We have explored the opto-electronic properties of a new series of hole-transport materials based on main-chain triphenylamine-based poly(azomethine)s. 4,4 0 -Diaminotriphenylamine (TPA) was polymerized under benign conditions with either terephthalaldehyde (TPA-14Ta), 2,5-thiophenedicarboxaldehyde (TPA-25Th) or 1,3-isophthalaldehyde (TPA-13Iso) to yield polymers with an M n of 5700-16 000 g mol À1 . Despite the non-linear, or 'kinked', backbone geometry, all polymers form lyotropic solutions in chloroform and this liquid crystal (nematic) ordering could be maintained in the solid film after spin casting. All polymers exhibit high glass-transition temperatures (T g > 250 C) and display outstanding thermal stabilities, i.e. 5% wt loss in excess of 400 C under nitrogen. The HOMO and LUMO energy levels of these polymers were in the range of 5.0-5.3 and 2.4-3.3 eV below the vacuum level, respectively. Introduction of a thiophene heterocycle (TPA-25Th) resulted in a material with a low optical band-gap of approximately 2.0 eV, whereas TPA-14Ta and TPA-13Iso showed optical band gaps of 2.3 and 2.6 eV, respectively. A photovoltaic device based on a TPA-25Th/PCBM blend (1 : 3) showed an EQE of 20% at 500 nm. Under simulated sunlight, the device gives an open-circuit voltage of 0.41 V, a short-circuit current of 1.23 mA cm À2 and a fill factor of 0.24, leading to a power conversion efficiency of 0.12%.

Nanostructured metal hydrides are able to efficiently detect hydrogen in optical sensors. In the literature, two nanostructured systems based on metal hydrides have been proposed for this purpose each with its own detection principle: continuous sub-100 nm thin films read out via optical reflectance/transmittance changes and nanoparticle arrays for which the detection relies on localized surface plasmon resonance. Despite their apparent similarities, their optical and structural response to hydrogen has never been directly compared. In response, for the case of Pd1–yAuy (y = 0.15–0.30) alloys, we directly compare these two systems and establish that they are distinctively different. We show that the dissimilar optical response is not caused by the different optical readout principles but results from a fundamentally different structural response to hydrogen due to the different nanostructurings. The measurements empirically suggest that these differences cannot be fully accounted by surface effects but that the nature of the film–substrate interaction plays an important role and affects both the hydrogen solubility and the metal-to-metal hydride transition. In a broader perspective, our results establish that the specifics of nanoconfinement dictate the structural properties of metal hydrides, which in turn control the properties of nanostructured devices including the sensing characteristics of optical hydrogen sensors and hydride-based active plasmonic systems.

Dynamic mechanical and thermal properties of a certain liquid crystalline (LC) diepoxide cross-linked with three different aromatic diamines were studied. For one epoxy-amine mixture, the position of the gel point was determined with the aid of frequency-dependent rheological measurements. The value of the critical relaxation exponent was 0.5. The gel point was also determined by solubility experiments. There was a clear agreement between the two methods. The degree of conversion of the epoxy groups at the gel point (55 ± 3%) corresponded well with the value predicted by the statistical theory for network formation in isotropic stoichiometric epoxy-amine mixtures. Mechanical measurements were carried out on macroscopically ordered networks in the direction of orientation. In highly ordered networks prepared from the LC diepoxide and a rigid aromatic diamine, the value of the rubber modulus deviated from the predictions of rubber elasticity theory by a factor of 30 times higher. In networks with the same high level of macroscopic orientation prepared from the LC diepoxide and a relatively more flexible diamine, the deviation from the classical theory was much less (factor of 1.7). In the rubbery region, the value of the Young's elastic modulus decreased as a function of temperature, which seems to be connected to the decrease of the order. This is confirmed by a theory, presented by T. Odijk, concerning the polymer nematic gels under tension (see Appendix). The thermal expansion coefficient of the macroscopically ordered networks was highly anisotropic. It was indeed possible to combine the good mechanical and thermal properties of conventional epoxy polymer networks with the special features that LC polymers offer.

