Surface Modification of Coatings through Self-Stratification
Dean C. Webster, Rajan B. Bodkhe, Stacy Sommer, Robert J. Pieper
North Dakota State University
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Ship Hull Coatings
Consequences of Biofouling: • Increased drag • Increased fuel consumption • Increased cost
• Fuel, maintenance • Reduction in speed, maneuverability • Increased air pollution • Transport of non-native species
Mitigating Biofouling: • Toxic Coatings
• Ecological consequences • Non-toxic Coatings
• Fouling-release coatings • Hull Cleaning/Grooming
• Hard coating
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Operational Impact of Fouling
Condition ∆ Shaft Power %∆ Shaft Power
Hydraulically smooth surface -- --
Typical as applied AF coating 50 2%
Deteriorated coating or light slime 250 11%
Heavy slime 458 21%
Small calcareous fouling or weed 781 35%
Medium calcareous fouling 1200 54%
Heavy calcareous fouling 1908 86%
Simulations for a Oliver Hazard Perry Class Frigate (FFG-7) Power required to maintain 15 knots
Schultz, MP, Biofouling, 23(5), 331-341
Even low amounts of fouling can result in significant power penalties
http://www.fas.org/programs/ssp/man/uswpns/navy/surfacewarfare/FFG7_oliverhazardperry.html
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Fouling-Release Coatings Organisms only weakly adhere to coating surface
Silicone Elastomer Properties: Low Surface Energy Stable Surface Energy Low Modulus
Toughness Good Adhesion to Primer
Brady, JCT, 2000, 72 (900), 45-56
Is there an optimum surface energy for low bioadhesion?
What role does modulus play?
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The Concept: Self-stratified Coating
Epoxy Primer
PDMS
Polyurethane
• PDMS Low Surface Energy • Polyurethane Tough • Polyurethane Good Adhesion • Crosslinking Stable Under Immersion
N=C=O
N=C=O O=C=N
NH2 H2N
OH
OH
HO
Polyol
PDMS
Polyisocyanate
Solvent(s) Catalyst
H2N
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Large Compositional Diversity Poly-
isocyanate
Polyol
Siloxane
Solvents
Catalyst Additives
CH2
Si O Si CH2
NH2NH2 33 m
NH
OO
H NH
OO
HCH2
Si O Si CH2
33 n
n
m
CH2
Si O Si CH2
OHOH 33 m
N
N
N
O
OO
RR
RN C O
N C ONCO CH3
CH3 CH3
CH2 6
R= IDT
HDT
*
O O
OH
R Ra
b
O OR
O
OOH
O
OOH
O
OOH
n
n
n
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High Throughput Screening Workflow
Design
Polymer Synthesis
Polymer Screening
Coating Formulation
Coating Deposition
Coating Screening
Data Analysis
Database
Caprolactone units/amine0 1 2 3 4
10
15
20
25
30
35
40
45
50
Biological Laboratory Assays
Determine fouling-release performance of experimental coatings
Ulva linza U. Birmingham
Navicula incerta
(Amphi)balanus amphitrite
Marine Bacteria Marine Algae Barnacle
C. lytica H. pacifica
Settlement and fouling-release Reattachment strength
Used to downselect experimental coatings for field testing
Cassé, et al. Biofouling 2007 23, 121 – 130 Stafslien, et al. Biofouling 2007, 23, 45-54 Stafslien, et al. Biofouling 2007, 23, 37-44
Rittschof, et al. Biofouling 2008 24(1) 1–9
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PDMS-PU Coating Systems
N=C=O
N=C=O O=C=N
NH2 H2N
OH
OH
HO
Polyol
PDMS
Polyisocyanate
Solvent(s) Catalyst
H2N
PDMS – 30k MW Monofunctional or Difunctional
IPDI-based crosslinker
Acrylic or Polyester polyol
WCA for all coatings > 100° Tensile modulus: ~400-700 MPa
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Field Testing
0
5
10
15
20
25
30
PCL-M10 PCL-M20 PCL-D10 PCL-D20 ACR-M10 ACR-M20 INT700
Aver
age B
arna
cle A
dhes
ion
(psi)
Florida – Barnacle Adhesion – 76 Days
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Criti
cal R
emov
al St
ress
(N/m
m2 )
15
15
23
17
30
3
2
3
California – Barnacle Adhesion 6 Months Immersion
Siloxane-polyurethane coatings can have similar release properties to commercial silicone FRC
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Underwater Hull Cleaning
• A Coating Cleanability Test at Port Canaveral
Mini Pamper
Hand Brush
SCAMP
Cavidyne
Coatings toughness demonstrated
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A Challenge 1 2 3 4 5 6 7 8
DC T2
IS 7
00
0
20
40
60
80
100
% R
emov
al
Coating ID
2 3 4 5 6 7 8
PU DC T2
IS 7
00
0
20
40
60
80
100
% R
emov
al
Coating ID
18 kPa 67 kPa 111 kPa
N. incerta - diatom Ulva linza – green algae
Sommer, et al., Biofouling, 26, 961-972 (2010).
