SYNTHESIS OF A NOVEL SELF-ASSEMBLING NLO POLYMERIC FILM*

By covalently binding chromophore NPP, N-(4-nitrophenyl)-(L)-prolinol, to a structurallycontrolled cage-like cross-linking polymer (SCCP), a modified nonlinear optical (NLO) polymeric filmprepared by "in situ poling and sol-gel" process successfully overcame the fundamental problem of NPPchromophores subliming out from the cages of the "doped" NLO polymeric film when heated or placed underUV light. Its d_(33) (coefficient of second harmonic generation) is 2.0×10~(-8) esu. measured by IR dichroism. Themodified film has a low decay of the SHG signal and preserves 94% of the initial value after 50 days at roomtemperature. These properties match that of the "doped" film, indicating that the modified film also retainsthe main advantages of the "doped" film.     

Effect of filler on kinetic characteristics of glass transition in polymer composite materials

Dynamic mechanical spectroscopy and differential scanning calorimetry were used to study the effect of various fillers (carbon fiber, glass fiber, and aramid fiber) on the kinetic characteristics of glass transition in polymer composite materials based on epoxy resin. It is shown that the composite based on carbon fiber is the most fragile among the materials studied, whereas the polymer composite material based on aramid fiber exhibits the lowest rate of variation of the relaxation time above the glass-transition temperature. A relationship is determined between the heat conductivity and fragility of polymer composite materials. The effect of various fillers on the curing kinetics of the epoxy matrix upon glass transition is prognosticated, with the difference in the degree of curing reaching a value of 4–5%. The strongest filler effect on the curing kinetics is observed in the chemically controlled region, which may be due to the catalytic effect of functional groups on the fiber surface.     

Synthesis and characterization of main‐chain NLO oligomers and polymer that contain 4‐dialkylamino‐ 4′‐(alkylsulfonyl)azobenzene chromophores

An ω‐amino carboxylic acid monomer that contained a nonlinear optical (NLO) chromophore was prepared by a convergent synthesis. Strategies for selective protection/deprotection of the amino and carboxylic acid functionalities were developed. The protected monomer, 4‐[N‐(4‐benzyloxycarbonyl)butyl‐N‐methylamino]‐4′‐[2″,5″‐bis(decyloxy)‐4″‐(phthalimidomethyl)benzylsulfonyl]azobenzene, could be deprotected selectively or sequentially to give HOOC‐monomer‐N‐phthaloyl, benzyl‐OOC‐monomer‐NH₂, or HOOC‐monomer‐NH₂. Sequential synthesis was performed to yield main‐chain NLO dimers and tetramers. This was accomplished by selective deprotection and dicyclohexylcarbodiimide coupling. The HOOC‐monomer‐NH₂ was polymerized by treatment with diphenylphosphoryl azide to give a main‐chain NLO polyamide. The monomer, dimer, tetramer, and polymer NLO materials were characterized by ¹H, ¹³C, IR, and UV–visible spectroscopy as well as by gel permeation chromatography, differential scanning calorimetry, and elemental analysis. The NLO properties of these materials were measured. Thin films of the oligomers and polymer were prepared by spin casting on indium‐tin oxide coated glass. The second‐order NLO properties of the oligomers and polymer thin films were studied by in situ corona poling/second‐harmonic generation and attenuated total reflection methods. The optimal poling temperatures were significantly lower than the melting temperatures or glass‐transition temperatures of the oligomers and polymer. The poling efficiency increased in the following order: monomer, oligomers, and polymer. An electro‐optic coefficient of 4 pm/V at 1.06 μm was obtained for the polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 546–559, 2000     

New strategy to reinforce and toughen composites via introducing thorns-like micro/nanofibers

In this work, we report a new strategy of introducing thorns-like fiber into composites, so that the resultant composites substantially benefit from strong fiber–matrix interface adhesion. Specifically, the “thorns” could increase in interlocking molecules chains and entangle with the surrounding matrix resin, which could impede the mobility of polymer chains, as like the roots with uplift capacity. Strong interfacial adhesion between fibers and matrices is suggested by the SEM images and the DMA studies. After the thorns-like fibers are embedded into epoxy resin, the glass transition temperature (T_g) and the storage modulus (E′) are higher than these of neat epoxy and untreated fibers-reinforced epoxy, respectively, and the flexural properties of the composites reinforced with thorns-like fibers are significantly increased. Therefore these novel three dimensional thorns-like fibers will be applicable for composite materials based upon its unique architecture, making it an attractive alternative to increase the performance of any matrix resin.     

