26 Bifunctional Silicas with Immobilized Lignin
409
interest. The successful combination of silica with a natural biopolymer, such
as lignin, can provide new products with unique dispersive, morphological, and
physicochemical properties. In this connection it is important to study the interaction
of polymer carrier at the interface and their mutual effect on properties of the
composite. In our study as an inorganic matrix, we used pyrogenic silica with
attached amino, silicon hydride, or methyl groups in mono- or bifunctional (methylhydride, methyl-amino, amino-hydride) layer. Modification of silica surface was
carried out to impart different hydrophobic/hydrophilic properties and chemical
activity of the surface. Impregnation of water-soluble lignin on silica bearing various
functional groups was carried out to study the effect of the functionalized silica
surface on structure and properties of lignin.
26.2 Experimental Section
26.2.1 Materials
Fumed silica with a specific surface area of 300 m 2 /g (Kalush, Ukraine) was used
as initial hydrophilic filler. 3-Aminopropyltriethoxysilane (APTES), triethoxysilane
(TES), and hexamethyldisilazane (HMDS) (Sigma-Aldrich) were used without
additional treating. The water-soluble commercially available kraft lignin from
softwood was obtained from Sigma-Aldrich.
26.2.2 Silica Surface Modification
Modification of silica surface was carried out on a well-known standard method
liquid-phase processing using appropriate organosilane in toluene solution [19].
Briefly, modification of silica surface with 3-aminopropyltriethoxysilane (A300NH 2 ) and triethoxysilane (A300-SiH) was performed by liquid-phase process.
Toluene solution of alkoxysilane-required concentration was added to silica. The
mixture was kept in the thermostat for 24 h at 60 or 80 ◦ C for amino or silicon
hydride group attaching, respectively. Then, modified silica was washed and dried at
low pressure and heating. The modification with hexamethyldisilazane (A300-CH 3 )
was performed by the gas-phase process at room temperature using a leak-proof
reactor with stirring at 25 ◦ C for 24 h. After modification the methyl-containing
silica was heated at 150 ◦ C for 30 min. Silica with grafted methylsilyl and
silicon hydride groups (methyl-hydride-containing silica) as well as methylsilyl and
aminopropyl groups (methyl-amino-containing silica) was prepared by interaction
of the methyl-containing silica with triethoxysilane or 3-aminopropyltriethoxysilane
in toluene at 80 ◦ C for 24 h. The modification degree for all types of silicas
was 30 and 100%. The concentration of the attached groups in the bifunctional
409
interest. The successful combination of silica with a natural biopolymer, such
as lignin, can provide new products with unique dispersive, morphological, and
physicochemical properties. In this connection it is important to study the interaction
of polymer carrier at the interface and their mutual effect on properties of the
composite. In our study as an inorganic matrix, we used pyrogenic silica with
attached amino, silicon hydride, or methyl groups in mono- or bifunctional (methylhydride, methyl-amino, amino-hydride) layer. Modification of silica surface was
carried out to impart different hydrophobic/hydrophilic properties and chemical
activity of the surface. Impregnation of water-soluble lignin on silica bearing various
functional groups was carried out to study the effect of the functionalized silica
surface on structure and properties of lignin.
26.2 Experimental Section
26.2.1 Materials
Fumed silica with a specific surface area of 300 m 2 /g (Kalush, Ukraine) was used
as initial hydrophilic filler. 3-Aminopropyltriethoxysilane (APTES), triethoxysilane
(TES), and hexamethyldisilazane (HMDS) (Sigma-Aldrich) were used without
additional treating. The water-soluble commercially available kraft lignin from
softwood was obtained from Sigma-Aldrich.
26.2.2 Silica Surface Modification
Modification of silica surface was carried out on a well-known standard method
liquid-phase processing using appropriate organosilane in toluene solution [19].
Briefly, modification of silica surface with 3-aminopropyltriethoxysilane (A300NH 2 ) and triethoxysilane (A300-SiH) was performed by liquid-phase process.
Toluene solution of alkoxysilane-required concentration was added to silica. The
mixture was kept in the thermostat for 24 h at 60 or 80 ◦ C for amino or silicon
hydride group attaching, respectively. Then, modified silica was washed and dried at
low pressure and heating. The modification with hexamethyldisilazane (A300-CH 3 )
was performed by the gas-phase process at room temperature using a leak-proof
reactor with stirring at 25 ◦ C for 24 h. After modification the methyl-containing
silica was heated at 150 ◦ C for 30 min. Silica with grafted methylsilyl and
silicon hydride groups (methyl-hydride-containing silica) as well as methylsilyl and
aminopropyl groups (methyl-amino-containing silica) was prepared by interaction
of the methyl-containing silica with triethoxysilane or 3-aminopropyltriethoxysilane
in toluene at 80 ◦ C for 24 h. The modification degree for all types of silicas
was 30 and 100%. The concentration of the attached groups in the bifunctional