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Electrochromic polymers (ECPs) receive great attention due to their facile colour tunablility, however colourless-to-black ECPs with high contrast ratio are still unattainable. Here the authors develop high contrast colourless-to-black switching polyimides by following specific molecular design criteria.

This paper presents the synthesis and characterization of polyimides, which contain a 4,4'-hexafluoroisopropylidene-bisphthalic anhydride (6FDA) unit in the backbone. These polyimides are a result of the use of the traditional method of "one step". The reactions occur between equimolar of a dianhydride and an aromatic diamine in presence of the solvent dimethylacetamide (DMAc), then cyclo-dehydrided by adding the acetic anhydride and pyridine. In this work, the 6FDA was used as the dianhydride and four different diamines were investigated: 3,3',5,5'-Tetramethyl-2,2- bis[4-( 4-aminophenoxy) phenyl] propane; 2,2-bis[4-(4-aminophenoxy)-phenyl] hexafluoropropane; 1,3-bis(4-aminophenoxy)benzene and 2,2'-dimethyl-4,4'-bis(4-aminophenoxy)biphenyl. The four polyimides (PA, PB, PC and PD) were characterized by tensile strength, infrared, inherent viscosity, Differential Scanning Calorimeter (DSC) to get the glassy transition temperature (Tg) and Gel Permeation Chromatograph (GPC) to obtain the average molecular weight (Mn).

A solution-processable functional polyimide (PYTPA-PI) containing triphenylamine-substituted diphenylpyridine moieties (PYTPA) and phthalimide moieties (PI) is prepared and analyzed. The electronic transitions and transport mechanisms associated with the memory effect are analyzed and the electrical switching performance in PYTPA-PI has illustrated the possibility of tuning memory properties in imide polymers.

The synthesis and the properties of the donor-acceptor containing polyfluorene derivative and its carbon nanotube composites prepared by Suzuki polymerization are described. These substrates are found to exhibit highly bistable electrical switching and a write-once read-many-times memory effect.

The reaction of 4,4-diaminotriphenylamine with hexafluoroisopropyl bis(phthalic di-anhydride), to form the corresponding poly(amic acid) synthesized the functional polyimides. The conclusion reveals that polyimides memory device distinguishes itself from other polymer devices by its superior thermal and chemical properties, while still possessing good processability and scalability.

Two novel near-infrared (NIR) electrochromic polynorbornenes, poly(NBDTPA) and poly(HNBDTPA), containing electroactive chromophores, were prepared viaring-opening metathesis polymerisation from a new norbornene derivative (NBDTPA) using Grubbs' catalysts followed by hydrogen reduction. The glass transition temperatures (Tg) of poly(NBDTPA) and hydrogenated poly(HNBDTPA) were 141 °C and 91 °C, respectively. The 10% weight-loss temperatures of hydrogenated poly(HNBDTPA) and poly(NBDTPA) were up to 440 °C and 397 °C, respectively. Hydrogenated poly(HNBDTPA) film showed excellent transparency (up to 91%). Poly(NBDTPA) showed a cyclic voltammogram and electrochromic behaviour that was similar to poly(HNBDTPA). The cyclic voltammogram of a poly(HNBDTPA) film cast onto an indium-tin oxide (ITO)-coated glass substrate exhibited three reversible oxidation redox couples at 0.63, 0.82 and 1.23 V vs.Ag/Ag+in acetonitrile solution. The electrochromic characteristics of poly(HNBDTPA) showed excellent stability and reversibility, with multi-stage colour changes from its colourless neutral form to green, light-blue and dark-blue with applied potentials of 0 to 1.75 V. The colour switching time and bleaching time of the poly(HNBDTPA) were 7.1 s and 4.2 s in the near-infrared region (1230 nm), and 7.4 s and 4.5 s in the UV-vis region (420 nm), respectively. [ABSTRACT FROM AUTHOR]

Pure exo‐functional norbornene monomers containing various chromophores such as fluorene, pyrene, and carbazole were successfully prepared via the Diels–Alder reaction and condensation reaction. The living ring‐opening metathesis polymerization (ROMP) of a fluorene‐containing monomer, exo‐2‐(fluorene‐9‐ylcarboxymethyl)norborn‐5‐ene (exo‐1), was observed and confirmed by the formation of a diblock copolymer and a linear relationship between the number‐average molecular weight and [M]/[I] ratios ([M] = monomer concentration; [I] = initiator concentration). The synthesis and characteristics of novel fluorene‐containing polymers based on pure exo‐1 are reported with Grubbs catalyst I {RuCl2(CHPh)[P(C6H11)3]2} with a high molecular weight of 3.18 × 104 in 90 s ([M]/[I] = 100). However, the ROMP of pyrene‐ and carbazole‐containing monomers [exo‐5‐(pyrene methoxy carbonyl)bicyclo[2.2.1]hept‐2‐ene and exo‐5‐(carbazole ethoxy carbonyl)bicyclo[2.2.1]hept‐2‐ene, respectively] were carried out in a nonliving fashion. All the chromophore‐containing polymers showed excellent solubility in various organic solvents, particularly in chloroform, N‐methyl‐2‐pyrrolidinone, and 1,2‐dichlorobenzene. The glass transition temperatures of polynorbornenes containing various chromophores were determined to be 80–109 °C (by differential scanning calorimetry) higher than that of ring‐opened polynorbornene (glass transition temperature = 35 °C), indicating that the incorporation of the pendant aromatic moieties (e.g., fluorene, pyrene, and carbazole) could enhance the transition temperature for segmental motions of polymer chains. The photoluminescence spectra of all polymer solutions showed a strong emission in the blue region of the visible spectra. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3022–3031, 2007 [ABSTRACT FROM AUTHOR]

