LYP/6-31G (d) basis set and were compared with experimental data. The luminol doped POPDs show significant in vitro anti-leishmanial activity. Live cell imaging also proved that these molecules bind with the organelle of Leishmania also. These luminol doped POPDs were found non-toxic at the used concentrations on THP-1 derived human macrophage cells through methyl tetrazolium (MTT) assay. The results revealed that luminol doped POPDs were potentially non-toxic to human cells though exhibited immense potential to be used as a fluorescent marker to label Leishmania donovani for diagnostic and other studies.

Comparative photophysical properties of poly(diphenylacetylene)s with different central atoms in side group

ABSTRACTPolydiphenylacetylene (PDPA) derivaitves consisting of different central atoms of C, Si, and Ge in the pendent group were comparatively investigated in normal, swollen, and acid-treated states. The Ge-containing PDPA was more emissive than the other two both in solution and in solid states. All the polymers showed emission enhancement in a swollen state: The PL quantum yields increased remarkably when swollen in an appropriate non-solvent. The Si and Ge atoms were easily removed from the polymer chain under acidic condition, as a result, the PL intensity was significantly decreased and the polymers turned to be insoluble in common organic solvents. Although the tert-butyl group of C-containing PDPA remained intact during the acid exposure, similar PL attenuation occurred.

Effect of Solvents on Controlling the Photophysical Properties of Poly[2-Methoxy-5-(2’-Ethylhexyloxy)-1,4-Phenylenevinylene] (MEH-PPV) Nanoparticle

Abstract. This study focuses on detailed investigation of solvent effects on controlling photophysical properties of poly [2-methoxy,5-(2’-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) nanoparticles prepared by using reprecipitation techniques. In this work, the MEH-PPV polymer is dissolved in various solvents, including chlorobenzene (CRB), toluene (TOL) and pyridine (PYR). The polymers in solutions adopt different conformations (i.e. collapsed or extended coils), depending on local polymer-solvent interactions. The differences of chain conformations cause the variations of chain packing within the nanoparticles. The majority of nanoparticles exhibit diameter of about 65-70 nm. The photophysical properties of MEH-PPV nanoparticles varied with type of solvents. The absorption spectra of nanoparticles exhibit a broad pattern with a long red tail at about 550 nm, indicating the formation of inter-and/or intrachain aggregates within the nanoparticles. However, the nanoparticle from TOL system shows blueshift of λmax, corresponding to the decrease of conjugation length due to the existence of collapsed coil. The photoluminescence (PL) spectra of MEH-PPV nanoparticles show consistent result with the shift of λmax to about 590 nm and vibronic shoulder at about 640 nm. The PL patterns vary with the type of solvents. In addition, the PL patterns depend on the variations of excitation wavelengths. These discrepancies indicated the variation of chain conformation and degree of aggregation within the nanoparticles. Our results demonstrate the simple method to prepare the conjugated polymer nanoparticle with different photophysical properties by changing solvents.

Novel conjugated polyelectrolytes based on polythiophene bearing phosphonium side groups

The synthesis and photophysical properties of poly{3-[6-(triethylphosphonium)hexyl]-thiophene-2,5-diyl bromide} and poly{3-[6-(triphenylphosphonium)hexyl]-thiophene-2,5-diyl bromide} are reported in the present contribution. Three various polymer precursors (poly[3-(6-bromohexyl)thiophene-2,5-diyl]s) with molecular weights 7.2, 11.8 and 13.2kgmol−1 respectively and head to tail regioregularity from 62% to 94% were prepared and consecutively transformed into the corresponding polyelectrolytes by a simple quaternization reaction with appropriate phosphines. Synthesized polyelectrolytes exhibited solvatochromism. Detailed aggregation experiments via changing water/DMSO ratio have been performed. Photoluminiscence spectra of the polyelectrolyte solutions indicate that the emission maxima are red-shifted gradually with the increasing solvent polarity. Fluorescence quenching has been studied by interaction with model quenchers: K4[Fe(CN)6] and K3[Fe(CN)6] in water using Stern-Volmer methodology.

New semi-conducting poly(phenylene vinylene-alt-anthrylene vinylene)s: Synthesis, characterization and photophysical properties

An anthracene-based semi-conducting polymer (P1) and its cyano-analogue (P2) were synthesized via the Wittig and Knoevenagel polycondensations. The polymers were soluble in common organic solvents and have number-average molecular weights of 13,750 and 6430gmol−1 for P1 and P2, respectively. The DSC analyzes show a good thermal stability and an amorphous morphology in solid state for these organic materials. The optical properties of the polymers were investigated by UV–visible absorption and fluorescence spectroscopies. The HOMO and LUMO levels were estimated using cyclic voltammetry analysis. The effect of cyano group on the photophysical properties of poly(phenylene vinylene-alt-anthrylene vinylene)s was investigated. The results demonstrate an enhancement in the ionization potential and a significant improvement of the fluorescence yield due to introduction of such groups into the π-conjugated system. Single-layer diodes based on these organic semiconductors have been fabricated and showed relatively low turn-on voltages.

