Three different co-crystalline phases of syndiotactic polystyrene with a nitroxide radical

Abstract

Extensive crystallization studies have been conducted on syndiotactic polystyrene in the presence of the nitroxide radical compound 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO). Depending on the selected crystallization conditions, three different co-crystalline phases are obtained: beside the known intercalate structure (guest layers intercalated with layers of alternated enantiomorphous helices), a δ-clathrate structure (isolated guests imprisoned into cavities formed between the same kinds of layers), and a ε-clathrate structure (guests confined into channels). All three s-PS/TEMPO co-crystalline phases exhibit a long-term stability for temperatures below 60 °C. The control of the polymorphism of the co-crystals, associated with the control of film morphology (axial and/or uniplanar orientations) allows a control of concentration and orientation of the radical guest molecules, which can be helpful for the preparation of new organic magnetic materials.