Figure 4.4
10
1
10 1
Elastic Modulus [MPa]
10
0
10
–1
10
–2
10
2
10
3
BNCgelatin
Gelatin
BNC
Fracture Stress [MPa]
BNCgelatin
Gelatin
10
0
10
–1
10
–3
10
0
10
1
Degree of Swelling
(a)
10 –2
10
0
10
1
Degree of Swelling
(b)
10
2
79
Tough Bacterial Nanocellulose Hydrogels Based on the Double-Network
Figure 4.4
ing.degree.for.BNC-gelatin.DN.(●),.gelatin.(○),.and.BNC.(□).gels..The.compression.was.performed.perpendicular.to.the.stratified.structure.of.the.BNC.and.BNC-gelatin.gels..(Reproduced.
with.permission.of.Nakayama.et.al..2004.)
Effect of AAm Monomer Concentration
The.effect.of.AAm.concentration.on.the.mechanical.properties.of.BNC-PAAm.
DN. gel. is. shown. in. Figure 4.5.. For. comparison,. the. swelling. degree,. q,. and.
mechanical.properties.of.ligament.are.also.shown.(Woo.et.al..2004)..To.measure.
the. mechanical. properties. of. BNC-PAAm. DN. gel,. tensile. tests. were. . carried.
out. on. samples. in. directions. parallel. to. the. stratified. structure. of. the. BNC.
gel..BNC.gel,.having.an.ultrafine.fibril.network.stacked.in.a.stratified.structure,.shows.mechanically.anisotropic.properties,.with.a.high.tensile.modulus.
(E = 2.9.MPa).along.the.fibril.layer.direction,.but.a.low.compressive.modulus.
(E.=.0.007.MPa).perpendicular.to.the.stratified.direction.(Hagiwara.et al..2010;.
Nakayama.et.al..2004)..Figure 4.5.shows.the.effect.of.the.concentration.of.AAm.
on.the.tensile.strength.of.BNC-PAAm.DN.gels.
The. swelling. of. the. BNC. gel. as. a. single. network. drastically. decreased.
(by about.10.times).after.the.BNC.gel.was.combined.with.AAm.(1.M).to.produce.BNC-PAAm.DN.gel..This.indicates.that.the.water.in.the.BNC.gel.. network.
was.replaced.by.the.PAAm.gel..The.swelling.of.the.BNC-PAAm.DN.gel.continued.to.decrease.with.increasing.concentrations.of.AAm.(Figure 4.5a)..Up to.
an.AAm.concentration.of.4.M,.the.swelling.of.BNC-PAAm.DN.gel.was 4.5..
This.swelling.was.still.greater.than.that.of.ligament.(q.=.2.86)..Meanwhile,.the.
tensile. modulus,. E,. of. BNC-PAAm. DN. gel. increased. linearly. with. increasing.AAm.concentration,.but.was.still.much.lower.(more.than.100.times).than.
the.tensile.modulus.of.ligament.(E.=.332.MPa)..The.tensile.fracture.stress,.σ F ,.
of.BNC-PAAm.DN.gel.tended.to.increase.with.increasing.AAm.concentration.and.was.more.than.20.times.slower.than.that.of.ligament.(ε F .=.38.6 MPa;.
Figure 4.5b).. However,. the. tensile. fracture. strain. of. BNC-PAAm. DN. gel.
10
1
10 1
Elastic Modulus [MPa]
10
0
10
–1
10
–2
10
2
10
3
BNCgelatin
Gelatin
BNC
Fracture Stress [MPa]
BNCgelatin
Gelatin
10
0
10
–1
10
–3
10
0
10
1
Degree of Swelling
(a)
10 –2
10
0
10
1
Degree of Swelling
(b)
10
2
79
Tough Bacterial Nanocellulose Hydrogels Based on the Double-Network
Figure 4.4
ing.degree.for.BNC-gelatin.DN.(●),.gelatin.(○),.and.BNC.(□).gels..The.compression.was.performed.perpendicular.to.the.stratified.structure.of.the.BNC.and.BNC-gelatin.gels..(Reproduced.
with.permission.of.Nakayama.et.al..2004.)
Effect of AAm Monomer Concentration
The.effect.of.AAm.concentration.on.the.mechanical.properties.of.BNC-PAAm.
DN. gel. is. shown. in. Figure 4.5.. For. comparison,. the. swelling. degree,. q,. and.
mechanical.properties.of.ligament.are.also.shown.(Woo.et.al..2004)..To.measure.
the. mechanical. properties. of. BNC-PAAm. DN. gel,. tensile. tests. were. . carried.
out. on. samples. in. directions. parallel. to. the. stratified. structure. of. the. BNC.
gel..BNC.gel,.having.an.ultrafine.fibril.network.stacked.in.a.stratified.structure,.shows.mechanically.anisotropic.properties,.with.a.high.tensile.modulus.
(E = 2.9.MPa).along.the.fibril.layer.direction,.but.a.low.compressive.modulus.
(E.=.0.007.MPa).perpendicular.to.the.stratified.direction.(Hagiwara.et al..2010;.
Nakayama.et.al..2004)..Figure 4.5.shows.the.effect.of.the.concentration.of.AAm.
on.the.tensile.strength.of.BNC-PAAm.DN.gels.
The. swelling. of. the. BNC. gel. as. a. single. network. drastically. decreased.
(by about.10.times).after.the.BNC.gel.was.combined.with.AAm.(1.M).to.produce.BNC-PAAm.DN.gel..This.indicates.that.the.water.in.the.BNC.gel.. network.
was.replaced.by.the.PAAm.gel..The.swelling.of.the.BNC-PAAm.DN.gel.continued.to.decrease.with.increasing.concentrations.of.AAm.(Figure 4.5a)..Up to.
an.AAm.concentration.of.4.M,.the.swelling.of.BNC-PAAm.DN.gel.was 4.5..
This.swelling.was.still.greater.than.that.of.ligament.(q.=.2.86)..Meanwhile,.the.
tensile. modulus,. E,. of. BNC-PAAm. DN. gel. increased. linearly. with. increasing.AAm.concentration,.but.was.still.much.lower.(more.than.100.times).than.
the.tensile.modulus.of.ligament.(E.=.332.MPa)..The.tensile.fracture.stress,.σ F ,.
of.BNC-PAAm.DN.gel.tended.to.increase.with.increasing.AAm.concentration.and.was.more.than.20.times.slower.than.that.of.ligament.(ε F .=.38.6 MPa;.
Figure 4.5b).. However,. the. tensile. fracture. strain. of. BNC-PAAm. DN. gel.