Polymers by Ion Implantation

Compositional and Structural Changes of Polymers under Low-to Medium-Energy Ion Implantation 

The implantation of low-to-medium energy ions changes only surfaee layer of polymers, with the thickness in nm-pm range, and preserves favorable bulk properties of polymers. By the ion implantation sueh surfaee properties as ehemieal strueture [108-111], wettability [109,110,112], eleetrieal eonduetivity [109,113-116], tribological properties [112,117,118] and bioaetivity [18,111-113,119] ean be ehanged in a manner which can be controlled by a proper ehoice of ion mass, energy and fluenee. 

At highest ion fluences the H and O contents achieves a saturated value which vary from 50-70 % of their original value in pristine polymer. Several semiempirical models have been suggested describing hydrogen desoption during ion implantation (see e.g. [122]). 

The PTFE samples were irradiated with 300 keV Ar ions to fluenees from 1x10 1x1 o cm . The thickness of ablated layer, determined by optical microscopy, was found to be an increasing fimction of the ion fluence for the fluence of IxlO cm about 14 pm of PTFE was removed by ion irradiation. XRD measurement shows gradual loos of PTFE crystalline phase with incresing ion fluence. 

---

OPTICAL EXTINCTION OF METAL NANOPARTICLES SYNTHESIZED IN POLYMER BY ION IMPLANTATION... 

Ochsner, R., Kluge, A., Zechel-Malonn, S., Gong, L., and Ryssel, H., Improvement of surface properties of polymers by ion implantation, Nucl. Instrum. Methods Phys. Res., B80/8I, 1050-1054 (1993). 

During the past few years the microhardness technique has frequently been applied to the characterization of super-hard-surfaced polymers obtained by ion implantation and to plasma-deposited hard amorphous carbon films (Balta Calleja Fakirov, 1997). These products represent an entirely new class of materials that are lightweight and have the flexibility of polymers combined with a surface microhardness and wear resistance greater than those of metallic alloys (Lee et al., 1996). 

The hardening and embrittlement of polyimides by ion implantation has been also studied (Pivin, 1994). Nanoindentation tests performed using a sharp diamond pyramid of apical angle 35° provided very quantitative depth profiles of microhardness in polyimides implanted with C, N, O, Ne or Si ions. In all cases the microhardness increased steeply when the amount of deposited energy reached the order of 20 eV atom". For energies of 200 eV atom" the polymer is transformed into an amorphous hydrocarbon and the microhardening factor saturates at a value of 13-20. However, the carbonized layer is poorly adherent, as is evidenced by reproducible discontinuities in the depth vs load curves, when the indenter tip reached the interface. 

Valenza, A. Visco, A.M. Torrisi, L. Campo, N. Characterization of ultra-high-molecular-weight polyethylene (UHMWPE) modified by ion implantation. Polymer 2004, 45, 1707-1715. 

In this chapter, we studied the formation of silver nanoparticles in PMMA by ion implantation and optical density spectra associated with the SPR effect in the particles. Ion implantation into polymers carbonizes the surface layer irradiated. Based on the Mie classical electrodynamic theory, optical extinction spectra for silver nanoparticles in the polymeric or carbon environment, as well as for sheathed particles (silver core -l- carbon sheath) placed in PMMA, as a function of the implantation dose are simulated. The analytical and experimental spectra are in qualitative agreement. At low doses, simple monatomic silver particles are produced at higher doses, sheathed particles appear. The quantitative discrepancy between the experimental spectra and analytical spectra obtained in terms of the Mie theory is explained by the fact that the Mie theory disregards the charge static and dynamic redistributions at the particle-matrix interface. The influence of the charge redistribution on the experimental optical spectra taken from the silver-polymer composite at high doses, which cause the carbonization of the irradiated polymer, is discussed. Table 8.1, which summarizes available data for ion synthesis of MNPs in a polymeric matrix, and the references cited therein may be helpful in practice. 

J. C. Pivin and P. Colombo, Conversion of inorganic-organic polymers to ceramics by ion implantation, Nucl. Instr. Meth. Phys. Res. B, 1996, 120, 262-265. 

Guzman, L., Celva, R., Miotello, A., Voltolini, E., Ferrari, R, Adami, M. (1998) Polymer surface modification by ion implantation and reactive deposition of transparent films. Surf Coat. Tech., 103-104,375-379. 

The carbon structures formed under ion implantation reinforce the polymer surface and result in a drastic increase in its hardness (Fig. 4). These carbon-rich structures, with sizes ranging up to 40 nm in the case of energetic ion implantation [34], were found to be the aggregates of much smaller carbon clusters several nanometers in size [34,54]. The hardness of the carbonaceous phase produced by ion implantation does not depend directly on the concentration of sp sites (the... 

Many applications currently exist for carbon composite and polymer materials. Ion implantation is a technique that can result in a combination of the best properties of polymers and of carbon composites. Polymers, used for stmctural and packaging applications, have disadvantages, which usually include softness, low thermal stability, high chemical permeability, and low electrical conductivity. The lack of electrical conduction can lead to problems such as triboelectrification and electrostatic charging. The electrical conduction properties of polymers can be controlled by ion implantation. Ion implantation can make any polymer surface electrically conductive, chemically impermeable, and mechanically hard. Some appli-... 

All the spectroscopic observations described in the case of PPP are similar to those of polyparaphenylenevi-nylene [40]. A band appears at 757 cm" (Figs. 21.10c and 21.10d) after cesium ion implantation with low energy ( = 30 keV) and the same dose level as with PPP (D = 4 X 10 ions/cm ). This behavior is typical of electroactive polymers doped by ion implantation. 

C. Le Hiie, A. Moliton, B. Lucas, and G. Froyer. Compensation phenomena by ion implantation doping of an electroactive polymer, poly(parapheny-lene), Adv. Mater. Opt. Electron. 7 173 (1992). 

---