Wood holocelluloses, softwood α-cellulose, bleached kraft pulps, and bacterial cellulose were dissolved in 8% LiCl/DMAc. The obtained solutions were diluted to 1% LiCl/DMAc and analyzed using an SEC/MALLS/RI/UV system. The holocelluloses and kraft pulps showed bimodal molecular-mass distributions because of the presence of high-molecular-mass (HMM) cellulose-rich and low-molecular-mass fractions. The neutral sugar compositions of the samples were also determined and compared with the data obtained by SEC/MALLS/RI/UV analysis. The results showed that hardwood holocelluloses and hardwood bleached kraft pulp had linear cellulose molecules in the HMM fractions and random coil conformations in the solution as in the case of bacterial cellulose. In contrast, softwood holocellulose, softwood α-cellulose, and softwood bleached kraft pulp were likely to have cellulose molecules partly branched with glucomannan molecules through lignin fragments in the HMM fractions.<br/><br/>Based on the results obtained above, SEC/MALLS/RI/UV analysis was further applied to Japanese cedar (JC) and eucalyptus (E) powders after delignification (D), 4% NaOH extraction (H), and acid hydrolysis (A) with different sequences of the D, H, and A treatments. All the delignified wood samples were dissolved in 8% LiCl/DMAc. The wood sample/LiCl/DMAc solutions were diluted, and subjected to the SEC/MALLS/RI/UV analysis. The cellulose molecules in HMM fraction of eucalyptus samples had random coil conformations as linear polymers. In contrast, the cellulose molecules in the HMM fraction of Japanese cedar-related samples, JC-D, JC-AD, JC-DHA, and JC-D-α-cellulose, had branched structures. The JC-ADH had, however, no branched structures in the HMM fraction. The results of SEC/MALLS/RI/UV and neutral sugar composition analyses of the Japanese cedar-related samples showed that chemical linkages are present between cellulose and glucomannan molecules through lignin or lignin fragments. The stability of the cellulose/glucomannan linkages present in the Japanese cedar holocellulose was investigated based on the results of samples prepared by different sequences.

Branched structures of cellulose molecules in high-molecular-mass fraction of softwood revealed by SEC/MALLS/IR/UV analysis

255th National Meeting (2018)

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