Elektrospray‐Abscheidung dünnerPolymerschichten
Thin polymer layers deposited by electrospray
J. Friedrich, K. Altmann, G. Hidde, R.‐D. Schulze, R. Mix,
Bundesanstalt für Materialforschung und –prüfung12200 Berlin
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Content
1. General Aspects to Polymer Surface Modification with(Monotype) Functional Groups
2. Principles of Dielectric Barrier Discharge (A-DBD)Atmospheric-Pressure Chemical Ionization (APCI)Electro Spray Ionization (ESI)
3. Modification of Polymer Surfaces with Monotype Functional Groups
4. Peel Strength of Aluminium Evaporated Layers fromModified Polyolefin Surfaces
5. Summary
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Polyolefin surfacesintroduction of reactive groups
Situation at the surface of polyolefins such as polyethylene or polypropylene-aliphatic structure (CH, CH2, CH3)-absence of any functional groups (OH, NH2, COOH….)-very weak interactions to polymers (dispersive forces-Heitler/London)-very weak adhesion-no possibility of selective reactions, such as introduction of functional groups-oxidative treatment occurs introduction of functional groups but also scissions of C-C bonds
Principal solutions:-(monosort) functionalization of polymer surface-deposition of adhesion-promoting
polymer layers with monosortfunctional groups
Applications:-adhesion-promotinglayers
-corrosion-inhibiting-biocompatible
Grant:DFG Fr975-24/1
OH
OH
OH
OH
OH
OH OH OH OH OH
OH OH OH OH OH
OH OH OH OH OH
deposited polymer layer containing functional groups
functional groups attached to macromolecules ofthe polymer substrate
functionalization
coverage withpolymer layer
polyolefin substrate
5/32
Metal‐polymer compositesadhesion promotion by flexible and water‐repellent spacer molecules
Br Br
Br Br N H
Si
HO
HO
Aluminium
polyolefinpolyolefinpolyolefin
OH
NH
Si
HO
HO OH
NH
Si
OH
HO OH
NH
Si
OHHOOH
Br2 plasma aminosilane
NH2 NH2NH2 NH2
N
Si
N
Si
N
Si
C
N
Si
OO O
HO
Aluminium
N
CH
CHO
N
CH
CHO
N
CH
CHO
N
CH
CHO
N
polyolefinplasma polymer
CH
C
N
CH
C
N
CH
CH
N
CH
polyolefinplasma polymer
polyolefinplasma polymer
polyolefin
OH
N
Si
N
Si
N
Si
C
N
Si
OO O
O
N
polyolefinplasma polymer
CH
C
N
CH
C
N
CH
CH
N
CH
O
Variant 1Attachment of functional groups onto polymer molecules
Variant 2Coating of polymer substrate by ultra‐thin adhesion promotingpolymer layers equippedwith functional groups
Goals:chemical bondingbetween metal and polymer along theinterface of metal‐polymer composites→ high adhesion→ high durability
Y. Huajie, R. Mix, J. Friedrich, J. Adhes. Sci. Technol. 25 (2011), in press
not peelable
not peelable
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Polyolefin surface modificationtechnically applied processes
laminating, coating, evaporation, sputtering
atmospheric‐pressurechemical oxyfluorination
low‐pressure plasmapretreatment
atmospheric DielectricBarrier Discharge (DBD)
flame treatment excimer‐irradiation laser‐irradiation
7/32
Principles of
Aerosol‐Dielectric Barrier Discharge (A‐DBD)
Atmospheric‐Pressure Chemical Ionization (APCI)
Electro Spray Ionization (ESI)
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New Atmospheric Deposition TechniquesDeposition of ultra‐thin adhesion‐promoting polymer films
polymer
coating
OH COOH OH O
polymer
coating
OH OH OH OH
Aerosol‐Dielectric BarrierDischarge (DBD)
Electro Spray Ionization(ESI)
metal‐capillary
spray cone
DBD‐plasma
polymer
polymer solution
polymer
coating
OH OH OH O
Atmospheric‐Pressure‐Chemical‐Ionization (APCI)
metal‐capillary
spray cone
DBD‐plasma
polymer
polymer solution
metal
high
voltage
metal capillary
spray cone
polymer
polymer solution
metall
metalmetal
polymer
OH COOH CHO O
Dielectric‐Barriere Discharge (DBD) in air ("Corona")
DBD‐plasma
polymer
actual technique new or advanced processes
OH OH OH OH OH OH
O2,N2
surface functionalizationwith different types of groups
substrate coverage with adhesion‐promoting (functional groups‐carrying) thinpolymer layers
high
voltage
gas drops
degradedmacromo-lecules
isolatedintactmacromo-lecules
9/32
ESI polymer layer depositionPolymer molecules are ionizedby high field strength and singularized.They are not exposed to any plasma. Therefore, degradation and oxidationdo not occur.
