Low loss second‐order non‐linear optical crosslinked polymers based on a phosphorus‐containing maleimide

A series of crossslinked organic and organic/inorganic polymers based on maleimide chemistry have been investigated for second‐order non‐linear optical (NLO) materials with excellent thermal stability and low optical loss. Two reactive chromophores (maleimide‐containing azobenzene dye and alkoxysilane‐containing azobenzene dye) were incorporated into a phosphorus‐containing maleimide polymer, respectively. The selection of the phosphorus‐containing maleimide polymer as the polymeric matrices provides enhanced solubility and thermal stability, and excellent optical quality. Moreover, a full interpenetrating network (IPN) was formed through simultaneous addition reaction of the phosphorus‐containing maleimide, and sol‐gel process of alkoxysilane dye (ASD). Atomic force microscopy (AFM) results indicate that the inorganic networks are distributed uniformly throughout the polymer matrices on a nano‐scale. The silica particle sizes are well under 100 nm. Using in situ contact poling, the r₃₃ coefficients of 2.2–17.0 pm/V have been obtained for the optically clear phosphorus‐containing NLO materials. Excellent temporal stability (100°C) and low optical loss (0.99–1.71 dB/cm; 830 nm) were also obtained for these phosphorus‐containing materials. Copyright © 2004 John Wiley & Sons, Ltd.     

Organic/Inorganic NLO materials based on reactive polyimides and a bulky alkoxysilane dye via sol/Gel process

A series of the organic–inorganic materials based on reactive polyimides and a bulky alkoxysilane dye (ASD) for second‐order nonlinear optics have been developed. Sol‐gel reaction of ASDs is utilized to grow a network in polymer matrices (composite) or to create inter‐polymer network among polyimide chains (hybrid). Moreover, a full interpenetrating polymer network (IPN) was formed through simultaneous free radical polymerization of a methacryloyl group containing polyimide, and sol‐gel process of ASDs. Scanning electron microscopy (SEM) results indicate that the inorganic networks are distributed uniformly throughout the polymer matrices on the molecular scale. The silica particle sizes are well under 1 µm based on AFM study. Second harmonic coefficients, d₃₃ of 4.5 to 48.5 pm/V have been obtained for the optically clear poled/cured polyimide/ASD samples. Excellent temporal stability was obtained for these NLO materials at 100 °C. The dynamic thermal and temporal stabilities of the IPN system were much better than those of composite and hybrid systems. Copyright ­© 2003 John Wiley & Sons, Ltd.     

POLYIMIDE/INORGANIC INTERPENETRATING POLYMER NETWORKS FOR STABLE SECOND-ORDER NONLINEAR OPTICS

Thermally stable NLO interpenetrating polymer networks (IPNs) based on an organosoluble polyimides functionalized with methacryloyl groups (PIB), and an alkoxysilane dye (ASD) have been developed. IPNs were formed through the free radical polymerization of methacryloyl group containing PIB, and sol-gel process of ASD. Optically clear samples exhibit large second-order optical nonlinearity (d₃₃ = 6.9-39.6 pm/V at 1064 nm) after poling and curing at 180°C for 2 hours. The temporal stability of the PIB/ASD IPN samples was much better than the inter-chain crosslinking polyimide/inorganic samples. The high rigidity of the polymer backbone and the interpenetrating structure of the polymer networks prevent the randomization of the aligned NLO chromophores     

Nonlinear optical polyimides consisting of chromophore‐containing dendrons with site‐isolation effect

