A novel cellulose solvent, 1.5M NaOH/0.65M thiourea aqueous solution, was used to dissolve cotton linters having a molecular weight of 10.1

In this article, a series of O-2-[2-(2-methoxyethoxy)ethoxy]acetyl celluloses with different degree of substitution (DS) values was synthesized by a homogeneous reaction of cellulose with 2-[2-(2-methoxyethoxy)ethoxy]acetyl chloride in a 10% (w/w) dimethylacetamide/lithium chloride solution, combined with pyridine as the acid acceptor. The total DS values of the derivatives in anhydroglucose units was determined by 1H and 13C NMR spectra, and ranged from 0.4 to 3.0, depending on the amount of acid chloride in the reaction. The effects of the total DS values and the O-2-[2-(2-methoxyethoxy) ethoxy] acetyl substituent distribution on the solubility of the derivatives were investigated. The lowest limit of the DS value for water-soluble O-2-[2-(2-methoxyethoxy) ethoxy] acetyl cellulose was approximately 0.5, which is lower than thatof methylcellulose. The amphiphilic derivatives with higher DS values than 1.7 exhibited a good solubility in both water and organic solvents, such as dimethyl sulfoxide, tetrahydrofuran, and chloroform. Sol-gel transition in aqueous solution was observed for the amphiphilic derivatives with a higher DS value than 1.7; the precipitation temperature (Tp) decreased as the DS value increased, showing that the derivatives are highly temperature sensitive. The thermal properties of the fully substituted derivative were measured using polarized microscopy, DSC, and X-ray diffraction; and are discussed in terms of phase transition of the sample derivatives.

β-D-Glucan PC3 (weight-average molecular mass=9.15•104, polydispersity=1.6), a linear glucan from Poria cocos sclerotium, was fractionated by a preparative size-exclusion chromatography (SEC) column packed with regenerated cellulose gels using dimethyl sulfoxide (DMSO) as mobile phase. The molecular masses and aggregation of the fractions were investigated by using analytical SEC, viscometry and membrane osmometry under different conditions. The results of SEC analysis proved that glucan PC3 forms partial aggregates in 0.25M LiCl/DMSO (namely, 0.25M LiCl in DMSO) at 40℃, showing a new shoulder peak of a higher-molecular-mass component in the chromatogram, and dissolves as a single-stranded chain at 80℃, giving a sharper peak. The mean apparent aggregation number (Nap) of the fractions in 0.25M LiCl/DMSO at 40℃ was 1.9, and much smaller than that of glucan PC3 in 20% cadoxen. It is indicated that the analytical SEC is more sensitive and direct in detection of the aggregates than other methods, and aggregation can be avoided by carrying out SEC measurement at 80℃. The Mark-Houwink equation for glucan PC3 in DMSO at 25℃ was established as [η]=0.107M0.50W in the Mw range of 7-11•104, suggesting that it behaves as a flexible coil.

Two kinds of regenerated cellulose microporous gel particles with mean pore sizes of 135nm and 370nm were satisfactorily prepared by mixing cellulose cuoxam with polyethylene glycol (PEG) as pore former. A preparative size-exclusion chromatography (SEC) column (550mm×320mm) packed with the gel particles mentioned above was used for the fractionation of a dextran in water. The exclusion limit and fractionation range of the stationary phase were molecular masses 7•105 and 3•103～7•105, respectively. The dextran (weight-average molecular mass=7.14•104, polydispersity=2) was fractionated into ten fractions with molecular masses range from 4•104 to 1•105, which were analyzed by an aqueous phase 21 analytical SEC. A daily throughput of 6.5g of the dextran was given with a flow-rate of 2.88ml min. The preparative SEC is simple, fast and cheap, and suitable for large-scale fractionation of the polysaccharides and other biopolymers.

Molecular morphologies and conformation transition of lentinan, a β-(1→3)-D-glucan from Lentinus edodes, were studied in aqueous NaOH solution by atomic force microscopy (AFM), viscometry, multiangle laser light scattering, and optical rotation measurements. The results revealed that lentinan exists as triple-helical chains and as single random-coil chains at NaOH concentration lower than 0.05M and higher than 0.08M, respectively. Moreover, the dramatic changes in weight-average molecular weight Mw, radius of gyration <s2>1/2, intrinsic viscosity [η], as well as specific optical rotation at 589nm [α]589 occurred in a narrow range of NaOH concentration between 0.05 and 0.08M NaOH, indicating that the helix-coil conformation transition of lentinan was carried out more easily than that of native schizophyllan and scleroglucan, and was irreversible. For the first time, we confirmed that the denatured lentinan molecule, which was dissolved in 0.15M NaOH to be disrupted into single coil chains, could be renatured as triple helical chain by dialyzing against abundant water in the regenerated cellulose tube at ambient temperature (15℃). In view of the AFM image, lentinan in aqueous solution exhibited the linear, circular, and branched species of triple helix compared with native linear schizophyllan or scleroglucan.