Internal structure and dynamics of commercial and natural cellulose were studied by measuring chemical shift anisotropy (CSA) parameters, and spin–lattice relaxation rate (1/T₁) at each and every chemically different carbon nuclear site. CSA parameters were measured by ¹³C two-dimensional phase adjusted spinning sideband (2DPASS) cross-polarization magic angle spinning (CP-MAS) NMR experiment. Site specific spin–lattice relaxation time was measured by Torchia-CP method. Anisotropy parameters of C4 and C6 regions are higher than C1 and C235 regions and asymmetry of C4 line is lower than any other carbon site. The higher values of CSA parameters of C4 and C6 nuclei arise due to the rotation of O4–C4, C1–O4, O5–C5–C6–O6 and C4–C5–C6–O6 bonds at torsion angles ψ, Φ, χ and χ′ respectively and the influence of interchain and intrachain hydrogen bondings. Two distinct peaks are also observed for C4 and C6 resonance line position—one peak arises primarily due to the nuclei in amorphous region and another one arises due to the same nuclei resides in paracrystalline region. The spin–lattice relaxation time and the CSA parameters are different at these two distinct peak positions of C4 and C6 line. Molecular correlation time of each and every chemically different carbon site was calculated with the help of CSA parameters and spin–lattice relaxation time. The molecular correlation time of the amorphous region is one order of magnitude less than the crystalline region. The distinction between amorphous and paracrystalline regions of cellulose is more vividly portrayed by determining spin–lattice relaxation time, CSA parameters, and molecular correlation time at each and every chemically different carbon site. This type of study correlating the structure and dynamics of cellulose will illuminate the path of inventing biomimetic materials.

中文翻译：

---

通过13 C-NMR弛豫法和2DPASS-MAS-NMR测量研究纤维素的内部结构和动力学

通过测量化学位移各向异性（CSA）参数以及在每个化学上不同的碳核位置处的自旋-晶格弛豫速率（1 / T ₁），研究了商业和天然纤维素的内部结构和动力学。通过¹³ C二维相位调整纺丝边带（2DPASS）交叉极化幻角纺丝（CP-MAS）NMR实验测量CSA参数。通过Torchia-CP方法测量特定位置的自旋-晶格弛豫时间。C4和C6区域的各向异性参数高于C1和C235区域，C4谱线的不对称性低于任何其他碳位点。C4和C6核的CSA参数值较高是由于在扭转角ψ，Φ，χ和χ′以及链间和链内氢键的影响。对于C4和C6共振线位置，还观察到两个不同的峰-一个峰主要是由于无定形区中的原子核而产生的，而另一个峰是由于相同的核位于准晶区中的原子而产生的。在C4和C6线的这两个不同的峰位置处，自旋晶格弛豫时间和CSA参数是不同的。借助CSA参数和自旋-晶格弛豫时间，可以计算出每个化学上不同的碳位点的分子相关时间。非晶区的分子相关时间比结晶区小一个数量级。通过确定自旋-晶格弛豫时间，可以更生动地描绘纤维素的非晶态和顺晶态区域之间的区别，CSA参数，以及每个化学上不同的碳位点的分子相关时间。这种与纤维素的结构和动力学相关的研究将阐明仿生材料的发明之路。