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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