A new cross-linking route via the unusual collision kinematics of hyperthermal protons in unsaturated hydrocarbons: the case of poly(trans-isoprene)

Abstract

The bombardment of a ∼18 nm film of poly(trans-isoprene) molecules (∼300 000 carbon atoms per molecule) with a mass-separated proton beam at 10 eV has been shown to induce highly efficient cross-linking of several macromolecules per incident proton. In this new method using physical means to conduct synthetic chemistry, the hyperthermal protons preferentially cleave C–H bonds because of their unusual kinematics in hydrocarbons, and the carbon radicals thus created initiate a polymerization chain reaction of the isoprene CC bonds. The method produces ultrathin polymeric films via cross-linking with a dry process having high chemical selectivity and reactivity but requiring no thermal cost and no chemical additives, conditions that are commonly required in the fabrication of microelectronics and photonics.