The (excess) power spectrum JΓ of the depolarized component of scattered light intensity was measured for eight samples of isotactic oligo- and poly(methyl methacrylate)s (i-PMMA), each with the fraction of racemic diads fr ≃ 0.01, in the range of weight-average degree of polymerization xw from 4 to 70.1 in acetonitrile at 28.0 °C (ϑ). The spin−lattice relaxation time T1 was also determined for the three samples with xw = 4, 5, and 70.1, and the nuclear Overhauser enhancement NOE, for the two samples with xw = 4 and 70.1, all in acetonitrile at 35 °C. As in the cases of atactic (a-) polystyrene (a-PS) and a-PMMA previously studied, it is found that JΓ may be well represented in terms of a single Lorentzian independently of xw and that the relaxation time τΓ defined from JΓ at infinite dilution increases with increasing xw and levels off to its asymptotic value in the limit of xw → ∞, being consistent with the recent theoretical prediction on the basis of the helical wormlike (HW) chain model. A comparison...