A highly ordered alginate/montmorillonite bionanocomposite structure is presented. The alignment of the bionanocomposites has been determined by environmental scanning electron microscopy (ESEM) and wide-angle X-ray scattering (WAXS). The ESEM micrographs show a high inplane orientation of the bionanocomposite, while 2D X-ray scattering images show a clear angle dependency that confirms preferential orientation of montmorillonite (MMT) platelets. The order parameter (⟨P 2 ⟩) was calculated from azimuthal intensity profiles derived from WAXS measured over the MMT 001 reflection, using the Maier−Saupe and the affine deformation model. We observe that the ⟨P 2 ⟩ values depend on the MMT concentration, which is explained by the MMT− alginate interaction. We propose an affine deformation model based on gel formation achieved by alginate adsorption on the edges of MMT, which develops yield stress and deforms the MMT platelets during drying resulting in high range ⟨P 2 ⟩ values.

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We have prepared (AB) n -multiblock copolymers based on N-(3′-hydroxyphenyl)­trimellitimide (IM), 4-hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) via a simple one-pot melt condensation method. The blocky nature is the result of phase separation taking place in the early stages of the melt polymerization process. The liquid crystal HBA/HNA fraction phase separates from the isotropic HBA/IM fraction and this phase separation effectively shuts down transesterification reactions, preventing randomization of the polymer backbone. The (AB) n -multiblock copoly­(esterimide)­s exhibit two distinct glass transition temperatures (T gs). The first T g at ∼120 °C can be assigned to the HBA/HNA rich A-block and the second T g at ∼220 °C can be assigned to the HBA/IM rich B-block. When introducing imide-based phenylethynyl end-groups, these reactive functionalities end-up exclusively at the termini of the HBA/IM rich B-blocks, effectively forming a phenylethynyl-terminated B­(AB) n -reactive oligomer. Upon thermal treatment, cross-linking via the phenylethynyl end-groups results in a thermoset where the T g of the B-block increases by as much as ∼106 °C. The T g of the HBA/HNA A-block remains unchanged. Scanning electron microscopy experiments show a gradual change in morphology, from a typical fibrous LCP texture for the HBA/HNA rich polymers to a more consolidated morphology for the HBA/IM rich polymers. Atomic force microscopy images confirm the presence of two distinct domains when 44 mol % of HBA was replaced by IM. The “hard” imide rich B-blocks form domains of ∼100–200 nm that are embedded in the imide poor or “soft” A-blocks.

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We have selected two amorphous all-aromatic poly(ether imide)s with similar chemical structures but with different backbone geometries as matrices for SWCNT-based nanocomposites. Up to 4.4 vol %, SWCNTs could be incorporated using an in situ polymerization method. Nanocomposites prepared from aBPDA-P3, a nonlinear matrix polymer with a T g of 230 °C, remains amorphous, and the presence of the SWCNTs reduces the T g by 11 °C. No effect on E′ or stress−strain behavior was observed. When ODPA-P3 was used as the matrix, the SWCNTs appear to be highly compatible with this more linear polymer host. The SWCNTs act as a nucleating agent at concentrations as low as 0.1 vol %. XRD and TEM measurements show that the SWCNTs become embedded in a highly crystalline polymer matrix. The result is a significant change in thermomechanical properties. The polymer T g was increased by 12 °C, from 196 to 208 °C, and due to the induced crystallinity, the modulus above T g showed a dramatic increase. The neat polymer fails at T g , but the 4.4 vol % nanocomposite shows a storage modulus of 1 GPa at 280 °C. Stress−strain measurements show a noticeable improvement in strain and toughness at low SWCNT loadings (0.1−0.3 wt %), which is indicative of good stress transfer between the SWCNTs and polymer matrix. At higher loadings the yield strength increases from 80 to 126 MPa at 4.5% strain. Our findings show that the poly(ether imide) backbone geometry determines whether the polymer is good host for SWCNTs. The more linear ODPA-P3 is able to maximize its interaction with the SWCNT surface. To the best of our knowledge, this is the first time that an amorphous polymer has been shown to develop a semicrystalline morphology in the presence of SWCNTs. Steric factors in aBPDA-P3 seem to inhibit favorable π−π interactions and prevent the polymer chains from adapting low-energy conformations that readily interact with the SWCNT surface.