Cyclization of deproteinized natural rubber (DPNR) or purified natural rubber latex was effectively performed in latex phase by using trimethylsilyl‐trifluoromethane sulfonate or trimethylsilyl triflate (TMSOTF) as a novel catalyst, which is still not reported in the case of natural rubber latex. Various cyclization conditions affecting the degree of cyclization were studied, such as dry rubber contents, temperature, TMSOTF concentrations, and time. The cyclized products were characterized by FTIR, Raman, 1H‐, and 13C‐NMR spectroscopies, as well as DSC and TGA. The degree of cyclization was estimated by 1H‐NMR spectrum. It was found that the degree of cyclization in NR was a function of cyclization conditions. The thermal stability of cyclized DPNR increased with the degree of cyclization. Solubility of the obtained rubber was good in chloroform, toluene, cyclohexanone, and cyclohexane, and bad in tetrahydrofuran. The average number molecular weight of cyclized DPNR with 76% degree of cyclization was about 4.2 × 104 g/mol. On the basis of FTIR, Raman, 1H‐, and 13C‐NMR, the C=C of cyclized DPNR dramatically decreased after prolonged reaction time. In addition, the topology of cyclization DPNR particles was rough on its rubber particle as analyzed by TEM. The mechanism for this reaction will also be discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007. [ABSTRACT FROM AUTHOR]

In order to investigate the photochemical tuning capability of chiral monomers and polymers containing end-capped menthyl groups, a new series of chiral dopants was synthesized and added to commercially available nematic liquid crystals to induce cholesteric liquid crystal (LC) phases. The addition of chiral dopants with azo structure led to phototunability of the reflection colour of the LC cells. Photochromic variation of the LC cells due to photoisomerization of the azo compound was investigated. After photopolymerization of the monomers inside the cholesteric LC cells, the centre wavelength of the reflected band of the incident light was found to be fixed and the reflected bandwidth was broadened, resulting in a red shift. A schematic representation of both the photoisomerization of the azo dopants and its effect on variation of twisting pitches is proposed. Real image recording was performed using 365 nm UV through a mask with text. The top and side views of the morphological network structures of a fabricated cholesteric LC cell were investigated using scanning electron microscopy. The results of this investigation demonstrated that RGB reflected colours of LC cells can easily be achieved through the addition of the menthyl-containing synthesized chiral compounds to nematic LCs. The addition of synthesized AzoM helped further in recording the patterns onto cholesteric LC films using 365 nm UV exposure. [ABSTRACT FROM AUTHOR]

A new diamine containing a pyridine heterocyclic group and a naphthalene substituent, 4‐(2‐naphthyl)‐2,6‐bis(4‐aminophenyl) pyridine (NBAPP), was synthesized with the Chichibabin reaction and used in the preparation of poly(pyridine imide) by direct polycondensation with 4,4′‐hexafluoroisopropylidenediphathalic anhydride in N‐methyl‐2‐pyrrolidinone (NMP). The poly(pyridine imide) derived from diamine NBAPP with naphthalene substituents was highly organosoluble: it was soluble in tetrahydrofuran, NMP, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, and γ‐butyrolactone at room temperature and in pyridine, dimethyl sulfoxide, and cyclohexanone upon heating at 70 °C. The poly(pyridine imide) was converted into lightly colored, optically transparent, flexible, and tough polyimide films via casting onto glass from a DMAc solution. This polymer exhibited good thermal stability (temperature of 10% weight loss = 527 °C) in air and high dielectric constants (as high as 4.20 at 1 kHz). The polyimide films had a tensile strength of 102 MPa and a tensile modulus of 1.8 GPa. As for the optical properties, the polymer exhibited UV–vis absorption bands in the region of 223–450 nm and possessed strong green‐yellow fluorescence (500 nm) after being protonated with acid. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2367–2374, 2007 [ABSTRACT FROM AUTHOR]

A new diamine containing a pyridine heterocyclic group and a pyrene substituent, 4-(1-pyrene)-2,6-bis(4-aminophenyl)pyridine (PBAPP), was synthesized and used in a preparation of poly(pyridine−imide) by direct polycondensation with 4,4‘-hexafluoroisopropylidenediphathalic anhydride (6FDA) in N-methyl-2-pyrrolidinone (NMP). The poly(pyridine−imide) derived from diamine (PBAPP) was highly soluble in several solvents such as THF, NMP, DMAc, DMF, pyridine, DMSO, and cyclohexanone at room temperature or upon heating at 70 °C and exhibited good thermal stability both in nitrogen and air (Td10>520 °C) and a high dielectric constant of 4.32 at 1 kHz. The poly(pyridine−imide) could be cast into a flexible and tough film from DMAc solution. The poly(pyridine−imide) film had a tensile strength of 118 MPa and a tensile modulus of 2.2 GPa. The optical properties exhibited the UV−vis absorption bands at the region of 200−400 nm and possessed strong orange fluorescent (560 nm) after protonated with protic acid. [ABSTRACT FROM AUTHOR]