(a) Chemical structures of the three chromophores used in this study: 4,4-difluoro-5,7-diphenyl-4-bora-3a,4a-diaza-s-indacene-3-dodecanoic acid (Bodipy C12), N,N ′ -Bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylenedicarbox-imide (BTBP), and N,N ′ -Dipentyl-3,4,9,10-perylenedicarboximide (DPPC). The double-sided arrow indicates the direction of the transition dipole moments of these dyes. (b) Chemical structures of the three polymers used in this study: polystyrene (PS), poly(4-tert-butyl styrene) (PtBS), poly(2-vinyl pyridine) (P2VP).
Schematic of instrumental apparatus: P, Polarizer; BS, beam splitter; S, shutter; ND, neutral density filter; λ/2 (λ/4), half-(quarter-) wave retardation plate; DM, dichroic mirror; H, pinhole; PBS, polarizing beam splitter; FC, fiber coupling; APD, avalanche photodiode; V, valve.
Wide field illumination image of bleached pattern used to measure reorientation of dye molecules; the hole in the TEM grid is tilted in the micrograph. Photobleached regions appear dark because less fluorescence originates from these regions. Numbers indicate measurement sequence: (1) z scan; (2) x scan; (3) y scan; (4) intensity measurement of bleached region (20 × 20 μm); (5) intensity measurement of unbleached region.
Temperature-ramping anisotropy measurement of BTBP reorientation in PS. (a) Fluorescence intensity data from unbleached region (open symbols, sequence 5 from Fig. 3) and bleached region (closed symbols, sequence 4 from Fig. 3). (b) Anisotropy as a function of temperature, calculated from intensity data of panel (a) using Eq. (3).
Temperature-ramped anisotropy measurements of BTBP reorientation in (a) PS and (b) PtBS, with different sample and measurement positions. Inset figures show (a) where the sample was placed along the z-axis and (b) where the measurement was performed relative to the TEM grid. Based upon these results, the sample temperature is known to within 1 K.
(a) Bleach depth as a function of temperature for DPPC in PS in oxygen gas and under oxygen-free conditions. (b) Anisotropy decays for bleaching conditions described in panel (a).
(a) Temperature profiles of single step (S) and multistep temperature-ramping anisotropy experiments on BTBP in PS. The numbered sequence defines the multistep temperature program: 340 K→ 378 K → 345 K → 390 K →345 K. (b) Anisotropy decays for BTBP in PS with the temperature programs indicated above.
Anisotropy decays for BTBP in three polymers (points) acquired by increasing temperature at 2 K/min. The sample thicknesses were 3–5 μm. Ramping rate was 2 K/min. The solid lines indicate DSC data for these polymers acquired while heating at 10 K/min rate and analyzed as described in the text.
Anisotropy decays for BTBP in freestanding PtBS thin films with thicknesses down to 22 nm. The temperature where the normalized anisotropy drops to the value of 0.5 is denoted as T 0.5.
Anisotropy decays of different dyes in bulk polystyrene films. The vertical straight line indicates the glass transition temperature measured by DSC.
Ramping rate dependence of the anisotropy decay for BTBP in PS. The vertical straight line indicates the glass transition temperature measured by DSC at 10 K/min.
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