To investigate the dendritic structure effects on the electro‐optical (EO) coefficients and thermal stability of the nonlinear optical (NLO) active materials, a bifunctional compound, IDD (4‐isocyanato‐4′(3,3‐dimethyl‐ 2,4‐dioxo‐acetidino)‐diphenylmethane) was used as a building block to synthesize a series of novel NLO chromophore‐containing dendritic structures including Generation 0.5 (G0.5) to Generation 3 (G3). The glass transition temperatures (T_g) of G1–G3 dendrons were in the range of 76–116°C, whereas only the G0.5 dendron exhibited a melting temperature (T_m), 98°C. Moreover, a series of NLO‐active guest–host systems ranging from polyimide‐G0.5 (PI‐G0.5) to polyimide‐G3 (PI‐G3) were prepared by blending 20 wt% chromophore‐containing dendron with a high T_g polyimide. EO coefficients ranged from 6.1 to 12.9 pm/V. The r₃₃/dye content ratio increased with increasing generation of dendron‐containing polyimide samples. Particularly, the improvement in r₃₃/dye content ratio of PI‐G2.5 sample tripled as compared to that of the guest–host sample with Disperse Red 1. Excellent temporal stability of PI‐G0.5 and PI‐G1.5 at 80°C was obtained. Moreover, waveguide properties for NLO polymers containing higher generation dendrons (3.1–3.6 dB/cm at 830 nm) were also obtained. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of stable second‐order nonlinear optical films by sol–gel technique

A stable nonlinear optical (NLO) film containing “T” type alkoxysilane dye was prepared by sol–gel technology. This crosslinked “T” type alkoxysilane dye was synthesized and fully characterized by FTIR, UV–Vis spectra, and ¹H‐NMR. Followed by hydrolysis and copolymerization processes of the alkoxysilane with γ‐glycidoxypropyl trimethoxysilane (KH560) and tetraethoxysilane (TEOS), high quality inorganic–organic hybrid second‐order NLO films were obtained by spin coating. The “T” type structure of the alkoxysilane was found to be effective for improving the temporal stability of the optical nonlinearity due to the reduction in the relaxation of the chromophore in the film materials. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and electro‐optic properties of novel X‐type polyurethane containing nitrophenylazonitroresorcinoxy group with highly enhanced thermal stability of dipole alignment

Novel X‐type polyurethane 4 containing 4‐(4‐nitrophenylazo)‐6‐nitroresorcinoxy groups as nonlinear optical (NLO) chromophores, which are parts of the polymer main chains, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It shows thermal stabilities up to 270 °C from thermogravimetric analysis with glass transition temperature obtained from differential scanning calorimetry of about 134 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1064 nm fundamental wavelength is 5.37 × 10^?9 esu. Polymer 4 exhibits a thermal stability up to T_g, and no significant SHG decay is observed below 135 °C, which is acceptable for NLO device applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 760–766     

The design,synthesis, and nonlinear optical properties of novel X‐type polyurethane containing dicyanovinylnitroresorcinoxy group with enhanced SHG thermal stability

Novel X‐type polyurethane 5 containing 4‐(2′,2′‐dicyanovinyl)‐6‐nitroresorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute parts of the polymer backbone, was prepared and characterized. Polyurethane 5 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It shows thermal stability up to 280 °C from thermogravimetric analysis with a glass transition temperature (T_g) obtained from differential scanning calorimetry thermogram of around 120 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1064‐nm fundamental wavelength is around 6.12 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 5 °C higher than T_g, and there was no SHG decay below 125 °C due to the partial main chain character of the polymer structure, which is acceptable for NLO device applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Dendronized tricyanopyrroline‐based chromophores in nonlinear optical active host polymer

We synthesized new nonlinear optical (NLO) chromophores containing a 3,5‐bis(3,5‐bisbenzyloxy‐benzyloxy)‐benzoate dendron. Tricyanopyrroline (TCP)‐based chromophores were designed and prepared by virtue of its strong electron withdrawing property. A soluble polyimide containing 6‐({4‐[2‐(1‐allyl‐4‐cyano‐5‐dicyanomethylene‐2‐oxo‐2,5‐dihydro‐1H‐pyrrol‐3‐yl)‐vinyl]‐phenyl}‐butyl‐amino)‐hexanoyl group in the side chain was also prepared as an NLO active host polymer. A benzoate dendron was tethered at two different binding positions of the chromophore to yield two different guest molecules. Thin‐film composites of these dendronized chromophores dissolved in the NLO active polyimide host were employed to fabricate the electro‐optic (EO) samples. The EO properties of new NLO polyimides containing dendronized chromophores were compared with those of the sample with nondendronized plain chromophores. The effect of a bulky dendron on the EO properties was investigated using an in situ reflection technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5064–5076, 2008     