Multi-walled carbon nanotubes functionalized with triethylenetetramine as fillers to enhance epoxy dimensional thermal stability

Multi-walled carbon nanotubes (MWCNT) have been used as fillers to improve thermal properties such as glass transition temperature (T _g) of epoxy materials. In this work, nanocomposites based on diglycidyl ether of bisphenol A resin and triethylenetetramine (TETA) were prepared by a three-roll mill process with TETA-functionalized (MWCNT–COTETA) and neat MWCNT. Thermogravimetric analysis of the nanofillers showed that in the case of MWCNT–COTETA, there is a 15 % mass loss that can be attributed to –COTETA and residual oxygen-containing functional groups. The influence of chemical modification on the behavior of the glass T _g was evaluated by dynamic scanning calorimetry. The MWCNT–COTETA allowed a ~20 °C reproducible increase of T _g in concentrations in the range of 0.5–1.0 mass%. Furthermore, images obtained by scanning electron microscopy were used to investigate the morphology of the polymer matrix and its interfaces. The quality of the dispersion and interaction of the nanotubes in the epoxy matrix was assessed from the images. Both the neat epoxy and the nanocomposite with MWCNT showed low thermal shrinkage upon curing.     

Viscoelastic properties and morphology of dicyanate ester/epoxy co-polymers modified with polysiloxane and butadiene–acrylonitrile rubbers

Dynamic mechanical analysis was conducted on specimens prepared from cyanate ester (CE) and epoxy (EP) resins cured together at various mass compositions. Increase of amount of epoxy resin in composition was shown to have a disadvantageous effect on glass transition temperature (T _g). It was shown that post-curing procedure was needed to produce a polymer matrix with a single glass transition relaxation, but increase in post-cure temperature up to 250 °C resulted in slight reduction in T _g for epoxy/cyanate copolymers. TG results proved that the presence of epoxy resin reduces thermal stability of the cyanate/epoxy materials. The neat CE and EP/CE systems containing 30 wt% of epoxy resin were modified using epoxy-terminated butadiene–acrylonitrile rubber (ETBN) and polysiloxane core–shell elastomer (PS). The scanning electron microscopy (SEM) results showed the existence of second phase of ETBN and PS modifiers. Only in the case of EP/CE composition modified with ETBN, well-dispersed second phase domains were observed. Analysis of SEM images for other CE- and EP/CE-modified systems revealed the formation of spherical aggregates.     

Uniaxial tensile tests and dynamic mechanical analysis of satin weave reinforced epoxy shape memory polymer composite

The utilization of epoxy shape memory polymer composite (SMPCs) as engineering materials for deployable structures has attracted considerable attention in recent decades due to high strength and satisfactory stiffness in comparison with shape memory polymers (SMPs). Knowledge of static and dynamic mechanical properties is essential for analyzing structural behavior and recovery properties, especially for new epoxy SMPCs. In this paper, a new weave reinforced epoxy shape memory polymer composite was prepared with satin weave technique and resin transfer molding technique. Uniaxial tensile tests and dynamic mechanical analysis were carried out to obtain basic mechanical properties and glass transition temperatures, respectively.The tensile strength and breaking elongation of warp specimens were comparable with those of weft specimens. The increment of elastic modulus and hysteresis loop areas became smaller with loading cycles, meaning that cyclic tests could obtain approximate stable mechanical properties. For dynamic mechanical properties, glass transition temperature (T_g) obtained from storage modulus curves was lower than that determined from tan delta curves and T_gs in the warp and weft directions were similar (29.4 °C vs 29.7 °C). Moreover, the storage modulus in response to T_g was two orders of magnitude less than that with respect to low temperature, which demonstrated the easy processibility of epoxy SMPCs near glass transition temperature. In general, this study could provide useful observations and basic mechanical properties of new epoxy SMPCs.     

