Structure–Property Relationships of Solution‐Processable Diarylethene‐Based Main‐Chain Photochromic Polymers

• Published in: Macromolecular chemistry and physics Vol. 225; no. 12
• Main Authors: Gwebu, Sandile, Marshall, David, Sonar, Prashant, Philippa, Bronson, Vamvounis, George
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.06.2024
• Subjects: Chloroform; Copolymers; diarylethenes; Dichloromethane; Glass transition temperature; organic electronics; photochromes; Photochromism; Photodegradation; Polymers; Tetrahydrofuran; Thermal stability; Thin films; Toluene
• DOI: 10.1002/macp.202300161
• ISSN: 1022-1352

A series of alternating copolymers of a dithienylethene with di‐n‐alkyl‐fluorene (P1–P3), di‐n‐hexylphenylene (P4), 9‐heptadecanylcarbazole (P5), and 4,8‐bis(3,5‐dioctyl‐2‐thienyl)‐1,5‐dithia‐s‐indacene (P6) are designed, synthesized, and characterized. All of the polymers are soluble in common organic solvents such as chloroform, dichloromethane, toluene, and tetrahydrofuran. The side‐chain length affected the solubility of the polymer, molecular weight, and the glass transition temperature. Solutions of P1–P6 show photochromism with high quantum yields of 6‐π electrocyclization (41–87%) and cycloreversion (0.4–1.1%). These polymers also formed uniform thin films and the rates of solid state photoisomerization are measured relative to P4, which has the highest cyclization and cycloreversion rates. The color of the photochromic polymer is tuned according to the comonomer and the maximum absorption wavelength ranged from 569 to 675 nm in the closed isomeric form. All the polymers are thermally stable and show no signs of photodegradation after being exposed to UV‐light for 120 min in air. Based on these promising results, these polymers may be useful for multifunctional organic electronic devices. A series of main‐chain dithienylethene‐based photochromic polymers are presented. These novel polymers form uniform thin‐films by spin‐coating. These films maintain their reversible photoswitching characteristics, are fatigue resistant and are color tunable by changing the comonomer. It is anticipated that this class of materials will be useful in light controlled organic microelectronic devices.