Figure 4.6
1.8
130
336
40
1
0
2
3
4
5
6
σ Ligament
ε Ligament
ε BNC
σ BNC
Tensile Modulus, E [MPa]
Tensile Failure Stress, σ
F [MPa]
1
2
3
4
5
q BNC
E Ligament
E BNC
q Ligament
Tensile Fracture Strain,
ε
F [mm/mm]
1.5
1.2
10
4
10
Swelling Degree, q
8
7.5
3
0.9
6
4
5
2.5
0
2
1
0
0.6
0.3
2
0
0
MBAA Concentration [M]
MBAA Concentration [M]
(a)
(b)
81
Tough Bacterial Nanocellulose Hydrogels Based on the Double-Network
Figure 4.6
The. effect. of. MBAA. cross-linker. concentration. on. the. tensile. strength. performance. of.
BNC-PAAm.gel.under.the.conditions.of.4.M.AAm.and.0.1.mol%.KPS:.(a).swelling.degree,.q,.
and.tensile.modulus,.E,.as.functions.of.the.concentration.of.MBAA.(mol%).in.the.BNC-PAAm.
gel..(b).Tensile.fracture.stress,.σ F ,.and.tensile.fracture.strain,.ε F ,.as.functions.of.the.concentration. of. MBAA. (mol%). in. the. BNC-PAAm. gel.. The. symbols. are. as. follows:. (a). (●). q BNC-PAAm ;.
(■) q BNC ,. (▲) q ligament ;. (○). E BNC-AAm ;. (□). E BNC ,. ( ). E ligament ;. (b). (●). σ F BNC/PAAm;. (■). σ F BNC;.
(▲) σ F .ligament;.(○) ε F BNC-PAAm;.(□).ε F BNC;.( ).ε F .ligament..(Reproduced.with.permission.
of.Hagiwara.et.al..2010.)
for. the. cross-linker. to. improve. the. tensile. strength. performance. of. the.
BNC-PAAm. DN. gel.. This. value. is. in. agreement. with. the. concentration. of.
cross-linker.for.any.DN.gel.synthesized.by.the.DN.method.(Gong.et.al..2003)..
The. compressive. moduli. of. BNC-PAAm. DN. gels. increased. with. increasing. MBAA. concentration. (Hagiwara. et. al.. 2010).. The. compressive. fracture.
stress,.σ F ,.increased.substantially.in.the.BNC-PAAm.DN.gels.with.increasing. MBAA. concentration.. The. maximum. tensile. and. compressive. fracture.
stress. was. observed. to. be. about. 3.5. and. 6.5. MPa,. respectively,. at. 5. mol%.
MBAA.concentration,.similar.to.the.compressive.and.tensile.fracture.stress.
of.the.BNC-gelatin.DN.gel.system.discussed.earlier.(Nakayama.et.al..2004)..
It.should.be.noted.that.these.values.are.still.lower.than.the.tensile.fracture.
stress.of.ligament.(σ F .=.39.MPa;.Woo.et.al..2004).and.the.compressive.fracture.
stress.of.articular.cartilage.(McCutchen.1978).
Effect of Water Content
In.order.to.investigate.whether.swelling.is.a.universal.parameter,.the.relationship.between.swelling.and.the.mechanical.properties.of.BNC-PAAm.DN.gels.
prepared.at.different.concentrations.of.AAm.(1–4.M).and.MBAA.(0–5 mol%).
were. investigated.. The. relationships. of. tensile. and. compressive. modulus,.
and.between.tensile.and.compressive.fracture.stress.and.strain,.are.plotted.
against.swelling.on.a.logarithmic.graph,.which.is.useful.to.elucidate.the.correlation.over.a.wide.range.of.these.parameters.(Figure 4.7)..In.Figures 4.7a.and.
4.7b,.it.can.be.seen.that.the.tensile.and.compressive.modulus.of.the.DN.gel.
