4.

(a) UV–vis absorption and photoluminescence spectra of LP1, LP2, and LP3, all showing clear vibronic progression. A clear blue shift is observed from LP3 to sterically congested LP1. (b) DLS profiles of LP1 (10 mg/mL), LP2 (10 mg/mL), and LP3 (1 mg/mL) dissolved in chlorobenzene at room temperature. (c) SANS profiles and curve fitting of LP1 (10 mg/mL) and LP2 (10 mg/mL) dissolved in 1,2-dichlorobenzene-d ₄ at 130 °C and LP3 (5 mg/mL) dissolved in chlorobenzene-d ₅ at 75 °C. A fractal number of nearly unity was found for both LP1 and LP2 under the experimental conditions, suggesting their single-chain features relative to the aggregate LP3. (d) Kratky plot of LP1 and LP2 showing a monotonic increase for q values above 0.2 Å^–1 that signifies the contrast of local rigidity and long-range semiflexibility.