Dendronized macromonomers for three-dimensional data storagew

A continuing trend in information storage is the desire for greater storage capacity, a feature that demands the development of both new storage techniques as well as new materials. One of the most promising approaches for achieving high density data storage is based on volume holography which allows data to be stored in 3 dimensions. This significant increase in capacity is in direct contrast to the fundamental size limitations found in traditional 2-D systems such as magnetic hard disk drives. In volume holography, information is stored in the form of optical interference patterns throughout the volume of a photosensitive material. This is accomplished by intersecting two coherent laser beams with the first, called the object beam, containing the information to be stored. The second, called the reference beam, is used to retrieve the stored information. When the object beam and the reference beam intersect in the storage medium, they cause a change in the chemical or physical properties of the material which results in refractive index modulation. By shifting the angular position of the storage media, multiple interference patterns (holograms) can be recorded within the same volume, enabling high density information storage.z While promising, this 3-D volumetric storage strategy has limited commercial implementation due to a variety of material challenges. An ideal storage media must meet numerous stringent requirements including high photosensitivity, high storage capacity, non-volatile read-out, dimensional stability, millimetre thickness, and low-cost. Photopolymer systems fulfill many of these requirements and are promising candidates for three-dimensional data storage applications. Typically they consist of a mixture of monomer and photoinitiator dissolved in a thick, crosslinked network (Fig. 1). Upon holographic exposure, a polymerization reaction initiates in the bright regions of the holographic media leading to consumption of the monomer in the bright regions and generation of a concentration gradient with associated diffusion of the