2,2′-Bipyrimidine as a Building Block for the Design of Emissive Conjugated Polymers for Hybrid LED Lighting

Qiqiao Lin (1) , Xiaoguang Huang (1) , Sasikumar Ramachandran (1) , Xinyang Wang (1) , Rachod Boonsin (2) , Yasmine Khendriche (2) , Rodolphe Valleix (2) , Jean-Philippe Roblin (2) , Damien Boyer (2) , Geneviève Chadeyron (2) , Gaël Zucchi (1)

1 LPICM - Laboratoire de physique des interfaces et des couches minces [Palaiseau]
2 SIGMA Clermont - SIGMA Clermont

This work introduces 2,2′-bipyrimidine as an acceptor unit in the design of donor−acceptor conjugated polymers. Regularly alternating this moiety with the electron-rich 2,7-dihexyl fluorene and 3,6-carbazole units lead to polymers P1 and P2, respectively, which both showed a red-shifted emission with respect to the parent polyfluorene and polycarbazole derivatives. Investigations on the thermal properties showed that P1 and P2 both possess decomposition temperatures higher than 250°C under a mixture of N 2 and O 2. P1 was used as a representative example of this family of conjugated polymers to design white-emitting materials, both in solution and in the solid state. P1 and P2 were investigated as phosphors for LED lighting. Two composite films elaborated with P1 and P2 embedded into a PMMA matrix labeled P1c and P2c, respectively, were irradiated with a 375 nm-LED at a power as high as 48 W/m 2. P1c was found to show a lower photostability. Two ways to improve the stability under UV exposure were investigated. On the one hand, replacing 2,7-dihexyl fluorene by 3,6-hexyl carbazole approximately improved the photostability by a factor of 2, while on the other hand, embedding the polymers into a liquid sol−gel hybrid matrix allowed an improvement of the stability by a factor of 3. We could obtain a stabilization of the intensity of P2c at ∼half of its initial intensity, thus showing an improvement of the photostability of more than five times with respect to pure P1.

Mots clés: LED lighting; photostability; hybrid phosphor; conjugated polymers; Metrics & More Article Recommendations 2; 2′-bipyrimidine

Domaines: Chimie de coordination

Qiqiao Lin, Xiaoguang Huang, Sasikumar Ramachandran, Xinyang Wang, Rachod Boonsin, et al.. 2,2′-Bipyrimidine as a Building Block for the Design of Emissive Conjugated Polymers for Hybrid LED Lighting. ACS Applied Polymer Materials, 2020, 2 (12), pp.5581-5591. ⟨10.1021/acsapm.0c00915⟩. ⟨hal-03426123⟩