Domain-size effects in optical diffraction from polymer/composite microparticles

Poly(ethylene glycol) [PEG] microparticles were doped with ceramic or latex nanoparticles in order to examine domain-size and refractive index effects of nanometer-sized guest inclusions on two-dimensional diffraction pattern s, Composite microparticles were examined for different inclusion sizes and polymer/nanoparticle weight ratios in order to determine the size and numb er-density threshold of detection for guest nanoparticles within the polyme r host as indicated by fringe distortion in 2-D angular scattering. PEG hos t particles having a 10 mu m (nominal) diameter were formed with three diff erent guest nanoparticles (Al2O3, TiO2 and latex nanospheres with respectiv e sizes of 46, 29, and 14 nm), For the ceramic nanoparticle inclusions, dis tortion was observed at relative guest-host weight fractions of 5-10%. For the 14 nm latex inclusions, no distortion was observed at any weight fracti on. A perturbation method was used to simulate the effect of nanometer-size inclusions on 2-D optical diffraction from polymer host microparticles and to suggest how the distortions should vary with inclusion size, refractive index, and number.