Synthesis and photophysical properties of poly(arylene ethynylene) small-molecules and polymers derivatized with leucine substituents

Abstract Aminoacidic/peptidic functionalized poly(aryleneethynylenes) (PAEs) are bio-inspired smart hybrids of great potential as active components in sensing devices. These materials synergically combine the superb photophysical properties of highly ethynylated unsaturated backbones with the large possibility of aminoacid and peptide design towards specific target-analyte binding. Conformational changes and/or electron density variations occurring along the PAE conjugated path, as a consequence of analyte binding to the aminoacidic/peptidic receptor site, might dramatically change the optoelectronic properties of the material, thus signaling the presence of the analyte. In this paper, we have studied the photochemistry of two groups of L-leucine/polyarylene-etynylene small molecules and polymers with the aim of optimizing the photochemical performances of aminoacidic derivatized PAE structures, in view of their use for metal sensing. Taking into account that among the different chemical sensors, fluorescence-based ones present many advantages in terms of sensitivity, selectivity, no need of references, and multiple readout signals, we have searched for more insight into the evolution of the optical properties of oligomers and polymers as a function of the structure of the PAE aminoacidic assembling.

Solvent effects on the photophysical properties of poly[1,4-dihydroxyanthraquinoneimine-1,3-bis(phenylene-ester-methylene)tetramethyldisiloxane

Absorption and fluorescence spectra of a polyquinoneimine, PQI, built on 1,4-dihydroxyanthraquinone and a siloxane diamine, 1,3-bis(amino-phenylene-ester-methylene)tetramethyldisiloxane, have been investigated in solvents of different polarities. The effect of solvents on the spectral properties was investigated using Lippert–Mataga and Bakhshiev polarity functions and Catalán’s multiple linear regression approach. Absorption and fluorescence spectra in studied solvents exhibit hypsochromic and bathochromic shifts, respectively. The polarity of the solvent was the main parameter which changes the spectral properties of PQI. Also, the binary mixtures of chloroform with methanol and dimethyl sulfoxide were used to analyze the intermolecular interactions and preferential solvation. The preferential solvation parameters (local mole fraction (X2L), excess function (δs2) and preferential solvation constant (KPS)) were calculated from spectral data and discussed as a function of cosolvent content. The values of quantum yield, decreased linearly with increasing solvent polarity (for non-polar and polar solvents).

Effect of permodified β-cyclodextrin on the photophysical properties of poly[2,7-(9,9-dioctylfluorene)-alt-(5,5′-bithiophene)] main chain polyrotaxanes

The photophysical properties of two polyrotaxanes (PFBTh•PSβCD and PFBTh•PMeβCD) composed of fluorene and bithiophene encapsulated into permodified β-cyclodextrin cavities have been investigated and compared with those of the reference PFBTh. Rotaxane formation results in improvements of the thermal stability, solubility in common organic solvents, as well as better film forming ability combined with a high transparency. As expected PFBTh and its encapsulated forms absorb at wavelengths beyond 510 nm, and time-resolved photoluminescence (PL) in solution shows a well-define vibronic structures with a predominance of the 0-0 transitions and an energy difference of 0.16 eV. The fluorescence lifetimes follow a monoexponential decay with a value τ = 630 ± 30 ps. Atomic force microscopy, AFM, indicated a tendency of polyrotaxanes to organize into fibers. The advancing contact angles indicated higher surface hydrophobicity and lower surface free-energy values for polyrotaxanes compared with their unthreaded analogues. The device based on PFBTh•PSβCD:PCBM in a 1/1 w/w ratio under simulated AM 1.5G illumination at 100 mW cm−2 exhibited improved photovoltaic parameters of cells, resulted in high Voc (0.68 V), Jsc (1.65 mA cm−2), FF (31.6%), and PCE (0.35) values, compared with PFBTh or PFBTh•PMeβCD, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 460–471

Resonance Raman Investigation of β-Cyclodextrin-Encapsulated π-Conjugated Polymers

