Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble...
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Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September 10-11, 2019 Distribution A: Approved for Public Release Erick B. Iezzi , Eugene Camerino, Grant C. Daniels and James H. Wynne U.S. Naval Research Laboratory Chemistry Division Center for Corrosion Science and Engineering Washington, DC
Transcript of Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble...
Cross-Linked Coatings that Disassemble
with Fluoride Salts
2019 Coatings Trends and Technologies (CTT) ConferenceSeptember 10-11, 2019
Distribution A: Approved for Public Release
Erick B. Iezzi, Eugene Camerino, Grant C. Daniels and James H. Wynne
U.S. Naval Research LaboratoryChemistry Division
Center for Corrosion Science and EngineeringWashington, DC
CTT Conf. 2019 | 2
Cross-Linked Coatings
Distribution A: Approved for Public Release
Examples of Cross-Linked Coatings
Cross-linked coatings are three-dimensional networks that are formed from thechemical reaction of molecules. Unlike thermoplastic coatings, these networks areirreversible, cannot be solvated, and cannot be heated and reflowed.
Cross-linked network of tangled polymeric chains
Heat, UV
Covalent bond formation
Aerospace Automotive Marine Beverage
Reactive groups
Cross-linked networks provide unique thermal, mechanical, chemical, and UV-resistant properties
Liquid or soft-solid molecules
CTT Conf. 2019 | 3
Methods of Coating Degradation and Removal
Distribution A: Approved for Public Release
Chemical Strippers- methylene chloride - benzyl alcohol and blends
Abrasive Materials- mechanical sanders- abrasive blasting - hand-sanding
Thermal Treatments- laser ablation- incineration
Cross-linked coatings are degraded and removed using various methods
Issues:
• Coating removal methods are non-selective
• Commercial coatings are designed to be durable
and not easily degraded and removed
Coatings are difficult to degrade due to
their network of tangled chains and
covalent bonds
CTT Conf. 2019 | 4
Chemically Degradable Networks
Distribution A: Approved for Public Release
J. R. Griffith, ACS Symp. Ser. 1979, 114, 259.
Literature examples:
• Harsh conditions, such as strong acids, required to
facilitate bond cleavages
• Localized cleavages
• Uncontrolled degradation
• Structures don’t resemble those used in high-performance
coatings; lack required performance properties
Research on chemically degradable networks has focused on
designing materials with cleavable bonds and linkages
S. Buckwalter, J. Polym. Sci. Part A: Polym. Chem. 1996, 34, 249.
J. R. Griffith, ACS Symp. Ser. 1979, 114, 259.
J. M. García, Science 2014, 344, 732.
CTT Conf. 2019 | 5
Network Disassembly via Cascading Bond Cleavage
Distribution A: Approved for Public Release
Aliphatic Silyl-Containing Molecules
Internal Trigger
Cross-Linked NetworkDisassembled into
Small Molecules
chemical stimulus
Multi-directional disassembly
Loss of
volatiles
(+S)Cross-linking molecule
(-NCO terminal groups)
Newly formed
carbamate groups
-OH group
