Syntheses and properties of polyurethanes containing side‐chain azobenzene groups

Polymers containing azobenzene groups have the characteristic reaction of photo‐induced cis–trans isomerism. The study of new materials for optical information storage has prompted making use of these photo‐isomerizations. In this study, we report the syntheses and properties of four different polyurethanes (DR‐PUns) containing azobenzene groups in the side‐chains. The structurally similar polyurethanes (DR‐PUns) were synthesized by the polycondensation reaction of Disperse Red 19 (DR 19) and four different diisocyanates in dimethylformamide. By introducing of DR 19 into the polymer, we obtained polymers containing a photochromic group in the side‐chain. The weight‐average molecular weights of the DR‐PUns were in the range 5500–12 900. The T_gs of the DR‐PUns range from 119.5 °C to 157.0 °C, depending on the structure of the diisocyanate. Optical properties and solubilities of the polyurethanes were compared. The diffraction efficiencies of films were measured as a function of the reaction time. Typically, the diffraction efficiencies of the DR‐PU1 film prepared from toluene 2,4‐diisocyanate were observed up to a level of 0.25%. For the DR‐PU1 film, the effect of the intensity of the induced laser beam on the diffraction efficiency is also discussed. © 2003 Society of Chemical Industry     

Influence of azobenzene units on imidization kinetic of novel poly(ester amic acid)s and polymers properties before and after cyclodehydration

In this article, the imidization reaction kinetic of novel poly(ester amic acid)s with azobenzene units as side groups was studied by dynamic experiments by means of differential scanning calorimetry. Polymers differ in the number of chromophore moieties in their repeating unit and position in which azobenzene group is attached to the polymer chain. The kinetic parameters of poly(ester amic acid)s conversion to poly(ester imide)s was compared with data calculated for parent polymer, that is, without azobenzene groups. For the first time to our knowledge, the imidization kinetic of polymers with side azobenzene groups was studied. Kinetic parameters, such as the activation energy and frequency factor were estimated with the by Ozawa model [(E(O) and A(O)), respectively] and Kissinger model [(E(K) and A(K), respectively]. The values of activation energy determined with both models were in the range 167.1–198.3 kJ/mol. The lowest activation energy of imidization reaction exhibited polymer in which azobenzene units were placed between amide linkages. Polymers were characterized by FTIR, ¹H‐NMR, X‐ray, and UV–vis methods. The glass transition temperature of resultant poly(ester imide)s was in the range of 217–237°C. The presence of chromophore units slightly decreased T_g and significantly improved their solubility and optical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A low onset voltage WORM type polymer memory based on functional PES

A high‐performance polymer polyethersulfone (CN‐Azo‐PES), with a flexible ethoxyl linkage between the azobenzene chromophore side chain and the PES backbone, has been designed and successfully synthesized for an application in a WORM type memory device as an active polymer layer. CN‐Azo‐PES has excellent thermal properties with T_g of 151°C and the degradation temperature higher than 373°C, which can contribute to a better performance of the device. The device based on CN‐Azo‐PES exhibits a write‐once read‐many (WORM) type memory performance with an onset voltage as low as ?1.0 V and an ON/OFF current ratio higher than 10² at a reading voltage of 0.4 V. Moreover, the data can be maintained for longer than 4 × 10⁵ s once written and can be read for more than 400 cycles under a reading voltage of 0.4 V. Thus CN‐Azo‐PES can serve as an energy saving memory material in the data storage field of next generation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42644.     

Light‐triggered reversible solubility of α‐cyclodextrin and azobenzene moiety complexes in PDMAA‐co‐PAPA via molecular recognition

Photoresponsive polymer with azobenzene pendant group (PDMAA‐co‐PAPA) was synthesized by radical polymerization of N,N‐dimethylacrylamide (DMAA) and N‐4‐phenylazophenyl acrylamide (PAPA), and the characterization of the inclusion complexes of the PDMAA‐co‐PAPA with α‐cyclodextrin (α‐CD) were performed by FTIR, GPC, ¹H NMR, 2D NOESY, and UV–vis spectroscopy. It was found that the solubility of PDMAA‐co‐PAPA and α‐CD inclusion complexes in aqueous solution showed tunable property, which could be triggered by alternating UV–vis light irradiation at a certain temperature due to the effect of molecular recognition of α‐CD with azobenzene moiety in the polymer. After UV irradiation, the lower critical solution temperature (LCST) of the polymer aqueous solution increased slightly without α‐CD while the LCST decreased sharply at presence of α‐CD. Furthermore, UV spectroscopy showed that the photoisomerization of the polymer solution went on rapidly and reversibly, and 2D NOESY data suggested that the inclusion complexation of α‐CD with trans azobenzene moiety and the decomplexation with cis azobenzene resulted in reversible solubility behavior when objected to UV and Vis light irradiation alternately. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photochromic polyacylsemicarbazides based on azobenzene containing dihydrazide

