Poly line broadening

In contrast, in the case of poly(cyclohexyl methacrylate), the calculated correlation time is much longer. Its value agrees nicely with a strong line broadening of the ring carbon NMR peaks. 

Wong and coworkers. [82, 83] used solution and solid-state NMR to study the cure of the norbornene end-capped poly(imide)s 2NE/DDM and PMR-15. At lower cure temperatures, exo-endo isomerization was observed to be a major product [84]. Loss of cyclopentadiene was suggested to result in initiation of the partner maleimide, as well as Diels-Alder addition of cyclopentadiene with norbornene. There was no evidence of internal double bonds formed by incorporation of the cyclopentadiene into the polymer backbone. The solid-state spectra were very poorly resolved, but did allow confirmation of the mechanism of reaction [83]. Spectra obtained at higher fields did not show improved resolution, indicating that the dominant mechanism for line-broadening in these materials is the dispersion of isotropic chemical shifts resulting from frozen conformations. In later work, Milhourat-Hammadi and coworkers [84, 85] reported solution-state and NMR studies of PMR-15 prepolymers. 

Figure 10. Effect of sonication time on P NMR signals of poly(dAdT) poly-(AAdT) 0 min, 31 C 10 min, 26°C 1 h, 28 C and 3 h, 20 C, each with 3 Hz line broadening. The average chair lengths determined by gel electrophoresis were 690, 195,116, and 84 bp, respectively (22).

Chlorine. The interaction between Cl and linear and branched poly-ethyleneimine has been investigated using C1 and C1 NMR spectroscopy. Iodine. Oxygen exchange in H5IO6 has been investigated by NMR line broadening at elevated pressures. ... 

Fig. 6. (A) P-NMR of poly(A)-oligo(U) (1.32 1) in 10 mM MgClj temperatures (°C) 80.99 MHz. Total nucleotide concentration, 8.4 mAf. Exponential line broadening.

Thus, at room temperature, the molecular motions responsible for the mechanical losses of poly(cyclopentyl methacrylate) and poly(cycloheptyl methacrylate) are very rapid processes, having too-high a frequency to broaden the line widths of MAS CP DD 13C NMR spectra, in agreement with the absence of observable motional broadening in the spectra of these two polymers (Fig. 8a and c). 

---