Goal: Develop networks that can disassemble via cascading bond cleavage when
treated with a selective and mild chemical stimulus
• break several bonds with a single reagent
• design with similar structures and linkages found in commercial coatings
(e.g., thermosetting polyurethanes, UV-curable urethane acrylates)
CTT Conf. 2019 | 6Distribution A: Approved for Public Release
DegradeAssemble
Illustration of Assembly and Degradation Concepts Using a Brick House
Network Disassembly via Cascading Bond Cleavage
CTT Conf. 2019 | 7
Synthesis of Trigger-Containing Molecules for Cross-Linked Networks
Distribution A: Approved for Public Release
Synthesis of aliphatic silyl-containing diols with different
electrophilicity (i.e., at silicon) and chain lengths
CTT Conf. 2019 | 8
Formation of Silyl-Containing Polyurethane Networks
Distribution A: Approved for Public Release
Reacted silyl-containing aliphatic diols with an aliphatic isocyanate trimer to form
highly cross-linked and rigid thermosets with good thermal stability
chemical
trigger
Diol ThermosetGel
FractionInitial Tg (C)
Onset Degradation Temp. (C)
D1 T1 (control) 0.97 40.7 320
D2 T2 0.92 68.1 298
D3 T3 0.97 40.6 291
D4 T4 1.00 45.0 286
D5 T5 0.99 51.6 289Networks were ~2 mm thick
TGA of Thermosets
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Control
0 100 200 300 400 500 600
0
20
40
60
80
100
We
igh
t (%
)
Temperature (°C)
T1
T2
T3
T4
T5
CTT Conf. 2019 | 9Distribution A: Approved for Public Release
Exposure of Networks to a Fluoride Ion Stimulus
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
1.0 M fluoride salt solutions in water and tetrahydrofuran (THF)
- tetrabutylammonium fluoride (TBAF)
- potassium fluoride (KF)
Silyl-containing polyurethane thermosets were immersed in static solutions of
fluoride salts for 24 hours and 1 week at room temperature
2 mm thick piece of thermoset
Silyl-containing polyurethane networkwith silicon atoms highlighted in red
Fluoride SaltDegradedNetwork
CTT Conf. 2019 | 10Distribution A: Approved for Public Release
500100015002500300035004000
0.00
0.38
0.76
1.14
0.00
0.46
0.92
1.38
0.00
0.41
0.82
1.23
0.00
0.36
0.72
1.08
0.00
0.37
0.74
1.11
Wavelength (cm-1)
Unexposed
T1
24h THF
24h KF (aq)
Ab
sro
ba
nce
(A
)
24h TBAF (aq)
24h TBAF (THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.44
0.88
1.320.00
0.43
0.86
1.29
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
Wavelength (cm-1)
Unexposed
24h THF
24h KF(aq)
Ab
sro
ba
nc
e (
A)
24h TBAF(aq)
T2
24h TBAF(THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
0.00
0.24
0.48
0.72
0.00
0.24
0.48
0.720.00
0.25
0.50
0.75
Wavelength (cm-1)
Unexposed
24h THF
24h KF (aq)
Ab
sro
ba
nc
e (
A)
24h TBAF (aq)
24h TBAF (THF)
T3
100030004000
0.00
0.43
0.86
1.29
0.00
0.42
0.84
1.26
0.00
0.29
0.58
0.870.00
0.23
0.46
0.69
0.00
0.23
0.46
0.69
Wavelength (cm-1)
Unexposed
T4
THF
24h KF(aq)
Ab
sro
ba
nc
e (
A)
24h TBAF(aq)
24h TBAF(THF)
A B
C D
500100015002500300035004000
0.00
0.38
0.76
1.14
0.00
0.46
0.92
1.38
0.00
0.41
0.82
1.23
0.00
0.36
0.72
1.08
0.00
0.37
0.74
1.11
Wavelength (cm-1)