Polyacylsemicarbazides exhibiting photochromic behaviour were synthesised by solution polymerisation of azobenzene chromophore containing dihydrazide and various diisocyanates (aliphatic, cycloaliphatic and aromatic). A model compound was also prepared from o‐tolylene isocyanate and dihydrazide. The structures were confirmed by ¹H NMR and FTIR techniques. The polymers were found to exhibit λ_max values around 330 nm corresponding to the trans isomer which reduced with irradiation of the solutions of polymers in DMAc due to trans→cis isomerisation as observed by UV‐VIS spectrometry. The reverse reaction (cis→trans isomerisation) was found to take place photochemically when irradiated with visible light or when kept in the dark. The rates of isomerisation reactions were found to be independent of the chromophore concentration and the nature of the polymer backbone. The inherent viscosity of the solutions of polymers in DMAc reduced upon irradiation with UV light and was regained in the dark. Thermal studies showed that the polymer degradation started with the simultaneous cleavage of imino (N? N) and aromatic azo (? N?N? ) bond and that recrystallisation occurred on heating the samples. Copyright © 2004 Society of Chemical Industry     

Synthesis and chemical properties of dielectric polyphenylenes with nitro group

Polyphenylenes consisting of nitrophenylene and didodecyloxy‐p‐phenylene units have been synthesized by Pd‐catalyzed organometallic polycondensation. The polymers showed good solubility and had number–average molecular weights (M_n) of 13,000–37,000. Their spin‐coated films showed fairly high dielectric constants (ε) of 3.75–6.36. The polymers were electrochemically active with electrochemical reduction peaks in the range of ?1.72 to ?1.99 V versus Ag⁺/Ag in an acetonitrile solution of [NEt₄]BF₄ (0.10M). The polymer composed of 2,3′‐dinitrobiphenyl and didodecyloxy‐p‐phenylene units showed thermotropic liquid crystalline phase at about 240°C. Cast films of the polymer had a birefringent phase at room temperature, suggesting self‐assembly of the polymer in the solid. XRD studies revealed that the polymers assumed an ordered structure assisted by aggregation of the long alkoxy side chains in the solid. The polymer main chain in the cast film is considered to be aligned parallel with respect to the surface of substrates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

New soluble cyano‐containing poly(arylene ether) copolymers bearing pendant xanthene groups

Homopolymers and copolymers of poly(arylene ether nitrile) (PAEN)‐bearing pendant xanthene groups were prepared by the nucleophilic substitution reaction of 2,6‐difluorobenzonitrile with 9,9‐bis(4‐hydroxyphenyl)xanthene (BHPX) and with various molar proportions of BHPX to hydroquinone (100/0 to 40/60) with N‐methyl‐2‐pyrrolidone (NMP) as a solvent in the presence of anhydrous potassium carbonate. These polymers had inherent viscosities between 0.61 and 1.08 dL/g, and their weight‐average molecular weights and number‐average molecular weights were in the ranges 34,200–40,800 and 17,800–20,200, respectively. All of the PAENs were amorphous and were soluble in dipolar aprotic solvents, including NMP, N,N‐dimethylformamide, and N,N‐dimethylacetamide and even in tetrahydrofuran and chloroform at room temperature. The resulting polymers showed glass‐transition temperatures (T_g's) between 220 and 257°C, and the T_g values of the copolymers were found to increase with increasing BHPX unit content in the polymer. Thermogravimetric studies showed that all of the polymers were stable up to 422°C with 10% weight loss temperatures ranging from 467 to 483°C and char yields of 54–64% at 700°C in nitrogen. All of the new PAENs could be cast into transparent, strong, and flexible films with tensile strengths of 106–123 MPa, elongations at break of 13–17%, and tensile moduli of 3.2–3.7 GPa. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

pH‐responsive polyzwitterions: A comparative study of acrylamide‐based polyampholyte terpolymers and polybetaine copolymers