Synthesis and nonlinear optical properties of novel Y‐type polyester containing tricyanovinylthiazolylazoresorcinoxy group with enhanced thermal stability of dipole alignment

Novel Y‐type polyester 4 containing 5‐methyl‐4‐{5‐(1,2,2‐tricyanovinyl)‐2‐thiazolylazo}resorcinoxy groups as nonlinear optical (NLO) chromophores, which are parts of the polymer backbone, was prepared, and its NLO properties were investigated. Polyester 4 is soluble in common organic solvents such as N,N‐dimethylformamide and dimethylsulfoxide. Polymer 4 shows a thermal stability up to 250 °C from thermogravimetric analysis with glass‐transition temperature obtained from differential scanning calorimetry of approximately 94 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1560‐nm fundamental wavelength is 8.12 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 6 °C higher than glass‐transition temperature (T_g), and no significant SHG decay is observed below 100 °C due to the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of film thickness on the photoinduced decrease in magnetism for thin films of the cobalt iron Prussian blue analogue Rb0.7Co4[Fe(CN)6]3.0

Films of the photomagnetic Prussian blue analogue Rb_0.7Co₄(Fe(CN)₆)_3.0(Co–Fe PBA) were deposited onto a Melinex^® substrate using two different multiple sequential adsorption methods. Film thickness, measured using atomic force microscopy, was controlled by the number of deposition cycles. The photoinduced magnetism known for the bulk Co–Fe PBA at low temperatures is also seen in the thin films, although the response is anisotropic. A photoinduced increase in magnetization is observed when the film is parallel (∥) to the applied magnetic field (H_E), while a photoinduced decrease is observed when the film is perpendicular (⊥) to a weak H_E. The relationship between the film thickness and the photoinduced decrease in magnetization is explored in this article. The photoinduced decrease is observed for films less than ∼200 nm thick. The behavior is explained by invoking a dipolar interaction between primordial ferrimagnetic domains and the photoswitchable pairs arrayed in the quasi-2D thin film.     

Stabilization of Film Morphology in Polymer‐Fullerene Heterojunction Solar Cells

Abstract

The fixation of film morphology is essential for the long‐term stability of heterojunction polymer photovoltaic (PV) cells. An epoxy‐functionalized fullerene C₆₀ derivative was synthesized for this purpose. This material can be polymerized at acidic conditions and was found to stabilize the phase‐separated morphologies within blended polythiophene–fullerene heterojunction films. The phase stability of the films was characterized by UV‐VIS spectroscopy and optical microscope. Crosslinkable polythiophene derivatives were also prepared but these materials were much less effective in stabilizing film morphology when mixed into PCBM (C61‐butyric acid methyl ester). Heterojunction polymer PV cells were prepared from these materials and their performance was compared with cells made from conventional materials.     

Synergic improvement of DGEBA/CSP/HBP composite on mechanical behavior

Hyperbranched polymer with amino end groups (HBPA) and core-shell particle (CSP, which is fabricated through grafting HBPA onto the surface of silica nanoparticle) were incorporated into an epoxy matrix to fabricate a high performance composite. The effects of CSPs contents on the mechanical properties of composites were studied, discussing the results from tensile, flexural, and impact tests. The composites revealed noticeable improvements in tensile strength, elongation, flexural strength and impact strength in comparison to the neat epoxy or epoxy/HBPA system. The glass transition temperature (T_g) was also improved by the addition of CSP. Field emission scanning electron micrograph (FESEM) indicated that HBPA could favorable improve the compatibility between CSP and epoxy matrix. And the toughening mechanisms were the synergic effect of shearing deformation, phase separation, crack propagation, crack deflection, and crack pinning.     

Synthesis and characterization of poly(ethylene glycol) diacrylate copolymers containing azobenzene groups prepared by frontal polymerization

A novel polymer matrix containing amino–nitro substituted azobenzene groups was obtained by frontal polymerization. (E)‐2‐(Ethyl(4‐((4‐nitrophenyl)diazenyl)phenyl)amino)ethyl methacrylate (MDR‐1) was copolymerized with poly(ethylene glycol) diacrylate (PEGDA) using this easy and fast polymerization technique. The effect of the amount of the incorporated azo‐monomer into the polymer matrix was studied in detail and correlated to front velocity, maximum temperature, initiator concentration, and monomer conversion. The obtained materials were characterized by infrared spectroscopy (Fourier transform infrared), and their thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. Moreover, the optical properties of the polymers were studied by absorption spectroscopy in the UV–Vis region. Absorption spectra of the copolymers exhibit a significant blue shift of the absorption bands with respect to the azo‐monomer, due to the presence of H‐aggregates. Cubic nonlinear optical (NLO) characterizations of the PEGDA/MDR‐1 copolymers were performed according to the Z‐Scan technique. It has been proven that samples with higher MDR‐1 content (0.75 mol %) exhibited outstandingly high NLO‐activity with negative NLO‐refractive coefficients in the promising range of n₂ = ?8.057 × 10^?4 esu. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of nonlinear optical maleimide copolymer by polymer reaction and their electro-optic properties

