Preparation and thermal stability of initiator fragments end-capped oligomers/silica nanocomposites

A variety of initiator fragments end-capped oligomers [X ∼ (M) _n  ∼ X; M = N, N-dimethylacrylamide (DMAA), acrylic acid (ACA), N-(1,1-dimethyl-3-oxobutyl)acrylamide (DOBAA), and acryloylmorpholine (ACMO); X = initiator fragments] were synthesized by oligomerization of the corresponding monomers catalyzed by the radical initiators such as ammonium persulfate (APS), 2,2′-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) (VA-086), and azobisisobutyronitrile (AIBN). These initiator fragments end-capped oligomers were found to cause a gelation toward not only water but also traditional organic media such as methanol, 2-propanol, propylene carbonate, 1,2-dichloroethane, and tetrahydrofuran. These obtained oligomers were applied to the nanocomposite reactions with silica nanoparticles in the presence of tetraethoxysilane (TEOS) under alkaline conditions to provide the corresponding oligomers/silica nanocomposites. In these nanocomposites, X ∼ (M) _n  ∼ X/SiO₂ nanocomposites, which were prepared by using APS as an initiator, were found to afford the clear weight loss in proportion to the contents of the oligomers in the composites after calcination at 800 °C. However, interestingly, X ∼ (M) _n  ∼ X/SiO₂ nanocomposites, which were prepared by using VA-086 and AIBN, afforded no weight loss corresponding to the contents of the oligomers in the composites even after calcination at 800 °C.