Enhancing the glass‐transition temperature of polyimide copolymers containing 2,2′‐bipyridine units by the coordination of nickel malenonitriledithiolate

Polyimide copolymers containing 2,2′‐bipyridine were synthesized and characterized. The glass‐transition temperatures (T_g's) of the polymers ranged from 260 to 300 °C. In contrast to most known organic chromophore‐containing polyimides, the polyimide copolymers in this study showed elevated T_g's (270–320 °C) after coordination with nickel malenonitriledithiolate inorganic chromophores. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 498–503, 2000     

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     

Highly Thermal Stable Main‐Chain Nonlinear Optical Polyimide Based on Two‐Dimensional Carbazole Chromophores

Summary: A new NLO‐active lambda‐shaped main‐chain polyimide that comprises a two‐dimensional carbazole chromophore was synthesized. This polyimide exhibits high thermal and temporal stability. It can endure temperatures of up to 240 °C for a transient time and maintain a large SH signal at 100 °C for a long time because embedding the two‐dimensional chromophores into the polymer backbone effectively suppresses the randomization of the oriented dipole at high temperatures.

     

Synthesis of nonlinear optical polyimides containing azodiamine derivative chromophores and their electrooptic and thermal properties

Some thermally stable second‐order nonlinear optical (NLO) polyimides were synthesized. The polyimides were prepared by the ring‐opening polyaddition of 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride and pyromellitic dianhydride with two aromatic azodiamine derivatives as the NLO chromophores. These chromophores, based on a nitro group connected with azobenzene as the acceptor end of a donor–π‐bridge–acceptor chromophore and a diamine group as the donor end, had specific chemical stability. On the basis of ZERNER'S INDO methods, according to the sum‐over‐states formula, a program for the calculation of nonlinear second‐order optical susceptibilities was devised. The resulting polyimides had high number‐average and weight‐average molecular weights of up to 26,000 and 53,500, respectively, and a large glass‐transition temperature of 248 °C. With an in situ poling and temperature ramping technique, the optimal temperatures (T_opt's) for corona poling were obtained for the largest second‐order NLO response. The electrooptic coefficient (γ₃₃) of a polyimide at a wavelength of 830 nm was up to 21 pm/V after corona poling under its T_opt, and the value remained at elevated temperatures (>90.6% was retained at 240 °C for >120 h). The thermal stability of the NLO polyimides was studied with UV spectrometry after poling of the films. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2478–2486, 2002     

Synthesis and nonlinear optical properties of novel Y‐type polyurethane containing tricyanovinylthiazole with enhanced thermal stability of second harmonic generation

A novel Y‐type poly[iminocarbonyloxyethyl‐5‐methyl‐4‐{2‐thiazolylazo‐4‐(1,2,2‐tricyanovinyl)}resorcinoxyethyloxycarbonylimino‐(3,3′‐dimethoxy‐4,4′‐biphenylene)] 4 containing 5‐methyl‐4‐{5‐(1,2,2‐tricyanovinyl)‐2‐thiazolylazo}resorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute part of the polymer backbone, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It showed a thermal stability up to 250 °C in thermogravimetric analysis thermogram and the glass‐transition temperature (T_g) obtained from differential scanning calorimetry thermogram was around 118 °C. The second harmonic generation coefficient (d₃₃) of poled polymer films at 1560 nm fundamental wavelength was around 8.43 × 10^?9 esu. The dipole alignment exhibited a thermal stability even at 12 °C higher than T_g, and there was no SHG decay below 130 °C due to the partial main‐chain character of the polymer structure, which is acceptable for NLO device applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1166–1172, 2010     

Enhanced Temporal Stability of an NLO Polyurethane via a Two‐Dimensional Chromophore

A new NLO‐active polyurethane (T_g = 145°C) based on a two‐dimensional NLO chromophore has been investigated. Two ends of this lambda‐shaped chromophore can be directly bound to the main chain of polyurethane. After poling, fast relaxation of the effective second harmonic (SH) coefficient was observed at temperatures higher than 122°C. Moreover, excellent temporal stability at 100°C was obtained despite the operating temperature being very close to the fast relaxation temperature. This is due to the fact that embedding the rigid lambda‐shaped chromophores into the polymer backbone effectively restricts molecular motion at temperatures close to T_g.     