Organisms use different adhesives Challenging to design a coating having low adhesion for all
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Amphiphilic Coatings Polymers such as PEG and poly(sulfobetaine) are known to be protein resistant Combine with hydrophobic polymer to generate amphiphilic surfaces
Figure 9. Percent removal of 7 day old sporelings of Ulva from amphiphilic coatings 4 plotted as a function of surface water pressure (kPa). Coatings were exposed to a 5 range of different surface pressures from the water jet. PDMSe is a reference sample composed of SilasticR 6 T2 and SEBS is a MD6945 SEBS control.
Ulva sporeleings removal
Figure 10. Final density of attached diatoms on amphiphilic coatings after gentle 4 washing and exposure to a shear stress of 52 Pa. Bars show 95% confidence limits.
Navicula settlement
Sundaraman, et al., ACS Appl. Mater. Int., 2011, 3, 3366–3374, DOI: 10.1021/am200529u.
Ober Group, Cornell University
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Photopolymerized Amphiphilic Coatings
Wang, et al., Langmuir, 2011, 27,10365–10369, DOI: 10.1021/la202427z
DeSimone Group – University of North Carolina
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Zwitterionic Surfaces
Ulva removal
Navicula settlement
Zhang, et al., Langmuir, 2009, 25 , 13516–13521
Shaoyi Jiang Group, University of Washington
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Self-Stratified Amphiphilic Surfaces
X X
PDMS stratifies to surfaces - Low surface energy
X X X X
If we attach hydrophilic groups to the PDMS, can we create an amphiphilic surface on the polyurethane?
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Stratified Acid Functional Siloxane-polyurethane Coatings
Carboxylic Acid Groups
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Synthesis of PDMS with Orthogonal Acid Groups
Si OSi
OSiO
Si
OSi O
Si
OSiO
Si
O++ H2N.(CH2)3.Si
CH3
CH3
O Si.(CH2)3.NH2
CH3
CH3
D4vi D4
BAPTMDS
Benzyltrimethylammoniumhydroxide80 0C
H2N.(CH2)3.Si
CH3
CH3
O Si
CH3
O Si O
CH3
CH3
Si.(CH2)3.NH2
nCH3
CH3
Tolueneexcess.HSCH2CH2COOH
AIBN
H2N.(CH2)3.Si
CH3
CH3
O Si
CH3
O Si O
CH3
CH3
Si.(CH2)3.NH2
m n CH3
CH3
SCOOH
m
m n
APT-PDMVS
Acid functional siloxane polymer
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Acid Functional Siloxane –polyurethane Coatings
OH
OH
HO
Polyol
Acid functional PDMS
N=C=O
N=C=O O=C=N
Polyisocyanate
Solvent(s) Catalyst
NH2 H2N
COOH
-COOH groups
Substrate polyurethane matrix
Self- stratified Siloxane-polyurethane Coatings
Moles of D4 Moles of D4V Target Mn g/mole
% Weight content
Coatings IDs
75 25 5000 10 A1-10%
75 25 5000 20 A1-20%
50 50 5000 10 A2-10%
50 50 5000 20 A2-20%
75 25 10000 10 A3-10%
75 25 10000 20 A3-20%
50 50 10000 10 A4-10%
50 50 10000 20 A4-20%
100 0 10000 10 D1-10%
100 0 10000 20 D1-20%
100 0 20000 10 D2-10%
100 0 20000 20 D2-20%
Acid Functional Coatings (PDMS-A)
PDMS-A
PDMS
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Confocal Raman Microscopy
1000 2000 3000
Inte
nsity
Si-O-Si
C-S
50 100
5000
10000
15000
20000
25000
Thickness (µm)
C-H Si-O-Si
Presence of –COOH on surface demonstrated
4000
1000
12000
4000
9000
Photons of monochromatic light – absorbed and reemitted Intensity of bands is proportional to concentration of molecules
Quantitative Analysis: Compositional gradients as a depth profile
0
C=O C=O
C=O
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Hydrophilicity of Coatings
Presence of – COOH on surface
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Navicula incerta removal at 20 PSI
Biofouling Performance
PDMS-A PDMS Standards
Improved performance of PDMS-A coatings over PDMS and silicone standards
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Biofouling Performance
