Structural study of hybrid organic/inorganic polymer gels using time-resolved fluorescence probing

Thin films made of hybrid organic/inorganic polymers, synthesized through the sol-gel method and composed of silica with grafted poly(ethylene oxide) or poly(propylene oxide) chains, are studied by time-resolved fluorescence-probing analysis. The fluorescence-probing technique is employed both to structurally characterize these nanoheterogeneous materials and to demonstrate the capacity of this technique to detect important differences in materials having approximately the same chemical structure. It is found that the films consist of interpenetrating networks of organic and inorganic domains constituting two distinguishable subphases, an organic and an inorganic one. The volume fraction of the organic phase is larger than that of the inorganic phase, and it increases with increasing poly(ethylene oxide) or poly(propylene oxide) chain length. In addition, hydrophobic interactions tend to organize the organic domain, forming organic clusters that can accommodate hydrophobic probes. This is particularly true for large polyether chains.