Ion Beam Irradiation Ion Beam Irradiation Effects on Polymers  Effects on Polymers  

Mircea ChiparaMircea ChiparaNow at:Now at:

The University of TexasThe University of TexasPan AmericanPan American

Department of Physics and Department of Physics and Geology, Edinburg, TX Geology, Edinburg, TX

7854178541

1.1. Excitations of individual atoms and molecules.Excitations of individual atoms and molecules.2.2. Excitations of several atoms and molecule, leading to Excitations of several atoms and molecule, leading to

collective motions inside the target.collective motions inside the target.3.3. Phonons generation and sample heating. Phonons generation and sample heating. 4.4. Breaking of chemical bonds. Breaking of chemical bonds. 5.5. Ionizations, bond scissions, formation or radicals and Ionizations, bond scissions, formation or radicals and

radical ions. radical ions. 6.6. Atoms sputtering from surface and atom Atoms sputtering from surface and atom

displacements (point defects) within the bulk.displacements (point defects) within the bulk.7.7. Emission of electromagnetic radiation from the Emission of electromagnetic radiation from the

irradiated samples during ion beam bombardmentirradiated samples during ion beam bombardment8.8. The recombination of free radicals (crosslinkingThe recombination of free radicals (crosslinking reactions).reactions).

7.7.

Ion Beam Irradiation Effects Ion Beam Irradiation Effects in Polymersin Polymers

Free radicals generation Free radicals generation in ion beam irradiated polymersin ion beam irradiated polymers

Macromolecular chain scissionMacromolecular chain scission

In chain radicalIn chain radical End chain radicalsEnd chain radicals

Macromolecular chain crosslinkMacromolecular chain crosslink

Not very efficient due to steric restrictions

In chain radicalsIn chain radicals

Macromolecular chain crosslinkMacromolecular chain crosslink

In chain radicalIn chain radical

End chain radicalEnd chain radical

Macromolecular chain crosslinkMacromolecular chain crosslink

End chain radicalEnd chain radical

End chain radicalEnd chain radical

A stack consisting of 18 polycarbonate (MAKROFOL) A stack consisting of 18 polycarbonate (MAKROFOL) layers, each of 8 layers, each of 8 m thickness, with a diameter of 5 cm, m thickness, with a diameter of 5 cm, has been irradiated with Uranium ions accelerated up has been irradiated with Uranium ions accelerated up

to about 10 MeV/nucleon, at “Gesellschaft fur to about 10 MeV/nucleon, at “Gesellschaft fur Schwerionenforschung”, Germany. Schwerionenforschung”, Germany.

The flux of incident ions was about 10The flux of incident ions was about 1088 ions/cm ions/cm22s s and the fluency 10and the fluency 1010 10 ions/cmions/cm22. .

The samples were analyzed by ESR, UV-VIS, The samples were analyzed by ESR, UV-VIS, and luminescence spectroscopy. and luminescence spectroscopy.

Experimental MethodsExperimental Methods

PC+URANIUM IONS

ESR spectrum ESR spectrum shape, position shape, position and tempera-and tempera-ture dependen-ture dependen-ce support for ce support for

the same the same mechanism for mechanism for

ion beam ion beam bombarded bombarded and gamma/ and gamma/

electron electron irradiated PCirradiated PCRadical RRadical R11 is converted into R is converted into R22. above . above

The glass transition temperature, TThe glass transition temperature, TGG..

Gamma irradiatedGamma irradiated

The dependence of ESR line parameters (line intensity The dependence of ESR line parameters (line intensity I and peak to peak line width HI and peak to peak line width HPP PP

on the penetration depthon the penetration depth

The dependence of free radicals concentration The dependence of free radicals concentration on the linear energy transferon the linear energy transfer

UV-VIS spectra of ion beam irradiated PCUV-VIS spectra of ion beam irradiated PC

Ion beam irradiation effect on the energy gap Ion beam irradiation effect on the energy gap of PC- as estimated from UV-VIS spectraof PC- as estimated from UV-VIS spectra

The luminescence spectrum of ion beam bombarded PC

The dependence of the ESR line intensity, luminescence The dependence of the ESR line intensity, luminescence line intensity, energy gap and deposited dose on the line intensity, energy gap and deposited dose on the

penetration depth for the U irradiated PC stack.penetration depth for the U irradiated PC stack.

CONCLUSIONSCONCLUSIONS Polymer chain scission mechanisms implies the generation of free radicals, while the crosslinking can be associated to the free radical decay.ESR is an efficient tool in the study of free radical. Spectroscopic investigations (ESR, VUV, and luminescence) revealed that for ion beam irradiated polycarbonate films the local heating is relatively modest. At least 75% of the latent track is not heated above the melting temperature. ESR data shows that the free radicals are coupled by extreme exchange interactions in clusters along the incident particle track, that the exchange interactions are anisotropic. The linear dependence of the free radical generation on the linear energy transfer is demonstrated.

REFERENCESREFERENCES  1. F. Banhart, Rep. Prog. Phys. 62, 1181(1999). 2. A. M. Ektessabi and T. Sano, Rev. Sci. Instrum. 71, 1012 (2000). 3. M. Chipara and L. Georgescu, Nucl. Instrum. Meths. Phys. Res. B, 209/210, 401 (1983). 4. M. Chipara, I. Bunget, R. Georgescu, E. Georgescu, and I. Vilcov, Nuclear Instruments and Methods Nucl. Instrum. Meths. Phys. Res B, 209/210, 395 (1983). 5. M. Chipara, and J. Reyes-Romero, Nucl. Instrum. Meths. Phys. Res. B 185, 77 (2001). 6. O. Puglisi, M. Chipara, W. Enge, G. Compagnini, J. Reyes Romero, U. Bacmeister, and M. D. Chipara, Nucl. Instrum. Meths. Phys. Res. B 166-167, 944 (2000). 7. M. Chipara, Nucl. Instrum. Meths. Phys. Res. B, 131, 85 (1997). 8. J. D. Ferry, Viscoelastic Properties of Polymers (Wiley, New York (1977), pp. 106-127. 9. C. K. Ong, Z. G. Song, and H. Gong, J. Phys.: Condens. Matter 9, 9289 (1997).