Thermally stable poly(α-methyl styrene-co-maleimide) (MSMI) and poly(α-methyl styrene-co-4-carboxyphenyl maleimide) (MSCM) substrate polymers were obtained readily by free radical polymerization of comonomers. Introduction of a DR1 chromophore to the maleimide units of MSMI substrate polymer by the Mitsunobu reaction was dependent on the reaction solvent. The degree of substitution of DR1 into the MSMI polymer was bound to be 91.1 mol % and 0.4 mol % by UV spectrometers in the THF and DMF solvent, respectively. DR1 chromophore was, however, substituted in the MSCM polymer at 33.0 mol % by Mitsunobu reaction in the THF solvent. Both substrate and NLO polymer exhibited high thermal stability due to the incorporation of maleimide units in the polymer chain. The glass transition temperature (T_g) and initial decomposition temperature (T_i) of the NLO polymer were in the range of T_g = 185°C and T_i = 310–345°C. The electro-optic coefficient (r₃₃) of NLO polymer was determined with an experimental setup capable of the real-time measurement while varying both the poling field and temperature. The NLO polymer MSMI-THF had a higher r₃₃ value than MSCM-DR due to an increased degree of substitution of DR1 chromophore. MSMI-THF had a maximum r₃₃ value of 16 pm/V at 135 MV/m poling field with a 632.8 nm light source. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3715–3722, 1999     

聚酰亚胺多层膜的制备及其在非线性光学中的应用

报道了一种通过旋涂制备NLO聚合物多层膜的方法.紫外-可见吸收光谱及膜的厚度表征说明,在所得多层膜的结构中,聚合物单层膜的厚度可以较好地控制在100~200nm之间,所得含有5个双层的NLO多层膜(厚度1.6μm)具有良好的结构均一性,光学显微镜下没有观察到明显的结构缺陷.与单层具有较大厚度的NLO聚合物薄膜(如2~4μm)相比,所得聚合物多层膜可以允许掺杂更多的发色团而不发生相分离.     

The synthesis and characteristic study of 6FDA-6FHP-NLO polyimide/SiO2 nanohybrid materials

Hybrid nanocomposite films of silica (SiO₂) in polyimide (PI) from 4,4^′-(hexafluoroisopropylidene) diphthalic arhydride (6FDA), 2,2-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane (6FHP) and nonlinear optical (NLO) molecule have been successfully fabricated by an in situ sol-gel process. The silica content in the hybrid films was varied from 0 to 22.5 wt%. These nanocomposite films exhibit fair good optical transparency. Fourier transform infrared (FTIR) spectroscopy results confirm the formation of SiO₂ particles in PI matrix. Scanning electron microscope (SEM) images show that the SiO₂ phase is well dispersed in the polymer matrix. Their glass transition behavior and thermal stability were investigated by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TG).     

Effects of organophilic montmorillonite on hydrogen bonding, free volume and glass transition temperature of epoxy resin/polyurethane interpenetrating polymer networks

Epoxy resin nanocomposites containing organophilic montmorillonite (oM) and polyurethane were prepared by adding oM to interpenetrating polymer networks (IPNs) of epoxy resin and polyurethane (EP/PU). The dispersion degree of oM in EP/PU matrix was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fourier transform infrared spectrometry (FT-IR) showed that strong interactions existed between oM and EP/PU matrix, and oM had some effect on hydrogen bonding of these EP/PU IPNs nanocomposites. Positron annihilation spectroscopy (PALS) and differential scanning calorimetry (DSC) measurements were used to investigate the effect of oM and PU contents on free volume and glass transition temperature (T_g) of these nanocomposites. The PALS and DSC results clearly showed that the presence of oM led to a decrease in the total fractional free volume, which was consistent with increasing T_g upon addition of oM, ascribed to increasing hydrogen bonding in interfacial regions of oM and EP/PU matrix and enhancing the miscibility between EP phase and PU phase. In addition, with increasing PU content, the total fractional free volume increased, corresponding to decreasing T_g.     

