SANS Investigation of Global and Segmental Structures of Hyperbranched Aliphatic-Aromatic Polyesters

SANS measurements in THF-d(6) were carried out at the D11 instrument at ILL, Grenoble with two aliphatic aromatic hyper-branched (hb) samples with nearly the same degree of polymerization (DP approximate to 90), containing hydroxyl (OH) and silyl-ether (SY) terminal groups. The choice of a large region of momentum transfer q permitted probing the global shape and the local structure. The scattering of both samples showed pronounced concentration dependence. Using Zimm's well-known scattering equation the true size and shape of the macromolecules at finite concentration were derived. Agreement of the data and curves at finite concentration with those at c = 0 was obtained. The scattering curves were analyzed on the basis of the Sinha et al.'s refinement of fractals. Complete agreement with the experimental scattering curves was achieved. The apparent anomalous behavior at very large q-values was shown to arise from the monomer and segmental contributions. Molecular dynamics (MD) simulation of an uniform hb sample (DP 35) revealed the monomer contribution in agreement with the experiment. The discrepancy of the experimental curve at. small q-values is shown to arise from the broad molar mass distribution. When Flory's molar mass distribution was combined with the MD simulation data, the experimental results were described well.