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Alkyne creation in aliphatic polymers: influence of side groups
Yvette Ngono-Ravache1, Dominique Corbin, Christophe Gaté
1CIRIL, Unité Mixte CEA-CNRS-ENSICAEN, BP 5133, 14070 Caen Cedex 5, France. ngono@ganil.fr
The Journal of Physical Chemistry. B
|April 4, 2007
Summary
Side groups significantly influence terminal alkyne creation in polymers exposed to swift heavy ions. Polymers with C=C bonds in side chains show reduced alkyne formation thresholds compared to polyethylene.
Area of Science:
- Polymer Science
- Materials Science
- Radiation Chemistry
Background:
- Swift heavy ion irradiation induces chemical modifications in polymers.
- Terminal alkyne creation is a key radiation-induced process in polymers.
- The influence of polymer side groups on radiation effects is not fully understood.
Purpose of the Study:
- To investigate the effect of side groups on terminal alkyne creation in aliphatic polymers under swift heavy ion irradiation.
- To compare alkyne formation in polyethylene and substituted polymers with varying side groups.
- To determine the influence of alkyl and allyl side groups on the threshold electronic stopping power for alkyne formation.
Main Methods:
- Aliphatic polymers (polyethylene, polypropylene, polybutene, EPDM linear, EPDM cyclic) were irradiated with swift heavy ions under vacuum.
- Fourier transform infrared (FTIR) spectroscopy was used to analyze the irradiated samples.
- Terminal alkyne creation was quantified and correlated with electronic stopping power (dE/dx)e.
Main Results:
- Terminal alkyne creation requires the electronic stopping power to exceed a threshold value.
- Alkyl side chains moderately influenced this threshold, while C=C bonds in side chains clearly reduced it.
- In saturated polymers, alkyne formation occurred below the threshold after a latent dose, independent of side-chain length, and was linked to prior double bond formation.
- The radiation chemical yield (G0) for alkyne formation in EPDM linear was four times higher than in polyethylene.
Conclusions:
- Side groups play a crucial role in modulating terminal alkyne creation during swift heavy ion irradiation.
- The presence of C=C bonds in side chains significantly lowers the energy required for alkyne formation.
- Energy transfer from the polymer backbone to side-chain double bonds is a key mechanism, especially in unsaturated polymers.
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