Basics of Electrospray Ionization (ESI)Aerosol‐DBD polymer layer depositionPolymeric coating material as well as polymer substratebecome activated but also partiallydegraded by the atmospheric DBDplasma. Drops of polymer solution aredeposited as film.
APCI polymer layer depositionPolymer molecules are ionizedby atmospheric corona plasma. Themacromolecules are singularized butpartially degraded.
Atmospheric‐pressure deposition of ultra‐thin (monomolecular) polymer films byelectrospray ionization (ESI)
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Electrospray Ionization (ESI) Deposition of Polymers
J. Magulick, M. M. Beerbom and R. Schlaf: "Investigation of Adenine, Uracil, and Ribose Phosphate Thin Films Preparedby Electrospray In‐Vacuum Deposition Using Photoemission Spectroscopy", Thin Solid Films 516 (9), pp.2396‐2400 (2008).
Vacuum deposition of mono‐molecular (bio) films by ESI
New plasmas for polymer surface functionalization, J. F. Friedrich, A. Meyer‐Plath, R. Mix, R.‐D. Schulze, R. Joshi, Proceed. ISPC‐18, Kyoto (2007); New plasmatechniques for polymer surface functionalization J. F. Friedrich, R. Mix, R.‐D. Schulze, A. Meyer‐Plath, R. Joshi, S. Wettmarshausen, Plasma Proc.& Polym. 5 (2008) 407‐423
Atmospheric‐pressure deposition of ultra‐thin (monomolecular) polymer filmsby aerosol Dielectric‐Barrier Discharge (DBD)
substrate
polymeragglomeration
polymermono layer
11/32
Solutions of either ionic or polar polymers were sprayed under applying of high‐voltage towards thecounter electrode (or substrate). Polar polymers were ionized by high field strength. Solvent evaporates, droplets shrink and charges converge. Equal charges repel under Coulomb explosion to smaller ionic droplets. The disintegration cascade forms charged isolated polymer ions. These non‐degraded ions were discharged at the counterelectrode and form a („monomolecular“) thin film.
ESI principle
solvent evaporation
shrinking of droplet diameter
isolatedmacromo-
lecules
drift of ions
depositedlayerFormation of multiple charged (non-
fragmented) macromolecular ions
←ESI-MSJ. FalkenhagenS. Weidner (I.3)
ESI-polymerlayer →deposition
13/32
Aerosol‐DBD treatment of polypropylene in airoxidation in presence of a soft air plasma at atmospheric pressure
0 2 4 6 8 10
0
2
4
6
8
10
12
14
16
after DBD treatmentand washing with ethanol
ox
ygen
con
cent
ratio
n [O
per
100
C]
energy density [J/cm2]
after DBD treatment
0 2 4 6 8 10
0
5
10
15
20
25
30
35
washed with ethanol
unwashed
polar component
surfa
ce e
nerg
y [m
J/m
2 ]
energy density [J/cm2]
unwashed
washed with ethanol
surface energy
Oxygen‐ uptake and changes in surface energy by on exposure of the polypropylene foil to the dielectric barrier discharge at atmospheric pressure as a function of applied energy density
0 2 4 6 8 10 12 14 16 18 2002468
101214161820222426283032
steady-state functionalization-etchingpenetration
O-in
trodu
ctio
n [O
per
100
C-a
tom
s]exposure time [s]
functionalization
low-pressure rf O2 glow discharge
atmospheric-pressure DBD in air
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1000 1500 2000 2500 30000
3000
6000
9000
12000
15000
18000
MN = 1687± 10 Da
inte
nsity
[cts
.]
molar mass [Da]
1000 1500 2000 2500 3000
0
2000
4000
6000
8000
10000
MN = 1323 ± 30 Da
inte
nsity
[cts
.]
