Photochemistry and photophysics of poly(organophosphazenes) and related compounds: A review. I. Monomolecular processes

In this review we report an outline of the synthesis, UV-Vis spectral characterization, and light-induced reactivity in monomolecular processes of poly(organophosphazenes). The photoreactivity of phosphazene polymers, both in solution and in solid state, strongly depends on the nature of the chromophore attached to the phosphorus atoms of the inorganic –P=N – backbone. In fact, polyphosphazenes not bearing mobile hydrogen atoms in the side moieties undergo, in the first excited singlet state, homolytic eleavage of the bonds connecting the substituents to the inorganic backbone: free radicals of the substituents and phosphazene macroradicals are formed. Moreover, for polyphosphazenes containing labile hydrogens in the side groups, C–H bond scission takes place with the formation of free hydrogens and radicals located in the phosphazene substituents. From these species degradation or crosslinking of the macromolecules will follow according to the experimental conditions.This review is in three parts. Parts II and III will appear sequentially in the next two issues of this journal.     

两种蔡酰亚胺类化合物及其聚合物荧光性质的研究

本文以１,８萘酰亚胺为原料,合成了两种萘酰亚胺类型的化合物,系统地研究了它们在不同溶剂中的吸收光谤和荧光光谱。并以这两种化合物单体为基础,通过共聚合成了它们与甲基丙烯酸甲酯和Ｎ－乙烯基咔唑的嵌段共聚物。研究了聚合物在溶液和薄膜中的荧光性质。结果证明,所得共聚物不但保持了单体的基本荧光特性,其溶解性、成膜性、热稳定性等都得到了大大改善,是一种有应用前景的有机发光半导体材料。此外,本文还利用荧光猝灭的     

Synthesis and properties of photoluminescent copolymer containing 1,3,4‐oxadiazole and carbazole rings

The luminescent copolymer 2‐phenyl‐5‐[3′‐(methacrylamido)phenyl]‐1,3,4‐oxadiazole and vinylcarbazole (PMAPO–VCZ), combining hole‐facilitating moiety, carbazole ring, and electron‐facilitating moiety, 1,3,4‐oxadiazole, as side groups, was synthesized by a radical polymerization of the olefinic monomer PMAPO and VCZ. For comparison, the homopolymer P‐PMAPO was also synthesized by similar procedures. The solubility, thermal, and optical properties of the copolymers were investigated. The synthesized copolymer was soluble in common organic solvents but the homopolymer of PMAPO was dissolved only by hot THF. Thermogravimetric analysis and differential scanning calorimetry measurements showed that the copolymer and homopolymer exhibit good thermal stability up to 360 and 340°C with glass‐transition temperatures higher than 105 and 65°C, respectively. The photoluminescence properties were investigated. The results showed that the copolymer emits blue and blue‐green light and the emission spectra of monomer and polymers exhibit obvious solvent effect. With the increase of polarity of solvents, the fluorescence spectra distinctly change, appearing with a red shift at room temperature. The concentration‐dependent emission spectra change significantly with the increase of concentration. In addition, when N,N‐dimethylaniline (DMA) was gradually added to the solution of copolymers, the emission intensity of fluorescence was dramatically increased. However, when the concentration of DMA was increased beyond a certain level, the emission intensity of fluorescence gradually decreased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2777–2783, 2004     

Synthesis and Characterization of CNT Composites for Laser‐Generated Ultrasonic Waves

