Magnetic properties of simple alkylene-aromatic polymers

This paper describes the results of the magnetization and the electron-spin resonance (ESR) measurements of the simplest members of alkylene-aromatic polymers (AAPs). In contrast with the previous claim of the observation of the ferromagnetism in AAPs, a distribution of the spin alignment giving 1 < S < 3/2 on the average has been concluded from the magnetization measurement. The spin concentration certainly coming from carbon π spins has turned out to be relatively small (∼10¹⁷-10¹⁸ spins·g ^-1). The ESR observation has revealed a forbidden Δm _s = ± 2 transition characteristic of a triplet or higher multiplet state of radical pairs in agreement with the observation of the local spin alignment. The relationship between the spin state and the chemical structure of AAPs has also been examined with the use of the ¹³C NMR spectroscopy. It is concluded that in the present material there is a ferromagnetic coupling between a few of spins such as triphenylmethyl radicals forming spin clusters of triplet or higher spin multiplet state diluted in the whole bulk.