CP/MAS ~(13)C NMR技术对木浆纤维微观结构的研究

利用交叉极化结合魔角旋转技术~(13)C核磁共振法(CP/MAS ~(13)C NMR)对桉木浆纤维的微观结构进行研究,为进一步研究木质纤维素材料开发过程中反应障碍特征奠定基础.通过对NMR光谱C1区(δ 102～108)进行洛仑兹拟合,得到桉木浆纤维中纤维素Iα的相对含量为26.92%,纤维素Iβ的相对含量为52.04%,主要以纤维素Iβ晶体形式为主.通过计算纤维素C4结晶区(δ 86～92)和非结晶区(δ 80～86)的相对含量得到桉木浆的纤维素结晶度为47%.通过洛仑兹和高斯函数的混合模型对NMR光谱C4区(δ 80～92)进行拟合得到基原纤尺寸和微原纤横向尺寸分别为4.0与17.9 nm,并通过计算不同形态的结晶纤维素的相对含量得到纤维素结晶度为51%,证实了在微原纤内部次晶纤维素的存在.

CP/MAS ~(13)C NMR Spectroscopy Study of the Ultrastructure of Wood Pulp Fiber

The ultrastructure of eucalyptus kraft pulp fibers was studied by using solid-state cross polarisation magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS ~(13)C NMR) in combination with spectral fitting. Their NMR spectra were analyzed in detail and some structure parameters such as the cellulose crystallinity, allomorph composition, relative amounts of different cellulose allomorphs present and lateral dimensions for cellulose elementary fibrils and microfibrils were determined. The results show that the relative contents of cellulose la allomorph and cellulose Iβ allomorph obtained by the spectral fitting for the cellulose C1-region (δ 102～108) are 26.92% and 52.04%, respectively. The cellulose crystallinity calculated by the NMR method was 47%. The lateral dimensions for cellulose elementary fibrils and microfibrils obtained by the spectral fitting for the cellulose C4-region (δ 80～92) were 4.0 and 17.9 nm, respectively. The cellulose crystallinity calculated by relative amounts of different cellulose allomorphs was 51%. It has been proved that the para-crystalline cellulose has a well-ordered "in-core" structure.