Unexposed
T1
24h THF
24h KF (aq)
Ab
sro
ba
nce
(A
) 24h TBAF (aq)
24h TBAF (THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.44
0.88
1.320.00
0.43
0.86
1.29
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
Wavelength (cm-1)
Unexposed
24h THF
24h KF(aq)
Ab
sro
ba
nc
e (
A)
24h TBAF(aq)
T2
24h TBAF(THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
0.00
0.24
0.48
0.72
0.00
0.24
0.48
0.720.00
0.25
0.50
0.75
Wavelength (cm-1)
Unexposed
24h THF
24h KF (aq)
Ab
sro
ba
nc
e (
A)
24h TBAF (aq)
24h TBAF (THF)
T3
100030004000
0.00
0.43
0.86
1.29
0.00
0.42
0.84
1.26
0.00
0.29
0.58
0.870.00
0.23
0.46
0.69
0.00
0.23
0.46
0.69
Wavelength (cm-1)
Unexposed
T4
THF
24h KF(aq)
Ab
sro
ba
nc
e (
A)
24h TBAF(aq)
24h TBAF(THF)
A B
C D
500100015002500300035004000
0.00
0.38
0.76
1.14
0.00
0.46
0.92
1.38
0.00
0.41
0.82
1.23
0.00
0.36
0.72
1.08
0.00
0.37
0.74
1.11
Wavelength (cm-1)
Unexposed
T1
24h THF
24h KF (aq)
Ab
sro
ba
nce
(A
) 24h TBAF (aq)
24h TBAF (THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.44
0.88
1.320.00
0.43
0.86
1.29
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
Wavelength (cm-1)
Unexposed
24h THF
24h KF(aq)
Ab
sro
ba
nc
e (
A)
24h TBAF(aq)
T2
24h TBAF(THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
0.00
0.24
0.48
0.72
0.00
0.24
0.48
0.720.00
0.25
0.50
0.75
Wavelength (cm-1)
Unexposed
24h THF
24h KF (aq)
Ab
sro
ba
nc
e (
A)
24h TBAF (aq)
24h TBAF (THF)
T3
100030004000
0.00
0.43
0.86
1.29
0.00
0.42
0.84
1.26
0.00
0.29
0.58
0.870.00
0.23
0.46
0.69
0.00
0.23
0.46
0.69
Wavelength (cm-1)
Unexposed
T4
THF
24h KF(aq)
Ab
sro
ban
ce
(A
)
24h TBAF(aq)
24h TBAF(THF)
A B
C D
A
500100015002500300035004000
0.00
0.47
0.94
0.00
0.53
1.06
0.00
0.49
0.98
0.00
0.32
0.64
0.00
0.39
0.78
Wavelength (cm-1)
Unexposed
T5
24h THF
24h KF(aq)
24h TBAF(aq)
24h TBAF(THF)
Ab
sro
ba
nce
(A
)
500100015002500300035004000
0.00
0.38
0.76
1.14
0.00
0.46
0.92
1.38
0.00
0.41
0.82
1.23
0.00
0.36
0.72
1.08
0.00
0.37
0.74
1.11
Wavelength (cm-1)
Unexposed
T1
24h THF
24h KF (aq)
Ab
sro
ba
nce
(A
) 24h TBAF (aq)
24h TBAF (THF)
C D
IB
II
50 100 150 200
0.0000
0.0005
0.0010
Ion C
urr
ent
(mA
)
26 amu
44 amu
Weight %
d(Weight) / d(Time)
Time (min)
T2
20
30
40
50
60
Weig
ht
%
-1.5
0.0
1.5
3.0
d(W
eig
ht)
/ d
(Tim
e)
(%/m
in)
E F
T1
9.5 10.0 10.5 11.0
0
500000
1000000
1500000
10.164
4041.1
42.1
43.1
44.1
45 5455.1
56.1
57.1
73.1100
101
102.1
Tota
l Ion
Cou
nt
Time (min)
50 100
0
20
40
60
80
100
Rel
ativ
e ab
unda
nce
m/z
500100015002500300035004000
0.00
0.38
0.76
1.14
0.00
0.46
0.92
1.38
0.00
0.41
0.82
1.23
0.00
0.36
0.72
1.08
0.00
0.37
0.74
1.11
Wavelength (cm-1)
Unexposed
T1
24h THF
24h KF (aq)
Ab
sro
ba
nce
(A
) 24h TBAF (aq)
24h TBAF (THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.44
0.88
1.320.00
0.43
0.86
1.29
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
Wavelength (cm-1)
Unexposed
24h THF
24h KF(aq)
Ab
sro
ban
ce
(A
)
24h TBAF(aq)
T2
24h TBAF(THF)
500100015002500300035004000
0.00
0.39
0.78
1.17
0.00
0.39
0.78
1.17
0.00
0.24
0.48
0.72
0.00
0.24
0.48
0.720.00
0.25
0.50
0.75
Wavelength (cm-1)
Unexposed
24h THF