molar mass [Da]
Δmpeak-to-peak = 100 Da
MALDI-ToF mass spectra of PMMA before (left) and after (right) ESI (APCI) deposition
APCI poly(methyl methacrylate) (PMMA) layerdeposition in presence of soft plasma in air
1000 1500 2000 2500 30000
3000
6000
9000
12000
15000
18000
inte
nsity
[cts
.]
molar mass [Da]
PMMA as received
PMMA as APCI-deposited film
degradation ΔMN
H2C C
O‐CH3
CH3
n
C O
PMMA
ESI-deposition of PMMA (o-MMA) with plasma-activation (APCI)(measured by S. Weidner)
J. FRIEDRICH, R. MIX, R.-D. SCHULZE, A. RAU, J. ADHES. SCI. TECHNOL. 24 (2010) 1329-1350
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ConclusionPMMA forms a nearly pin-hole free layer afterdeposition of about 10 nanometers thickness
ESI is an electrophoreticprocess, which closes allholes automatically
ESI poly(methyl methacrylate) (PMMA) layerdeposition without any plasma
0 2 4 6 8 10
0
10
20
30
40
0
20
40
60
80
100Au concentration [A
u/100 C]
O c
once
ntra
tion
[O/1
00 C
]
deposition time [min]
theor. stoichiometry of PMMA
incr
easi
ng c
over
age
of A
u by
PM
MA
coating of Au surface
PMMA
Au
AFM-micrographs from gold-coated Si-wafer before deposition (a), after deposition of 10 nm (b) and after deposition of 50 nm PMMA (c) by means of ESI
a) b) c)
10 nm 50 nm
10 nm ESI‐deposited layer of o‐PMMAcovered underlying gold layer on Si wafer
0 nm 10 nm 50 nm
ESI-deposition of PMMA withoutplasma-activation
gold layer on Si wafer
16/32
No indications for any degradationduring the ESI deposition process in absence of discharges4000 3500 3000 2500 2000 1500 1000 500
0,00
0,02
0,04
0,06
0,08
0,10
0,12 PMMA as ultra-thin ESI deposit PMMA as cast layer
(reference)
abso
rban
ce
wavenumber [cm-1]
PMMA deposited onto gold
ESI poly(methyl methacrylate) (PMMA) layerdeposition without any plasma
296 294 292 290 288 286 284 282 280 278
0
1000
2000
3000
4000
5000
6000
7000
8000
in
tens
ity [c
ts.]
binding energy [eV]
PMMA casted onto gold
C1s peaks of 10 nmPMMA films deposited by ESI or casting (reference)are nearly identical
IR spectra of PMMA films (30 nm) deposited by ESI or casting (reference) measured by Grazing Incidence Reflectance-FTIR (GIR-IRRAS) and normalized to νC=O (1700 cm-1) arenearly identical
ESI-deposition of PMMA (oligo-MMA)films without presence of any plasma
17/32
PEG‐g‐PVA copolymer layer deposited by ESIused as adhesion‐promoting interlayer in metal‐polymer composites
300 295 290 285 280 275
0
1000
2000
3000
4000
5000
221
CH2O
CHCH2
OCH2
CHO
CH2CH2
OCH2
O
CH2
CH OH
CH2
CH OH OHCH
CH2
OHCH
CH2
inte
nsity
[cts
.]
binding energy [eV]
Kollicoat IR (PEG-PVA)
1
2
12
PEG-PVAESI
C1s
300 295 290 285 280 275
0
1000
2000
3000
4000
5000
inte
nsity
[cts
.]
binding energy [eV]
C1s
PEG-PVAcast layer
536 534 532 530 528 5262000
4000
6000
8000
10000
inte
nsity
[cts
.]
binding energy [eV]
PEG-PVAESI
538 536 534 532 5301000
2000
3000
4000
5000
6000
7000
binding energy
inte
nsity
[cts
.]
