Abstract
The spin–lattice relaxation time T1 and nuclear Overhauser enhancement NOE were determined for three samples of atactic oligo- and poly(α-methylstyrene)s (a-PαMS) with weight-average degree of polymerization xw = 2, 3, and 67.1 in cyclohexane at 30 °C. A comparison is made of the present data for T1 and NOE with the helical wormlike (HW) chain theory, and it is shown that the theory may explain well the data for large xw (≳ 10). For smaller xw, the rigid sphere model having the radius equal to the apparent root-mean-square radius of gyration of the HW chain fails to give a quantitative explanation of T1 in contrast to the case of the relaxation time τΓ determined from dynamic depolarized light scattering measurements, indicating that the nuclear magnetic relaxation and dynamic depolarized light scattering cannot be described in terms of a common single relaxation time. However, it is shown that there is an effective (mean) magnetic relaxation time τM approximately equal to 0.6τΓ. From a comparison of the present results for T1 for a-PαMS with previous ones for typical flexible polymers, it is also shown that the behavior of T1 for them, including a-PαMS, may be consistently explained by the use of τM (proportional to τΓ).
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