Dynamics of macromolecular chains. VII. Nuclear magnetic relaxation of monosubstituted polystyrenes in solution

The 1H spin‐echo and 13C spin–lattice relaxation times have been measured for solutions of polystyrene derivatives: ortho, meta, and para‐halo (F, Cl, Br) and ortho, meta, para, and α‐methyl. Results obtained from these two techniques permit comparison of the intramolecular mobility of these polymers with that of polystyrene. Poly(α‐methylstyrene) does not differ from polystyrene except for a slight slowing of both segmental reorientation and internal phenyl‐group motions and apparent hindrance of the methyl‐group rotation. Segmental reorientation of poly(m‐methylstyrene) is similar to that of polystyrene; rotation of the methyl group is free, while the internal phenyl‐ring process is slower. Poly(p‐methylstyrene) and poly(o‐methylstyrene) also contain freely rotating methyl groups; the intramolecular mobility decreases from the para to the ortho position of the substituent. Finally, in poly(o‐bromostyrene) and poly(o‐chlorostyrene), the internal motion of the phenyl ring is completely overshadowed by the segemental reorientation, which is itself quite reduced.