PEG-PVADBD
536 534 532 530 528 526
2000
4000
6000
8000
10000
inte
nsity
[cts
.]
binding energy [eV]
PEG-PVAcast layer
300 295 290 285 280 275
0
1000
2000
3000
4000
5000
inte
nsity
[cts
.]
binding energy [eV]
PEG-PVADBD
XPS (X-ray Photoelectron Spectroscopy) measured C1s signals of reference, ESI and DBD deposited PEG-PVA without presence of any plasma
significant difference
broadening
reference ESI Aerosol‐DBD
difference
no significant difference
no significant difference
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Poly(acrylic acid) layer deposited by ESIused as adhesion‐promoting interlayer in metal‐polymer composites
292 288 284 280-500
0
500
1000
1500
2000
2500
3000
inte
nsity
[cts
.]
binding energy [eV]
PAAESI
C1s
292 288 284 280
0
1000
2000
3000
4000
5000
inte
nsity
[cps
.]binding energy [eV]
PAAcast film
C1s
very similar
CH2 CH
COOHn
poly(acrylic acid)MW=400,000 g/mol
XPS (X-ray Photoelectron Spectroscopy) measured C1s signals of reference and ESI deposited poly(acrylic acid) (PAA) without presence of any plasma
completecoveragewith PAA(10 nm)
partialcoveragewith PAA(2 nm)
thick layerof PAA withedge forthicknessmeasure‐ment (36 nm)
19/32
Polyolefin functionalization and polymer layerdeposition by aerosol‐DBD
gaspolymermodifying
vapourspolymermodifiying
polymerspolymer layer depositing
aerosol DBD (dielectric barrier discharge or „corona“) degrades the polymer!
21/32
Polyolefin surface coverage by aerosol DBDcoating with PVA‐g‐PEG copolymer ‐ yield in OH groups
O- and OH-concentration after deposition of PVA-g-PEG copolymer (Kollicoat) in presence of air, 1% aqueous solution
before after deposition
0 4 8 12 16
0
2
4
6
8
10
12
14
PE - 500 WOH
energy density [J/cm2]
O o
r OH
con
cent
ratio
n [p
er 1
00 C
]
250 W 500 W 1000 W
PPOtotal
PE - 500 WOtotal
CH2O
CHCH2
OCH2
CHO
CH2CH2
OCH2
O
CH2
CH OH
CH2
CH OH OHCH
CH2
OHCH
CH2
PVA-g-PEG copolymer(Kollicoat)
PE PE
PVA-PEG
→ 3-5 OH groupsper 100 C
22/32
Polyolefin surface modification by aerosol DBDeffect on peel strength of aluminium
DBD treatment in air, water aerosol and polymer aerosol (PEG-g-PEG, 1% solution) for improving the metal adhesion on polyolefin surfaces measured by 90° peel tests
0 2 4 6 8 10 12 14 160
100200300400500600700800900
100011001200
interface failure(adhesive failure)
250 W 500 W
energy density [J/cm2]
peel
stre
ngth
[N/m
]
(a)
Al-PP composite is not peelable(cohesive failure in PP)
0 2 4 6 8 10 12 14 160
100200300400500600700800900
100011001200
interface failure(adhesive failure)
Al-PP composite is not peelable(cohesive failure in PP)
250 W 1000 W
peel
stre
ngth
[N/m
]
energy density [J/cm2]
(b)
0 2 4 6 8 10 12 14 160
100200300400500600700800900
100011001200
interface failure(adhesive failure)
Al-PP composite is not peelable(cohesive failure in PP)
pe
el s
treng
th [N
/m]
energy density [J/cm2]
250 W PEG-PVA 500 W PEG-PVA 1000 W PEG-PVA 250 W PAA
(c)
air water aerosol
DBD‐assisted coating with :PEG‐g‐PVA aerosolPAA [poly(acrylic acid)]
moderate peel strength
support
reinforcing tape mounted with glue
Al
PP
peel test
moderate peel strength excellent peel strength(cohesive failure) with PAA
air water PAA
23/32
Electrophoretic Character of ESIbackside coating of carbon fibres
carbon fibres
spray cone
capillary capillary
carbon fibre
ESI layer
24/32
Electrophoretic Character of ESIenwrapping of carbon fibres with poly(acrylic acid)
carbon fibre
COOH
COOH
COOH
COOH
CO
OH
COOHCO
OH
HOOC
HOOC
HOOC
