Control of the microstructure of polymer network and effects of the microstructures on light scattering properties of UV‐cured polymer‐dispersed liquid crystal films

Abstract

Polymer‐dispersed liquid crystals (PDLC) films were prepared from ultraviolet (UV) irradiation‐induced polymerization of the photopolymerizable monomers in photopolymerizable monomers/nematic liquid crystal (LC) mixtures. The effects of the composition of the mixtures, the curing temperature, and the UV light intensity on the microstructure of the polymer network in the PDLC films were investigated. Furthermore, the effects of the microstructures on the light scattering properties of the PDLC films in the wavelength region of 300–2500 nm were studied experimentally and theoretically based on the combination of three kinds of classical light scattering theories: the Rayleigh‐Gans (RG) approach, the anomalous diffraction (AD) approach, and the geometrical optics (GO) approach. It was found that the sizes of LC domain in PDLC films increased with the increase of the LC content as well as the decrease of the UV curing intensity, while increased at first and then decreased with the increase of the curing temperature. Moreover, smaller LC domain sizes could exhibit strong scattering properties in a smaller VIS wavelength region and the transmittance in NIR region (especially in the wavelength range of 1300–2500 nm) obviously decreased with the increasing sizes of LC domain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2090–2099, 2008

Nanostructured Multiphase Polymer Networks

“…Evidence has been presented for the impact of reaction kinetics on macromolecular diffusion and gelation, ultimately dictating final polymer structure and properties in all methacrylate systems, without the addition of prepolymers [58]. Processing conditions such as temperature [73,74], irradiance (for photopolymerizable systems) [36], and initiator concentration [42] are of key importance in determining phase-separation behavior since they directly control reaction kinetics and onset of gelation. In thermally polymerized materials, temperature has two distinct and, more often than not, antagonist effects.…”

“…Therefore, light scattering (or light transmission) through a sample is a commonly used technique not only to infer the onset of heterogeneity formation in polymers but also to estimate domain size and distribution [17,36]. In general, the turbidity has been correlated to the cube of the domain size and to the fourth power of the incident wavelength, and these relationships need to be adjusted for much bigger droplets due to anomalous diffraction [36]. This means that one can estimate the size of the domain based on the wavelength it scatters the most.…”

Electrically controllable microstructures and dynamic light scattering properties of liquid crystals with negative dielectric anisotropy

“…[26][27][28][29] The RG approximation for light scattering is appropriate for submicron-sized scattering particles, and is shown to describe accurately the scattering properties of very small LCs droplets, as well as that of small polymer crystallites. [26][27][28][29] The RG approximation for light scattering is appropriate for submicron-sized scattering particles, and is shown to describe accurately the scattering properties of very small LCs droplets, as well as that of small polymer crystallites.…”

Liquid crystal based electrolyte with light trapping scheme for enhancing photovoltaic performance of quasi-solid-state dye-sensitized solar cells

“…(11). As reported, many studies focused on the light scattering property of the nematic LC [43][44][45] especially in the field of polymer dispersed liquid crystals (PDLCs) [16,[46][47][48] containing the anisotropic LC molecules in the isotropic polymer matrix. Generally, when the LC was introduced into the polymer matrix, it forms micrometer-sized LC droplets filled with LC molecules and distributes randomly [49].…”