Fluorene‐based rib waveguides with optimized geometry for long‐term amplified spontaneous emission stability

Amongst the different optoelectronic applications of conjugated polymers, waveguide amplifiers and optically pumped lasers are those requiring larger photochemical stability, owing to the large irradiation conditions under operation. In this context, suitable waveguide optimization enabling the reduction of amplified spontaneous emission (ASE) threshold values appears as important as synthetic chemistry protocols to promote polymer robustness against photo‐oxidation. In this work, we develop rib waveguides with different geometries based on four different fluorene‐based compounds and assess the influence of rib confinement on ASE properties. We observe ASE threshold values as low as 8.9 × 10^?4 mJ cm^?2, being among the lowest threshold values reported so far on blue emitting polymer/oligomer waveguides. We demonstrate that the enhanced ASE efficiency on some of these rib waveguides leads to a fivefold increase in operation lifetime respect to spin‐coated slab waveguides, thus confirming the impact of waveguide geometry on ASE operation stability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1040–1045     

Low thresholds for a nonconventional polymer blend—Amplified spontaneous emission and lasing in F81−x:SYx system

A mixture of two polymer materials, poly (9,9‐dioctylfluorene) (F8), and one of the poly(para‐phenylenevinylene) derivatives, superyellow (SY) have been used to make F8_1?x:SY_x polymer blend system. Under a 3–5 ns pulsed‐laser excitation, this system showed excellent optical properties with low threshold values of ≈14 µJ/cm² and ≈8 µJ/cm² for amplified spontaneous emission and optically pumped lasing, respectively. The proposed system was also electroluminescent and an interesting candidate for future research on polymer injection lasers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 15–21     

Melt-processed polymer multilayer distributed feedback lasers: Progress and prospects

Reflecting recent progress in the functionalization of roll-to-roll processed polymer multilayers, this review describes the development and characterization of versatile large-area multilayer distributed feedback (DFB) lasers. These developments are reviewed in the broader context of microresonator lasers, with a brief tutorial on the theory and experiment needed to understand their unique features. Of particular interest is the broad tunability of these DFB lasers by simple modification of their structure, mechanical stretching, and temperature. Prospects for commercialization of polymer multilayer DFB lasers are also discussed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 251–271     

Luminescent poly(phenylene vinylene) derivatives with m‐terphenyl or 2,6‐diphenylpyridine kinked segments along the main chain: Synthesis,characterization, and stimulated emission

Two new poly(phenylene vinylene)s containing m‐terphenyl or 2,6‐diphenylpyridine kinked units along the main chain were synthesized and were used as luminescent and laser materials. They were prepared from Heck coupling of 2,5‐didodecyloxy‐1,4‐divinylbenzene with 4,4″‐dibromo‐3′‐phenyl‐m‐terphenyl or 2,6‐di(4‐bromophenyl)‐4‐phenylpyridine. The kinked units along the main chain caused a partial interruption of the conjugation leading to emission at a shorter wavelength as compared with poly(p‐phenylene vinylene). The polymers presented blue‐green emission in solution and green‐yellow emission in the solid state with photoluminescence maxima at 465–497 and 546–550 nm, respectively. Polymer containing 2,6‐diphenylpyridine segments emitted at a longer wavelength than that containing m‐terphenyl and displayed higher quantum yields in solution (0.61 and 0.40, respectively). The influence of the solvent and polymer concentration on the photoluminescence characteristics was investigated. The photoluminescence properties of protonated polymer containing 2,6‐diphenylpyridine segments were investigated both in solution and in film. Amplified spontaneous emission and tunable laser action were also obtained from the two polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2214–2224, 2004     

Silafluorene‐based polymers for electrochromic and polymer solar cell applications

In this study, four novel silafluorene (SiF) and benzotriazole (Btz) bearing conjugated polymers are synthesized. In the context of electrochemical and optical studies, these polymers are promising materials both for electrochromic device (ECD) and polymer solar cell (PSC) applications. All of the polymers are ambipolar (both p‐ and n‐dopable) and multichromic. Electrochemistry experiments indicate that incorporation of selenophene instead of thiophene unit increases the HOMO energy level of the polymers. Power conversion efficiency of the PSCs reached 1.75% for PTBTSiF, 1.55% for PSBSSiF, 2.57% for PBTBTSiF, and 1.82% for PBSBSSiF. The hole mobilities of the polymers are estimated through space charge limited current (SCLC) model. PBTBTSiF has the highest hole mobility as 2.44 × 10^?3 cm² V s^?1. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1541–1547     