24h KF (aq)
Ab
sro
ban
ce
(A
)
24h TBAF (aq)
24h TBAF (THF)
T3
100030004000
0.00
0.43
0.86
1.29
0.00
0.42
0.84
1.26
0.00
0.29
0.58
0.870.00
0.23
0.46
0.69
0.00
0.23
0.46
0.69
Wavelength (cm-1)
Unexposed
T4
THF
24h KF(aq)
Ab
sro
ba
nc
e (
A)
24h TBAF(aq)
24h TBAF(THF)
A B
C D
Ab
so
rban
ce (
A)
Ab
so
rban
ce (
A)
Ab
so
rban
ce (
A)
Ab
so
rban
ce (
A)
Ab
so
rban
ce (
A)
Thermoset T1 (control) Thermoset T2 Thermoset T3
Thermoset T4 Thermoset T5
Chemical Analysis after Thermoset Exposure to Fluoride Salt Solutions for 24 Hours
Attenuated Total Reflectance Infrared (ATR-IR) Spectroscopy
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Si-F Si-F
Si-F Si-F
CTT Conf. 2019 | 11Distribution A: Approved for Public Release
Surface Roughness of Thermoset T5 After Exposure to Various Solutions for 24 Hours
0.0006.70813.4220.1326.8333.5440.2546.9653.6760.3867.0873.7980.5087.2193.92100.6107.3114.0120.8127.5134.2140.9147.6154.3161.0167.7174.4181.1187.8194.5201.3
100 µm
0.0006.22012.4418.6624.8831.1037.3243.5449.7655.9862.2068.4274.6480.8687.0893.3099.52105.7112.0118.2124.4130.6136.8143.1149.3155.5161.7167.9174.2180.4186.6
100 µm
I
IV
III
II
µm
µm
Unexposed
THF TBAF (THF)
TBAF (aq)
Chain in Thermoset T5
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Confocal Microscopy of Thermoset after Exposure
CTT Conf. 2019 | 12Distribution A: Approved for Public Release
Glass Transition Temperature of Thermosets After Exposure to Fluoride Salt Solutions for 24 Hours
1.04
-21.4
-23.4
-37.1
-44
T1 T2 T3 T4 T5-50
-40
-30
-20
-10
0
10
Tg for 24 h Exposure
[Exposed TBAF(THF) - Unexposed]
T
g (C
)
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Change () in thermoset Tg due to fluoride ion exposure
CTT Conf. 2019 | 13
Thermal and Chemical Analysis of Thermosets T2 and T5 After 24 Hours Immersion
Distribution A: Approved for Public Release
Analysis via Thermogravimetric Analysis / Mass Spectrometry (TGA-MS)
and Gas Chromatography (GC) / Mass Spectrometry (GC-MS)
40 60
0
20
40
60
80
100
Weig
ht
(%)
Sample Weight
d(Weight) / d(Time)
26 amu
44 amu
Temperature (°C)
0
2
4
d(W
eig
ht)
/ d
(Tim
e)
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
T2
Ion C
urr
ent (m
A)
30 35 40 45 50 55 60 65 70
20
40
60
80
100
T5
Weig
ht
(%)
Sample Weight
d(Weight) / d(Time)
26 amu
44 amu
Temperature (°C)
-2
0
2
4
6
d(W
eig
ht)
/ d
(Tim
e)
0.0000
0.0001
0.0002
0.0003
0.0004
Ion C
urr
ent (m
A)
Thermoset T2 Thermoset T5
9.5 10.0 10.5 11.0
0
500000
1000000
1500000
10.164
Tota
l Io
n C
oun
t
Time (min)
41.1
42.1
43.1
44.1
56.1
57.1
101
40 60 80 100 120 140 160 180 200
0
50
100
Rela
tive a
bundance
m/z
Ethylene + CO2
Ethylene + CO2
3-methyloxazolidin-2-one
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
CTT Conf. 2019 | 14Distribution A: Approved for Public Release
Mechanisms of Network Disassembly with Fluoride Salts
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Chain in Thermoset T4/T5
Chain in Thermoset T2/T3
Partially disassembled network withSi-F bonds highlighted in green
Cascadingdisassembly
Silyl-containing polyurethane networkwith silicon atoms highlighted in red
