422
Y. Bolbukh et al.
a
b
-50
50
150
250
350
Temperature,
o
C
Heat flow (Endo UP)
Heat flow (Endo UP)
Lignin
1
2
3
4
5
185 255
322
ΔH2
-50
50
150
250
350
Temperature,
o C
Lignin
6
7
8
185 255
322
ΔH2
Fig. 26.7 DSC curves of silica/lignin composites. Figures represent DSC curves of the second heat
run obtained in two cycles of heating/cooling measurement at temperatures −50–350C. The first
heating run (not presented) was conducted at T = 20–150C. Illustration shows the thermal behavior
of lignin immobilized on pristine silica (1, Lig-A1); methylated silica with modification degree 100
(2, Lig-A2) and 30% (3, Lig-A3); hydride-contained silica (4, Lig-A4) and aminated silica with
modification degree 100% (5, Lig-A5); and silica with bifunctional amino-methyl (6, Lig-A6),
hydride-methyl (7, Lig-A7), and hydride-amino surface layer (8, Lig-A8). Sample description is
represent in Table 26.1
the other side, 30% of the methyl groups on silica surface promotes increase of
enthalpy of process at 227 ◦ C (Table 26.3). A more intensive endotherm and highest
value of the enthalpy (H 2 ) were marked for samples based on aminated silica
(Lig-A5). It should be noted that the presence of silicon hydride groups on silica
surface reflected endotherm narrowing that indicates the compressing of polymer
layer near the surface. For bifunctional silicas, more structured layer was obtained
on amino-silicon hydride-containing surface.
The enthalpy of endothermic process (Table 26.3) during degradation of polymer
layers on totally methylated silica (Lig-A2) is significantly lower than for samples
with silicon hydride (Lig-A4) or amino groups (Lig-A5) with the same modification
degree. Obviously, the hydrophobicity of the silica surface has a significant effect
on the structure of the polymer layer formed. If a fully hydrophilic surface of the
pristine silica contributes to the amorphization of the polymeric layer structure,
a reverse effect from a completely hydrophobic surface (methylated silica with
modification degree 100%) should be expected. However, the highest enthalpy
Y. Bolbukh et al.
a
b
-50
50
150
250
350
Temperature,
o
C
Heat flow (Endo UP)
Heat flow (Endo UP)
Lignin
1
2
3
4
5
185 255
322
ΔH2
-50
50
150
250
350
Temperature,
o C
Lignin
6
7
8
185 255
322
ΔH2
Fig. 26.7 DSC curves of silica/lignin composites. Figures represent DSC curves of the second heat
run obtained in two cycles of heating/cooling measurement at temperatures −50–350C. The first
heating run (not presented) was conducted at T = 20–150C. Illustration shows the thermal behavior
of lignin immobilized on pristine silica (1, Lig-A1); methylated silica with modification degree 100
(2, Lig-A2) and 30% (3, Lig-A3); hydride-contained silica (4, Lig-A4) and aminated silica with
modification degree 100% (5, Lig-A5); and silica with bifunctional amino-methyl (6, Lig-A6),
hydride-methyl (7, Lig-A7), and hydride-amino surface layer (8, Lig-A8). Sample description is
represent in Table 26.1
the other side, 30% of the methyl groups on silica surface promotes increase of
enthalpy of process at 227 ◦ C (Table 26.3). A more intensive endotherm and highest
value of the enthalpy (H 2 ) were marked for samples based on aminated silica
(Lig-A5). It should be noted that the presence of silicon hydride groups on silica
surface reflected endotherm narrowing that indicates the compressing of polymer
layer near the surface. For bifunctional silicas, more structured layer was obtained
on amino-silicon hydride-containing surface.
The enthalpy of endothermic process (Table 26.3) during degradation of polymer
layers on totally methylated silica (Lig-A2) is significantly lower than for samples
with silicon hydride (Lig-A4) or amino groups (Lig-A5) with the same modification
degree. Obviously, the hydrophobicity of the silica surface has a significant effect
on the structure of the polymer layer formed. If a fully hydrophilic surface of the
pristine silica contributes to the amorphization of the polymeric layer structure,
a reverse effect from a completely hydrophobic surface (methylated silica with
modification degree 100%) should be expected. However, the highest enthalpy