A comparative study of pH‐responsive polyzwitterions (PZs) with polyampholyte or polybetaine architectures was conducted with well‐defined model polymer systems. Low‐charge‐density PZs, including ampholytic terpolymers composed of acrylamide (AM), sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride and carboxybetaine copolymers composed of AM and 3‐(3‐acrylamidopropyldimethylammonio)propionate, were prepared via free‐radical polymerization in 0.5M NaCl to yield ter‐ and copolymers with random termonomer and comonomer distributions. Sodium formate was used as a chain‐transfer agent during the polymerizations to eliminate the effects of the monomer feed composition on the degree of polymerization (DP) and to suppress gel effects and broadening of the molecular weight distributions. The polymer compositions were determined via ¹³C‐NMR spectroscopy, and the residual counterion content was determined via elemental analysis for Na⁺ and Cl^?. The molecular weights (MWs) and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering (SEC–MALLS); the polymer MWs ranged from 1.4 to 1.5 × 10⁶ g/mol, corresponding to DPs of 1.6–1.9 × 10⁴ repeat units, with all the polymers exhibiting PDIs less than or equal to 2.1. The intrinsic viscosities determined from SEC–MALLS data and the Flory–Fox relationship agreed with the intrinsic viscosities determined via low‐shear dilute‐solution viscometry. Data from the SEC–MALLS analysis were used to analyze the radius of gyration/molecular weight (R_g–M) relationships and the Mark–Houwink–Sakurada intrinsic viscosity/molecular weight ([η]–M) relationships for the PZs. The R_g–M and [η]–M relationships and viscometric data revealed that under size exclusion chromatography conditions, the poly[acrylamide‐co‐3‐(3‐acrylamidopropyldimethylammonio)propionate] betaine copolymers had more open, random‐coil conformations and greater polymer–solvent interactions than the ampholytic poly[acrylamide‐co‐sodium 3‐acrylamido‐3‐methylbutanoate‐co‐(3‐acrylamidopropyl)trimethylammonium chloride] terpolymers. The pH‐ and salt‐responsive dilute‐solution viscosity behavior of the PZs was examined to assess the effects of the polymer structure and composition on the solution properties. The polyampholyte terpolymers had greater solution viscosities and more pronounced stimuli‐responsiveness than the polybetaine copolymers because of their stronger intramolecular interactions and increased chain stiffness. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 24–39, 2004     

Preparation and characterization of poly(silyl ester)s containing 2,2‐bis(p‐dimethylsiloxy‐phenyl)propane units in the polymer backbones

The two poly(silyl ester)s containing 2,2‐bis(p‐dimethylsiloxy‐phenyl)propane units in the polymer backbones have been prepared via polycondensation reaction of di‐tert‐butyl adipate and di‐tert‐butyl fumarate with 2,2‐bis(p‐chloro dimethylsiloxy‐phenyl)propane to give tert‐butyl chloride as the condensate. The polymerizations were performed under nitrogen at 110°C for 24 h without addition of solvents and catalysts to obtain the poly(silyl ester)s with weight average molecular weights typically ranging from 5000 to 10,000 g/mol. Characterization of the poly(silyl ester)s included ¹H NMR and ¹³C NMR spectroscopies, infrared spectroscopy, ultraviolet spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA), gel permeation chromatography, and Ubbelohde viscometer. The glass transition temperatures (T_g) of the obtained polymers were above zero because of the introducing 2,2‐bis(p‐dimethylsiloxy‐phenyl)propane units in the polymer backbones. The TGA/DTG results showed that the obtained poly(silyl ester)s were stable up to 180°C and the residual weight percent at 800°C were 18 and 9%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1937–1942, 2006     

Ionomeric polyurethanes of pyridinium type with side azobenzene groups

New polyurethane cationomers synthesized by a two‐step substitution postreaction of urethane hydrogen atoms with nitroazobenzene groups were studied. As a starting polymer, a polyurethane based on poly(tetramethylene oxide)diol, isophorone diisocyanate, and 2,6‐bis(hydroximethyl)pyridine was used. After a preliminary metalation of the above polymer with natrium hydride, by reaction of polyurethane N‐sodate with 4‐nitro‐4′(β–iodoethylurethane)azobenzene, chromophoric groups between 2.85 and 10.53 wt % could be incorporated instead of hydrogen. Such polymers partially functionalized with azobenzene and further quaternized with methyl iodide led to the formation of pyridinium polyurethane cationomers N‐modified with nitroazo groups. The photosensible properties of the azobenzene chromophore in a polymer solution and film state indicated important differences in their photoresponse. In the polymer solution, the trans–cis photoisomerization of the chromophore is accompanied by an irreversible photobleaching effect, while under the same UV irradiation conditions, the ionomeric films exhibited an enhanced photostability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1240–1247, 2002     

