Light Scattering Study of Internal Motions of Model Hyperbranched Polystyrene Chains in a Theta‐Solvent System

ABSTRACT Resolving internal motion in hyperbranched chains under theta conditions is essential for separating branched connectivity from excluded‐volume screening, yet experimental benchmarks remain scarce. A model hyperbranched polystyrene (h‐PS; f = 3) assembled from a narrowly distributed V‐shaped macromonomer was fractionated and examined by static and dynamic light scattering. In toluene at 298.1 K, the selected fraction had M w = 4.35 × 10 7 g/mol, ⟨Rg⟩ = 178 nm, and an apparent low‐angle ⟨Rh⟩ = 149 nm. In dilute cyclopentane from 312.1 to 299.1 K, the low‐angle distributions remained unimodal while apparent ⟨Rh⟩ decreased from 124.4 to 97.9 nm. For qR h > 2, D app / D 0 scaled as ( qR h ) u with u = 0.40–0.44, whereas Γ scaled as q v with the algebraically coupled v = 2.40–2.44. Γ *( q ) declined over qR h < 3.5 and its terminal trend approached 0.010 without reaching a plateau, below the good‐ and marginal‐solvent h‐PS references and the linear‐chain theta benchmark. Faster components became resolvable near qR h ≈0.5 and ≈1.0, and their relative integrated area A f /( A f + A s ) increased overall with qR h while the temperature series remained intermingled. Thus, the lower high‐q response is consistent with theta‐solvent conditions and branching while intrachain relaxation persists. Together, these analyses distinguish whole‐chain transport from internal relaxation.