Effect of solvent aromaticity on poly(9, 9-dioctylfluorene) (PFO) chain solution behavior and film condensed state structure. (17th December 2019)

• Record Type: Journal Article
• Authors: Liu, Bin; Zhang, Hao; Ren, Jiaxuan; Ma, Tengning; Yu, Mengna; Xie, Linghai; Lu, Dan
• Is Part Of: Polymer. Volume 185(2019)
• Publication Date: 2019-12-17
• Subjects: Conjugated polymer -- Aromatic solvent -- π-π interaction -- Excluded volume -- Solution behavior; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2019.121986
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Solvent media is crucial to the dynamic evolution process of conjugated polymer condensed state structures from solution state to film. Especially, aromatic solvent can arouse strong π-π interaction with conjugated polymer backbone. Poly(9, 9-dioctylfluorene) (PFO) is a classic hairy-rod conjugated polymer. Chlorobenzene (CB) and toluene (Tol) were used as aromatic solvents, while tetrahydrofuran (THF) and chloroform (CF) were used as non-aromatic solvents. It was firstly found that PFO chain solution behaviors were closely connected to solvent aromaticity with broad concentration range from 0.005 mg/mL to 5 mg/mL. Owing to the bigger chain exclude volume in CB and Tol solvents, in dilute solution with PFO concentration ≤ 0.7 mg/mL, PFO single chains adopted more extended and rigid chain conformation than those in THF and CF solvents, thus, needed conjugated length of β conformation could be easily achieved, and β conformation could be firstly formed; PFO solution concentration increased to ≥ 1 mg/mL, chain aggregation began formation, but aggregation sizes were larger meanwhile chain packing density decreased according to the fractal dimension parameter d f ; Until PFO solution concentration increased to ≥ 3 mg/mL, only β conformation characteristic peaks began appearance in the all PL spectra. The different solution state behaviors directly affect film condensed structures. A fiber and ordered structure formed in films from CB and Tol solvents, meanwhile circular sheet and short rod-like morphology formed in films from THF and CF solvents, respectively. Solvent effect is significant not only to deeply understand the physical essence both condensed state structure formation and photoelectric performance enhancement but also to well control conjugated polymer condensed state structure to achieve photoelectric devices with high efficiency and stability. Graphical abstract: Image 1 Highlights: PFO single chain were more extended and rigid in CB and Tol aromatic solvents. β conformation could be firstly formed in CB and Tol solvents. Aggregation sizes were larger but chain packing density decreased in aromatic solvents owing to the bigger net excluded volume. The different solution state behaviors directly affect film condensed structures. Fiber and ordered structure formed from CB and Tol solvents, meanwhile circular sheet and short rod-like morphology formed from THF and CF solvents.