Elektrospray Abscheidung dünner Polymerschichten Thin polymer layers deposited by electrospray

Transcription

1 Elektrospray Abscheidung dünner Polymerschichten Thin polymer layers deposited by electrospray J. Friedrich, K. Altmann, G. Hidde, R. D. Schulze, R. Mix, Bundesanstalt für Materialforschung und prüfung 122 Berlin

2 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 from Modified Polyolefin Surfaces 5. Summary 2/32

3 General Aspects to Polymer Surface Modification with (Monotype) Functional Groups 3/32

4 Polyolefin surfaces introduction of reactive groups Situation at the surface of polyolefins such as polyethylene or polypropylene -aliphatic structure (CH, CH 2, CH 3 ) -absence of any functional groups (OH, H 2, 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 monosort functional groups polyolefin substrate functionalization functional groups attachedto macromolecules of the polymer substrate OH OH OH OH OH Applications: -adhesion-promoting layers -corrosion-inhibiting -biocompatible coverage with polymer layer OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH Grant: DFG Fr975-24/1 deposited polymer layer containing functional groups 4/32

5 Metal polymer composites adhesion promotion by flexible and water repellent spacer molecules Variant 1 Attachment of functional groups onto polymer molecules HO HO HO Si OH Aluminium HO Si OH HO Si OH HO OH OH Si OH not peelable polyolefin Br 2 plasma Variant 2 Coating of polymer substrate by ultra thin adhesion promoting polymer layers equipped with functional groups H 2 H 2 H 2 H 2 Br Br Br polyolefin CHO CHO CHO CHO CH CH CH CH Br HO Si O Si C C CH CH aminosilane OH O O Si C Si CH CH CH H H H H polyolefin Aluminium O Si O O Si O Si Si O C CH C C CH CH CH CH Goals: chemical bonding between metal and polymer alongthe interface of metalpolymer composites high adhesion high durability not peelable polyolefin plasma polymer polyolefin plasma polymer polyolefin plasma polymer polyolefin plasma polymer polyolefin Y. Huajie, R. Mix, J. Friedrich, J. Adhes. Sci. Technol. 25 (211), in press 5/32

6 Polyolefin surface modification technically applied processes atmospheric Dielectric Barrier Discharge (DBD) flame treatment excimer irradiation laser irradiation low pressure plasma pretreatment atmospheric pressure chemical oxyfluorination laminating, coating, evaporation, sputtering 6/32

7 Principles of Aerosol Dielectric Barrier Discharge (A DBD) Atmospheric Pressure Chemical Ionization (APCI) Electro Spray Ionization (ESI) 7/32

8 ew Atmospheric Deposition Techniques Deposition of ultra thin adhesion promoting polymer films actual technique new or advanced processes polymer solution OH OH OH OH OH OH polymer solution polymer solution gas DBDplasma DBDplasma O 2, 2 drops DBDplasma metal capillary degraded macromolecules metal capillary isolated intact macromolecules metal capillary polymer spray cone polymer spray cone polymer high voltage spray cone polymer high voltage metal metall OH COOH CHO O polymer OH COOH OH O coating polymer OH OH OH O coating polymer OH OH OH OH coating polymer Dielectric Barriere Discharge (DBD) in air ("Corona") surface functionalization with different types of groups Aerosol Dielectric Barrier Discharge (DBD) metal Atmospheric Pressure Chemical Ionization (APCI) metal Electro Spray Ionization (ESI) substrate coverage with adhesion promoting (functional groups carrying) thin polymer layers 8/32

9 Basics of Electrospray Ionization (ESI) Aerosol DBD polymer layer deposition Polymeric coating material as well as polymer substrate become activated but also partially degraded bytheatmospheric DBD plasma. Drops of polymer solution are deposited as film. APCI polymer layer deposition Polymer molecules are ionized byatmospheric corona plasma. The macromolecules are singularized but partially degraded. ESI polymer layer deposition Polymer molecules are ionized by high fieldstrengthand singularized. They are not exposed to any plasma. Therefore, degradation and oxidation do not occur. 9/32

