Special Topics on Materials Chemistry

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Special Topics on Materials Chemistry ? ? ?
? Part IIIB Conducting polymers ? ? ? ? ?
? ? ? ?   ? ? ? ? ? ??
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Conducting Polymers
Polyaromatics
(aromatic vinyl)
Polyheteroaromatics
(aromatic lone pair e)
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Polymerization of aniline
APS Ammonium persulfate (NH4)2
S2O8 1.25 equiv. gives the best yield Low pH
gives the best quality Polymerization induction
time 1-5 min Obtained green powder (doped form)
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Interconversion between Various Redox Forms of
Polyaniline
LB
EB
PB
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Cyclovoltammetry (CV) curve of polyaniline
LB ? EB
EB ? PB
Oxidation Cycle ?
? Reduction cycle
Pani is an ideal material for electrochromic
display
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a)
b)
c)
a) Easier to be air oxidized b) Very stable
in air c) Susceptible to hydrolytic cleavage
and crosslinking reactions
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UV-vis Spectra of polyaniline of different
oxidation states
?-?
exciton
?
?
???
exciton
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?1-6-1-2 ????(electron transfer)??? exciton
???????
Benzenoid ring ? ? Quinoid ring ?
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Protonic Acid Doping of Pani
Polaron lattice
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Pani-Sol-P3.ppt
LITERATURE REPORTED SOLVENTS FOR POLYANILINE
Doped, Conductive PAni
Sulfuric Acid
Undoped, Neutral PAni
NMP DMF DMSO
Sulfuric Acid, Formic Acid, Acetic Acid
Common processes for making Pani articles
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Syntheses of Substituted-Polyanilines via the
Conventional Oxidative Polymerization Method
HX
HX
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CP-Sol-P1.ppt
Solution Processing Chemistry In-Situ Dedoping
and Redoping Method
Solvent R3N
Conductive, Green Powder
Blue Solution
Conductive, Green
Blue Films, Coatings, Fibers
C.C. Han et.al.
(Non-Conductive)
World Patent No. WO 9218572 A2 921029
(1992) World Patent No. WO 9211644 A1 920709
(1992) World Patent No. WO 9211645 A1 920709
(1992) European Patent No. EP 0563281 A1 931006
(1993) European Patent No. EP 0563289 A1 931006
(1993) US patent 5,278,213 (1994) European Patent
No. EP 0581886 A1 940209 (1994)
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Solubility Modification via Dopant Moieties
HX

Neutral
Conductive
C. C. Han
MRS Meeting, December 1991 University of
Polytech, Brooklyn, December, 1991 University of
Rhode Island, April 1992 World Patent No. WO
9305519 A1 930318 (1993) European Patent No. EP
0601105 A1 940615 (1994).
"Solubility Modification of Conductive Codjugated
Backbone Polymers via the Dopant Moieties."
A. Heeger et.al., ICSM 1992, August
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Pani-Sol-P4.ppt
In Situ Dedoping / Redoping Solution Processing
Technique
Dual Function Lewis Base
NR3 Piperidine, Pyrrolidine, Morpholine,
Picoline Butyl amine, Propyl amine,
Ethylenediamine Imidazole,
Pyrrolidinone, HMPA, .....etc
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1. Good quality film can be prepared from these
amine solutions 2. However, the color of the
amine solution changed gradually from
blue to purple during the storage,
showing degrarded conductivity
Concurrent Reduction and Substitution
Emeraldine Base
Substituted Leucoemeraldine Base
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CRS-Mech3.ppt
Results of Control Experiments
Faster rate
Emeraldine
No reaction
Emeraldine
No reaction
Leucoemeraldine
Twice more substituents
Pernigraniline
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CRS-Mech1.ppt
Proposed Mechanism for Concurrent Reduction and
Substitution
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Concurrent reduction and substitution (?????????)
Actually, RSH reacts at least thousand times
faster than amine
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Mechanism for the CRS reaction
Although C-S is much weaker than C-H bond, the
gain in aromaticity stabilization help to promote
the reaction
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Preparation of copolymers by the oxidative
copolymerization (OCP) method