Synthesis and electro‐optical properties of novel Y‐type polyurethanes containing dioxynitrostilbene

3,4‐Di‐(2′‐hydroxyethoxy)‐4′‐nitrostilbene (2) was prepared by the reaction of 2‐iodoethanol with 3,4‐dihydroxy‐4′‐nitrostilbene. Diol 2 was condensed with 2,4‐toluenediisocyanate, 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate and 1,6‐hexamethylenediisocyanate to yield novel Y‐type polyurethanes 3–5 containing dioxynitrostilbene as a non‐linear optical (NLO)‐chromophore. Polymers 3–5 were soluble in common organic solvents, such as acetone and DMF. These polymers showed thermal stability up to 280 °C in TGA thermograms with T_g values in the range of 100–143 °C in DSC thermograms. The approximate lengths of aligned NLO‐chromophores of the polymers estimated from AFM images were around 2 nm. The SHG coefficients (d₃₃) of poled polymer films were around 4.5 × 10^?8 esu. Poled polymer films had improved temporal and long‐term thermal stability owing to the hydrogen bonding of urethane linkage and the main‐chain character of the polymer structure, which are acceptable for NLO device applications. Copyright © 2004 Society of Chemical Industry     

Synthesis of novel polyurethanes containing dioxybenzylidenecyanoacetate,as non‐linear optical chromophores and their properties

Methyl 3,4‐di‐(2′‐hydroxyethoxy)benzylidenecyanoacetate (3) was prepared by hydrolysis of methyl 3,4‐di‐(2′‐vinyloxyethoxy)benzylidenecyanoacetate (2). Diol 3 was condensed with 2,4‐toluenediisocyanate, 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate, and 1,6‐hexamethylenediisocyanate to yield polyurethanes 4, 5 and 6 containing the non‐linear optical (NLO) chromophore 3,4‐dioxybenzylidenecyanoacetate. The resulting polyurethanes 4–6 were soluble in common organic solvents such as acetone and DMF. T_g values of the polymers obtained from DSC thermograms were in the range 80–102 °C. Polymers 4–6 showed thermal stability up to 300 °C in TGA thermograms, and electro‐optic coefficients (r₃₃) of the poled polymer films were in the range 10–12 pm V^?1 at 633 nm, which are acceptable for NLO device applications. © 2002 Society of Chemical Industry     

Molecular design,synthesis, and electro‐optic properties of novel Y‐type polyesters with high thermal stability of second harmonic generation

3,4‐Di‐(2′‐hydroxyethoxy)‐4′‐nitrostilbene was prepared and condensed with terephthaloyl chloride, adipoyl chloride, and sebacoyl chloride to yield novel Y‐type polyesters containing NLO‐chromophore dioxynitrostilbenyl groups, which constituted parts of the polymer backbone. Polymers were found soluble in common organic solvents such as acetone and N,N‐dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis with glass‐transition temperatures obtained from differential scanning calorimetry in the range 110–152 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at a 1064 cm^?1 fundamental wavelength were around 3.51 × 10^?8 esu. The dipole alignment exhibited high thermal stability even at 10 °C higher than the glass‐transition temperature, and there was no SHG decay below 120 °C for one of these polymers due to the partial main‐chain character of polymer structure, which was acceptable for NLO device applications. Copyright © 2005 Society of Chemical Industry     