Halomonas pacifica removal at 25 PSI Cytophaga lytica removal at 20 PSI
C. lytica and H. pacifica performance comparable to siloxane and silicone standards
PDMS-A PDMS Standards PDMS-A PDMS Standards
Biofouling Performance Ulva
Ulva adheres well to acid functional surfaces
University of Birmingham, UK
PDMS-A PDMS Standards
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Biofouling Performance Barnacle adhesion strength
Barnacles adhere well to acid functional surfaces
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Substrate Coating matrix
PDMS Poly(SBMA) Poly(SBMA)
Higher concentration of poly(SBMA) on the surface
N=C=O
N=C=O O=C=N
Polyisocyanate
Solvent(s) Catalyst
Acrylic Polyol80 % BA 20 % HEA
Poly(sulfobetaine methacrylate) – PDMS Block Copolymers
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H2N Si O Si O Si NH2
+
triethylamine, 0-200 C
APT-PDMS 875
Bifunctional ATRP macroinitiator
O
ON+ SO3
-
n
SBMA
Cu(I)BrbpyRT
OBr
BrO
OOH
O Br
OO
O
+
NH
Si O Si O Si NHn
Michael Addition
OO
O
O
OO
O
O
BrBr
NH
Si O Si O Si NHn
OO
O
OO
O
OO
O
N+
SO3-
mO
O
N+
SO3-
m
Siloxane zwitterionic triblock copolymers using ATRP
Poly(SBMA)-PDMS-Poly(SBMA)
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PDMS chain lengthg/mole
SBMA chain lengthg/mole
CoatingsID
245 5000 2.5K-250-2.5
875 5000 2.5K-875-2.5
5000 5000 2.5K-5K-2.5
245 10000 5K-250-5K
875 10000 5K-875-5K
5000 10000 5K-5K-5K
0 0 ACR-PU
10000 0 10K-D-10%
Zwitterionic Amphiphilic Siloxane-polyurethane Coatings
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Water Contact Angle of Coatings
Water contact angle data indicates self stratification
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Leachates were non toxic to the growth of organism
Leachate Toxicity to the growth of organism C. lytica
Biofouling Performance
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Biofouling Performance
Improved performance of zwitterionic coatings over PDMS and silicone standards
Navicula incerta removal at 20 PSI
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Biofouling Performance
Excellent C. lytica and H. pacifica performance Better removal than silicone standard
Cytophaga lytica removal at 20 PSI Halomonas pacifica removal at 25 PSI
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Biofouling Performance Ulva removal at 111 kPa
Ulva adheres strongly to zwitterionic siloxane-polyurethane coatings
University of Birmingham, UK
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Biofouling Performance Barnacle adhesion strength
Barnacles showed better performance than acid functional coatings Performance comparable to siloxane and silicone standards
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Conclusions
• Self-stratification is a viable approach to fouling-release coatings
• Self-stratification can be used to form amphiphilic surfaces
• Further tuning of compositions needed • Some selected samples are in field
testing
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Acknowledgements
• GRAs – Abdullah Ekin – Robert Pieper – Chavanin Siripirom – Stacy Sommer – Rajan Bodkhe
• CMRL – Bret Chisholm – David Christianson – James Bahr – Christy Gallagher-Lien – Plus many others…
• Collaborators – University of Birmingham
• James Callow, Maureen Callow, Franck Cassé, Stephanie Thompson – Florida Institute of Technology
• Geoff Swain, Emily Ralston – University of Hawaii – Mike Hadfield, Brian Nedved – CalPoly SLO – Dean Wendt, Lenora Brewer – University of Singapore – Serena Teo, Gary Dickenson
• Office of Naval Research
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Questions?
Center for Nanoscale Science and Engineering
Department of Coatings and Polymeric Materials
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