• Conductivity reduction
• Probably caused by the electronic effect of SR,
• instead of the steric hindrance effect
• The competing electronic influence vs NH
• on the placement of the next joined
  repeat unit

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Conductivity of copolymers of aniline and
ethylaniline
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Syntheses of Pani-SR via the CRS route
(S/cm) -H 2-3 -SC2H5
1-2 -SC3H7 2-3 -SC4H8 3-5 -SC8H17
7-9 -SC12H25 7-9
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UV-vis?????? CRS ????

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MPS-Pan is much more conductive than S-Pan
(S-Pan)
e. w. group
(MPS-Pan)
e. d. group
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Possible reaction sites
SO3
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MPS-Pan is thermally much more stable than S-Pan
MPS-Pan
Ti Tos
Tmaj MPS-Pan gt260 270 470 S-Pan
185 230 273
S-Pan

• The conductivity of S-Pan actually decreases
• with its storage time (even at RT)

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Table 2. S/N atomic ratios of MPS-Pan and S-Pan
after heated at different
temperatures
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The origin for the high thermal stability of
MPS-Pan
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Corrosion Protection Based on Polyaniline
In fact, Pani contains enormous number of redox
states ? ? 2n
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CV curve of Polyaniline (in 0.5 M H2SO4)
most stable states in air (EB form) (?0.3 - 0.55
V)
LB ? EB
EB ? PB
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Passivation of steel in 2N H2SO4
SS-430 (-0.2 to 1.00 V) passivation region
S-1018 (0.50 to 0.95 V) passivation region
Pani
MacDiarmid, Synthetic Metals 78 (1996) 103-110
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Corrosion of iron
e
Fe
Fe2
e
e
Fe
Fe2
e
e
Fe2
Fe
e
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Electrochemical Passivation Regions
Type of iron passivation region
Passive state current
(V)
(mA/cm2) Fe wire (99.99) 0.55 to
1.15 0.5 Fe strip
(99.87) 0.50 to 0.95
2.03 S-1018
0.50 to 0.95
30 SS-304 -0.1 to
0.85 0.0014 SS-410
0.1 to 1.00
0.0047 SS-430
-0.2 to 1.00
0.095
MacDiarmid, Synthetic Metals 78 (1996) 103-110
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Passivation with Pani for metals (e.g., iron,
steel, Cu, Al) corrosion potential shifted in the
direction of nobel metals
St-37 (Iron)
St-37/Pani
V2A (steel)
Cu
V2A/Pani
Cu/Pani
Fe, Cu in 1 M NaCl SS in 0.1 M H2SO4
Corrosion I-V curves
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Wessling, Adv. Mater. (1994) , 6 , No.3 , P226
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Iron passivated with Pani of different coat
thickness (Pani was removed before the
electrochemical measurement)
Corrosion I-V curves (in 1 M NaCl)
0.3 µ
1.5 µ
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Wessling, Adv. Mater. (1994) , 6 , No.3 , P226
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Environmental testing for mild steel (in Kenedy
Space Center for 7 months)
PU/Pani TCNQ or PU/Pani TsOH
Pani works effectively for anti-corrosion
protection
PU
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Thompson, ACS polymer preprints 35 (1994) 265
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Mild steel in 0.1 N HCl (aq) for 8 weeks
Protective coat
Epoxy
Epoxy/ Pani TCNQ
Pani can also repair the scratch damage, similar
to Cr (VI)
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Thompson, ACS polymer preprints 35 (1994) 265
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???????????????
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Cr6?????
Cr6 conversion coating

• ???????????????(????)
• ?????????????(Cr6? Cr3)

Cr(OH)3
Cr6
Zn plating
Carbon steel
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????????????

