Abstract
The photophysical properties of two polyrotaxanes (PFBTh center dot PSCD and PFBTh center dot PMeCD) composed of fluorene and bithiophene encapsulated into permodified -cyclodextrin cavities have been investigated and compared with those of the reference PFBTh. Rotaxane formation results in improvements of the thermal stability, solubility in common organic solvents, as well as better film forming ability combined with a high transparency. As expected PFBTh and its encapsulated forms absorb at wavelengths beyond 510 nm, and time-resolved photoluminescence (PL) in solution shows a well-define vibronic structures with a predominance of the 0-0 transitions and an energy difference of 0.16 eV. The fluorescence lifetimes follow a monoexponential decay with a value = 630 +/- 30 ps. Atomic force microscopy, AFM, indicated a tendency of polyrotaxanes to organize into fibers. The advancing contact angles indicated higher surface hydrophobicity and lower surface free-energy values for polyrotaxanes compared with their unthreaded analogues. The device based on PFBTh center dot PSCD:PCBM in a 1/1 w/w ratio under simulated AM 1.5G illumination at 100 mW cm(-2) exhibited improved photovoltaic parameters of cells, resulted in high V-oc (0.68 V), J(sc) (1.65 mA cm(-2)), FF (31.6%), and PCE (0.35) values, compared with PFBTh or PFBTh center dot PMeCD, respectively. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 460-471