Nonlinear Optical Properties and Liquid‐Crystalline Behavior of New Polyesters with Dipole Moments Aligned Transverse to the Backbone

Side‐chain azobenzene‐based second‐order nonlinear optical (NLO) polyesters ( PNPAR , PNPAPAR , PPAR‐TC , PPAPAR‐TC ) containing nitro or tricyanovinyl groups as acceptors with their dipole moments aligned transverse to the polymer backbone, were synthesized and characterized, and their thermal properties, liquid‐crystalline (LC) phase behavior, and NLO properties studied. Polymers containing nitro groups as acceptors were found to exhibit LC properties, while those containing tricyanovinyl groups as acceptors did not. The LC polymers were of smectic nature. The polymer PNPAR with a nitro group, when poled at the LC phase‐transition temperature range, was found to exhibit higher NLO activity than that with a tricyanovinyl group ( PPAR‐TC ). When polymer PNPAPAR containing a nitro group, also exhibiting an LC phase, was poled at a temperature different from that of its transition temperature, the NLO activity observed was comparable to, and/or lower than, that of the similar polymer ( PPAPAR‐TC ) having a tricyanobvinyl group in the place of the nitro group. All the polymers were found to possess moderate temporal stability of second harmonic generation activity and were found to have stability over the whole process.     

High‐Performance Photorefractive Composite Based on Non‐conjugated Main‐Chain,Hole‐Transporting Polymer

The photorefractivity of a non‐conjugated main‐chain polymeric composite, composed of electron‐rich N,N‐di‐toly‐N,N′‐diphenylbiphenyldiamine doped with 2‐{3‐[(E)‐2‐(piperidino)‐1‐ethenyl]‐5,5‐dimethyl‐2‐cyclohexenylidene}‐malononitrile (P‐IP‐DC) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM), is studied using two‐beam coupling and degenerate four‐wave mixing at 633 nm. The N,N′‐di‐toly‐N,N′‐diphenylbiphenyldiamine‐based composite shows a gain coefficient of 215 cm^?1 at 80 V μm^?1 with s‐polarized beams and a diffraction efficiency of 67% at 30 V μm^?1, with a response time of the diffraction efficiency of 344 ms at T_g + 4.6 °C. Comparing the photorefractive grating response time of the 3,3′‐dicarbazole‐containing polymer composite with that of the N,N′‐di‐toly‐N,N′‐diphenylbiphenyldiamine‐based composite shows that the former is more than three times faster.     

All Organic NLO Sol‐Gel Material Containing a One‐Dimensional Carbazole Chromophore

A NLO‐active polymer has been developed via combining chromophoric photorefractive characteristics and film optical quality of melamine network. A carbazole‐containing NLO‐phore can be acquired via a facile synthetic route, namely Knoevenagel condensation. Guest‐host prepolymer was obtained by doping the chromophores into benzoguanamine matrix. After poling and curing process, a NLO‐active organic sol‐gel material with large second‐order nonlinearity and excellent optical quality film has been achieved. Thermal stability of the polymer was analyzed via DSC and TGA. UV‐vis spectra and second harmonic generation measurement were utilized to characterize the linear and nonlinear optical properties. Reorientation dynamic stability was used to study temperature dependence of NLO signal. The d₃₃ and d₃₁ values for the polymer are 19 pm/V and 9 pm/V, respectively. Long‐term NLO stability was investigated by measuring effective second harmonic (SH) coefficient as a function of time. The effective SH coefficient retained 47% of its original value and leveled off after 10 h of thermal ageing at 80°C.     

Quasi‐Solid‐State Dye‐Sensitized Solar Cells Using Nanocomposite Gel Polymer Electrolytes Based on Poly(propylene carbonate)

Poly(propylene carbonate) (PPC) is synthesized from the copolymerization of CO₂ and propylene oxide. Novel nanocomposite gel polymer electrolytes (GPEs) are prepared by utilizing PPC, organic solvents containing a redox couple, and aluminum oxide nanoparticles for application in dye‐sensitized solar cells (DSSCs). The quasi‐solid‐state DSSC assembled with optimized nanocomposite GPEs exhibits a relatively high conversion efficiency of 6.16% at 100 mW cm^?2 and better stability than DSSC with liquid electrolyte.     