In the last few years, extensive progress in ultrasonic wave generation by using multiwalled carbon nanotubes (MWCNTs) in combination with polydimethylsiloxane (PDMS), functional composites, has been achieved. Due to high optical absorption of MWCNTs as perfect absorbers for laser beams and the high thermal expansion coefficient of PDMS, a compact transducer for ultrasonic wave generation at higher frequency can be realized. This study reports a novel method to synthesize MWCNT–PDMS composites deposited on a glass substrate by spray coating, which is done in a short time of 2 h. The layers (0.9–32.2 µm) show low optical transmission properties of 13.9–0.0% at a wavelength of 1047 nm. Apart from using a 1% Triton‐X‐100 stock solution and then diluted to a 0.1% relatively nonhazardous solution, no toxic chemicals are used. The Triton‐X‐100 solution is not hazardous for lab handling and is a commonly used lab detergent for the treatment of biological cells. The achieved sound pressure level is 3.4 MPa with a frequency bandwidth of 9.7 MHz. These results show the potential for a fast and nontoxic production of laser‐generated ultrasonic transducers, which can be used well in the field of nondestructive material testing of layered materials or in medicine with an appropriate frequency range.     

Control of Dynamical Processes in Solution: An Overview and Personal Perspective

A brief overview of studies of optical control of dynamical processes in solution is presented, with a focus on control of selection of product in a chemical reaction. It is argued that there are circumstances under which adiabatic population transfer in the liquid phase is possible, and that variations of such transfer processes can be used to control dynamical processes in solution.     

Synthesis and chemical modification of new luminescent substituted poly(p-phenylene) polymers

A new acyl-functionalized poly(p-phenylene) (Ac-PPP) was synthesized by Yamamoto cross-coupling and chemically modified to obtain an anthracene-containing derivative (An-PPP). The chemical structures of the polymers were confirmed by ¹H-NMR, ¹³C-NMR, and FTIR spectroscopic analysis. They are fully soluble in common organic solvents and have number-average molecular weight of 2.70 × 10³ and 5.26 × 10³ g mol⁻¹ for Ac-PPP and An-PPP, respectively. The optical properties of the polymers were investigated by UV–visible absorption and photoluminescence spectroscopies. A green emission was observed in Ac-PPP solid thin film and a yellow one in the anthracene-containing polymer An-PPP. The optical bandgap values were 3.21 and 3.08 eV for Ac-PPP and An-PPP, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

New fluorene–pyrazino[2,3‐g]quinoxaline‐conjugated copolymers: Synthesis,optoelectronic properties,and electroluminescence characteristics

New donor–acceptor conjugated copolymers called poly}2,7‐(9,9′‐dihexylfluorene)‐co‐5,10‐[pyrazino(2,3‐g)quinoxaline]{s or PFPQs [where F represents the 2,7‐(9,9′‐dihexylfluorene) moiety and PQ represents the 5,10‐(pyrazino[2,3‐g]quinoxaline) moiety], synthesized by the palladium‐catalyzed Suzuki coupling reaction, are reported. The PQ contents in the PFPQ copolymers were 0.3, 1, 5, and 50 mol %, and the resulting copolymers were named PFPQ0.3, PFPQ01, PFPQ05, and PFPQ50, respectively. Absorption spectra showed a progressive redshift as the PQ acceptor content increased. The relatively small optical band gap of 2.08 eV for PFPQ50 suggested strong intramolecular charge transfer (ICT) between the F and PQ moieties. The photoluminescence emission peaks of the PFPQ copolymer films also exhibited a large redshift with enhanced PQ contents, ranging from 551 nm for PFPQ0.3 to 592 nm for PFPQ50. However, the PFPQ copolymer based electroluminescence (EL) devices showed poor device performances probably due to the strong confinement of the electrons in the PQ moiety or significant ICT. This problem was resolved with a binary blend of poly[2,7‐(9,9‐dihexylfluorene)] (PF) and PFPQ with a volume ratio of 95/5 (BPQ05). Multiple emission peaks were observed at 421, 444, 480, 516, and 567 nm in the BPQ05‐based EL devices because the low PQ content led to incomplete energy transfer. The Commission Internationale de L'Eclairage 1931 coordinates of the BPQ05‐based EL device were (0.31, 0.32), which were very close to the standard white emission of (0.33, 0.33). Furthermore, the maximum luminescence intensity and luminescence yield were 524 cd/m² and 0.33 cd/A, respectively. This study suggested that a pure white light emission was achieved with the PFPQ copolymers or PF/PFPQ blends through the control of the energy transfer between F and PQ. Such PFPQ copolymers or PF/PFPQ blends would be interesting for electronic and optoelectronic devices. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,characterization, and photophysics of a novel conjugated polymer with 1,3,4‐oxadiazole,carbazole, and naphthalene units

