A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Photoinduced motions in azo-containing polymers.

Alkylsabstituted polyfluorenes have emerged as a very attractive class of conju gated polymers, especially for display applications, owing to their pure blue and efficient electroluminescence coupled with a high charge-carrier mobility and good processability. The availability of specific and highly regroselective coupling reactions provides a rich variety of taifored polyfluorene-type paly mers and copolymers. The focus of this review, therefore, is on reliable structure-property relationships regarding (i) the interplay of substitution pattern, solid state morphology, and optical/electronic properties, and (ii) the key role of degradation-induced keto defect sites in fluorerse-type polymers, and strategies for obtaining defect-free polyfluorenes.

Semiconducting Polyfluorenes—Towards Reliable Structure–Property Relationships

Photochromic materials are a family of compounds which can undergo reversible photo-switches between two different states or isomers with remarkably different properties. Inspired by their smart photo-switchable characteristics, a variety of light-driven functional materials have been exploited, such as ultrahigh-density optical data storage, molecular switches, logic gates, molecular wires, optic/electronic devices, sensors, bio-imaging and so on. This review commences with a brief description of exciting progress in this field, from systems in solution to modified functional surfaces. Further development of these photo-switchable systems into practical applications as well as existing challenges are also discussed and put in prospect.

Photochromic Materials: More Than Meets The Eye

Stable polymeric materials for nonlinear optics: a review based on azobenzene systems

Photoaddressable polymers (PAPs) are side-chain copolymer systems functionalized with azobenzene chromophores and mesogenic side groups. They show very large birefringence values after illumination with polarized light. The molecular mechanisms involved are photoinduced isomerization cycles of the azo side groups, which induce strong molecular reorientations (cooperative motion of light-absorbing azobenzene chromophores and non-absorbing mesogenic groups). Due to the long-term and high-temperature stability of their light-induced birefringence, PAPs are very promising recording materials for optical data storage applications such as high-capacity DVDs and holographic memory.

Photoaddressable Polymers for Optical Data Storage

Optical data storage has had a major impact on daily life since its introduction to the market in 1982. Compact discs (CDs), digital versatile discs (DVDs), and Blu-ray discs (BDs) are universal data-storage formats with the advantage that the reading and writing of the digital data does not require contact and is therefore wear-free. These formats allow convenient and fast data access, high transfer rates, and electricity-free data storage with low overall archiving costs. The driving force for development in this area is the constant need for increased data-storage capacity and transfer rate. The use of holographic principles for optical data storage is an elegant way to increase the storage capacity and the transfer rate, because by this technique the data can be stored in the volume of the storage material and, moreover, it can be optically processed in parallel. This Review describes the fundamental requirements for holographic data-storage materials and compares the general concepts for the materials used. An overview of the performance of current read-write devices shows how far holographic data storage has already been developed.

From the surface to volume: concepts for the next generation of optical-holographic data-storage materials.

Liquid-crystalline (LC) polyfluorenes have been successfully aligned on photoaddressable polymers (PAPs). This is the first example of the alignment of a LC main chain polymer on a photoaligned layer. The degree of molecular alignment in the fluorescent polyfluorene layer on top of an ultra-thin PAP layer is shown to depend strongly on the chemical nature of the PAP. Good alignment with dichroic ratios of more than 10 was only achieved with PAPs containing liquid-crystalline side chains. Patterning with laterally structured alignment was realized in several ways, utilizing reorientation with orthogonally polarized light. Thin PAP layers have further been utilized as hole-conducting alignment layers in polymer light-emitting diodes (LEDs) with polarized emission. In order to facilitate hole transport through the alignment layer, different concentrations of a hole-transporting molecule (HTM) have been mixed into the PAP layer. These hole-conducting alignment layers retained their aligning abilities even at HTM concentrations of 20 wt.-%. LEDs with photometric polarization ratios in emission of up to 14 at a brightness of up to 200 cd/m2 and an efficiency of 0.3 cd/A could be realized.

Photoaddressable Alignment Layers for Fluorescent Polymers in Polarized Electroluminescence Devices

This paper describes a new class of recording materials for volume holographic applications suitable to meet commercial
manufacturing needs. These next-generation holographic photopolymers have the ability to satisfy the unmet demand
for color and depth tuning that is only possible with volume holograms. Unlike earlier holographic photopolymers, these
new materials offer the advantages of no chemical or thermal processing combined with low shrinkage and detuning.
Furthermore, these materials exhibit high transparency, a high resolution of more than 5000 lines/mm and are
environmentally robust. Bayer MaterialScience plans to commercialize these materials, which combine excellent
holographic characteristics with compatibility to mass-production processes. In this paper, we will briefly discuss the
potential markets and applications for a new photopolymer, describe the attributes of this new class of photopolymers,
relate their ease of use in holographic recording, and discuss potential applications of such materials..

http://www2.engr.arizona.edu/~ece527/Bayer%20SPIE.pdf

New recording materials for the holographic industry

We have been developing a new class of recording materials for volume holography, offering the advantages for full
color recording and depth tuning without any chemical or thermal processing, combined with low shrinkage and
detuning. These photopolymers are based on the two chemistry concept in which the writing chemistry is dissolved in a
preformed polymeric network. This network gives the necessary mechanical stability to the material prior to recording.
In this paper we show that the recording process in these materials can be successfully described within a reactiondiffusion
model. For the first time the combination of plane-wave recording data in transmission and reflection geometry
was used to extract the model parameters. This was achieved via a master curve construction of the respective power
density response functions of the photopolymer at saturation recording conditions. Within that model, power density
response, spatial frequency response, non-locality effects, beam ratio effects and even dosage response can be predicted
and explained for a wide range of CW recording conditions which are important for various holographic applications of
these new materials.

Rainer Hagen

Papers

Photoaddressable Polymers for Optical Data Storage

From the surface to volume: concepts for the next generation of optical-holographic data-storage materials.

Photoaddressable Alignment Layers for Fluorescent Polymers in Polarized Electroluminescence Devices

New recording materials for the holographic industry

Reaction-diffusion model applied to high resolution Bayfol HX photopolymer