1.8
130
336
40
1
0
2
3
4
5
6
σ Ligament
ε Ligament
ε BNC
σ BNC
Tensile Modulus, E [MPa]
Tensile Failure Stress, σ
F [MPa]
1
2
3
4
5
q BNC
E Ligament
E BNC
q Ligament
Tensile Fracture Strain,
ε
F [mm/mm]
1.5
1.2
10
4
10
Swelling Degree, q
8
7.5
3
0.9
6
4
5
2.5
0
2
1
0
0.6
0.3
2
0
0
MBAA Concentration [M]
MBAA Concentration [M]
(a)
(b)
81
Tough Bacterial Nanocellulose Hydrogels Based on the Double-Network
Figure 4.6
The. effect. of. MBAA. cross-linker. concentration. on. the. tensile. strength. performance. of.
BNC-PAAm.gel.under.the.conditions.of.4.M.AAm.and.0.1.mol%.KPS:.(a).swelling.degree,.q,.
and.tensile.modulus,.E,.as.functions.of.the.concentration.of.MBAA.(mol%).in.the.BNC-PAAm.
gel..(b).Tensile.fracture.stress,.σ F ,.and.tensile.fracture.strain,.ε F ,.as.functions.of.the.concentration. of. MBAA. (mol%). in. the. BNC-PAAm. gel.. The. symbols. are. as. follows:. (a). (●). q BNC-PAAm ;.
(■) q BNC ,. (▲) q ligament ;. (○). E BNC-AAm ;. (□). E BNC ,. ( ). E ligament ;. (b). (●). σ F BNC/PAAm;. (■). σ F BNC;.
(▲) σ F .ligament;.(○) ε F BNC-PAAm;.(□).ε F BNC;.( ).ε F .ligament..(Reproduced.with.permission.
of.Hagiwara.et.al..2010.)
for. the. cross-linker. to. improve. the. tensile. strength. performance. of. the.
BNC-PAAm. DN. gel.. This. value. is. in. agreement. with. the. concentration. of.
cross-linker.for.any.DN.gel.synthesized.by.the.DN.method.(Gong.et.al..2003)..
The. compressive. moduli. of. BNC-PAAm. DN. gels. increased. with. increasing. MBAA. concentration. (Hagiwara. et. al.. 2010).. The. compressive. fracture.
stress,.σ F ,.increased.substantially.in.the.BNC-PAAm.DN.gels.with.increasing. MBAA. concentration.. The. maximum. tensile. and. compressive. fracture.
stress. was. observed. to. be. about. 3.5. and. 6.5. MPa,. respectively,. at. 5. mol%.
MBAA.concentration,.similar.to.the.compressive.and.tensile.fracture.stress.
of.the.BNC-gelatin.DN.gel.system.discussed.earlier.(Nakayama.et.al..2004)..
It.should.be.noted.that.these.values.are.still.lower.than.the.tensile.fracture.
stress.of.ligament.(σ F .=.39.MPa;.Woo.et.al..2004).and.the.compressive.fracture.
stress.of.articular.cartilage.(McCutchen.1978).
Effect of Water Content
In.order.to.investigate.whether.swelling.is.a.universal.parameter,.the.relationship.between.swelling.and.the.mechanical.properties.of.BNC-PAAm.DN.gels.
prepared.at.different.concentrations.of.AAm.(1–4.M).and.MBAA.(0–5 mol%).
were. investigated.. The. relationships. of. tensile. and. compressive. modulus,.
and.between.tensile.and.compressive.fracture.stress.and.strain,.are.plotted.
against.swelling.on.a.logarithmic.graph,.which.is.useful.to.elucidate.the.correlation.over.a.wide.range.of.these.parameters.(Figure 4.7)..In.Figures 4.7a.and.
4.7b,.it.can.be.seen.that.the.tensile.and.compressive.modulus.of.the.DN.gel.