(PMA) as the additive to prepare a new kind of elastic GO/PAM hydrogels with
exceptional mechanical strength by the combination of the characteristics of conventional double-network hydrogel and nanocomposite hydrogel, as shown in
Fig. 5.15a. The authors explained that the Ca
2+ coordination-induced GO nanosheet
network and covalently cross-linked PAM network were intertwined by the hydrogen bonds between the GO sheets and PAM chains, owing to the rich hydroxyl and
epoxy groups on the GO. The special interaction between ion-induced GO and PMA
contributed to the dissipation of crack energy through unzipping and/or sliding of the
weak cross-links progressively or deforming the network conformation, which was
responsible for the high toughness and good elasticity of the GO/PMA composite.
Although the addition of organic polymer is beneficial to the mechanical strength of
graphene hydrogels, the nonconducting high-molecular polymer may be harmful to
the conductivity of the graphene which will hinder the application to the
photocatalysis. Hence, in our recent work, we employed the glucose as the linker
to synthesize the mesoporous TiO 2 nanocrystals growing in situ on graphene
aerogels [66]. The prepared aerogels also had a good mechanical strength, as
shown in Fig. 5.15e. The TiO 2 /GAs prepared in the presence of glucose unfolded
almost completely after removing of the external pressure.
Fig. 5.15 Photographs demonstrating the excellent mechanical behavior of the GO/PAM
hydrogels. PAM hydrogel is easily ruptured by stretching (a). The GO/PAM columnar hydrogels
recover their initial shapes after stretching to an irregular film (b). After compression testing
by>90% (c). The GO/PAM hydrogel fixed to two clamps is stretched to 11 times its initial length
in a tensile machine (d). Reprinted with permission from Ref. [63]. Copyright 2013, John Wiley and
Sons. (e) The compressibility of TiO 2 /GAs. TiO 2 /GAs can be squeezed into a pellet under pressure.
Once the external pressure is removed, the TiO 2 /GAs unfolds almost completely. (Reprinted with
permission from Ref. [66]. Copyright 2014, American Chemical Society)
122
5 Graphene-Modified TiO 2 with Enhanced Visible Light Photocatalytic Activities
exceptional mechanical strength by the combination of the characteristics of conventional double-network hydrogel and nanocomposite hydrogel, as shown in
Fig. 5.15a. The authors explained that the Ca
2+ coordination-induced GO nanosheet
network and covalently cross-linked PAM network were intertwined by the hydrogen bonds between the GO sheets and PAM chains, owing to the rich hydroxyl and
epoxy groups on the GO. The special interaction between ion-induced GO and PMA
contributed to the dissipation of crack energy through unzipping and/or sliding of the
weak cross-links progressively or deforming the network conformation, which was
responsible for the high toughness and good elasticity of the GO/PMA composite.
Although the addition of organic polymer is beneficial to the mechanical strength of
graphene hydrogels, the nonconducting high-molecular polymer may be harmful to
the conductivity of the graphene which will hinder the application to the
photocatalysis. Hence, in our recent work, we employed the glucose as the linker
to synthesize the mesoporous TiO 2 nanocrystals growing in situ on graphene
aerogels [66]. The prepared aerogels also had a good mechanical strength, as
shown in Fig. 5.15e. The TiO 2 /GAs prepared in the presence of glucose unfolded
almost completely after removing of the external pressure.
Fig. 5.15 Photographs demonstrating the excellent mechanical behavior of the GO/PAM
hydrogels. PAM hydrogel is easily ruptured by stretching (a). The GO/PAM columnar hydrogels
recover their initial shapes after stretching to an irregular film (b). After compression testing
by>90% (c). The GO/PAM hydrogel fixed to two clamps is stretched to 11 times its initial length
in a tensile machine (d). Reprinted with permission from Ref. [63]. Copyright 2013, John Wiley and
Sons. (e) The compressibility of TiO 2 /GAs. TiO 2 /GAs can be squeezed into a pellet under pressure.
Once the external pressure is removed, the TiO 2 /GAs unfolds almost completely. (Reprinted with
permission from Ref. [66]. Copyright 2014, American Chemical Society)
122
5 Graphene-Modified TiO 2 with Enhanced Visible Light Photocatalytic Activities