F4280 Technologie depozice tenkých vrstev a povrchových úprav 7.5.4 Plasma Polymers Lenka Zajíčková Přírodovědecká fakulta & CEITEC, Masarykova univerzita, Brno lenkaz@physics.muni.cz Central European Institute of Technology BRNO I CZECH REPUBLIC O 3 <5 • Functional Coatings • Why Amine Surfaces/Films? • Low Pressure Amine Plasma Polymers • Plasma Polymerization of Cyclopropylamine • Carboxyl Plasma Polymers • COOH Plasma Polymers at Atmospheric Pressure • Co-polymerization of MA and C2H2 Plasma. Technologies F4280 Technologie depozice a povrchových úprav: Functional Coatings Lenka Zajíčková 3/11 Functional Coatings Many types of functional coatings successfully prepared in atmospheric pressure DBD, homogeneous mode is preferred SiOx and organosilicon films hexamethyldisiloxane CH3 CH3 H3C-Si-0-Si-CH3 1 1 CH3 CH3 barrier and protective coatings hydrofilic/hydrophobic surface cross-linking improvement (stabilization of organic functionalities by co-polymerization) Carboxyl/ester/anhydride films acrylic acid o HO CH2 methyl methacrylate CH3 maleic anhydride interfacial adhesion, grafting of molecules with specific functionalities (reverse adhesion), improvement of cell colonization (tissue engineering), immobilization of biomolecules (biosensors, drug delivery systems). F4280 Technologie depozice a povrchových úprav: Functional Coatings Lenka Zajíčková 4/11 Plasma Polymerization in Pulsed RF Discharges Retaining monomer structure for highly functional films =>- pulsed discharges CD 11 O CL on -*~ ^off time pulse repetition frequency spills = 1 / (ion + /"off) duty cycle (DC) DC = . to* x 100% mean RF power Paver — Pnn X DC on Macroscopic approach for simplified understanding of the process: ► Composite parameter W/F proportional to the energy delivered per one molecule of monomer in gas phase W/F = aver Q [J/cm3] Q - monomer flow rate ► Energy dissipated per deposition rate R due to ion bombardment ^surf r,-£i mean R Vj ion flux, Emean mean ion energy D. Hegemann etal. Appl. Phys. Lett. 101 (2012) 211603 F4280 Technologie depozice a povrchových úprav: Why Amine Surfaces/Films? Lenka Zajíčková 5/11 Reactivity of primary amines is important for ► adhesion enhancement ► immobilization of biomolecules (for enzyme electrodes, immunosensors etc.) NH,NH,NH, -H-l- substrate gluteraldehyde (GA) PBS 1 h r.t. \ U. P N N N substrate NH2 antibody (AL-U1^ PBS 12 h 5°C N °U J N N N -I-1-1— substrate HSA antigen PBS 10 miti r.t. R1 \ H H f l 1 K. > J N N N -I "I "I— substrate ► cells interaction with surfaces (artificial tissue engineering) Cells interact with surfaces via extracellular matrix (ECM) Synergy sile + + + + + + + + + + + + ECM contains proteins like fibronectine that bonds well to protonated surfaces such as NH2 surfaces at neutral pH. F4280 Technologie depozice a povrchových úprav: Why Amine Surfaces/Films? ka Zajíčková 6/11 SAM of cysteamine I-s 1 ! -s -s NH2 NH2 NH2 NH2 -S (3-Aminopropyl)triethoxysilane (APTES) i -o ro—Si—nh2 -o -°\ -o—Si—nh2 ro/ Polyethyleneimine (PEI) nh2 ^-nJ---^NJ—[-n—^|nH2 o L Hjm ^nh2 -^nJ----isj-J—[*n----[nh2 o L Hjm ^NHz 'n|—-n|^n—-4nh2 Plasma polymerization - alternative to NH2 Example of plasma polymerized cyclopropylamine optimized for sensing performace conventional methods 0,90^-,-1-,-1-,-1-,-r- 3500 3000 2500 2000 1500 wavenumber (cm1) F4280 Technologie depozice a povrchových úprav: Low Pressure Amine Plasma Polymers Lenka Zajíčková 7/11 Surface plasma treatment, e.g. in N2 or NH3 discharges unstable functionalization of a thin near-surface layer with rather short duration Deposition from vapors of amine monomers: ► allylamine ► diaminocyclohexane ► ethylenediamine ► cyclopropylamine (CPA) ► etc. usually in pulsed RF discharges, substrate floating or grounded Deposition from gas mixtures: ► NH3/CH4 ► NH3/C2H4 usually in continous wave RF discharges, substrate at RF electrode Allylamine - commonly used due to presence of vinyl group (free radical polymerization) but highly toxic flammable chemical compound Cyclopropylamine - promising monomer for amine-rich coatings, non-toxic, vapor