10 Electrospray Ionization (ESI) Deposition of Polymers Atmospheric pressure deposition of ultrathin (monomolecular) polymer films by electrospray ionization (ESI) polymer agglomeration polymer mono layer Vacuum deposition of monomolecular (bio) films by ESI substrate ew plasmas for polymer surface functionalization, J. F. Friedrich, A. Meyer Plath, R. Mix, R. D. Schulze, R. Joshi, Proceed. ISPC 18, Kyoto (27); ew plasma techniques for polymer surface functionalization J. F. Friedrich, R. Mix, R. D. Schulze, A. Meyer Plath, R. Joshi, S. Wettmarshausen, Plasma Proc.& Polym. 5 (28) J. Magulick, M. M. Beerbom and R. Schlaf: "Investigation of Adenine, Uracil, and Ribose Phosphate Thin Films Prepared by Electrospray In Vacuum Deposition Using Photoemission Spectroscopy", Thin Solid Films 516 (9), pp (28). Atmospheric pressure deposition of ultra thin (monomolecular) polymer films by aerosol Dielectric Barrier Discharge (DBD) 1/32

11 Formation of multiple charged (nonfragmented) macromolecular ions ESI-MS J. Falkenhagen S. Weidner (I.3) ESI principle solvent evaporation deposited layer ESI-polymer layer deposition drift of ions shrinking of droplet diameter isolated macromolecules Solutions of either ionic or polar polymers were sprayed under applying of high voltage towards the counter 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 nondegraded ions were discharged at the counterelectrode and form a ( monomolecular ) thin film. 11/32

12 Modification of Polymer Surfaces with Monotype Functional Groups 12/32

13 Aerosol DBD treatment of polypropylene in air oxidation in presence of a soft airplasmaat atmospheric pressure O-introduction [O per 1 C-atoms] functionalization penetration steady-state functionalization-etching exposure time [s] low-pressure rf O 2 glow discharge oxygen concentration [O per 1 C] after DBD treatment and washing with ethanol energy density [J/cm 2 ] after DBD treatment surface energy [mj/m 2 ] atmospheric-pressure DBD in air unwashed surface energy washed with ethanol unwashed polar component washed with ethanol energy density [J/cm 2 ] 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 13/32

14 APCI poly(methyl methacrylate) (PMMA) layer deposition in presence of soft plasma in air CH 3 H 2 C C C O O CH 3 PMMA n intensity [cts.] degradation ΔM PMMA as received ESI-deposition of PMMA (o-mma) with plasmaactivation (APCI) (measured by S. Weidner) 3 PMMA as APCI-deposited film molar mass [Da] 18 M = 1687± 1 Da 1 M = 1323 ± 3 Da 15 8 intensity [cts.] 12 9 intensity [cts.] 6 4 Δm peak-to-peak = 1 Da molar mass [Da] molar mass [Da] MALDI-ToF mass spectra of PMMA before (left) and after (right) ESI (APCI) deposition J. FRIEDRICH, R. MIX, R.-D. SCHULZE, A. RAU, J. ADHES. SCI. TECHOL. 24 (21) /32

15 ESI poly(methyl methacrylate) (PMMA) layer deposition without any plasma O concentration [O/1 C] ESI-deposition of PMMA without plasma-activation increasing coverage of Au by PMMA PMMA theor. stoichiometry of PMMA 1 nm 5 nm coating of Au surface Au deposition time [min] a) b) c) nm 1 nm 5 nm AFM-micrographs from gold-coated Si-wafer before deposition (a), after deposition of 1 nm (b) and after deposition of 5 nm PMMA (c) by means of ESI 1Au concentration [Au/1 C] nm ESI deposited layer of o PMMA covered underlying gold layer on Si wafer gold layer on Si wafer Conclusion PMMA forms a nearly pinhole free layer after deposition of about 1 nanometers thickness ESI is an electrophoretic process, which closes all holes automatically 15/32

