Structural control of silane-grafted polymethylsilsesquioxane

► This study presents the preparation and fabrication of a series of silane-grafted polymethylsilsesquioxane. ► The refractive index (RI) of PMSQ can be controlled by molecular structure. ► The RI of PMSQ at 583 nm decreased from 1.50 to 1.42 merely by heating it to 80 °C. ► The SGPMSQ is more flexible and has greater thermal stability than pure PMSQ.