Resonance Raman (RR) spectroscopy is used to investigate the effect of β-cyclodextrin encapsulation on the structural and photophysical properties of poly(4,4'-diphenylenevinylene). We especially focus on the thermal stability of the polymer. We find that within the range of 10-55 °C the uninsulated polymer exhibits decreased Raman intensity in all the vibrational bands with temperature, along with changes in the relative intensity of the C-C inter-ring stretch mode at 1270 cm(-1) with respect to the ring C-H in-plane symmetric bend at 1187 cm(-1), which provides evidence for conformational changes as a function of temperature. No changes are observed in the intensity of the in-phase CH out-of-plane wag of the vinylene group at 968 cm(-1). Therefore, the conformational changes involve mainly dihedral angle modification between the adjacent phenyl rings toward planarization, and little or no change in the planarity of the trans-vinylene group. The decrease of the optical absorption at 55 °C with respect to that at room temperature and the appearance of a new absorption band at lower energies explain the decrease in the RR intensities and the wavelength dependence of the relative intensities of the Raman band. We note that the conformational change into a more planar geometry, which affects a significant portion of the polymer population, is irreversible and consistent with thermally induced aggregation. Such a planarization is unexpected in view of the usually observed thermochromic behavior of conjugated polymers, which leads to an increase of the energy gap for increasing temperature, as the average dihedral angles are increased due to excitation of a larger number of vibrational modes. Interestingly, the higher threading ratio polymers are resistant to any conformational changes within this temperature range, as reflected by their unchanged RR spectra, due to the rotaxane's ability to suppress intermolecular interactions and aggregation. Interestingly, the conformation of the uninsulated polymer at room temperature appears to be the same as that in the threaded analogues, which suggests that the cyclodextrin cavity hosts the polymer without physically interacting with it.

Photophysical properties and energy transfer mechanism of PFO/Fluorol 7GA hybrid thin films

Photophysical properties of poly (9,9′-di-n-octylfluorenyl-2.7-diyl) (PFO)/2-butyl-6- (butylamino)benzo [de] isoquinoline-1,3-dione (Fluorol 7GA) and energy transfer between them have been investigated. In this work, both PFO and Fluorol 7GA act as donor and acceptor, respectively. Based on the absorption and luminescence measurements, the photophysical and energy transfer properties such as fluorescence quantum yield (Φf), fluorescence lifetime (τ), radiative rate constant (kr), non-radiative rate constant (knr), quenching rate constant (kSV), energy transfer rate constant (kET), energy transfer probability (PDA), energy transfer efficiency (η), critical concentration of acceptor (Co), energy transfer time (τET) and critical distance of energy transfer (Ro) were calculated. Large values of kSV, kET and Ro suggested that Förster-type energy transfer was the dominant mechanism for the energy transfer between the excited donor and ground state acceptor molecules. It was observed that the Förster energy transfer together with the trapping process are crucial for performance improvement in ITO/(PFO/Fluorol7GA)/Al device.

Synthesis and photophysical properties of poly(aryleneethynylene)s containing dibenzosilole unit

Abstract A series of poly(aryleneethynylene)s containing dibenzosilole unit has been synthesized by palladium-catalyzed Sonogashira cross-coupling reactions with 2,7-diethynyl-9,9-dihexyl-3,6-dimethoxy-9 H -dibenzosilole ( 4 ) as the key monomer. Their photo-physical properties in solution were investigated. All of the polymers showed intense fluorescence with high quantum efficiencies.

H-Aggregated Form II Spherulite of Poly(3-butylthiophene) Grown from Solution.

New large-size poly(3-butylthiophene) (P3BT) spherulites are obtained by solution aging. These P3BT spherulites are composed of nanoribbons, and the P3BT molecules arrange into Form II structure with a backbone π-stacking distance of 0.47 nm. P3BT lamellae adopt "flat-on" orientation at the edge of the spherulite, and the spherulite preferentially grows along the π-π stacking direction. These spherulites could be obtained in bulk solution or at the top or bottom of the solution, depending on the competition of gravity and Brownian motion. Temperature-dependent photoluminescence spectra demonstrate that the polymer chains are arranged in H-aggregation model. The 0-0 transition in UV-visible absorption spectra blue shifts from 2.03 eV (610 nm, Form I) to 2.11 eV (589 nm, Form II). These results provide a further understanding of the crystallization and photophysical properties of poly(3-alkylthiophene) (P3AT), and the preparation method of large size and pure P3AT spherulites shows potential in applications of organic electronics.

Preparation and properties of novel low dielectric constant benzoxazole‐based polybenzoxazine

AbstractA novel benzoxazine monomer containing a benzoxazole group was synthesized using a nonsolvent method and then named DAROH‐a. The structure of DAROH‐a was confirmed by FTIR, 1H NMR, elemental analysis, and mass spectrometry. The curing reaction activation energy was calculated at 140 kJ/mol. Its corresponding crosslinked polybenzoxazines, poly(DAROH‐a), displayed a higher glass transition temperature at 402 °C, a 9% weight loss at the said temperature, and a high char yield of 42 wt % (800 °C, in nitrogen). Moreover, the dielectric constants of poly(DAROH‐a) were low and changed only slightly at different temperatures. Furthermore, the dielectric constants and dielectric loss of poly(DAROH‐a) at the same frequency barely changed from room temperature to 150 °C. The photophysical properties of poly(DAROH‐a) film were also investigated. Poly(DAROH‐a) showed an absorption peak at 280 nm. The photoluminescent emission spectrum of poly(DAROH‐a) film displayed predominant emission peaks at 521 nm. It might have potential application as high‐performance materials because of its excellent dielectric constants stability and thermal stability under high temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Conformational structure and aggregation behavior of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] in toluene/nonane solutions