Laser emission in a 3D nanoporous polymer replica of amorphous blue phase III

Wide‐temperature polymer stabilized cubic blue phases (BPI and BPII) facilitated the emergence of practically feasible band‐edge BP lasers. However, the mysterious “blue fog” amorphous BPIII always remained elusive in terms of its applicability to photonic devices due to its random amorphous structure devoid of photonic bandgaps and due to the difficulty in effectively identifying and stabilizing it for practical applications. We present the first photonic device based on amorphous BPIII by demonstrating that a three‐dimensional BPIII polymer scaffold or template, when infiltrated with liquid crystal and laser dye, forms a system where random lasing action is generated due to multiple scattering events occurring in the nanoporous and disordered polymer replica of BPIII. This study represents a facile approach for the development of photonic devices which favorably exploit unique polymer network morphologies for laser emission. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 551–557     

Fluorous solvent‐soluble imaging materials containing anthracene moieties

Highly fluorinated photoresist polymers that can undergo photodimerization reactions were designed using an anthracene‐based monomer. Through the random radical copolymerizations of 6‐(anthracen‐9‐yl)hexyl methacrylate ( AHMA ) and semiperfluorodecyl methacrylate ( FDMA ) with four different compositions, polymers with M_n = 20,000–27,000 (M_w/M_n = 2.0–2.9) were prepared in benzotrifluoride. The polymers, in particular fluorous solvent‐soluble imaging material‐2 ( FSIM‐2 ), showed sufficient solubility in fluorous solvents, including hydrofluoroethers, but were rendered insoluble by UV exposure (365 nm). This photochemical solubility change was evaluated quantitatively by a quartz crystal microbalance technique, along with tracing the chemical reaction by UV–vis spectroscopy. Finally, FSIM‐2 and fluorous solvents were applied to the photolithographic patterning of organic light‐emitting diode pixels. In the patterning protocol involving the lift‐off of resist films in fluorous solvents, FSIM‐2 was recognized as a promising photoreactive material when compared with a reference polymer P(FDMA‐MAMA) , which necessitates acidolysis reactions for lithographic imaging. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1252–1259     

Thiophene π bridge effect on bulky side‐chained benzodithiophene‐based photovoltaic polymers

Recently, we have used terthiophene side chain to modify benzo[1,2‐b:4,5‐b′]dithiophene (BDT) to form novel building block for BDT polymers. In this paper, this building block is used to copolymerized with thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) and thieno[3,4‐b]thiophene (TT). This building block and TPD‐ or TT‐based polymers (P1 and P3) show high open circuit voltage (V_OC) (ca. 0.9–0.95 V) and low energy loss (E_g–eV_OC) in solar cells devices compared with similar polymers without bulky side chain. We further introduce thiophene π bridge into these polymers backbone to form two other polymers (P2 and P4). We find this thiophene π bridge does contribute to this bulky side chained benzodithiophene polymer photovoltaic performances, especially for power conversion efficiencies (PCEs). The polymer solar cells (PSCs) performances are moderate in this article due to the serious aggregation in the PSCs active layer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1615–1622     

Novel hyperbranched polymers synthesized via A3 + B(B′) approach by radical addition‐coupling polymerization

In this study, a novel application of radical addition‐coupling polymerization (RACP) for synthesis of hyperbranched polymers is reported. By Cu/PMDETA‐mediated RACP of 2‐methyl‐2‐nitrosopropane with trimethylolpropane tris(2‐bromopropionate) or a bromo‐ended 3‐arm PS macromonomer, two types of hyperbranched polymers with high degree of polymerization are synthesized under mild conditions, respectively. The chemical structures of the hyperbranched polymers are carefully characterized. By selective degradations of the ester groups and weak bonds of NO? C in the polymers, high degree of alternative connection of the two monomers in the synthesized polymers have been identified. Based on the experimental results, mechanism of formation of the hyperbranched polymer is proposed, which includes formation of carbon radicals from the tribromo monomer through single electron transfer, its capture by 2‐methyl‐2‐nitrosopropane that results in nitroxide radical, and cross‐coupling reaction of the nitroxide radical with other carbon radicals. Hyperbranched polymer can be formed in a step‐growth mode after multiple steps of such reactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 904–913     

A facile synthesis of catechol‐functionalized poly(ethylene oxide) block and random copolymers

Herein we develop a facile synthetic strategy for the functionalization of well‐defined polyether copolymers with control over the number and location of catechol groups. Previously, the functionalization of polyethylene oxide (PEO)‐based polymers with catechols has been limited to functionalization of the chain ends only, hampering the synthesis of adhesive and antifouling materials based on this platform. To address this challenge, we describe an efficient and high‐yielding route to catechol‐functionalized polyethers, which could allow the effects of polymer architecture, molecular weight, and catechol incorporation on the adhesive properties of surface‐anchored PEO to be studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2685–2692     

