Disclosed are rigid random coils, having a contour length larger than a diameter thereof, an average bending ratio Db of 0.1˜0.8, and a weight average molecular weight of 1×108˜9×108 g/mole, and a resin composition or organic solvent composition including the same. The rigid random coils have the properties intermediate between those of polymers and rigid rod particles, and thus may be used as filler of various resins, aqueous solutions or organic solvents.