Dynamics of polar aromatic molecules confined in a nanocavity of δ-phase of syndiotactic polystyrene as studied by dielectric spectroscopy

Abstract

Rotational dynamics was examined in detail for four polar aromatic molecules, benzonitrile (BN), p-methylbenzonitrile (p-MBN), o-methylbenzonitrile (o-MBN), and m-methylbenzonitrile (m-MBN), accommodated in a nano-cavity regularly arranged inside the crystalline region (δ-form) of syndiotactic polystyrene (sPS) by means of dielectric relaxation measurements. Except for m-MBN, for which the co-crystalline structure was monoclinic δ-intercalate and no dielectric relaxation process arising from the crystalline region appeared, other three polar guests in the monoclinic δ-clathrate form exhibited the specific dielectric relaxation process. The relaxation times of o-MBN, BN, and p-MBN at room temperature were ranged from 10−7s to 10−1s, and in the order of o-MBN<BN<p-MBN. From the analysis of dielectric intensity data as functions of temperature, new insights about the stable and quasi-stable states of the guest molecules inside the cavity were obtained based on the two site model.