Synthesis and photovoltaic properties of thieno[3,4‐b]pyrazine or dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2‐d]imidazole‐containing conjugated polymers

Novel conjugated polymers composed of benzo[1,2‐b:4,5‐b′]dithiophene and thieno[3,4‐b]pyrazine or dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2‐d]imidazole units are synthesized by Stille polycondensation. The resulting polymers display a longer wavelength absorption and well‐defined redox activities. The effective intramolecular charge‐transfer and energy levels of all polymers are elucidated by computational calculations. Bulk‐heterojunction solar cells based on these polymers as p‐type semiconductors and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) as an n‐type semiconductor are fabricated, and their photovoltaic performances are for the first time evaluated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1067–1075     

Synthesis and radical polymerization of methacrylate endowed with bicyclobis(γ‐butyrolactone) moiety through methylene linker

A series of methacrylates bearing bicyclobis(γ‐butyrolactone) (BBL) moiety were synthesized and radically polymerized to afford the corresponding poly(methacrylate)s bearing BBL moiety in the side chain, with expecting that the high polarity and rigidity of BBL would be inherited by the polymers. The resulting polymers were soluble in polar aprotic solvents such as dimethyl sulfoxide and N,N‐dimethylformamide because of the high polarity of the BBL moiety. The glass transition temperatures (T_g) of the polymers depended on the length of methylene linker that tethered the methacrylate and BBL moieties, making the use of shorter linkers lead to higher T_gs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2462–2468     

Fabrication of fluorescent holographic micropatterns based on the rare earth complexes using azobenzene‐containing poly(aryl ether)s as macromolecular ligands

In this work, on the basis of photoinduced surface relief gratings (SRGs) with the rare earth complexes using azo‐polymers as macromolecular ligands, a series of novel materials for fabricating rewritable fluorescent two‐dimensional micropatterns, whose color can be easily adjusted by changing the species of the rare earth ions, are demonstrated. The rare earth complexes are prepared using a series of poly(aryl ether)s containing azobenzene chromophores and carboxyl group as macromolecular ligands and 1,10‐phenanthroline as co‐ligands. The fluorescence properties of the rare earth complexes and the influence of the contents of azobenzene chromophores on the fluorescent intensity are investigated by means of fluorescence excitation and emission spectroscopy. By exposing the films of the rare earth complexes to an interference pattern laser beam, SRGs can be formed on the films. Under the excitation, fluorescent patterns of the SRGs can be observed by the measurement of fluorescence microscopy. © 2015 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym. Chem. 2015 , 53, 936–943     

Preliminary results of heterodyne detection with quantum-cascade lasers in the 9 μm region

In this paper, we describe recent results in mid-infrared heterodyne detection using quantum-cascade (QC) lasers as local oscillator (LO). In the 9 μm range, the heterodyne detection technique was first developed with CO₂ lasers and then with Pb-salt diode lasers. Quantum-cascade lasers are promising high quality tunable mid-infrared sources. We developed a quantum-cascade laser based heterodyne spectrometer. Atmospheric absorption spectra of ozone are presented.     

Feature size reduction in two‐photon polymerization by optimizing resin composition

In the last decades, an increasing refinement over submicroscopic scales has played a decisive role in boosting scientific and technological progress. When dealing with miniaturized devices, organic materials have drawn considerable attention, not only for requiring lower energies during processing but also for allowing functionalization with ease, exhibiting biocompatibility and presenting high optical quality. In this scenario, the modification of acrylate polymers by femtosecond lasers has become an important mechanism. Among the main techniques based upon this principle, two‐photon polymerization (2PP) stands out due to its capability of producing fine features. Still, 2PP has often been combined with sophisticated methods devised to further improve spatial resolution and miniaturized devices. However, such measures invariably raise the cost of the experiments by demanding either the addition of other chemical compounds or a second laser system. In this study, we discuss how the relative proportion of acrylate monomers and different concentrations of a photoinitiator influence the final dimension of structures fabricated using polymeric samples, which are widely used in 2PP experiments. Furthermore, we demonstrate that it is possible to produce finer features only by varying the proportion of these constituents, achieving linewidths on the order of 360 nm and heights on order of 300 nm. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1158–1163     

Extremely fragile glass‐formers? Calorimetric and rheological determinations

We use calorimetry and rheology to investigate reports of extremely fragile polymers and the speculation that d,l ‐lactic acid should be extremely fragile. The dynamic fragilities of lactic acid, polysulfone, bisphenol‐A polycarbonate, and poly(vinyl chloride) were studied. The polymers were used as received and after a wash‐precipitation treatment. The current dynamic fragility findings are not in agreement with those reported by C. Evans, H. Deng, W. Jager, J. Torkelson, Macromolecules 2013 , 46 (15), 6091–6103 of extremely high fragilities for the mentioned polymers. We also found no sample preparation history effect on the dynamic fragility values. The calorimetric and rheological results for the d,l ‐lactic acid show dynamic fragility values that are consistent with each other and are not extremely fragile. Calorimetric measurements that use a broad range of cooling rates gave smaller dynamic fragility values than those obtained from a limited range at higher cooling rates. The importance of the results is discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1261–1272     

