Photoinitiation and Inhibition under Monochromatic Green Light for Storage of Colored 3D Images in Holographic Polymer-Dispersed Liquid Crystals

Abstract

Holographic photopolymer composites have garnered a great deal of interest in recent decades, not only because of their advantageous light sensitivity but also due to their attractive capabilities of realizing high capacity three-dimensional (3D) data storage that is long-term stable within two-dimensional (2D) thin films. For achieving high performance holographic photopolymer composites, it is of critical importance to implement precisely spatiotemporal control over the photopolymerization kinetics and gelation during holographic recording. Though a monochromatic blue light photoinitibitor has been demonstrated to be useful for improving the holographic performance, it is impractical to be employed for constructing holograms under green light due to the severe restriction of the First Law of Photochemistry, while holography under green light is highly desirable considering the relatively low cost of laser source and high tolerance to ambient vibration for image reconstruction. Herein, we disclose the concurrent photoinitiation and inhibition functions of the rose bengal (RB)/N-phenylglycine (NPG) system upon green light illumination, which result in significant enhancement of the diffraction efficiency of holographic polymer-dispersed liquid crystal (HPDLC) gratings from zero up to 87.6 ± 1.3%, with an augmentation of the RB concentration from 0.06 × 10 to 9.41 × 10 mol L. Interestingly, no detectable variation of the ϕk/k, which reflects the initiation efficiency and kinetic constants, is given when increasing the RB concentration. The radical inhibition by RBH is believed to account for the greatly improved phase separation and enhanced diffraction efficiency, through shortening the weight-average polymer chain length and subsequently delaying the photopolymerization gelation. The reconstructed colored 3D images that are easily identifiable to the naked eye under white light demonstrate great potential to be applied for advanced anticounterfeiting.

Effect of ketyl radical on the structure and performance of holographic polymer/liquid-crystal composites

“…The photo-generated ketyl radical shows a clear inhibition capability [13,14,53,54], which is recently realized to be able to boost the spatiotemporal control over photopolymerization [11,13,54]. Nevertheless, the inhibition mechanism is still unclear.…”

“…Holography is a powerful technique that encodes information via the wave field interference [1]. Due to its unique capability of simultaneously reconstructing the whole information of coherent waves (e.g., amplitude, phase and polarization), holography has become a con-stant innovation source in ultrafast temporal imaging [2,3], optical shaping [4,5], particle assembly [6,7], threedimensional (3D) display [8,9], colored 3D image storage [10][11][12][13][14][15][16], and holographic polymer electrolyte construction [17]. On the other hand, polymer/liquid-crystal (LC) composites have attracted considerable attention due to their unique electro-optic response capability [18][19][20][21].…”

Современное Состояние Разработки Светочувствительных Сред Для Голографии (Обзор)

“…Для регистрации объемных голограмм в фотополи-меризующейся среде, содержащей ЖК, использовалась фотоинициирующая система, включающая Бенгальскую Розу XLVIII и N-фенилглицин XLIX [163]. Фотоини-циирующие свойства последнего компонента и инги-бирующие функции первого компонента этой системы позволяли регистрировать голограммы с η = 87%.…”

Crosstalk‐Free Patterning of Cooperative‐Thermoresponse Images by the Synergy of the AIEgen with the Liquid Crystal

“…To address this hurdle, we hypothesized to pattern a thermoresponsive fluorescent image in a thermoresponsive holographic image, since the former can be controlled by deliberately designing a luminophore while the latter can be patterned by precisely tuning the micro/nanoscale structure . Thermoresponsive holographic images, in the form of periodically alternative polymer‐rich and liquid crystal (LC)‐rich phases, can be patterned through photopolymerization‐induced phase separation of homogeneous monomer/LC mixtures upon exposure to laser interference patterns . However, it still remains challenging to realize the thermoresponse of fluorescent images within the polymer‐based holographic image owing to the constrained movement of the luminophore by the cross‐linked polymer network.…”