pressure of 32 kPa at 25 °C. NH F4280 Technologie depozice a povrchových úprav: Plasma Polymerization of Cyclopropylamine Lenka Zajíčková 8/11 ► in RF (13.56 MHz) capacitively coupled discharges ► continuous wave and pulsed modes ► ► ron = 660 fis, roff = 1340 /zs fpuls = 500 Hz, DC = 33% ► in CPA/Ar mixtures NH2 reactor R3, substrate at floating potential reactor R2, substrate at RF electrode gas mixture blocking matching rf generator capacitor unit gas mixture rf generator (^v)-1 |_C =±= blocking capacitor matching unit ► Ar 28 seem, CPA 0.1-1.0 seem ► pressure 120 Pa ► RF power 20-30 W ► electrode diameter 80 mm ► interelectrode distance 185 mm ► Q(Ar) = 28 seem, Q(CPA) = 2.0sccm ► pressure 50 Pa ► RF power 30-250 W ► electrode diameter 420 mm ► interelectrode distance 55 mm F4280 Technologie depozice a povrchových úprav: Carboxyl Plasma Polymers Lenka Zajíčková 9/11 Carboxyl-rich coatings Carboxyl-rich coatings are of high interests due to their wide application potential: ► improvement of adhesion, ► grafting of molecules with specific functionalities (reverse adhesion), ► improvement of cell colonization (tissue engineering), ► immobilization of biomolecules (biosensors, drug delivery systems). -c o \ OH Plasma processing of carboxyl surfaces by PECVD from simple molecules ► H20/C02[1] ► C2H4/C02 [2] by plasma (co-)polymerization of COOH-based monomers ► acrylic acid (AA) [2,3,4] ► maleic anhydride (MA) [5,6] o HO II CH2 acrylic acid maleic anhydride [1] N. Medard, J.-C Soutif, F. Poncin-Epaillard, Langmuir, 2002, 18, 2246 [2] D. Hegemann, E. Koerner, S. Guimond Plasma Process. Polym. 2009, 6, 246 [3] L. Detomasso, R. Gristina, G. Senesi, R. d'Agostino, P. Favia, Biomaterials 2005, 26, 3831 [4] A. Fahmy, R.Mix, A. Schonhals, J. Friedrich Plasma Process. Polym. 2011, 8, 147 [5] A. Manakhov, M. Moreno-Couranjou, N. D. Boscher et al., Plasma Process. Polym. 9 (2012) 435 [6] M. M. Brioude, M.-P. Laborie, A. Airoudj et al., Plasma Process. Polym. (2015) doi:10.1002/ppap.201400224 F4280 Technologie depozice a povrchových úprav: COOH Plasma Polymers at Atmospheric Pressure ka Zajíčková 10/11 COOH-Films Deposited at Atmospheric Pressure DBD plasma polymerization of acryic acid in He A.J. Beck, R.D. Short, A. Matthews, Surf Coat Technol 203 (2008) 822-825: ► percentage of functional groups by fitting XPS C1s signal (~ 289.3 eV binding energy for C(0)=0, i.e. carboxyl and ester groups) ► films with high retention of the monomer structure for low energetic conditions (low W/F) =>- up to 29.7 % of COOR ► Bioapplications require sufficient stability in aqueous media but cross-linking improves the layer stability at expenses of the functional group concentration. ► Plasma co-polymerization offers an additional possibility to tune the film stability and carboxyl functionalization efficiency Thomas et al. Plasma Process. Polym. 4 (2007) S475 Manakhov et al. PPP 9 (2012) 435 - copolymerization of maleic anhydride (MA) and vinyltrimethoxysilane (VTMOS) in DBD m 'E U) c Ä c 0.6 kW 0.1 ml/min frC0\0Ri COOR 1.0 kW 0.1 ml/min 1.2 kW 0.05 ml/min 295 r.......f........r" (Si) HOOG COOH n 0 H —I-Si—O-- d) -sí-o- o (Si) ■(Si) -H,0 HOOC ■ a F4280 Technologie depozice a povrchových úprav: Co-polymerization of MA and c2^2 Lenka Zajíčková 11/11 Co-polymerization of MA and C2H2 ► dielectric barrier discharge at 6.6 kHz, 12 W ► distance between dielectrics 1.6 mm o + HC = CH ► top electrode made of two parts, each 55 x 20 mm, spaced by 20 mm ► rectangular bottom electrode 150 x 60 mm ► central gas inlet, 9 mm in diameter ► buffer chamber distributing gas flow into a slit, 2 mm wide and 48 mm long gas inlet chamber movement zzzzzzzzzzzzzzzzzn HV electrodes HV generator ceramics substrate pump plastic tube buffer chamber exit slit bottom ceramics rnrEr^ör [electrode underneath) COppSl electrodes MA : C2H2 flow rate ratio varied by changing flow rate of C2H2 and Ar through MA. ► Ar flow rate through MA bubbler Qai—ma = 0.25-1.5 slm => QMA = 0.06-0.33 seem ► C2H2 flow rate Qc2H2 = 2-3 seem ► total Ar flow rate Qat-ma + Oat = 1 -5 slm