Layer-by-layer peeling of surface molecules of native cellulose microfibrils was performed using a repeated sequential process of 2,2,6,6-tetramethylpiperidine-1-oxyl radical-mediated oxidation followed by hot alkali extraction. Both highly crystalline algal and tunicate celluloses and low-crystalline cotton and wood celluloses were investigated. Initially, the C6-hydroxy groups of the outermost surface molecules of each algal cellulose microfibril facing the exterior had the gauche–gauche (gg) conformation, whereas those facing the interior had the gauche–trans (gt) conformation. All the other C6-hydroxy groups of the cellulose molecules inside the microfibrils contributing to crystalline cellulose I had the trans–gauche (tg) conformation. After surface peeling, the originally second-layer molecules from the microfibril surface became the outermost surface molecules, and the original tg conformation changed to gg and gt conformations. The plant cellulose microfibrils likely had disordered structures for both the outermost surface and second-layer molecules, as demonstrated using the same layer-by-layer peeling technique.

中文翻译：

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层剥离法揭示天然纤维素微纤维中表面纤维素分子的不同构象

使用2,2,6,6-四甲基哌啶-1-氧基自由基介导的氧化的重复顺序过程，然后进行热碱萃取，对天然纤维素微纤维的表面分子进行逐层剥离。研究了高结晶度藻类和束缚纤维素以及低结晶度棉和木质纤维素。最初，面对外部的每个藻类纤维素微纤维的最外层表面分子的C6-羟基具有gauche-gauche（gg）构象，而面对内部的那些具有gauche-trans（gt）构象。微纤维内部的纤维素分子的所有其他C6-羟基基团有助于结晶纤维素I的反式薄纱（tg）的构象。表面剥离后，来自微纤维表面的最初的第二层分子变为最外表面分子，并且最初的tg构象变为gg和gt构象。如使用相同的逐层剥离技术所证明的那样，植物纤维素微纤丝对于最外层表面和第二层分子都可能具有无序的结构。