Photorefractivity of Perylene Bisimide‐Sensitized Poly(4‐(diphenylamino)benzyl acrylate)

A perylene bisimide derivative of N,N′‐diisopropylphenyl‐1,6,7,12‐tetrachloroperylene‐3,4,9,10‐tetracarboxyl bisimide (PBI) is synthesized and used as a sensitizer for a photorefractive (PR) polymer composite. Small amount (0.1 wt%) of PBI sensitizer gives the maximum PR performance of composite based on poly(4‐(diphenylamino)benzyl acrylate) (PDAA) (45 wt%), 2‐(4‐(azepan‐1‐yl)benzylidene)malononitrile (35 wt%), and (4‐(diphenylamino)phenyl)methanol (24.9 wt%). High external diffraction efficiency of 49%, response time of 47 ms, and sensitivity of 28 cm² J^?1 are obtained under an applied electric field of 40 V μm^?1 at writing beam of 532 nm. PBI sensitizer effectively forms a charge‐transfer complex with PDAA, which favors the generation of the charge carriers followed by the space‐charge formation. Furthermore, low PBI concentration contributes to low absorption coefficient at 532 nm, which leads to better PR performance.

     

Atom Transfer Radical Polymerization and Third‐Order Nonlinear Optical Properties of New Azobenzene‐Containing Side‐Chain Polymers

The atom transfer radical polymerization (ATRP) technique has been successfully applied to synthesize a series of nonlinear optically (NLO) active homopolymers, 4‐(4‐nitrophenyl‐diazenyl) phenyl acrylate ( P ‐ NPAPA ) and 4‐(4‐methoxyphenyl‐diazenyl) phenyl acrylate ( P ‐ MPAPA ), containing azobenzene groups on the side chain. The third‐order NLO properties of the polymer films were measured by the degenerated four‐wave mixing (DFWM) technique. A dependence of the χ⁽³⁾ values and response times of polymers on their number‐average molecular weight and the electronic effect of the substituent (nitro‐ or methoxy‐) on the azobenzene group have been evidenced. The increasing χ⁽³⁾ value of the polymer films at the magnitude of about 10^?10 was displayed with increasing molecular weight and the presence of the push‐pull electronic system contributes much in enhancing the third‐order NLO susceptibility of polymers.

     

Chromophore‐Functionalized Poly(ether sulfone)s with High Poling Stabilities of the Nonlinear Optical Effect

Summary: Nonlinear optical (NLO) polymers with high glass transition temperatures were prepared by the functionalization of poly(ether sulfone)s with hydroxyalkyl chromophores via the Mitsunobu reaction. Glass transition temperatures obtained were in the range of 158–212 °C. Thin spin‐coated films of the polymers were corona‐poled and analyzed by second‐harmonic generation measurements; second‐order susceptibility values (d₃₃) up to 181 pm · V^?1 were obtained. Poled‐order stability measurements over a period of 1 600 h showed that the percentage of the remaining NLO‐response at 125 °C was 84–96% under nitrogen and 54–76% in air.

Structures of chromophores a–c.     

3D Network Binder via In Situ Cross‐Linking on Silicon Anodes with Improved Stability for Lithium‐Ion Batteries

Silicon (Si) has attracted intensive academic and commercial attention due to its extremely high theoretical capacity. However, it is still far away from practical application because of its fast capacity fading, which is caused by the huge volume change. Here, a novel network polymer binder is synthesized through in situ thermal crosslinking of water‐soluble carboxymethyl cellulose (CMC) and maleic anhydride (MAH). The as‐obtained polymer binder network can effectively restrict the huge volume change of Si anodes upon lithiation. Because of the significantly enhanced structural stability, the Si anodes with network polymer binder deliver enhanced electrochemical performance, with a capacity of 996 mAh g^?1 at a high current density of 1 A g^?1 after 120 cycles under high mass loading. Most importantly, a high average Coulomb efficiency (CE) of 99.4% is obtained, which is superior over the average CE (98.7%) of Si only using CMC as binder. It is considered that this novel 3D network cross‐linking binder can be used for high‐capacity anode materials in next‐generation Li‐ion batteries.     

New second-order nonlinear optical (NLO) epoxy polymer treated by sol-gel processing

We have demonstrated a novel approach to achieve a stable second-order NLO polymer by incorporating NLO moieties into a processable epoxy polymer and hardening with crosslinkable sol-gel technique. The crosslinked polymer showed high nonlinearity (d₃₃ = 41 pm/V) and better thermal stability compared to the prepolymer, which maintained its nonlinearity up to 100°C without significant loss of NLO activity.     