16 ESI poly(methyl methacrylate) (PMMA) layer deposition without any plasma PMMA casted onto gold ESI-deposition of PMMA (oligo-mma) films without presence of any plasma intensity [cts.] absorbance ,12,1,8,6,4,2, PMMA as ultra-thin ESI deposit PMMA as cast layer (reference) binding energy [ev] PMMA deposited onto gold wavenumber [cm -1 ] C1s peaks of 1 nm PMMA films deposited by ESI or casting (reference) are nearly identical IR spectra of PMMA films (3 nm) deposited by ESI or casting (reference) measured by Grazing Incidence Reflectance-FTIR (GIR-IRRAS) and normalized to ν C=O (17 cm -1 ) are nearly identical o indications for any degradation during the ESI deposition process in absence of discharges 16/32

17 PEG g PVA copolymer layer deposited by ESI used as adhesion promoting interlayer in metal polymer composites XPS (X-ray Photoelectron Spectroscopy) measured C1s signals of reference, ESI and DBD deposited PEG-PVA without presence of any plasma intensity [cts.] reference ESI Aerosol DBD binding energy [ev] PEG-PVA cast layer C1s intensity [cts.] no significant difference 2 1 CH2 CH 1 2 OH CH OH 2CH2 CH CH 2 2O 1 2 CH O CH CH 2CH2 O CH 2 CH 2 CH 2 O 2 Kollicoat IR (PEG-PVA) O CH OH CH OH binding energy [ev] 2 C1s 1 PEG-PVA ESI intensity [cts.] significant difference binding energy [ev] PEG-PVA DBD intensity [cts.] PEG-PVA cast layer intensity [cts.] 1 8 no significant difference 6 4 PEG-PVA ESI difference intensity [cts.] broadening PEG-PVA DBD binding energy [ev] binding energy [ev] binding energy 17/32

18 Poly(acrylic acid) layerdeposited byesi used as adhesion promoting interlayer in metal polymer composites XPS (X-ray Photoelectron Spectroscopy) measured C1s signals of reference and ESI deposited poly(acrylic acid) (PAA) without presence of any plasma intensity [cts.] C1s PAA ESI 5 4 very similar intensity [cps.] 3 2 C1s PAA cast film CH 2 CH COOH n poly(acrylic acid) M W =4, g/mol binding energy [ev] binding energy [ev] partial coverage with PAA (2 nm) complete coverage with PAA (1 nm) thick layer of PAA with edge for thickness measurement (36 nm) 18/32

19 Polyolefin functionalization and polymer layer deposition by aerosol DBD polymers polymer layer depositing gas polymer modifying vapours polymer modifiying aerosol DBD (dielectric barrier discharge or corona ) degrades the polymer! 19/32

20 Peel Strength of Aluminium Evaporated Layers from Modified Polyolefin Surfaces 2/32

21 Polyolefin surface coverage by aerosol DBD coating 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 O or OH concentration [per 1 C] PE - 5 W OH PP O total energy density [J/cm 2 ] PE - 5 W O total 25 W 5 W 1 W 3-5 OH groups per 1 C PE O CH 2 CH OH CH OH CH 2 CH 2 CH OH CH OH CH 2 CH 2O CH O CH 2 PVA-g-PEG copolymer (Kollicoat) PVA-PEG PE CH 2 CH CH 2CH2 O CH 2 O 21/32

22 Polyolefin surface modification by aerosol DBD effect on peel strength of aluminium Al peel test air water PAA PP peel strength [/m] reinforcing tape mounted with glue support Al-PP composite is not peelable (cohesive failure in PP) interface failure (adhesive failure) air 25 W 5 W energy density [J/cm 2 ] (a) moderate peel strength peel strength [/m] water aerosol Al-PP composite is not peelable (cohesive failure in PP) interface failure (adhesive failure) (b) 25 W 1 W energy density [J/cm 2 ] moderate peel strength peel strength [/m] DBD assisted coating with : PEG g PVA aerosol PAA [poly(acrylic acid)] 25 W PEG-PVA 5 W PEG-PVA 1 W PEG-PVA 25 W PAA Al-PP composite is not peelable (cohesive failure in PP) interface failure (adhesive failure) (c) energy density [J/cm 2 ] excellent peel strength (cohesive failure) with PAA DBD treatment in air, water aerosol and polymer aerosol (PEG-g-PEG, 1% solution) for improving the metal adhesion on polyolefin surfaces measured by 9 peel tests 22/32

