Field-cycling NMR relaxometry of polymers confined to artificial tubes: verification of the exponent 3/4 in the spin–lattice relaxation dispersion predicted by the reptation model

2H field-cycling NMR relaxometry was applied to deuterated linear polyethyleneoxide (PEO) of different chain lengths confined in a porous matrix of cross-linked polyhydroxyethylmethacrylate (PHEMA). The PHEMA pore diameter was of the order of 10 nm, i.e. smaller than or similar to the dimension which the PEO coils would have in the unconfined melt. The frequency and molecular weight dependences of the spin–lattice relaxation time predicted by de Gennes as T1∝M0ω3/4 on a timescale short compared with the Rouse relaxation time are well reproduced experimentally.