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.