Synthesis and properties of novel poly(meth)‐acrylates containing tricyanocyclopropyl groups for piezoelectric applications

o‐(2,2,3‐Tricyano‐3‐carbomethoxycyclopropyl)phenoxyethyl acrylate ( 5a ) and o‐(2,2,3‐tricyano‐3‐carbomethoxycyclopropyl)phenoxyethyl methacrylate ( 5b ) were prepared by reactions of bromomalononitrile with methyl o‐(2‐acryloyloxyethoxy)benzylidenecyanoacetate and methyl o‐(2‐methacryloyloxyethoxy)benzylidenecyanoacetate respectively. The dipole moments of 5a and 5b , calculated by atom superposition and electron delocalization molecular orbital method, were 2.75–3.47 D. Monomers 5a and 5b were polymerized with free‐radical initiators to obtain the polymers with tricyanocyclopropane ring as a piezoelectric chromophore in the pendant group. The resulting polymers 6a and 6b were soluble in common organic solvents such as acetone and DMF. Polymers 6a and b showed thermal stability up to 280 °C in TGA thermograms. T_g values obtained from DSC thermograms were in the range 125–140 °C. Piezoelectric coefficients (d₃₁) of the poled films were 1.2–1.4 pC N^?1. These polymers showed good temporal and long‐term thermal stabilities which are acceptable for piezoelectric device applications. Copyright © 2003 Society of Chemical Industry     

Functional copolymers of p‐cumyl phenyl methacrylate and glycidyl methacrylate: Synthesis,characterization, and reactivity ratios

Free‐radical polymerization of p‐cumyl phenyl methacrylate (CPMA) was performed in benzene using bezoyl peroxide as an initiator at 80°C. The effect of time on the molecular weight was studied. Functional copolymers of CPMA and glycidyl methacrylate (GMA) with different feed ratios were synthesized by free‐radical polymerization in methyl ethyl ketone at 70°C, and they were characterized by FTIR and ¹H‐NMR spectroscopy. The molecular weights and polydispersity indexes of the polymers and copolymers were determined by gel permeation chromatography. The copolymer composition was determined by ¹H‐NMR. The glass‐transition temperature of the polymer and the copolymers was determined by differential scanning calorimetry. The reactivity ratios of the monomers were determined by the Fineman–Ross and Kelen–Tudos methods. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 336–347, 2005     

Synthesis of star‐shaped poly(ϵ‐caprolactone) by samarium‐based tetrafunctional initiator and its dilute‐solution properties

An in situ–generated tetrafunctional samarium enolate from the reduction of 1,1,1,1‐tetra(2‐bromoisobutyryloxymethyl)methane with divalent samarium complexes [Sm(PPh₂)₂ and SmI₂] in tetrahydrofuran has proven to initiate the ring‐opening polymerization of ?‐caprolactone (CL) giving star‐shaped aliphatic polyesters. The polymerization proceeded with quantitative conversions at room temperature in 2 h and exhibited good controllability of the molecular weight of polymer. The resulting four‐armed poly(?‐caprolactone) (PCL) was fractionated, and the dilute‐solution properties of the fractions were studied in tetrahydrofuran and toluene at 30°C. The Mark–Houwink relations for these solvents were [η] = 2.73 × 10^?2M_w^0.74 and [η] = 1.97 × 10^?2M_w^0.75, respectively. In addition, the unperturbed dimensions of the star‐shaped PCL systems were also evaluated, and a significant solvent effect was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 175–182, 2006     

Characterization of photo‐ and thermoresponsible amphiphilic copolymers having azobenzene moieties as side groups

Two series of amphiphilic copolymers, poly(HPMA‐co‐MPAP) I–V with n = 0.05–0.29 of the molar ratio of MPAP and poly(HPMA‐co‐MPAH)‐I–V with n = 0.05–0.23 of the molar ratio of MPAH, were prepared by radical copolymerization of N‐(2‐hydroxypropyl) methacrylamide (HPMA) with azo‐monomers such as 4‐(4‐methoxyphenylazo) phenyl methacrylate (MPAP) and 6‐[4‐(4‐methoxyphenylazo) phenoxy] hexyl methacrylate (MPAH) using 2,2′‐azobisisobutyronitrile as an initiator. Self‐organization of these copolymers in water was confirmed by disappearance of the proton signal of the methoxyazobenzene in ¹H‐NMR spectra measured in the solvent system of D₂O and CD₃OD. It was also found from the λ_max, located near 344 nm, that azobenzene groups self‐organized to form the dimeric chromophore type of aggregate. The aqueous solutions of poly(HPMA‐co‐MPAP) and poly(HPMA‐co‐MPAH) exhibited the lower critical solution temperature (LCST) from at 68 to 40°C and from at 70 to 52°C in the dark state, respectively, with increasing the molar ratios of azo‐monomers. On the other hand, the LCST measured in the photostationary state showed the higher temperature by 2–4°C compared with that in the dark state. It was found that the adsorption of poly(HPMA‐co‐MPAP)‐V (n = 0.29) on polystyrene microspheres was photoregulated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3056–3063, 2001     