23 Electrophoretic Character of ESI backside coating of carbon fibres capillary capillary spray cone carbon fibre carbon fibres ESI layer 23/32

24 Electrophoretic Character of ESI enwrapping of carbon fibres with poly(acrylic acid) carbon fibre 24/32 COOH COOH COOH HOOC COOH HOOC COOH HOOC COOH HOOC COOH HOOC

25 Electrophoretic Character of ESI planned: enwrapping of carbon fibres with poly(allylamine) and reaction with glycidylmethacrylate (GMA) H2 H2 H2 H2 H2 H2 H 2 H 2 H 2 H 2 carbon fibre O O H 2 H 2 H 2 H 2 O carbon fibre H2 H2 H2 H 2 H 2 H2 H2 H 2 H 2 CH2 =CH-CO-O-CH 2 -CH(OH)-CH 2 -H crosslinking 25/32

26 Electrophoretic Character of ESI planned: enwrapping of carbon fibres with poly(allylamine) and reaction with glycidylmethacrylate (GMA) H2 H2 H2 H2 H2 H2 H 2 H 2 H 2 H 2 H 2 carbon fibre carbon fibre H 2 H 2 H 2 H2 H2 H2 H 2 H 2 H2 H2 H 2 H 2 Epoxy resin-ch(oh)-ch2 -H CF-epoxy resin composites 26/32

27 Electrophoretic Character of ESI enwrapping of carbon fibres with poly(acrylic acid) in isopropanole top back 27/32

28 completeness coating with PAA [%] Electrophoretic Character of ESI enwrapping of carbon fibres with poly(acrylic acid) in isopropanole 1% completeness of PAA coating means 1% C1s peak of PAA (285 ev=42%, ev=29%, 289. ev=29%) 29%= pure PAA Thickness of PAA layer is independent on distance nozzle-substrate!! distance [mm] Coating ratio on top-side (face to face to ESI nozzle) 2 nm 5 nm 1 nm completeness of coating [%] intensity [cps.] distance [mm] binding energy [ev] 2 nm 5 nm 1 nm Coating ratio on back-side (shadowed by fibres to ESI nozzle) 28/32

29 3 25 Electrophoretic Character of ESI enwrapping of carbon fibres with poly(acrylic acid) in isopropanole washed 3 25 washed C 1s intensity [cps] C-C, C-H C-O C 1s intensity [cps] C-C, C-H C-O binding energy [ev] unwashed binding energy [ev] unwashed intensity [CPS] O-C=O C 1s C-C,C-H C-C-O C-O intensity [cps] O-C=O C-C, C-H C-C-O C-O C 1s binding energy [ev] Top-side (face to face to ESI nozzle) binding energy [ev] Back-side (shadowed by fibres) 29/32

30 Electrophoretic Character of ESI washability of poly(acrylic acid) coatings measured in terms of IR ν C=O,1 absorbance [au],9,8,7,6,5,4,3 v(c=o) = 1726 cm -1 2 nm 2 nm - washed 5 nm 5 nm - washed 1 nm 1 nm - washed,2,1, wavenumber [cm -1 ] Washability of (linear) poly(acrylic acid) on top-side of carbon fibres (face to face to ESI nozzle) 3/32

31 Summary Aerosol-DBD atmospheric gas plasma in air non-selective oxidation atmospheric gas plasma in water aerosol unspecific functionalization new polymer molecule deposition in atmospheric gas plasma substrate and coating material were plasma-activated partial degradation of polymers and loss of functional groups adhesion-promoting poly(acrylic acid) produced excellent peel strength (non-peelable) ESI singularized macromolecules can be deposited on substrates as polymer mono layers closed (pin-hole free) polymer layers were found with minimal thickness of 1 nm island and homogeneous film growths were found no degradation, no loss in functional groups open question is, if ESI layers adhere well on polymer and other substrates (work in progress) backside-coating because of electrophoretic character 31/32

32 Authors J. Friedrich C. Altmann G. Hidde R.-D. Schulze R. Mix 32/32