Chemical vapor deposition of thin polymer films
Chemical vapor deposition (CVD) is a widely used technology for the preparation of conformal and defect-free inorganic thin films with systematically tunable properties. Polymers are a desirable class of materials for surface modification because of their low cost, wide array of chemical and physical functionality, and mechanical flexibility. Initiated and oxidative chemical vapor deposition (iCVD and oCVD) are polymer CVD methods that combine the benefits of CVD processing with the possibilities of polymeric materials. Using these technologies, our laboratory has synthesized a number of functional, biocompatible, and electrically conducting polymers as thin films on micro- and nano-structured surfaces. iCVD and oCVD are simple, scalable methods for the production of conformal thin films on virtually any substrate.
Tenhaeff,W. E.; Gleason, K. K., Initiated and Oxidative Chemical Vapor Deposition of Polymeric Thin Films: iCVD and oCVD. Advanced Functional Materials 2008, 18, (7), 979-992. Invited Feature Article
Martin, T. P.; Chan, K.; Gleason, K. K., Combinatorial initiated chemical vapor deposition (iCVD) for polymer thin film discovery. Thin Solid Films 2008, 516, 681-683.
Initiated Chemical Vapor Deposition (iCVD)
In iCVD, monomer and initiator flow into a vacuum chamber where they contact resistively heated filaments. The initiator breaks down into radicals, beginning a free-radical polymerization of the monomer at the substrate surface. By replicating solution-phase free-radical polymerization in the vapor phase, a wide variety of thin polymer films can be deposited. More than 50 different polymers or copolymers have been deposited via iCVD, including anti-microbial polymers, hydrogels, superhydrophobic polymers, biopassive insulators, alternating copolymers, and click functional polymers.
The inherently conformal nature of CVD allows us to produce a variety of structures. To the right are electron microscope images of a humidty-responsive Bragg mirror (top left), an array of polymer nanobowls produced using colloidal lithography (top right), hydrogel coatings around particles (bottom right), and reactive polymer coatings around carbon nanotubes (bottom left).
We are currently interested in using iCVD to create patterned polymer surfaces, chemical sensors, conformal coatings for nano-scale features, and smart responsive surfaces.
Lab Researchers: Dr. Gozde Ince, Dr. Ayse Asatekin, Dr. Rama Sreenivasan, Mahriah Alf, Salmaan Baxamusa, Christy Petruczok, Wyatt Tenhaeff, Nathan Trujillo, Jingjing Xu
(click on a name to learn more).
Trujillo, N.J.; Baxamusa, S.H.; Gleason, K.K. Grafted Functional Polymer Nanostructures Patterned Bottom-Up by Colloidal Lithography and Initiated Chemical Vapor Deposition (iCVD). Chemistry of Materials 2009, 21, 742-750.
S. G.; Bong, K. W.; Kim, B. S.; Baxamusa, S. H.; Hammond, P. T.; Doyle,
P. S.; Gleason, K. K., Patterning Nanodomains with Orthogonal
Functionalities: Solventless Synthesis of Self-Sorting Surfaces. Journal of the American Chemical
Society 2008, 130, (44),
S. H.; Montero, L.; Dubach, J. M.; Clark, H. A.; Borros, S.; Gleason,
K. K., Protection of Sensors for Biological Applications by
Photoinitiated Chemical Vapor Deposition of Hydrogel Thin Films. Biomacromolecules 2008, 9, (10), 2857-2862.
M.; Kooi, S. E.; Gleason, K. K., Vapor deposition of hybrid
organic-inorganic dielectric bragg mirrors having rapid and reversibly
tunable optical reflectance. Chemistry
of Materials 2008, 20,
Tenhaeff, W. E.; Gleason, K. K., Initiated chemical vapor deposition of
alternating copolymers of styrene and maleic anhydride. Langmuir 2007,
23, (12), 6624-6630.
Martin, T. P.; Kooi, S. E.; Chang, S. H.; Sedransk, K. L.; Gleason, K.
K., Initiated chemical vapor deposition of antimicrobial polymer
coatings. Biomaterials 2007, 28, (6), 909-915.
Lau, K. K. S.; Gleason, K. K., Particle surface design using an all-dry
encapsulation method. Advanced Materials 2006, 18, (15),
Lau, K. K. S.; Gleason, K. K., Initiated chemical vapor deposition
(iCVD) of poly(alkyl acrylates): A kinetic model. Macromolecules 2006,
39, (10), 3695-3703.
Oxidative Chemical Vapor Deposition (oCVD) of conducting polymers
oCVD can deposit various conducting polymer films, including poly (3, 4-ethylenedioxythiophene) (PEDOT), poly aniline, poly pyrrole, poly alkylthiophene, and functionalized poly thiophene. The properties of the polymer film can be controlled by tuning the deposition parameters. For example, the conjugation length, and therefore the electrical conductivity, can be tuned over six orders of magnitude by changing the substrate temperature.The highest achieved conductivity is about 1000 S/cm. In oCVD, the monomer flows into the reactor where it meets an oxidizing agent, beginning a step polymerization resulting in the conducting thin film.
With this simple one-step method, PEDOT films can be grafted on various kinds of organic substrates. Large increases in adhesion strength are consistently observed. With this grafting technique, nanometer-scale (down to 60 nm) PEDOT patterns can be obtained on flexible substrates. The electronically active conducting polymers can be applied to a variety of organic electronic devices. We are currently working to show that conducting polymer films can enhance the performance of organic solar cells and chemical sensors. Furthermore, organic light-emitting diodes and thin film transistors can be fabricated with this technique.
Lab Researchers: Dr. Sreeram Vaddiraju, Miles Barr, Hitesh Chelawat, Rachel Howden (click on a name to learn more).
Tenhaeff, W. E.; Gleason, K. K., Initiated and Oxidative Chemical Vapor Deposition of Polymeric Thin Films: iCVD and oCVD. Advanced Functional Materials 2008, 18, (7), 979-992.
Lock, J. P.; Lutkenhaus, J. L.; Zacharia, N. S.; Im, S. G.; Hammond, P. T.; Gleason, K. K., Electrochemical investigation of PEDOT films deposited via CVD for electrochromic applications. Synthetic Metals 2007, 157, 894-898.
Im, S. G.; Yoo, P. J.; Hammond, P. T.; Gleason, K. K., Grafted conducting polymer films for nano-patterning onto various organic and inorganic substrates by oxidative chemical vapor deposition. Advanced Materials 2007, 19, 2863-+.
Im, S. G.; Olivetti, E. A.; Gleason, K. K., Systematic control of the electrical conductivity of poly (3,4-ethylenedioxythiophene) via oxidative chemical vapor deposition (oCVD). Surface & Coatings Technology 2007, 201, (22-23), 9406-9412.
Im, S. G.; Gleason, K. K.; Olivetti, E. A., Doping level and work function control in oxidative chemical vapor deposited poly (3,4-ethylenedioxythiophene). Applied Physics Letters 2007, 90, (15).
Im, S. G.; Gleason, K. K., Systematic control of the electrical conductivity of poly(3,4-ethylenedioxythiophene) via oxidative chemical vapor deposition. Macromolecules 2007, 40, (18), 6552-6556.