Optical properties of thermotropic hydrogels (a review)

Dense microparticles form in thermotropic hydrogels upon temperature increase above the temperature of a volume phase transition, which causes a hydrogel transition from a transparent state to a milky-white light scattering state. Experimental and analytical data related to light scattering properties of thermotropic hydrogels are analyzed. The size of dense hydrogel particles plays a crucial role in determining the character of transmission and scattering of solar radiation. A considerable part of solar radiation experiences backscattering when the size of the microparticles exceeds 200 nm, which enables using such hydrogels for controlling the amount of transmitted solar radiation. Addition of dispersed plasmon nanoparticles into a hydrogel allows tuning its transition from transparent to light-scattering state so that it takes place at fixed intensity of solar radiation.