A novel pH‐ and thermo‐sensitive PVP/CMC semi‐IPN hydrogel: Swelling,phase behavior,and drug release study

Poly(N‐vinyl‐pyrrolidone) (PVP) hydrogel has been considered as a very interesting and promising thermosensitive material. The most vital shortcoming of PVP hydrogel as thermosensitive material is that it does not exhibit thermosensitivity under usual conditions. In this work, semi‐interpenetrating polymer network (semi‐IPN) hydrogels based on PVP and carboxymethylcellulose (CMC) were prepared. The volume phase transition temperature (VPTT) of the hydrogels was determined by swelling behavior and differential scanning calorimetry (DSC). The results showed that the VPTT was significantly dependent on CMC content and the pH of the swelling medium. The amount of CMC in the semi‐IPN hydrogels was 0.050, 0.075, and 0.100 g, the VPTT in buffer solution of pH 1.2 was 29.9 °C, 27.5 °C and 24.5 °C, respectively. In addition, the VPTT occurred in buffer solution of pH 1.2, but did not appear in alkaline medium. Bovine serum albumin (BSA) as a model drug was loaded and the in vitro release studies were carried out in different buffer solutions and at different temperatures. The results of this study suggest that PVP/CMC semi‐IPN hydrogels could serve as potential candidates for protein drug delivery in the intestine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1749–1756, 2010     

Synthesis and properties of novel Y‐type nonlinear optical polyimides with high thermal stability of second harmonic generation

2,4‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐1‐(2,2‐dicyanovinyl)benzene dianhydride (4) was prepared and reacted with 4,4′‐oxydianiline, 4,4′‐diaminobenzanilide and 4,4′‐(hexafluoroisopropylidene)dianiline to yield novel Y‐type polyimides 5‐7 containing 2,4‐dioxybenzylidenemalononitrile groups as nonlinear optical (NLO) chromophores, which constitute parts of the polymer backbone. The resulting polyimides 5‐7 are soluble in polar solvents such as dimethylsulfoxide and N,N‐dimethylformamide. Polymers 5‐7 showed a thermal stability up to 330 °C in thermogravimetric analysis thermograms with T_g values obtained from differential scanning calorimetry thermograms in the range 179–194 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064 nm fundamental wavelength were around 5.56 × 10^?9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 20 °C higher than the glass‐transition temperature there was no SHG decay below 215 °C because of the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3078–3087, 2008     

Molecular design,synthesis, and properties of Y‐type nonlinear optical polyester containing tricyanovinylthiophene with enhanced thermal stability of second harmonic generation

1‐{3,4‐Di‐(2‐hydroxyethoxy)phenyl}‐2‐(2‐thiophenyl)ethene (5) was prepared and condensed with terephthaloyl chloride to yield polyester (6). Polymer 6 was reacted with tetracyanoethylene to give a new Y‐type polyester (7) containing 1‐(3,4‐dioxyethoxy)phenyl‐2‐{5‐(2,2,3‐tricyanovinyl)‐2‐thiophenyl)}ethenyl groups as NLO‐chromophores, which are components of the polymer backbones. Polyester 7 is soluble in common organic solvents such as N,N‐dimethylformamide and acetone. Polymer 7 showed a thermal stability up to 300 °C in thermogravimetric analysis with glass transition temperature (T_g) obtained from differential scanning calorimetry near 126 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at the 1560 nm fundamental wavelength was around 6.57 × 10^?9 esu. The dipole alignment exhibited high thermal stability up to the T_g, and there was no SHG decay below 125 °C due to the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1911–1919, 2009     

Design and synthesis of a thermally stable second‐order nonlinear optical chromophore and its poled polymers