Fluoride Salt
CTT Conf. 2019 | 15Distribution A: Approved for Public Release
Glass Transition Temperature of Thermosets After Exposure to Fluoride Salt Solutions for 1 Week
-2.89
-31.7
-34.1
-51.2
0
T1 T2 T3 T4 T5-60
-50
-40
-30
-20
-10
0
Tg for 1 wk Exposure
[Exposed TBAF(THF) - Unexposed]
De
com
po
se
d
T
g (C
)
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Change () in thermoset Tg due to fluoride ion exposure
CTT Conf. 2019 | 16Distribution A: Approved for Public Release
Demonstrated that disassembly is:
• Selective – occurs on-demand with fluoride salts in organic solvent (e.g., 1 M TBAF (THF))
• Cascading – multiple bonds cleaved upon reaction with a single fluoride ion
• Controllable – time of disassembly can be tailored by modifying electrophilicity and chain length of silyl-diol
First example of a thermoset that disassembles via cascading bond cleavage
CompleteDisassembly
Immersion in Non-Stirred Liquids at Room Temperature
Complete Disassembly of a Silyl-Containing Polyurethane Thermoset
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
CTT Conf. 2019 | 17Distribution A: Approved for Public Release
No change in bond structure and minimal
change in Tg after 1 week of exposure
- good acid and base stability, unlike previously
reported degradable thermosets
Exposure of Silyl-Containing Polyurethane Thermosets to Strong Acid and Base
500100015002500300035004000
0.00
0.35
0.70
1.05
0.00
0.36
0.72
1.08
0.00
0.48
0.96
1.44
0.00
0.40
0.80
1.20
0.00
0.44
0.88
1.32
Wavelength (cm-1)
Unexposed
24h NaOH(aq)
24h HCl(aq)
Ab
sro
ba
nce
(A
)
1wk NaOH(aq)
1wk HCl(aq)
T5
Ab
so
rban
ce (
A)
Thermoset T5
-2.45
-9.37
16.10
-1.30
-2.49
T1 T2 T3 T4 T5-20
-10
0
10
20
Tg for 1 wk Exposure
[Exposed HCl(aq) - Unexposed]
T
g (C
)
-1.71
-12.80
4.97
0.09
-5.29
T1 T2 T3 T4 T5
-15
-10
-5
0
5
10
15
20
Tg for 1 wk Exposure
[Exposed NaOH(aq) - Unexposed]
T
g (C
)
Stimuli: 1.0 M HCl and 1.0 M NaOH Aqueous Solutions
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
CTT Conf. 2019 | 18Distribution A: Approved for Public Release
Reduced cross-links resulted in lower Tgs and enabled faster disassembly
Diol Thermoset Initial Tg (°C)Tg (°C) after 24 hours
in THFTg (°C) after 24 hours
in 1 M TBAF (THF)Tg (°C) after 1 week in 1 M TBAF (THF)
D1 T6 (control) 26.85 25.71 22.82 26.83
D2 T7 56.55 55.20 17.5 8.21
D3 T8 48.84 44.85 -26.17 Disassembled
D4 T9 36.57 37.31 Disassembled N/A
D5 T10 43.4 45.31 Disassembled N/A
Thermosets T6-T10
Polyurethane Thermosets Based on Isocyanate Mixtures
Thermosets with Reduced Cross-Link Density and Immersion in Fluoride Salt Solutions
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Immersion of Thermosets in Static THF Solutions
50/50 mixture of di- and tri-isocyanates
CTT Conf. 2019 | 19Distribution A: Approved for Public Release
Thermosets with Reduced Cross-Link Density and Immersion in Fluoride Salt Solutions
Disassembly occurs in alternative solvents, although slower than in THF
Diol Thermoset Initial Tg (°C)Tg (°C) after 24 hours
in 1 M TBAF (Acetone)Tg (°C) after 24 hours
