Molecular Motion of Peroxy Radicals at Ends of Isolated and Nonisolated Polyethylene Chains Tethered on Powder Surface of Poly(tetrafluoroethylene) in a Vacuum

Abstract

Molecular motion of peroxy radicals at the ends of isolated (IPE) and nonisolated polyethylene (NIPE) chains tethered on the powder surface of poly(tetrafluoroethylene) (PTFE) was investigated in a vacuum in the temperature range from 3.4 to 223 K by electron spin resonance (ESR) and a spectral simulation. The IPE and the NIPE chains were produced by radical polymerization of ethylene initiated by PTFE radicals located on the surface. The isotropic and the anisotropic tumbling motions of the ends of IPE chains on the PTFE surface were observed, and their activation energies were estimated. At 223 K, the anisotropic tumbling motion mode of all the ends of IPE chains on the PTFE surface converted into a free rotational motion mode having a rate of 1.00 × 109 s-1, in which the ends were protruding from the PTFE surface. The ends of IPE chains had noninteractions with both neighboring intra- and interchains of IPE. In contrast, the isotropic and the anisotropic tumbling motions of the ends of NIPE chains on the PTFE surface were slower than those of IPE chains. Even at 223 K, the tumbling motion of the ends on the surface still had anisotropic rates of 1.18 × 108 and 6.25 × 108 s-1. The slow and anisotropic rates of the ends of NIPE chains on the PTFE surface were due to the interactions with both neighboring intra- and interchains of NIPE.