Search

Highly ordered organic semiconductor micropatterns of the liquid-crystalline small molecule 2,7-didecylbenzothienobenzothiophene (C10 -BTBT) are fabricated using a simple method based on template-assisted self-assembly (TASA). The liquid crystallinity of C10 -BTBT allows solvent-free fabrication of high-performance printed organic field-effect transistors (OFETs).

One of the most challenging tasks encountered in developing highly efficient electro-optic (EO) devices is to find a material system that possesses all desirable properties such as large EO coefficients, good thermal and mechanical stability, and low optical loss. In order to meet this stringent requirement, we have developed a series of crosslinkable EO dendrimers using the standardized AJL8-type chromophore as the center core and the furyl- and anthryl-containing dendrons as the periphery. Upon adding a trismaleimide (TMI) dienophile, these dendrimers could be in-situ crosslinked via the Diels-Alder cycloaddition and efficiently poled under a high electric field. Through this dynamic process, the spatially voided and π-electron-rich surrounding of the chromophore core changes into a dense and more aliphatic network, with the dipolar chromophore embedded and aligned inside. The resultant materials exhibit large EO coefficients (63-99 pm V -1 at 1.31 μm), excellent temporal stability (the original r 33 values remain unchanged at 100 °C for more than 500 h), and blue-shifted near-IR absorption. With these combined desirable properties, a poled EOD2/TMI film could be processed through multiple lithographic and etching steps to fabricate a racetrack-shaped micro-ring resonator. By coupling this ring resonator with a side-polished optical fiber, a novel broadband electric-field sensor with high sensitivity of 100 mV m -1 at 550 MHz was successfully demonstrated.

Organic and polymer light-emitting diodes (LEDs) have been the subject of intensive investigation in recent years because of their potential as emissive elements for flat-panel displays and white-light sources for general lighting. As dualinjection devices, multilayer structures with discrete hole-injection layers (HILs) and/or hole-transport layers (HTLs), light-emitting layers (EMLs), and electron-transport layers (ETLs) are necessary for high efficiency, where these layers can be optimized, respectively, according to their functions. [1–3] For LEDs based on small molecules, it is rather straightforward to adopt this multilayer strategy via layer-bylayer vacuum deposition. However, for polymer-based LEDs, where solution-based casting or spin-coating is the basic way to form films, it is very challenging to form multilayer structures, because of solvent erosion of previously deposited layers during spin-coating. [4] To overcome this problem, a

Poled electro-optic (EO) polymers have enabled many advances in the exploration of high-speed and broadband information technologies. Polymer based EO devices have been demonstrated to have large bandwidths (over 110 GHz), low driving voltages, and sustain their performance in a flexible form or under extreme environmental conditions. For optical circuits, EO polymers can be easily integrated with striplineor ring-structured waveguides made of sol–gels, low-loss fluorinated polymers, silicon slots, conducting oxides, and photonic crystals. Recently, EO polymers have also been utilized for the generation/detection of a gap-free pulsed THz system with a bandwidth up to ca. 12 THz. Large numbers of discrete photonic components need to be inserted into integrated systems of telecommunication and silicon microphotonics, especially where an extreme amount of data is required to travel in a very small space. Therein lies the great challenge for polymer-based EO technologies: to have thermally stable EO coefficients (r33) of around 500 pm V at wavelengths of 1.31 or 1.55 lm. Currently, the most commonly used materials for polymeric EO devices are based on poled polymers with r33 values around 50–80 pm V at wavelengths of 1.31 or 1.55 lm. In these materials, dipolar nonlinear optical (NLO) chromophores have been doped or incorporated at a level of ca. 20– 25 wt % to reach their maximum r33 values. [5–10] Beyond such a moderate loading of chromophores, strong intermolecular electrostatic interactions severely limit the poling-induced polar order and cause phase-separation problems between chromophores and polymers. To further improve EO activity, research efforts have focused on developing shape-engineered chromophores with high molecular optical nonlinearities (lb), where lb is a product of first hyperpolarizability and the dipole moment of the NLO chromophore, and increasing order within the matrices by controlling the nanoscale architecture of macromolecules. In our recent study we have demonstrated, using Diels–Alder (DA) “click chemistry” to post-functionalize NLO chromophores onto polymers, that high chromophore loading levels (up to 35 wt %) and large r33 values (up to 110 pm V) could be achieved in in situ generated side-chain dendronized NLO polymers with non-reacted chromophores as guest dopants. This opens a new avenue to explore optimal host–guest combinations and to develop an efficient way to control lattice hardening in these hybrid polymers. The ultimate goal is to simultaneously achieve very large EO activity, good thermal stability, high optical transparency, and excellent mechanical properties within the same material via molecular design and facile processing. In this paper, we report a novel method to disperse a highly efficient secondary chromophore into in situ crosslinked NLO polymer networks, leading to both enhanced EO activity (> 260 pm V at 1.31 lm) and alignment stability at 85 °C. In photorefractive (PR) polymers and liquid-crystal (LC) systems, binary chromophore mixtures have been shown to elevate the loading density of small dipolar dyes without causing phase separation. We have extended this further by incorporating highly polarizable NLO chromophores into these binary systems. In addition, DA click chemistry has also been employed to improve the physical properties of these materials. This combined effort demonstrates that binary mixtures of large-bl chromophores can be loaded into side-chain NLO matrices and efficiently poled to give EO activities higher than the summed value of two added chromophores. These systems can also be mildly cured to ensure a thermally stable EO response. The EO polymers studied in this work exist as a three-component host–guest system (Fig. 1). The host polymer is a copolymer, poly[(methyl methacrylate)-co-(9-anthracenyl methyl methacrylate)] (PMMA-AMA), with around 10 mol % of the anthracenyl moiety. To this host, AJC146 was added together with compound 1a, 1b, or 1c as binary guest chromoC O M M U N IC A TI O N S

Contractive cyclization of the 1,14-bisformyl-16-oxa-tripyrromethane with 1,2-diamine gave new corinoid macrocycles depending on the nature of heteroatoms in the core.

Condensation of aldehydes with pyrrole in the presence of acid catalyst gave the mixture of dipyrromethanes and tripyrromethanes. The major product was switched from dipyrromethanes to tripyrromethanes according to the sequence of adding the reactants and catalyst. Higher oligomers such as tetrapyrromethane and pentapyrromethane were isolated and characterized from the reaction of 4-methoxycarbonylbenzaldehyde with pyrrole.

Second hole-transport layer (HTL) with perfect solvent-resistance is formed via spin-coating then thermally crosslinking on top of a pre-crosslinked HTL or p-type conducting polymer layer. By judiciously choosing the energy levels of the hole-transport moieties, cascade hole-injection can be realized for a light-emitting layer with phosphorescent blue emitters (and white thereafter).