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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

Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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Page 1: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 2: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 3: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 4: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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.

Page 5: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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)

Page 6: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 7: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 8: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 9: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 10: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 11: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 12: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 13: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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.

Page 14: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 15: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 16: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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.

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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.

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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

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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

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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.

Page 21: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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.

Page 22: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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

Page 23: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

CTT Conf. 2019 | 23

Acknowledgements

Distribution A: Approved for Public Release

Funding Provided By The Naval Research Laboratory’s Base Program

Page 24: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

CTT Conf. 2019 | 24

BACK-UP SLIDES

Distribution A: Approved for Public Release

Page 25: Cross-Linked Coatings that Disassemble with Fluoride Salts...Cross-Linked Coatings that Disassemble with Fluoride Salts 2019 Coatings Trends and Technologies (CTT) Conference September

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