Figure 12.6
Bacterial Nanocellulose as a Structured Platform for Conductive Biopolymers 249
Conductivity/S/cm
0
0.00005
0.0001
0.00015
1:10
2.35E–04
1.34E–04
1:5
0.0002
0.00025
0.0003
3h
6h
9h
12h
24h
Polymerization Time
Figure 12.6
(See color insert.).Effects.of.the.reaction.time.on.the.electrical.conductivity.of.BNC/PAni.HCl.
composites.
doped. with. and. without. PTSA. were. 1.3. S/cm. and. 0.8. S/cm,. respectively..
Cyclic.voltammetry.used.to.measure.the.electrochemical.redox.properties.of.
the.BNC/PAni.sample.revealed.that.it.was.thermodynamically.stable.
Figure 12.6. shows. results. obtained. by. our. research. group. on. the. effect.
of. the. polymerization. time. on. the. electrical. conductivity. of. BNC/Ani·HCl.
. composites.. BNC. (from. Gluconacetobacter xylinus. ATCC. 53582). was. produced.as.described.elsewhere.(Lopes.et.al..2011)..One.hundred.milligrams.
solved.in.0.2 M HCl.at.room.temperature..Under.constant.stirring,.a.solution.of.APS.in.0.2.M.HCl.was.slowly.added,.thus.totaling.100.ml.of.volume.
. reaction..At.specific.intervals,.the.reaction.was.stopped.by.removing.demodified.BNC.from.the.reaction.media..This.was.followed.by.extensive.washing.
with.acidified.(0.2.M.HCl).distilled.water.and.freeze-drying..The.following.
molar.proportions.of.BNC:Ani.were.assayed:.1:1,.1:5,.and.1:10..Figure 12.6.also.
shows.a.control.disk.of.BNC.(white).and.a.modified.disk,.obtained.following.polymerization.with.Ani.(dark.green)..Hydrated.disks.had.an.average.
diameter.of.2.5.cm.and.a.thickness.of.about.5.mm,.on.average..The.electrical.
conductivity. of. the. composites. was. measured. at. room. temperature. by. the.
standard.four-probe.method..These.results.(Figure 12.6).showed.an.increasing.conductivity.with.increasing.amounts.of.the.conducting.monomer..The.
conductivity. of. the. composites. obtained. using. the. proportions. of. 1:1. were.
too. low. (data. not. shown).. In. the. remaining. cases,. conductivity. reached. a.
peak,.with.a.tendency.to.decrease.with.the.polymerization.time..According.
to.Yin.et.al..(1997),.with.the.increase.in.the.reaction.time,.PAni.units.in.the.
emeraldine.form.may.be.further.oxidized.to.the.pernigraniline.state,.which.
is.less.conductive,.thus.decreasing.the.conductivity..Qaiser.et.al..(2009).also.
reported. that. when. APS. was. used,. from. an. initially. dark. green. color,. the.
Bacterial Nanocellulose as a Structured Platform for Conductive Biopolymers 249
Conductivity/S/cm
0
0.00005
0.0001
0.00015
1:10
2.35E–04
1.34E–04
1:5
0.0002
0.00025
0.0003
3h
6h
9h
12h
24h
Polymerization Time
Figure 12.6
(See color insert.).Effects.of.the.reaction.time.on.the.electrical.conductivity.of.BNC/PAni.HCl.
composites.
doped. with. and. without. PTSA. were. 1.3. S/cm. and. 0.8. S/cm,. respectively..
Cyclic.voltammetry.used.to.measure.the.electrochemical.redox.properties.of.
the.BNC/PAni.sample.revealed.that.it.was.thermodynamically.stable.
Figure 12.6. shows. results. obtained. by. our. research. group. on. the. effect.
of. the. polymerization. time. on. the. electrical. conductivity. of. BNC/Ani·HCl.
. composites.. BNC. (from. Gluconacetobacter xylinus. ATCC. 53582). was. produced.as.described.elsewhere.(Lopes.et.al..2011)..One.hundred.milligrams.
solved.in.0.2 M HCl.at.room.temperature..Under.constant.stirring,.a.solution.of.APS.in.0.2.M.HCl.was.slowly.added,.thus.totaling.100.ml.of.volume.
. reaction..At.specific.intervals,.the.reaction.was.stopped.by.removing.demodified.BNC.from.the.reaction.media..This.was.followed.by.extensive.washing.
with.acidified.(0.2.M.HCl).distilled.water.and.freeze-drying..The.following.
molar.proportions.of.BNC:Ani.were.assayed:.1:1,.1:5,.and.1:10..Figure 12.6.also.
shows.a.control.disk.of.BNC.(white).and.a.modified.disk,.obtained.following.polymerization.with.Ani.(dark.green)..Hydrated.disks.had.an.average.
diameter.of.2.5.cm.and.a.thickness.of.about.5.mm,.on.average..The.electrical.
conductivity. of. the. composites. was. measured. at. room. temperature. by. the.
standard.four-probe.method..These.results.(Figure 12.6).showed.an.increasing.conductivity.with.increasing.amounts.of.the.conducting.monomer..The.
conductivity. of. the. composites. obtained. using. the. proportions. of. 1:1. were.
too. low. (data. not. shown).. In. the. remaining. cases,. conductivity. reached. a.
peak,.with.a.tendency.to.decrease.with.the.polymerization.time..According.
to.Yin.et.al..(1997),.with.the.increase.in.the.reaction.time,.PAni.units.in.the.
emeraldine.form.may.be.further.oxidized.to.the.pernigraniline.state,.which.
is.less.conductive,.thus.decreasing.the.conductivity..Qaiser.et.al..(2009).also.
reported. that. when. APS. was. used,. from. an. initially. dark. green. color,. the.