We identified the conformational structure, aggregation behavior and photophysical properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) in various toluene/nonane solutions dependent on nonane content. In dilute solution region (e.g., below the overlap concentration, c*), static light scattering (SLS) revealed that the stiffness of MEH-PPV decreased as nonane content was increased, attributed to a stronger interaction force between MEH-PPV backbones. However, MEH-PPV chains presented a more extended-wormlike conformational structure in toluene. Therefore, a looser intermolecular micellelike aggregates occurred easily between the ether side chains of MEH-PPV at the concentration exceeded the overlapping concentration in toluene and toluene/nonane solutions. Nevertheless, at higher nonane content, the micellelike aggregates were became highly compacted by the π–π complex force between MEH-PPV backbones, dominating the dynamic behaviors and photophysical properties of MEH-PPV in toluene/nonane solution. These results proved that two types of segmental association with distinct stability were identified for the MEH-PPV/toluene/nonane solutions upon prolonged aging. The highly stable, which could not be disrupted by heating, was attributed to the interaction force between ether side chains of MEH-PPV in both solutions. Other type was a weaker affinity force through π–π complex, which could be disrupted thermally, making the micellelike aggregates more compact to form the network structure in MEH-PPV-enriched at higher nonane content.

Preservation of Photoluminescence Efficiency in the Ordered phases of Poly(2,3-diphenyl-1,4-phenylenevinylene) via Disturbing the Intermolecular π–π Interactions with Dendritic Aliphatic Side Chains

To understand the relation between the solid-state phase structures and the photophysical properties of poly(2,3-diphenyl-1,4-phenylenevinylene) (DP-PPV) derivatives, three DP-PPV derivatives, P1–P3, were designed, synthesized via Gilch polymerization and characterized. Among the polymers, P1 is a reported highly emissive poly(2,3-diphenyl-5-hexyl-p-phenylenevinylene), and P2 and P3 are novel DP-PPV derivatives, which are purposely designed to bear hydrophobic and hydrophilic Percec-type dendrons as side chains. The bulkiness and hydrophobic–hydrophilic natures of the side chains show strong effects on photophysical properties of the polymers. The solutions and as-casted films of P1–P3 all show remarkably high photoluminescence (PL) efficiency (ΦPL) (>80% in chloroform solution, and >63% for the as-casted films). However, ΦPL of P1 and P3 decrease significantly to 30% after cooled their polymer melts to room temperature. Through the phase behavior analysis by differential scanning calorimetry (DSC), and phase structure analysis by wide-angle X-ray diffraction (WAXD), the decrease of ΦPL can be elucidated and attributed to the ordering of the solid-state structures of P1 and P3. To our surprise, ΦPL of P2 is preserved even in an ordered solid-state phase, and it is insensitive to the structural ordering. Structural analysis of P2 revealed that the aliphatic dendritic side chains of P2 effectively disturbing the intermolecular π–π interactions among the conjugated backbones, which allows the preservation of ΦPL in the environment with ordered packing of DP-PPV molecules. The results of time-resolved PL decay experiments also confirmed that P2 possesses long-lived decay time because of excitons confined more effectively for emissive relaxation.

Cis- and trans-isomerization-induced transition of charge transport property in PPV oligomers

Photoisomerization of vinylenes is well known to cause remarkable changes in the photophysical properties of poly (p-phenylene vinylene) (PPV) derivatives. C is-/ trans- isomerization is also expected to induce significant changes in their charge transport properties. In this study, the charge transport properties of cis- and trans-isomers of 2,5-diphenyl-1,4-distyrylbenzene (DPDSB, model compound of PPV) were investigated using a Marcus hopping model. As expected, this conformational transition from cis- to trans-isomer gives rise to a significant difference between hole and electron transport properties. Cis-DPDSB demonstrates an overwhelmingly superior hole transport ( μ h / μ e = 51), which is even higher than that of trans-DPDSB. By contrast, trans-DPDSB exhibits approximately balanced carrier transport property ( μ h / μ e = 1.79). These results are understood on a molecular level by considering the structure-transport relationship through two key parameters: transfer integral and reorganization energy. This finding may be helpful in understanding and extrapolating the structure–property relationship and charge transport property of the corresponding PPV polymers derivatives.