Intrahelical empty channels of nanoporous-crystalline α and β forms of PPO. (5th October 2022)

• Record Type: Journal Article
• Authors: Golla, Manohar; Nagendra, Baku; Daniel, Christophe; Rizzo, Paola; Auriemma, Finizia; Tarallo, Oreste; Guerra, Gaetano
• Is Part Of: European polymer journal. Volume 179(2022)
• Publication Date: 2022-10-05
• Subjects: Axially oriented amorphous and crystalline phases -- Infrared linear dichroism -- Film birefringence -- Intrahelical guest placement; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2022.111568
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: Highlights: First linear dichroism study on polyphenyleneoxide, by Polarized FTIR. Signs of dichroism of peaks of α and β phases opposite with respect to amorphous phases. Large crystalline polymer helices, with intrahelical guest location. Abstract: A linear dichroism study of vibrational peaks of amorphous and semi-crystalline axially stretched poly(2, 6-dimethyl-1, 4-phenylene)oxide (PPO) films shows an unusual behaviour of co-crystalline and nanoporous-crystalline (α and β form) phases. In fact, signs of dichroism for all vibrational peaks of α and β phases are opposite with respect to those observed for amorphous phases. This behaviour indicates the occurrence in PPO α and β forms of large polymer helices, whose thermodynamic stability can be rationalized by placement of guest molecules in intrahelical channels. A large diameter helix, with chain periodicity of 1.06 nm, is compatible with layer-line position in WAXD patterns of axially stretched α form films. The occurrence for both α and β NC forms of PPO of intrahelical empty channels, can rationalize the very high guest diffusivity of semi-crystalline PPO films, which becomes particularly high when crystalline helical axes are preferentially perpendicular to the film plane.