Association behavior of linear ω‐functionalized polystyrenes in dilute solutions

Linear polystyrenes with dimethylamino end groups were prepared by anionic polymerization, using 3‐(dimethylamino)propyllithium as initiator and high vacuum techniques. The amino group was transformed to a sulfozwitterionic moiety by reaction with 1,3‐propanesultone. The dilute solution properties were studied by means of membrane osmometry (MO), low‐angle laser light scattering (LALLS) and viscometry in solvents with different polarity. The amine‐capped polymers, studied by LALLS in tetrahydrofuran (THF), toluene and CCI₄ show no evidence of association. In contrast, the zwitterionic samples exhibited a relatively strong association in CCI₄ (relative permittivity ε = 2.24), weak in THF (ε = 7.4), and intermediate in toluene (ε = 2.4). The association numbers were lower than those found for linear polyisoprenes and polybutadienes with the same end groups. Viscosity measurements supported the results drawn from LALLS. The results provide strong evidence that the micelles behave hydrodynamically as star polymers. The association behavior is best described by the linear head packing model.