Optimization of Photorefractivity Based on Poly(N‐vinylcarbazole) Composites: An Approach from the Perspectives of Chemistry and Physics

The optimization of photorefractivity (PR) based on a poly(N‐vinylcarbazole) (PVCz) composite devise is proposed from the perspectives of chemistry and physics. The device's PR chemistry (dependence of PVCz's molecular weight) and physics (dependence of grating periodicity and laser wavelength) are studied. Increasing the molecular weight of PVCz from 23 000 to 1 270 000 g mol^?1 significantly increases diffraction efficiency, grating build‐up speed (inverse of response time), and sensitivity. Narrowing grating period from 5.1 to 1.1 μm gives faster response time and larger optical gain. Shorter wavelength of writing laser from 633 to 532 nm provides higher diffraction efficiency, faster response time, and larger optical gain.

     

Conjugated Microporous Polytetra(2‐Thienyl)ethylene as High Performance Anode Material for Lithium‐ and Sodium‐Ion Batteries

A novel, thiophene‐rich conjugated microporous polymer of polytetra(2‐thienyl)ethylene (PTTE) is synthesized via FeCl₃‐catalyzed oxidative polymerization and applied as an anode material for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). Owing to the high surface area, high redox‐active thiophene content, and the plentiful nanoporous structures in PTTE, the assembled LIBs exhibit a high specific capacitance of 973 mA h g^?1 at 100 mA g^?1 with excellent rate performance, and the SIBs show a capacitance as high as 370 mA h g^?1 at a current density of 50 mA g^?1, excellent rate capability, and outstanding cycling stability with a capacity retention of 230 mA h g^?1 at 200 mA g^?1 after 100 cycles. These results demonstrate this thiophene‐rich conjugated microporous polymer as a promising electrode material for next‐generation energy storage devices.     

Synthesis of NLO diacrylate monomers and their photocopolymerizations with LC diacrylate monomers in mixed liquid crystalline state

The photocopolymerization (photocrosslinking) of mixed liquid crystals (LCs) consisting of LC diacrylate monomers and nonlinear optical (NLO) diacrylate monomers exhibiting no liquid crystallinity under contact poling at optimum temperature was investigated to obtain a thermally stable NLO polymeric material. Novel NLO monomers, BAASA and BAOSA , as well as LC monomers, BAOOB3 and PAOB , were synthesized and the liquid crystallinity of their mixed LCs was investigated. The affinity of BAOSA with the LC monomers is generally better than that of BAASA . LC mixtures prepared using BAOOB3 as LC matrix show only a smectic phase and do not respond to poling though fixation of the mixture by photocrosslinking occurs tightly. A PAOB matrix results in a nematic phase but not a smectic phase and the LC mixture responds not only to poling but also to photocopolymerization in the nematic phase. The photocrosslinking reaction of a BAOSA/PAOB (mole ratio 1/9) mixture under poling at 129°C (nematic phase) proceeds effectively and gives a thermally stable polymer film with a χ₃₃⁽²⁾ value of 1.2–1.7 × 10⁻⁸ esu

1 esu = electrostatic unit; 1 esu = 2.693 × 10¹⁴ C³/J².

, while the polymer film formed by photocrosslinking at 140°C (isotropic phase) shows a one order lower χ₃₃⁽²⁾ value (3–5 × 10⁻⁹ esu).     

Attachment of a 1,8‐Naphthalimide Moiety to a Conjugated Polythiophene Efficiently Improves the Sensing Abilities of Naphthalimide‐Based Materials

A novel polythiophene‐based conjugated polymer bearing 1,8‐naphthalimide‐based pendants is prepared by a two‐step modification of regioregular poly[3‐(6‐bromohexyl)thiophene] involving a nucleophilic substitution reaction of the bromide end‐groups with sodium azide followed by a robust, copper‐catalyzed Huisgen click reaction with a novel 1,8‐naphthalinmide derivative containing an active, N‐substituted propyne group. Both the polymer and the highly luminescent‐active synthesized dye are extensively studied in solution by UV–vis spectroscopy, photoluminescence, NMR, light‐scattering and isothermal titration calorimetry. The materials prepared are considered potential chemosensors for different transition metals, such as Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺. Luminescence quenching shows that these materials have a higher sensitivity to Fe²⁺ than to the other metal ions tested. Moreover, the 1,8‐naphthalimide‐based conjugated polymer is more efficiently quenched by Fe²⁺ metal ions, at a significantly lower concentration and with a higher binding constant than its parent 1,8‐naphthalimide derivative, thus indicating a high potential for sensor development.     

