hydrophilization of fluoropolymers and siliconesmedia.mycrowdwisdom.com.s3.amazonaws.com/asc/2017...
TRANSCRIPT
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Hydrophilizationof Fluoropolymers and Silicones
Wei ChenMount Holyoke College
2017 Adhesive and Sealant Council Spring Meeting
Aknowledgements:• NSF, NIH, Dreyfus, ACS-PRF, MHC• Bryony Coupe, Mamle Quarmyne, Lien Nguyen, Akchheta Karki, Yan Yan
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Introduction• Low surface tensions of fluoropolymers and silicones
18-20 mN/m poor wetting and weak adhesion
• Common surface modification methods
aggressive treatments surface degradation and mixed functionalities
• Biopolymers spontaneously adsorb to fluoropolymers
hydrophobic interactions “fouling”
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I. Hydrophilization of Fluoropolymers
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Our Approachl Adsorption of amphiphilic, synthetic polymers to FEP/water interface
FEP
PolymerAdsorption
XX
XX
XX
H2O
( )n( )n
CO2H NH3+ Cl-
PAA PAH PVOH
( )n
OH
Variables studied-kinetics-concentration-ionic strength-number of steps
Coupe, B.; Chen, W. Macromolecules 2001, 34,1533.Chen, W. U.S. Patent 2007, 7179506.
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Contact Angle Analysis
1763PVOH (cast film)
1967FEP-PVOH 89 h
1763FEP-PVOH 24 h
1965FEP-PVOH 5 h
2071FEP-PVOH 2 h
2074FEP-PVOH 1 h
2283FEP-PVOH 30 min
2083FEP-PVOH 10 min
93117FEP
θR (°)θA (°)
Kinetic StudiesXPS Analysis
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Polymer
OHOH
OHOH
OHOH
H2O
FEP: -(CF2-CF2)m-(CF2-CF)n-CF3
PET: -(C(O)-Ph-C(O)-OCH2CH2O)n-
PMP:( )n
PVOH Adsorption: A General Approach to Hydrophilize Polymer Surfaces
PVOH
( )n
OH
Driving forces: • hydrophobic interactions • PVOH crystallization
117/9363/17
115/8958/16
77/55 40/13
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PVOH Thickness and Film Morphology
AFM: 3 x 3 μm; 10 nmθA/θR : 60-70°/10-20°Γ: 25-30 Å, continuous
Kozlov, M.; Quarmyne, M.; Chen, W.; McCarthy, T. J. Macromolecules 2003, 36, 6054.
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PVOH Stability Studies
FEP-PVOH
180o
Pressure-sensitive adhesive tape(3M no. 810)
XPS analyses indicated cohesive failure in FEP substrate
• Mechanical Integrity
• Hydrolytic Stability
Lightly crosslinked PVOH is stable in water and organic solvents.
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Derivatizations of -OH groups
PET
-OH
PET -O-C(O)-NH-S(O)2-Ph
O=C=N-S(O)2-Ph
+ [CH3(CH2)10-CO2]2SnBu2
O=C=N-CH2CH2Cl
+ [CH3(CH2)10-CO2]2SnBu2
O=C=N-(CH2)17CH3
[CH3(CH2)10-CO2]2SnBu2
x
x PET
-O
PET -OH
S=O-O
-Cl
SOCl2 (Major product)
(Minor product)
-OH groups in PVOH are 2°alcohols
CF3CF2CF2CF2I
+ Et3N
x
PET
-O
-OCHR
RCHO/H+
Cl-C(O)-CF2CF2CF3
PET
-O-C(O)-CF2CF2CF3
PET
-O-C(O)-C16H33
CH3(CH2)16-C(O)-Cl
+ pyridine
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PVOH to SiO2 and TiO2
Quarmyne, M.; Chen, W. Langmuir 2003, 19, 2533.
SiO2
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II. Hydrophilization of Silicones
- low Tg = -123 °C- hydrophobicity, γ = 20 mN/m- good gas permeability- excellent thermal stability- reactivity toward acids and bases- nontoxicity- low cost- optical transparency- “hydrophobic recovery”
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Hydrophobic Recovery
CH3 CH3 CH3 CH3
SiOx
Silicone
CH3 O CH3OH OH OH
O2 Δt
Hydrophobic Recovery: spontaneous- reorientation of surface hydrophilic groups- condensation of surface silanol groups- migration of low molecular weight (LMW) species from the bulk to the surface- in-situ generated surface cracks facilitating migration of LMW
Solvent extraction?
OH
Fritz, J. L.; Owen, M. J. J. Adhesion 1995, 54, 33.Kim, J.; Chaudhury, M. K.; Owen, M. J.; Orbeck, T. J. Colloid Interf. Sci. 2001, 244, 200.
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0
20
40
60
80
100
120
0 5 10 15 20 25 30 35Dyn
amic
con
tact
ang
le (°
)
Time (day)Adv (DVDH) Rec (DVDH) Adv (Sylgard) Rec (Sylgard)
CH3 CH3 CH3 CH3
SiOx
OH OH
O2
CH3CH3 CH3 CH3 CH3
Vacuum extraction
Vacuum Extraction: Reduce Hydrophobic Recovery
56°/39°
51°/38°
Nguyen, L.; Hang, M. et al. ACS Appl. Mater. Interfaces 2014, 6, 22876.
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PVOH Adsorption to Hydrophilize Silicones?
Wu, D.; Luo, Y.; Zhou, X.; Dai, Z.; Lin, B. Electrophoresis 2005, 26, 211.
OHOH
OHOH
OHOH
PVOHH2O
PDMS
• Contact angle and IR analyses: PVOH does NOT adsorb to PDMS
• Thickness analysis?