Syntheses,antitumour activities and antiangiogenesis of 1,2,3‐tris(ethoxycarbonyl)‐2‐propyl acrylate and its polymers

A new monomer, 1,2,3‐tris(ethoxycarbonyl)‐2‐propyl acrylate (TPA), was synthesized by reaction of acryloyl chloride and triethyl citrate. The homopolymer of TPA and its copolymers with acrylic acid (AA), vinyl acetate (VAc) and maleic anhydride (MAH) were prepared by polymerization using lauroyl peroxide (LPO) at 70 °C for 24 h. The structures of TPA and its polymers were identified by FTIR, ¹H NMR, ¹³C NMR spectroscopies, and elemental analysis. The number average molecular weights and polydispersity indices of the synthesized polymers determined by GPC were in the range 4200–23 000 g mol^?1 and 1.1–2.1, respectively. The IC₅₀ values of the synthesized samples against cancer cell lines were greater than those of 5‐fluorouracil (5‐FU). The percentage inhibition values of SV40 DNA replication were 82.2 for TPA, 34.3 for poly (TPA), 81.9 for poly(TPA‐co‐AA), 82.0 for poly(TPA‐co‐VAc), 35.6 for poly(TPA‐co‐MAH) and 12.7 for 5‐FU. The inhibitions of SV40 DNA replication and antiangiogenesis for the synthesized TPA and its polymers are much greater than those of the control. © 2001 Society of Chemical Industry     

Synthesis and properties of novel crosslinkable second‐order nonlinear optical polymers based on 2,3,4,5,6‐pentafluorostyrene

Two crosslinkable second‐order nonlinear optical polymers were prepared by copolymerization of 2,3,4,5,6‐pentafluorostyrene, styrene (St), glycidyl methacrylate (GMA) and 1‐(4‐nitrophenyl)‐2‐(4‐{[2‐(methacryloyloxy) ethyl] ethylamino}‐phenyl) diazene (DR1M) via the sealed‐tube reaction technique. These polymers were characterized using ¹H, ¹³C and ¹⁹F NMR spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The crosslinkable polymers have high molecular weights, good organosolubility, excellent film‐forming properties and high glass transition (106–110 °C) and thermal decomposition temperatures (290–350 °C) after being crosslinked. Furthermore, the polymer films possess not only high values (12–16 pm V^?1) of electro‐optical coefficient (r₃₃) at 1.3 µm wavelength but also low optical loss (1.7 dB cm^?1) at 1.55 µm wavelength, which is of interest for applications in electro‐optical devices. Copyright © 2004 Society of Chemical Industry     

Synthesis,characterization, and thermo‐optical properties of azobenzene polyurethane containing chiral units

An optically active levoazobenzene polyurethane (PU) was synthesized and was based on the chromophore 4‐(4′‐nitrophenylazo) phenylamine, the chiral reagent L (?)‐tartaric acid, and toluene diisocyanate. The chemical structure and thermal properties were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, and differential scanning calorimetry. The PU had high number‐ and weight‐average molecular weights up to 52 300, a large glass‐transition temperature of 235.7°C, and an optical rotation of ?18.06°, The optical parameters, including the refractive index (n) and thermo‐optic coefficient (dn/dT); the dielectric constant (?) and its variation with temperature; and the thermal volume expansion coefficient and its variation with temperature of PU were obtained. The dn/dT and ? values for the polymer were in the range ?4.1200 to 3.6257 × 10^?4 °C^?1 and 2.00 ± 0.11, respectively. The dn/dT values were one order of magnitude larger than those of inorganic glasses, such as zinc silicate glass (5.5 × 10^?6 °C^?1) and borosilicate glass (4.1 × 10^?6 °C^?1), and were larger than organic materials, such as polystyrene (?1.23 × 10^?4 °C^?1) and poly(methyl methacrylate) (?1.20 × 10^?4 °C^?1). The ? values were lower than that of alicyclic polyimide and semiaromatic polyimide. The obtained PU is expected to be useful for optical switching and optical waveguide areas. The conclusion has a little significance for the development of a new digital optical switch. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010