AN INTRODUCTION TO PLASMA POLYMERIZATION

1. AN INTRODUCTION TO PLASMA POLYMERIZATION DEVENDRA A TAMBE DEPARTMENT OF MATERIALS SCIENCE AND ENGINEERING AUBURN UNIVERSITY AUBURN,AL –36849

2. General Outline • Introduction to plasma polymerization. • Property control of plasma polymerized films i.e process parameters for plasma polymerization. • Atomic nature of plasma polymerization. • Representative characteristics of plasma polymers. • Applications

3. WHAT IS PLASMA POLYMERIZATION? • Plasma polymerization refers to formation of polymeric materials under the influence of plasma, and are also termed as “Glow Discharge Polymerization.” • Polymer formation in plasma is regarded as “ATOMIC ( Non molecular)” process.

4. Why plasma polymerization is important? • Plasma polymer films can be easily formed with thickness of 5000A to 1 . • These films are highly coherent and adherent to variety of substrates like conventional polymers, glass, metals. • Films are highly dense and pinhole free. • Multilayer films or films with grading of chemical and physical characteristics can be easily prepared . • Most importantly it is one step process compared o conventional polymerization.

5. Schematic structure of plasma polymerized Ethylene

6. Different polymer formation processes • Plasma induced polymerization and plasma state polymerization. • Plasma polymerization and Graft polymerization. • Plasma polymerization and radiation polymerization.

7. Types of polymerization Processes • Classification based on Growth mechanism. • Step Growth polymerization. • Chain Growth polymerization. • Addition Polymerization. • Free radical polymerization. • Ionic polymerization. • Radiation polymerization. • Polymerization in Vacuum.

8. Control of properties for plasma polymerized films • Choice of monomers. • Hydrocarbons • Hydrocarbons with polar groups • Fluorocarbons • Silicon containing monomers • Metal containing plasma polymers • Generation of Glow Discharge. • DC/AC/RF/MICROWAVE • Reactor geometries.

9. Plasma polymerization process parameters • Monomer(s) flow rate. • Plasma pressure. • Geometrical factors. • Location of monomer inlet w.r.t. electrodes • Location of plasma polymer deposition w.r.t. monomer inlet and electrodes • Temperature of deposition site.

10. Effect of Geometrical parameters some illustrations

11. Effect of Geometrical parameters some illustrations (continued)

12. Effect of geometrical parameters some illustration(continued)

13. Kinetic and Mechanistic aspects of plasma polymerization • Role of ionization in plasma polymerization.

14. Kinetic and Mechanistic aspects of plasma polymerization (continued) • Growth mechanism of plasma polymerization.

15. Kinetic and Mechanistic aspects of plasma polymerization (continued) • Reactive species in plasma polymerization. • Dissociation of excited molecules • Dissociation of ions • Neutralization of radical ions • Ion – molecule reactions

16. Introduction of non polymerizable gases into plasma polymers • It is not just Trapping but Incorporation in polymer chain. • Incorporation of N2 in plasma polymer of styrene • This copolymerization is observed for N2,CO,H2O with monomer containing triple or double bond.

17. Characterization Methods • Elemental Analysis. • Infrared Spectra. • NMR. • Electron Spectroscopy for chemical analysis (X-PS).

18. Atomic (Non molecular) nature of Plasma polymerization • Plasma polymerization is characterized by; • Extensive fragmentation and/or rearrangements of structure/atoms in starting material. • Simultaneous occurring of reactions involving many kinds of chemical species. • One cann’t predict structure of plasma polymer as in case of conventional polymers from structure of monomers. • Atomic polymerization simply means the building blocks are no longer molecules which is why “Dimond” like structures can be formed. • Introduction of non polymerizable gases N2,CO,H2O is another proof of atomic nature.

19. General characteristics of plasma polymers • Free radicals in plasma polymers. • Internal stresses in plasma polymers.

20. General characteristics of plasma polymers (Continued) • Solubility and fusibility of plasma polymers. • Surface properties of plasma polymers. • Surface energies. • Frictional coefficient. • Durability of surface modification by plasma polymerization. • Permeability characteristics of plasma polymers. • Adhesion (Some thumb rules are) • slower deposition of plasma polymers. • Surface characteristics (Roughnesss,Cleanliness) • Adhesion on organic polymers is good but while poor on glass,materials. • Thin layers achieve good adhesion. • Improvement of adhesion by plasma polymerization.

21. Applications • Applications based on alterations of surface chemistry. • E.gmodifications of surface of polyimide fibers to improve adhesion to epoxy matrix. • Modification of CaCo3 prior to blending with polyethylene and PVC.

22. Application based on bulk properties of plasma polymers. • Material transport through plasma polymers. • Barrier and protective films. • Electrical applications. • Abrasion resistant coatings. • Optical applications.

23. References • H.Yasuda; “Plasma Polymerization” Academic Press Inc. 1985. • Riccardo D’Augastino; “Plasma Deposition, Treatment, and Etching of polymers” Academic Press Inc. Plasma materials interactions. • Mitchell Shan; “Plasma Chemistry ofPolymers” Marcel Dekkar Inc. • H.Boenig; “ Plasma Science andTechnology.” Cornell Univ. Press • H.Biederman, Y. Osada; “PlasmaPolymerization Processes” Elsevier pubilcations.