Biphenyl acetalized polyvinyl alcohol optical films with excellent extraordinary wavelength dispersion

The quarter-wave plate (QWP), utilized in the visible range, often exhibits significant extraordinary wavelength dispersion and is essential for enhancing the imaging quality of new display devices. However, current design strategies frequently encounter limitations in physical or optical properties, restricting their application potential. We proposed a design strategy based on polyvinyl alcohol (PVA) to obtain an adjustable extraordinary wavelength dispersion materials through a simple reaction. The biphenyl side group offers orientation perpendicular to the main chain, providing suitable negative birefringence, which facilitates our design based on birefringence dispersion control (BDC) methods. We synthesized materials varying degrees of acetalization and regulated their retardation values and wavelength dispersion through uniaxial stretching the prepared films. The film with a particularly wide wavelength dispersion range in the wavelength range of 400–800 nm is obtained, which provides an excellent basis for the fabrication of wideband quarter-wave plates. We proposed a molecular design that enables wide-range wavelength dispersion regulation and investigated the contribution of stretching conditions. This provides a theoretical support and design basis for the subsequent work to prepare films close to the ideal quarter-wave plate.