• AFM imaging?
X
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PDMS Substrates
Krumpfer, J. W.; McCarthy, T. J. Langmuir 2011, 27, 11514.
React PDMS (2 kDa, 9 kDa, 17 kDa, 49 kDa, 116 kDa) to Si wafers
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Experimental Protocols1. Clean wafers with O2 plasma
2. Drop cast PDMSon wafers
3. React PDMSat 100 °C for 24 h
5. Adsorb PVOHat r. t. for 24 h
4. Dissolve PVOHat 95 °C
• Contact Angle Goniometry• Ellipsometry• Optical Microscopy• Atomic Force Microscopy• Transmission Electron Microscopy
Si/SiO2
OHOHOHOH
Si(CH3)2Si(CH3)2Si(CH3)2Si(CH3)2
OHOHOHOH
O2 PDMS PVOHPDMS
PVOH
PDMS
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RMS(nm) 0.2 0.3 0.3 0.4 0.5
θA/θR (°) 101/79 107/102 109 /104 109/95 113/98
AFM Images (size: 2.5 x 2.5 μm; height: 10 nm):
y = 0.5695x - 1.7781R² = 0.9636
0
0.2
0.4
0.6
0.8
1
1.2
3 3.5 4 4.5 5 5.5
Log
(thic
knes
s (n
m))
Log (molecular weight (Da))
PDMS Thickness α (MW)0.57
(1 to 11 nm)
PDMS2k PDMS9k PDMS17k PDMS49k PDMS116k
PDMS Substrates: thickness, roughness, hydrophobicity
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Karki, A.; Nguyen, L.; Sharma, B.; Yan, Y.; Chen,W. Langmuir 2016, 32, 3191.
PVOH99% Thin Film Morphologies on PDMS
500 μm
PDMS2k PDMS9k PDMS17k PDMS49k PDMS116k
AFM images (size: 20 x 20 μm):
Optical micrographs (scale bar: 500 μm):
20 nm 30 nm 40 nm 100 nm 400 nm
continuous honeycomb fractal (small to large)
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Film Formation Mechanism: In situ Optical Microscopy
19
In-situ Time Lapse Movie:
PVOH dewetting on higher MW PDMS: higher contact angles, more surface defects, more liquid-like.
PVOH99%-PDMS49kPVOH99%-PDMS2k
Dried Films:
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PVOH88% Thin Film Morphologies on PDMS
PDMS2k PDMS9k PDMS17k PDMS49k PDMS116k
AFM images (size: 20 x 20 μm):
Optical micrographs (scale bar: 200 μm):
20 nm 20 nm 30 nm 100 nm 100 nm
200 μm
continuous honeycomb droplets
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ZnO PSS with added salt PEO
Spin cast
Adsorption (collagen on PS)
Crystallization is requiredto form fractal features?
Chen, L. et al. J. Phys. Chem. C 2008, 112, 14286–14291.Haberko, J. et al. Synth. Met. 2010, 160, 2459–2466.Bi, W.; Teguh, J. S.; Yeow, E. K. L. Phys. Rev. Lett. 2009, 102, 048302.Jacquemart, I.et al. J. Colloid and Interface Sci. 2004, 278, 63–70.
Morphologies of Dewetted Thin Films: Fractals
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TEM Electron Diffraction of PVOH99% and PVOH88%
(200)(010)
(110) (010)
Crystallization of PVOH99% fractal morphology PVOH88% common droplets
SiO2
PVOH-PDMS2k
PVOH99% PVOH88%
Karki, A.; Nguyen, L.; Sharma, B.; Yan, Y.; Chen,W. Langmuir 2016, 32, 3191.
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Minimize PVOH Dewetting
• Minimized PVOH dewetting• Improved wettability
I. Light plasma oxidation of PDMSnm to create pinning sites
PVOH99%-PDMS49k PVOH88%-PDMS49k
plasma treated
PDMS49k: 109°/95° to 101°/80° (1 s O2 plasma), similar to PDMS2k.
native plasma treated native
Karki, A.; Nguyen, L.; Sharma, B.; Yan, Y.; Chen,W. Langmuir 2016, 32, 3191.
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Minimize PVOH DewettingII. Attach PDMS2k to PDMSμm films
SiO2
OHOHOHOH
O2Spin castDVDH
PVOH
PDMS
PDMS
OHOHOHOH
PDMS2k
100 °C
PDMS
OHOHOHOH
PVOH
PDMS
118°/97° 27°/12°
111°/91° 93°/20°
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Hydrophobic Recovery of PDMS-PVOHs?
• Negligible hydrophobic recovery• Vacuum extraction is not necessary PVOH is a good barrier layer
PVOH (continuous)on PDMS2k
PVOHon PDMS2k-PDMSμm
0
20
40
60
80
100
120
0 40 80 120 160Dyn
amic
Con
tact
ang
les
(°)
Time (h)0 40 80 120 160
Time (h)
PVOH (honeycomb)on O2-PDMS49k
0 20 40 60 80 100 120Time (h)
w/o vac extraction w/ vac extraction
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Conclusions
• PVOH spontaneously adsorbs to hydrophobic substrates from aqueous solution• hydrophobic interactions• crystallization of PVOH
• PVOH adsorption can be used to hydrophilize and functionalize fluoropolymers and silicones
• Hydrophilization of silicones has additional challenges: dewetting and hydrophobic recovery• light plasma oxidation and attachment of PDMS2k
• Vacuum extraction• PVOH layer is an effective barrier
OHOH
OHOH
OHOH
H2O
( )n
OH
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Thank you!
Questions?