A multiple charge‐transfer second‐order nonlinear optical (NLO) chromophore 2,3‐bis(4‐aminophenyl)‐5,6‐dicyanopyrazine (BAPDCP) was successfully designed and synthesized. It was characterized by ¹H NMR, mass spectrometry, Fourier transform infrared spectroscopy, and elemental analysis. The first hyperpolarizability β of BAPDCP was measured with the Hyper–Rayleigh scattering technique, which was 123.5 × 10^?30 esu. The donor‐embedded prepolyimide and prepolyurea were also synthesized by a polyaddition reaction. Thermogravimetric analysis and differential scanning calorimetry demonstrated that either the chromophore or the polymers have fine thermal stability. The thin films of prepolymers were prepared by coating on ITO glass substrate and poled by corona poling at elevating temperature. The second‐order NLO coefficients d₃₃ of the films were measured by in situ second‐harmonic generation measurements. The d₃₃ were deduced as 27.7 and 16.5 pm/V for polyurea and polyimide at 1064 nm fundamental wavelength, respectively. The onset depoling temperature of the polyimide and polyurea were both as high as 200 °C. To understand the temperature effect to the orientation thermal stability of polyimide, two films were treated at different final poling temperatures. The depoling experimental results showed that the orientation stability is higher, as raising the final treated temperature but the d₃₃ value are almost similar. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2846–2853, 2003     

Synthesis and properties of a second‐order nonlinear optical side‐chain polyimide

A thermal stable aromatic polyimide (PI) with side‐chain second‐order nonlinear optical (NLO) chromophores has been developed. The PI was prepared by the ring‐opening polyaddition of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride with a new diamine having two N‐ethyl‐N‐[4‐[(6‐chlorobenzothiazol‐2‐yl)diazenyl]phenyl]‐2‐aminoethanol units as the NLO chromophore, followed by poling during or after the thermal imidization process. The resulting PI had number and weight‐average molecular weights (M_n, M_w) of 25,000 and 80,000, respectively, and a relatively high glass transition temperature of 180°C. The second harmonic coefficient (d₃₃) of PI at the wavelength of 1.064 μm was 138 pm/V (329.6 × 10⁻⁹ esu) and remained unchanged at elevated temperatures. The corona poling process of the NLO‐substituted poly(amic acid) to the PI was also studied in detail by measuring the second harmonic generation (SHG) from the polymer films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1321–1329, 1999     

Heterogeneity of glass transition dynamics in polyurethane‐poly(2‐hydroxyethyl methacrylate) semi‐interpenetrating polymer networks

The peculiarities of segmental dynamics over the temperature range of ?140 to 180 °C were studied in polyurethane‐poly(2‐hydroxyethyl methacrylate) semi‐interpenetrating polymer networks (PU‐PHEMA semi‐IPNs) with two‐phase, nanoheterogeneous structure. The networks were synthesized by the sequential method when the PU network was obtained from poly(oxypropylene glycol) (PPG) and adduct of trimethylolpropane (TMP) and toluylene diisocyanate (TDI), and then swollen with 2‐hydroxyethyl methacrylate monomer with its subsequent photopolymerization. PHEMA content in the semi‐IPNs varied from 10 to 57 wt %. Laser‐interferometric creep rate spectroscopy (CRS), supplemented with differential scanning calorimetry (DSC), was used for discrete dynamic analysis of these IPNs. The effects of anomalous, large broadening of the PHEMA glass transition to higher temperatures in comparison with that of neat PHEMA, despite much lower T_g of the PU constituent, and the pronounced heterogeneity of glass transition dynamics were found in these networks. Up to 3 or 4 overlapping creep rate peaks, characterizing different segmental dynamics modes, have been registered within both PU and PHEMA glass transitions in these semi‐IPNs. On the whole, the united semi‐IPN glass transition ranged virtually from ?60 to 160 °C. As proved by IR spectra, some hybridization of the semi‐IPN constituents took place, and therefore the effects observed could be properly interpreted in the framework of the notion of “constrained dynamics.” The peculiar segmental dynamics in the semi‐IPNs studied may help in developing advanced biomedical, damping, and membrane materials based thereon. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 963–975, 2007