in 1 M TBAF (PM Acetate)
D1 T6 (control) 26.85 16.83 24.62
D2 T7 56.55 43.04 50.62
D3 T8 48.84 -6.18 45.67
D4 T9 36.57 Disassembled -4.00
D5 T10 43.4 -25.75 3.98
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
Immersion of Thermosets in Static Solutions of Acetone and PM Acetate
Thermosets T6-T10
50/50 mixture of di- and tri-isocyanates
Polyurethane Thermosets Based on Isocyanate Mixtures
Tg (°C) after 1 week in 1 M TBAF (Acetone)
Tg (°C) after 1 week in 1 M TBAF (PM Acetate)
15.34 20.01
18.57 38.61
-10.79 23.41
N/A -12.10
Disassembled -31.75
CTT Conf. 2019 | 20
Polyurethane Thermoset Based on Aliphatic Silyl Triol
Distribution A: Approved for Public Release
Aliphatic Silyl-Containing Triol and Thermosetting Network Thereof
Gel Fraction
Initial Tg (C)(via DSC)
Onset Degradation Temp. (C)
0.97 61.2 304
Thermoset T11
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
CTT Conf. 2019 | 21Distribution A: Approved for Public Release
Thermosets in static 1.0 M TBAF (THF) and 1.0 M TBAF (acetone)
completely disassembled in 1.5 days and 3 days, respectively
Mechanism of chain disassembly
upon reaction with fluoride ion
Exposure of Silyl Triol Based Polyurethane Thermosets to Fluoride Salt Solutions
Fluoride Salts: Tetrabutylammonium fluoride (TBAF) and Cesium Fluoride (CsF)
-5.35
-7.43 -7.22
-15.03
-16.01
THF TBAF(aq)CsF(THF)
TBAF(Acetone)TBAF(THF)
-25
-20
-15
-10
-5
0
Tg for 24 h Exposure of Phenyl Triol-HDI
[Exposed - Unexposed]
T
g (C
)
24 hour
Ab
so
rban
ce (
A)
-4.77-3.91
-10.45
THF TBAF(aq) CsF(THF)
-15
-10
-5
0
Tg for 1 wk Exposure of Phenyl Triol-HDI
[Exposed - Unexposed]
T
g (C
)
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
CTT Conf. 2019 | 22
Summary
Distribution A: Approved for Public Release
Developed Novel Silyl-Containing Polyurethane Networks
That Selectively Disassembled in Static Fluoride Salt Solutions
• Disassembly occurs via cascading bond cleavage and in multiple directions
• Fluoride salts are relatively non-hazardous compared to methylene chloride
• Thermosets were resistant to disassembly in chloride salts; strong acid & base
• Time of network disassembly can be controlled by modifying the electrophilicity
and structure of the silyl diol
• Disassembly can occur in different solvents
• Technology has potential applications as selectively degradable topcoats and
primers in the coating industry
CTT Conf. 2019 | 23
Acknowledgements
Distribution A: Approved for Public Release
Funding Provided By The Naval Research Laboratory’s Base Program
CTT Conf. 2019 | 24
BACK-UP SLIDES
Distribution A: Approved for Public Release
CTT Conf. 2019 | 25Distribution A: Approved for Public Release
Surface Wetting and Swelling of Thermosetting Polyurethane Networks
T1 T2 T3 T4 T5
0
10
20
30
40
50
60
H2O
THF
Sw
elli
ng (
%)
Thermoset
Surface wetting and swelling experiments with water and tetrahydrofuran (THF)
G. C. Daniels, E. Camerino, J. H. Wynne and E. Iezzi, Mater. Horiz. 2018, 5, 831-836.
E. B. Iezzi, E. Camerino, G. Daniels and J. H. Wynne, U.S. Patent Appl. 15/843,181.
S =(𝑊𝑠−𝑊𝑑)
𝑊𝑑∗ 100
Greater swelling in THF