A polymer containing 1,3,4‐oxadiazole and carbazole units in the main chain and naphthalene moieties as side groups (P‐OCN) was synthesized by the Wittig reaction of [2,5‐bis(3‐tolylene)1′,3′,4‐oxadiazole]‐9‐(α‐naphthyl)‐carbazole polymer (P‐OCN). The optical properties were investigated with ultraviolet–visible absorption and fluorescence emission spectra. The results showed that the luminescence quantum yield of P‐OCN was 0.673 in chloroform, and it emitted blue and blue‐green light with a band gap of 3.49 eV estimated from the onset absorption. Thermogravimetric analysis and differential scanning calorimetry showed that the polymer exhibited good thermal stability up to 354°C with a glass‐transition temperature higher than 110°C. To investigate the donating and accepting capacities of P‐OCN, the fluorescent quenching technique was used to determinate the interactions between the polymer and the electron donor and electron acceptor. The results showed that the light emission could be quenched by both the electron donor (N,N‐dimethylaniline) and electron acceptor (dimethylterephthalate). Furthermore, the interaction between P‐OCN and fullerene was also studied with fluorescent quenching, and the processes followed the Stern–Volmer equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New Halogenated Water‐Soluble Chlorin and Bacteriochlorin as Photostable PDT Sensitizers: Synthesis,Spectroscopy, Photophysics,and in vitro Photosensitizing Efficacy

Chlorin and bacteriochlorin derivatives of 5,10,15,20‐tetrakis(2‐chloro‐5‐sulfophenyl)porphyrin have intense absorptions in the phototherapeutic window, high water solubility, high photostability, low fluorescence quantum yield, long triplet lifetimes, and high singlet oxygen quantum yields. Biological studies revealed their negligible dark cytotoxicity, yet significant photodynamic effect against A549 (human lung adenocarcinoma), MCF7 (human breast carcinoma) and SK‐MEL‐188 (human melanoma) cell lines upon red light irradiation (cutoff λ<600 nm) at low light doses. Time‐dependent cellular accumulation of the chlorinated sulfonated chlorin reached a plateau at 2 h, as previously observed for the related porphyrin. However, the optimal incubation time for the bacteriochlorin derivative was significantly longer (12 h). The spectroscopic, photophysical, and biological properties of the compounds are discussed in relevance to their PDT activity, leading to the conclusion that the bacteriochlorin derivative is a promising candidate for future in vivo experiments.     

Thermal curing of glass‐epoxy prepregs by luminescence spectroscopy

In this study, we investigated the application of the luminescence spectroscopy technique in steady‐state conditions to study glass fiber‐epoxy F161 prepregs. We conducted this study by comparing the results obtained from the intrinsic fluorescence with Fourier transform near infrared spectroscopy. The extrinsic fluorescence of 9‐anthroic acid (9‐AA) was also used. Fourier transform infrared spectroscopy was also used to characterize the epoxide resin. The prepregs containing 9‐AA and those that did not were heat‐treated at 177°C (F161) for 1100 min at a 2°C/min heating rate. The results obtained by both methods indicated that the crosslinking reaction could be monitored by analysis of the spectral changes of the emission bands of the prepreg and 9‐AA. The intrinsic emission at 320 nm was attributed to the fluorophore group containing the epoxy ring and was used to calculate the conversion degree. The photophysical behavior of the 9‐AA probe indicated a reduction of free volume of the polymeric matrix with curing process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010