• ?Cr6?????, Cr3???Cr6?????????
• Cr6??????????????,?????????????????????????,?????
  ????????, Cr3????????????,??????Cr6 ?
• ???????,?????????????????,??????????????????,?????
  ???,???????????,??Cr6????????????,?Cr3????????

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Corrosion monitoring of SS-430 in 0.1 N
HCl (polyphophoric acid / Pani EB)
SS-430 passivation region (-0.2 to 1.0 V)
MacDiarmid, Synthetic Metals 78 (1996) 103-110
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Pretreatment with chelating agents greatly
enhance the anticorrosion effect
Corrosion monitoring of SS-430 in 0.1 N HCl
Pretreatment Protection duration

(days) HFH3PO4/EB
11 Alizarin/EB
gt53 Chromotropic acid/EB gt51 Polyphophoric
acid/EB gt29
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MacDiarmid, Synthetic Metals 78 (1996) 103-110
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Pani undercoat also work for anticorrosion
protection
(Pani has a large protection throwing power)
Only the farthest edges show little or no
corrosion
all well passsivated
Pani undercoat
Throwing power 1.5 cm
passsivated
In the same humidity chamber (80 ? 48 h), the
unprotected samples were however all severely
corroded
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Epstein, Synthetic Metals 85 (1997) 1323-1326
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Iron plate in salt water or after one anodic
corrosion current measurement
uncoated
uncoated
Pani coated ? Passivation ? Remove
Pani ? Corrosion current measurement
Wessling, Adv. Mater. (1994) , 6 , No.3 , P226
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First phase of Pani passivation (an etching
step) (Pani was removed before SEM observation)
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Wessling, Adv. Mater. (1994) , 6 , No.3 , P226
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Second phase of passivation (deposition of thin
oxide layer)
oxide layer (?10-20 nm)
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Wessling, Adv. Mater. (1994) , 6 , No.3 , P226
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Subsequent phases of passivation (formation of
thick oxide layer)
oxide layer (?µm)
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Wessling, Adv. Mater. (1994) , 6 , No.3 , P226
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Pani protected cold rolled steel samples showed a
much slower growth rate for the Fe3O4 underlayer
loose layer
dense layer
Fe (CRS)
102 S/cm
35 Å
15 Å
The Fe3O4 layers remained at ?35 Å in 2 days
(without corrosion) and grown to ?85 Å in 7 days
(showing moderate corrosion) while the
unprotected control sample grew much thicker, to
?200 Å (in 2 days already severely corroded) and
to -500 Å (in 7 days)
Epstein, Synthetic Metals 85 (1997) 1323-1326
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Grain-boundaries pores model
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Robertson, Corrosion science vol.29 No.11/12
pp1275-1291(1989)
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Organic Field Effect Transistors
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Organic Light Emitting Devices
e
h
(cathode -)
-

(anode )
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Solar Cells
e
(anode -)
(cathode )
h
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?? ???????????????????? (Spanggaard and Krebs,
2004)
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Radar and EMI Shielding
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Field Smoothening in Cables
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Conducting Polymer Capacitors (high frequency)
-

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Conventional Liquid electrolyte MClO4 MPF6
MBF4 NR4PF6 Conducting Polymer electrolyte
transport electron only
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Through-hole Plating on Printed Circuit Boards
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Loudspeakers
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Antistatic Protective Bags
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Electrostatic Dissipation and Antistatic
Applications
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Welding of Plastics
1. Conducting polymer is heated by microwave
absorption 2. Use a powder mixture of polyaniline
and plastic
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Conducting Polymer Battery
p-doping store charge
n-doping store - charge
Low voltage
Higher voltage
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Electrochemical Polymer Actuator
Dimension change induced by doping as high as 10
doped and elongated
undoped and shrunk
undoped and shrunk
doped and elongated
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Electrochemical Sensors
Sensitive to lt 10-10 Coulombs of charge Response
time lt 100 µs Response to 10-15 mole of an oxidant
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Gas Separating Membranes