Low band‐gap diketopyrrolopyrrole‐containing polymers for near infrared electrochromic and photovoltaic applications

Donor–acceptor type polymers bearing diketopyrrolopyrrole and 3,4‐ethylenedioxythiophene units are reported. The polymers are green and exhibit very low band‐gaps (1.19 eV) with strong and broad absorption (maxima of about 830 nm) in the near infrared (NIR) region in their neutral film states. The polymers display color changes between dark green and light blue with exceptional optical contrasts in the NIR regions of up to 78 and 63% as thin films and single‐layer electrochromic devices, respectively. Fast switching, good stabilities as well as high coloration efficiencies (743–901 cm² C^?1) were also observed. The polymers could also be potentially used as photovoltaic material, with a power conversion efficiency of up to 1.68%. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1287–1295     

Novel panchromatic photopolymerizable matrices: N,N'‐dibutylquinacridone as an efficient and versatile photoinitiator

N,N'‐dibutylquinacridone (DBQA) is utilized here for the first time as a high‐performance panchromatic photoinitiator for the cationic polymerization (CP) of epoxides, the free radical polymerization (FRP) of acrylates, the thiol‐ene polymerization and the synthesis of interpenetrated polymer networks (epoxide/acrylate) under violet, blue, green and yellow lights (emitted from LED at 405 nm, 470 nm, 520 nm, or 594 nm, or laser diode at 532 nm). It confers a panchromatic character to the photopolymerizable matrices. Remarkably, the proposed DBQA based photoinitiating systems exhibit quite excellent efficiency (the final monomer conversion for multifunctional monomers at room temperature can reach 62% and 50% in CP and FRP, respectively) and appear as much more powerful than the camphorquinone or Eosin‐Y containing reference systems for visible light. For green light, DBQA is much more reactive than the literature reference (Eosin‐Y) and for blue light, a good reactivity is found compared with camphorquinone. The photochemical mechanisms are studied by molecular orbital calculations, steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis, and electron spin resonance spin trapping techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1719–1727     

Synthesis,characterization, and photovoltaic properties of dithienylbenzobisazole‐dithienylsilole copolymers

Three conjugated polymers comprised of dioctyl‐dithieno‐[2,3‐b:2',3'‐d]silole and a donor‐acceptor‐donor triad of either cis‐benzbisoxazole, trans‐benzobisoxazole or trans‐benzobisthiazole were synthesized via the Stille cross‐coupling reaction. The impact of varying the heteroatoms and/or the location within the benzobisazole moiety on the optical and electronic properties of the resulting polymers was evaluated via cyclic voltammetry and UV‐Visible spectroscopy. All of the polymers have similar optical band‐gaps of ～1.9 eV and highest occupied molecular orbital levels of ? 5.2 eV. However, the lowest unoccupied molecular orbitals (LUMO) ranged from ? 3.0 to ? 3.2 eV. Interestingly, when the polymers were used as donor materials in bulk‐heterojunction photovoltaic cells with PC₇₁BM as the electron‐acceptor, the benzobisoxazole‐based polymers gave slightly better results than the benzobisthiazole‐containing polymers with power conversion efficiencies up to 3.5%. These results indicate that benzobisoxazoles are promising materials for use in OPVs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1533–1540     

Synthesis and structure‐optoelectronic property relationships of a series of PPV and SFTV derived polymers

Engineering of the highest occupied molecular orbital and lowest unoccupied molecular orbitals through synthetic chemical structural modification has been the most widely used method to tuning optoelectronic properties in conjugated polymers. The electronic, thermal, optical, and physical properties can be tuned and exploited for optimization of optoelectronic devices. Through copolymerization of donor and acceptor type conjugated monomers, the frontier orbitals of four polymers were tailored. Through this synthetic engineering, the relationship between structural features, frontier orbital tailoring, and changes in optoelectronic and physical properties are discussed. Spectroscopic, thermal, and electronic analysis of the polymers indicated that polymers containing carbazole monomer moieties gave overall improved optoelectronic properties, but higher band gaps (2.61 and 2.18 eV) in comparison to their phenyl‐ based counterparts. This result is attributed to the higher electron density of the carbazole than the terephthaldicarboxaldehyde, and the possible deviation from planarity in the polymer main chain due to possible steric hindrance of the branched substituents. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2202–2213