Synthesis of Polymers Bearing Oligo‐Aromatic Esters for Second‐Order Nonlinear Optics

We synthesized methacrylate‐type polymers bearing oligo‐aromatic esters as side chains to create unique second‐order nonlinear optical (NLO) active polymers ( PMA n ‐x , PMA n C‐x , PMA2N‐x , and PBA3N‐x , x = oligo‐aromatic ester contents) for the investigation of the resulting architecture. The polymers were obtained from the polymerization of methacrylated oligo‐aromatic esters and the copolymerization of the esters with methyl methacrylate or tert‐butyl methacrylate using a radical initiator. The cut‐off wavelength (λ_co) of these polymers was shorter than the visible region aimed at, i. e. λ_co = ca. 330–370 nm, which is much shorter than λ_co of the typical second‐order NLO polymers containing groups such as azobenzene chromophores. Second‐harmonic generation (SHG) measurements of these polymer films after treatment by corona poling were carried out using the Maker‐fringe method. These polymer films exhibited good transparency in the visible region and a second‐order nonlinear optical coefficient d₃₃ of 2.2–9.8 pm·V^–1. The d₃₃ values of some derivatives decreased with an increase of the chromophore content, which is due to a strong interaction between the side chains with increasing chromophore content.     

Synthesis and nonlinear optical properties of aromatic esters with an electron donor and an electron acceptor end group

We synthesized a series of aromatic esters having an electron donating and an electron accepting end group as a new class of nonlinear optical (NLO) active chromophores ( ArESn D‐A , n = 2,3, D = MeO (as reference), MeS and Me₂N, A = CN). Second‐order NLO properties for poled polymer films consisting of poly(methyl methacrylate) ( PMMA ) doped with 10 wt.‐% ArESn D‐A ( ArESn D‐A/PMMA ) were investigated. The UV/vis spectra of these polymer films have cutoff wavelengths (λ_co) of about 350 ˜ 370 nm, which are much shorter than in the case of p‐nitroaniline (pNA) (λ_co = 473 nm) which is a typical strong donor‐acceptor (D‐π‐A) molecule. In addition, some of these polymer films exhibit higher second‐order nonlinear coefficients (d₃₃) than a PMMA film doped with 10 wt.‐% pNA ( pNA/PMMA ) (2.8×10^–9 esu). Namely, ArES3 Me₂N‐CN (d₃₃ = 5.6×10^–9 esu, 10 wt.‐% in PMMA) and ArES2 Me₂N‐CN (3.8×10^–9 esu, 10 wt.‐% in PMMA) showed excellent second‐order NLO activity as well as transparency in the visible region (λ_co: 362 nm for ArES3 Me₂N‐CN and 366 nm for ArES2 Me₂N‐CN , respectively).     

Novel Polymers with Inherent Conductivity and Enhanced Second‐Order NLO Activity

A new polythiophene derivative bearing an azobenzene substituent at the end of a ethylenic side‐chain was synthesized and characterized by FT‐IR spectroscopy, ¹H and ¹³C NMR spectroscopy, DSC, TGA, XRD, and UV‐vis spectroscopy. Its electrical conductivity was measured and its second‐order NLO activity was by SHG. Structure‐property relations were elucidated by comparison with a similar polymer only partially substituted by the NLO‐active chromophore. The molecular design of the chromophoric system allows high and stable non‐linear coefficients d₃₃ to be obtained, making these polymers suitable for the construction of second‐harmonic generators with improved efficiency and life‐time.

     

Synthesis and Characterization of a 2,4,6‐Tri(2‐thienyl)pyridine‐Based Conjugated Polymer for OFET Applications

2,4,6‐Tri(2‐thienyl)pyridine is used to synthesize the new conjugated polymer PBDTTPy for OFET applications. The concept of introducing electron‐deficient pyridine repeating units and meta‐linked structures into a conjugated polymer to reduce its HOMO energy level and thereby increase its ambient stability is tested. The absorption spectrum of the polymer thin film displays a large bathochromic shift compared with its solution absorption spectrum. The polymer PBDTTPy shows a typical amorphous structure in the solid state. The first OFET device based on a conjugated polymer with meta‐linked trithienylpyridine units is reported. PBDTTPy exhibits p‐type transport under ambient conditions in a bottom‐gate, top‐contact OFET device with a mobility of 2.4 × 10^?4 cm² V^?1 s^?1.     

