Crystal morphology of mesoporous silica thin films synthesized by the spin-coating method using PEO-PPO-PEO triblock copolymer

Abstract

Mesoporous thin films on Si substrates with thicknesses of about 460-610 rim have been synthesized by the spin-coating method using a Pluronic EO77PO29EO77 (F68), EO104PO39EO104 (F88), and EO133PO50EO133 (F108) triblock copolymer system. The triblock copolymers were preserved within the synthesized mesoporous thin films. Transmission electron microscopy (TEM) characterization of these films clearly demonstrates that long-range mesostructural ordering strongly depends on the molecular weight of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer, with lower molecular weight producing higher degrees of order. Plane and cross-sectional high-resolution TEM studies coupled with X-ray diffraction (XRD) analysis also show that highly ordered F68 mesoporous silica thin film forms a cubic structure with a lattice spacing a = 6.70 nm.