Designing polymer surfaces via vapor deposition


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Designing polymer surfaces via vapor deposition

  1. 1. Ayse Asatekina, Miles C. Barra, Salmaan H. Baxamusaa, Kenneth K.S. Laub, Wyatt Tenhaeffa, Jingjing Xua and Karen K. Gleasona, Presented by: Paula Soares Martins Antunes Superfícies, Interfaces e Colóides Mestrado Integrado em Engenharia Biomédica 5º ano, 2º semestre 07 /06/2010
  2. 2. Film polymerization methods Emulsion Bulk Solution Solution chemestry fabricating surface modification by polymer-based grafting desired functional devices polymers
  3. 3. Chemical Vapor Deposition (CVD) is a technique used to obtain a thin polymer film, typically performed by evaporating monomers under ultrahigh vacuum conditions and depositing a film on a target substrate. Polymerization (condensation reaction) Monomer Monomer Thin film 1 2 cured or annealed
  4. 4. A tissue paper substrate which cannot survive exposure to harsh solvents or high temperatures… Without CVD With CVD PTFE PTFE A tissue before (a) and after (b) CVD surface modification of a tissue with a 40 nm thickness of CVD poly(tetrafluoroethylene) (PTFE). A 40 nm thick CVD PTFE renders the surface of the tissue non-wetting. CVD Treatment Conventional sintering step Room temperature 400 ºC
  5. 5. POLYMERIZATION VIA VAPOR DEPOSITION: WHAT WE HAVE Advantages • Film stress can be controlled monomer by high/low frequency mixing techniques Low pressures • Control over stoichiometry via process conditions. reactor bombardment by free electrons generating more Electrons, ions, radicals, atoms, and molecules in excited states resulting in fragmentation of the monomer and its Deposition through non-specific, complex chemical reactions
  6. 6. POLYMERIZATION VIA VAPOR DEPOSITION: WHAT WE HAVE Do not use: • plasma • an initiator specie (thermal initiator/photo initiator) • an oxidative specie. • VDP • both monomers enter the chamber simultaneously • MDP • sequential, alternating sequence of monomers for better control over film growth.
  7. 7. POLYMERIZATION VIA VAPOR DEPOSITION: THE YOUNGER Initiated The heated gas surrounding the Oxidative the oxidant and monomer are filaments creates the reactive species while the delivered to the substrate through the vapor cooled substrate promotes the absorption of phase. Adsorption and spontaneous reaction these species onto the growth surface proceed directly on the substrate. No additional excitation of reactants is required
  8. 8. POLYMERIZATION VIA VAPOR DEPOSITION: THE YOUNGER Acrylate polymer films PEDOT films (oCVD) (iCVD) Non planar substrates having micro and/or nano scale features. When microtrenches are solution coated with acrylate polymers, the coating is non-conformal (f), as Large increases in adhesion strength are consistently compared to conformal iCVD acrylate coating (g) observed. With this grafting technique, nanometer-scale (down to 60 nm) PEDOT patterns can be obtained on flexible conformal coatings substrates. • polymeric thin films displaying uniform thickness over the geometric features present in the substrate.
  9. 9. CVD POLYMERS APPLICATIONS Synthetic control over the functional groups displayed at the surfaces • surface attachment of fluorescent dyes, bioactive molecules, and inorganic nanoparticles. • copolymerization with monomers with multiple vinyl groups results in controllably cross-linked films which are resistant to solvent damage yet remain mechanically flexible. • coat microparticles to encapsulate them for controlled release, and change their surface chemistry. Conventional methods iCVD Aggregation of the small particles Solvent-free Fragility of drug molecules Room temperature Potential solubility of drug molecules
  10. 10. CVD POLYEMERS APPLICATIONS Formation of the selective layers of composite membranes This treatment prevents the coatings from delaminating through volume changes by over 10 times, as well as ultrasonication. Manufacture of micrometer scale resistive sensors In these applications, the swelling of a thin, CVD-deposited polymer layer to the analyte of interest is converted into a change in electrical resistance.: • Inorganic microcantilever coated with a CVD-polymerized layer that reacts with amines. This results in the swelling of the polymer, which causes the cantilever to deflect and complete a circuit • Microtrenches coated with a conformal layer of poly(4-vinyl pyridine) (P4VP).
  11. 11. CVD POLYMERS APPLICATIONS Responsive layers that can transduce chemical and biological events into electrical and/or optical responses Changes in film thickness can result from swelling upon exposure to a specific analyte, or switching of the surface energy can occur in response to a change in temperature, external field, or pH.
  12. 12. SUMMARY