Conjugated Side Chain Tuning Effect of Indacenodithieno[3,2‐b]thiophene and Fluoro‐Benzothiadiazole‐Based Regioregular Copolymers for High‐Performance Organic Field‐Effect Transistors

Two regioregular indacenodithieno[3,2‐b ]thiophene and fluoro‐benzothiadiazole‐based donor–acceptor (D–A) type copolymers with different conjugated side chains of hexyl‐phenyl or hexyl‐thienyl are designed and synthesized to study the effects of the side chain on performance of organic field‐effect transistors (OFETs). The effect of the different conjugated side chains on the energy levels, optoelectronic properties, film morphology, and transistors performance as well as the solvent effect on the performance of both D–A copolymers are thoroughly studied. Top‐gate/bottom‐contact OFETs with a hexyl‐thienyl substituted polymer show higher hole mobility up to 0.211 cm² V⁻¹ s⁻¹ than 0.086 cm² V⁻¹ s⁻¹ observed for the polymer with hexyl‐phenyl side chains. In addition, the hexyl‐thienyl substituted side chain polymer shows relatively better stability under bias stress compared to hexyl‐phenyl conjugated side chain. This result sheds light on the impact of conjugated side chain engineering on the performance and stability of OFETs with D–A copolymers.     

Bis‐Diketopyrrolopyrrole and Carbazole‐Based Terpolymer for High Performance Organic Field‐Effect Transistors and Infra‐Red Photodiodes

Carbazoles constitute one of the most widely used donor moieties for organic semiconductors due to their excellent hole transport and high environmental stability. However, they are seldomly used in recent high performance donor–acceptor (D–A) copolymers. In the present study, a planar regular terpolymer, PCbisDPP, composed of carbazole and thiophene flanked bis‐diketopyrrolopyrrole (bis‐DPP) for application as an active layer for high‐performance organic devices is reported. Organic field‐effect transistors with PCbisDPP as the active layer exhibit field‐effect mobility up to 1.48 cm² v^?1 s^?1, which to the best of the current knowledge corresponds to the highest hole mobility reported to date for carbazole‐based D–A polymers. The high mobility is achieved via a tailored polymer‐design resulting in high crystallinity and a strong aggregating property without sacrificing solubility. PCbisDPP is applied as an active donor material in organic photodiode with fullerene derivative PC₆₁BM as an acceptor in a bulk heterojunction blend. Binary additive combinations (tetralin: 1,8‐diiodooxtane (3:3) v/v%) utilization achieves an impressive performance with an external quantum efficiency of 80%, an average responsivity of 309.1 mA W^?1, and specific detectivity of 4.73 × 10¹¹ Jones in the near infra‐red light region (730 nm) utilizing a simple single layer organic photodiode structure as ITO/PEDOT:PSS/PCbisDPP:PC₆₁BM/LiF/Al.     

Phase Control Behavior of Lateral Polymer Photodetectors Using Strong Aggregation Bulk Heterojunction Film

The aggregation behavior of polymers can ultimately have a significant impact on the performance of polymer photodetectors depends mainly on the main solvent, solvent additive, thermal annealing treatment, and so on. In this work, a phase control behavior of lateral polymer photodetectors (L‐PPDs) is realized by changing the acceptor concentration or introducing 1,8‐diiodooctane (DIO) in strong aggregation of bulk heterojunction (BHJ) films, which can effectively regulate the minority carriers trapping under high PC₆₁BM ratio. Additionally the responsivity (R), gain (G) and specific detectivity (D*) value of the L‐PPDs can reach 94.4 A W^?1, 289.7, and 1.33 × 10¹⁴ Jones under 0.0031 mW cm^?2 @405 nm, respectively. The structure of the L‐PPDs is optimized as quartz/ PMMA (30 nm)/ PffBT4T‐2OD:PC₆₁BM (D/A ratio = 1:1.2)/ Ag–Ag electrodes. Furthermore, the phase separation of the thin films is promoted by introducing 3% DIO, resulting in a clear increase of response speed (fall time is about tenfold faster than that of the control device), and an improved switching performance about 60‐fold higher under strong light (10.42 mW cm^?2). This research represents an important step forward in the fabrication of high‐performance polymer photodetectors, which show promising application potential.