The β Phase Formation Limit in Two Poly(9,9-di-n-octylfluorene) based Copolymers

• Published in: Macromolecular rapid communications. 2011-07, Vol.32 (13), p.983-987
• Main Authors: Bright, Daniel W., Moss, Kathryn C., Kamtekar, Kiran T., Bryce, Martin R., Monkman, Andrew P.
• Format: Article
• Language: English
• Subjects: copolymers; dibenzothiophene-S; dibenzothiophene‐S,S‐dioxide; Fluorenes - chemistry; Kinetics; monomers; polyfluorene; Polymerization; Polymers - chemical synthesis; Polymers - chemistry; S-dioxide; Thiophenes - chemistry; β phase
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.201100221

Random copolymers of poly(9,9‐di‐n‐octylfluorene) (PF8) incorporating 0, 8, 12, 15, and 20% dibenzothiophene (DBT), and copolymers with 2, 5, 8, 12, and 15% dibenzothiophene‐S,S‐dioxide (S‐unit) were synthesised. Absorption and emission spectra of thin films indicate that the DBT system shows a linear decrease of toluene vapour induced β phase with increasing DBT content to a 20% cutoff, whilst in the S‐unit copolymers the β phase is present up to 12% co‐monomer content, and at 15% the characteristic absorption peak is absent or masked. These results demonstrate the limits, in thin films, at which the β phase can be formed in widely used PF8 copolymer systems for device applications and clearly show that it is practical to use copolymers having electron or hole transport units in the polyfluorene backbone and still be able to form efficient β phase emission sites. β Phase is shown to form in thin films of PF8 copolymers up to a limit of 20% dibenzothiophene or 15% dibenzothiophene‐S,S‐dioxide as co‐monomer, as currently used for research into charge‐transfer polymers for white light devices.