Quantum dot doped solid polymer electrolyte for device application

ZnS capped CdSe quantum dots embedded in PEO:KI:I₂ polymer electrolyte matrix have been synthesized and characterized for dye sensitized solar cell (DSSC) application. The complex impedance spectroscopy shows enhance in ionic conductivity (σ) due to charges provide by quantum dots (QD) while AFM affirm the uniform distribution of QD into polymer electrolyte matrix. Cyclic voltammetry revealed the possible interaction between polymer electrolyte, QD and iodide/iodine. The photovoltaic performances of the DSSC containing quantum dots doped polymer electrolyte was also found to improve.     

Partially sulfonated ethylene–vinyl alcohol copolymer as new substrate for 3,4‐ethylenedioxythiophene vapor phase polymerization

A new conducting composite polymer film is obtained by vapor phase polymerization of 3,4‐ethylenedioxythiophene (EDOT) on a biocompatible polyanion derived from the partial sulfonation (32%) of statistical ethylene vinyl alcohol copolymer (EVAL32). EVALS32 and the oxidant (iron(III) p‐toluenesulfonate, [PTS]) are contemporaneously spin coated from a methanol/water solution on glass slide. EVALS32–PTS‐coated glass slides are exposed to EDOT vapors, and the polymerization is followed by Vis–NIR spectroscopy. We observed that PEDOT slowly grows into the bulk of EVALS32 matrix. Thanks to the sulfonic groups of the polyanion acting as doping agents, a highly conjugate p‐doped EVALS32‐PEDOT composite film with a good conductivity (1.6 × 10² S cm^?1), transparency, and stability in water is obtained. The EVALS32–PEDOT film seems an ideal candidate for the preparation of organic devices to be applied in electronics, biosensor, or actuation technology. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1203–1210     

In situ formed silver nanoparticles on glass fibers grafted with polyacrylamide and their antibacterial activity

In this paper, grafted polyacrylamide from the surface of glass fibers was prepared by surface initiated atom transfer radical polymerization in order to control the matrix surface structure and properties. The uniform and stable grafted polymer layer was utilized to prepare silver ions complexes, and then the silver ions were reduced by AlLiH₄ to form in situ silver nanoparticles. The structure, composition, properties and surface morphology of the modified glass fibers were characterized by X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. The antibacterial activities of modified glass fibers against E. coli, B. subtilis and S. cerevisiae had been studied respectively by Shake Flask Method. The results show that the antibacterial ratio of Ag nanoparticles loaded glass fibers is significantly improved than that of Ag⁺ loaded, and the highest antibacterial ratio is 72.2% against E. coli.     

Synthesis,characterization, and application of metal-free sulfonamide-vitamin C adduct to improve the optical properties of PVA polymer

Improving optical properties is an important topic in the field of polymer science. In this research, a novel, metal-free, and inexpensive vitamin C sulfonamide adduct has been developed to enhance the optical behaviors of polyvinyl alcohol (PVA). Initially, the vitamin C adduct has been fabricated through atom economic reaction and then characterized using several spectroscopic techniques, including ¹H NMR, ¹³C NMR, DEPT-135, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Accordingly, a dramatic chemical alteration in ascorbic acid structure has been confirmed and led to enhancing chemical interactions with the host polymer. The ascorbic acid adduct has been doped into PVA to prepare a flexible film of polymer composites with potential optical behaviors. The identity of composite film has specified from FTIR, XRD, and UV–vis spectroscopy. The XRD pattern of the hybrid polymer has revealed a remarkable boost in its amorphous structure compared to the PVA host. The FTIR data of both matrix PVA and its composites reveal the potent chemical interactions of functional groups within the hybrid PVA. The main optical information of synthesized hybrid film was obtained from the UV–vis spectra. The refractive index (n) and dielectric loss (ε_i) values are elevated notably, whereas the optical band gap energy (E_g) declined from 6.3 to 3.6 eV. The direct electronic transition between the valence band (VB) and conduction band (CB) was determined by implementing Tauc’s model. These preliminary results suggest that the fabricated flexible composite will have an excellent opportunity to use in the manufacturing optical devices.