Effects of chain-transferring thiol functionalities on the performance of nanoparticle-polymer composite volume gratings

We report influences of varying functionalities of thiols as chain transfer agents on the spatial frequency response, polymerization shrinkage, and thermal stability of a volume grating recorded in a photopolymerizable ZrO₂ nanoparticle-polymer composite film. It is shown that a substantial increase in the saturated refractive index modulation is realized at high spatial frequencies by doping with multifunctional thiols. Moreover, the incorporation of multifunctional thiols considerably suppresses polymerization shrinkage of recorded volume gratings and thermal changes in refractive index and film thickness as compared with the case of mono-thiol. These results indicate that multifunctional thiols provide effective control of the properties of nanoparticle-polymer composite volume gratings for various applications in light and neutron optics.