HOOC
HOO
C
25/32
Electrophoretic Character of ESIplanned: enwrapping of carbon fibres with poly(allylamine) and reaction with
glycidylmethacrylate (GMA)
carbonfibre
NH2
NH2
NH 2
NH2
NH
2
NH2N
H2
H2 N
H2N
H2N
H 2N
H 2N
O
O
O carbonfibre
NH2
NH2
NH 2
NH2
NH
2
NH2N
H2
H2 N
H2N
CH2=CH-CO-O-CH2-CH(OH)-CH2-H
N
H 2NH 2N
crosslinking
26/32
Electrophoretic Character of ESIplanned: enwrapping of carbon fibres with poly(allylamine) and reaction with
glycidylmethacrylate (GMA)
carbonfibre
NH2
NH2
NH 2
NH2
NH
2
NH2N
H2
H2 N
H2N
H2N
H 2N
H 2N
carbonfibre
NH2
NH2
NH 2
NH2
NH
2
NH2N
H2
H2 N
H2N
Epoxy resin-CH(OH)-CH2-HN
H 2NH 2N
CF-epoxy resin composites
27/32
Electrophoretic Character of ESIenwrapping of carbon fibres with poly(acrylic acid) in isopropanole
top
back
28/32
Electrophoretic Character of ESIenwrapping of carbon fibres with poly(acrylic acid) in isopropanole
30 40 50 60 70 80 90 100 1100
25
50
75
100
com
plet
enes
s co
atin
g w
ith P
AA
[%]
distance [mm]
200 nm 50 nm 10 nm
30 40 50 60 70 80 90 100 1100
25
50
75
100
com
plet
enes
s of
coa
ting
[%]
distance [mm]
200 nm 50 nm 10 nm
100% completeness of PAA coating means 100% C1s peak of PAA(285 eV=42%, 285.5 eV=29%, 289.0 eV=29%)
Coating ratio on top-side(face to face to ESI nozzle)
Coating ratio on back-side(shadowed by fibres to ESI nozzle)
Thickness of PAA layer is independent on distance nozzle-substrate!! 296 292 288 284 280
inte
nsity
[cps
.]
binding energy [eV]
29%=pure PAA
296 294 292 290 288 286 284 282 2800
500
1000
1500
2000
2500
3000
inte
nsity
[cps
]
binding energy [eV]
C 1s
C-C, C-H
C-C-OC-O
O-C=O
29/32
Electrophoretic Character of ESIenwrapping of carbon fibres with poly(acrylic acid) in isopropanole
Top-side (face to face to ESI nozzle) Back-side (shadowed by fibres)
296 294 292 290 288 286 284 282 2800
500
1000
1500
2000
2500
3000
inte
nsity
[cps
]
binding energy [eV]
C 1s
C-C, C-H
C-O
296 294 292 290 288 286 284 282 2800
500
1000
1500
2000
2500
3000
inte
nsity
[cps
]
binding energy [eV]
C 1s
C-C, C-H
C-O
296 294 292 290 288 286 284 282 2800
500
1000
1500
2000
2500
3000
inte
nsity
[CP
S]
binding energy [eV]
C 1s
C-C,C-H
C-C-O
O-C=O C-O
washed washed
unwashed unwashed
30/32
Electrophoretic Character of ESIwashability of poly(acrylic acid) coatings measured in terms of IR‐νC=O
Washability of (linear) poly(acrylic acid) on top-sideof carbon fibres (face to face to ESI nozzle)
1850 1800 1750 1700 1650 1600 1550
0,00
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0,09
0,10
abso
rban
ce [a
u]
wavenumber [cm-1]
200 nm 200 nm - washed 50 nm 50 nm - washed 10 nm 10 nm - washed
v(C=O) = 1726 cm-1
31/32
Summary
Aerosol-DBD• atmospheric gas plasma in air →
non-selective oxidation• atmospheric gas plasma in
water aerosol → unspecificfunctionalization
• new→ polymer moleculedeposition in atmospheric gas plasma
• substrate and coating material were plasma-activated
• partial degradation of polymersand loss of functional groups
• adhesion-promoting poly(acrylicacid) produced excellent peelstrength (non-peelable)
ESI• singularized macromolecules
can be deposited on substratesas polymer „mono“ layers
• closed (pin-hole free) polymer layers were found with minimal thickness of 10 nm
• island and homogeneous film growths were found
• no degradation, no loss in functional groups
• open question is, if ESI layersadhere well on polymer and other substrates (work in progress)
• backside-coating because of electrophoretic character