Entanglement network of agarose in various solvents

Abstract

INTRODUCTIONThe molecular structure of polysaccharides has led to the belief that these polymers are stiff. The characteristic ratio (C N ) for polysaccharides is rather high, although reported C N values are limited to typical polysaccharides such as cellulose 1 and gellan. 2 If we can prepare concentrated solutions of polysaccharides, we can determine the molecular weights between entanglements in the molten state (M e,melt ) for these polysaccharides, 3-5 which reflects the chain properties, that is, the flexibility of the chain. Since the first report that cellulose has good solubility in ionic liquids, 6 many studies have been conducted to determine the solution properties of polysaccharides at high concentrations. We prepared concentrated solutions of several kinds of polysaccharides in an ionic liquid 1-butyl-3-methylimidazolium chloride (BmimCl) and carried out rheological measurements for the solutions to determine M e,melt for the polysaccharides. 7-9 The experiments yielded rather small values of M e,melt for the polysaccharides; for example, 8 M e,melt was 2.3Â10 3 for agarose, which is composed of (1,3)-b-D-galactopyranose and (1,4)-3,6-anhydro-a-L-galactopyranose. 10 This value appears to be much smaller than expected for a stiff polymer and is actually comparable to the M e,melt for the simplest flexible polymer polyethylene (M e,melt ¼1.3Â10 3 ), 3 although no reported value of C N for agarose is available. Why the M e,melt for polysaccharides is so small is not clear at present. The M e,melt for amylose was also determined and was much larger than that for cellulose. 7 To explain the M e,melt values, it is necessary to examine whether the use of an ionic liquid as a solvent affects the estimation of M e,melt . It has been proposed that ionic liquids form three-dimensional structures even in the liquid state because of cation-anion hydrogen bonding and cation-cation ring stacking. [11][12][13] The threedimensional structure may contribute to the modulus of the solutions; if the elasticity due to the network of solvent molecules contributes to the plateau modulus (G N 0 ), then M e,melt is reduced. The aim of this study is to clarify whether or not the network formed by the ionic liquid molecules contributes to G N 0 . Concentrated solutions of agarose were prepared by using formamide (FA), N-methylformamide (MFA) and BmimCl as solvents. Angular frequency (o) dependence curves of the storage and loss moduli (G¢ and G 00 , respectively) were compared among these solutions.

Fibrous hydrogels under biaxial confinement

“…This difference is due to the different mechanism of deformation of fibrin and agarose microgel networks that are composed of flexible 24 and stiff 25 filaments, respectively. Biaxial compression of a flexible gel leads to the decrease of its volume and the related increase of concentration and osmotic pressure that results in gel elongation in the unconstrained direction.…”

Some remarks on rheological properties of concentrated solutions of galactomannans

“…An ionic liquid 1-butyl-3-methylimidazolium chloride (BmimCl; Aldrich, USA) was used as a solvent. This solvent was the same as that in the previous studies (Horinaka, Yasuda, & Takigawa, 2011a, 2011b. The galactomannan solutions in BmimCl were prepared at about 80 C. The details are described in the previous papers (Horinaka et al, 2011a(Horinaka et al, , 2011b.…”

Recent Advances in Engineering Bioinks for 3D Bioprinting

“…First, good biocompatibility provides a 3D environment for cell growth in a bionic environment. [119][120][121] Second, good transmissibility provides controllable permeation of oxygen and nutrients. Additionally, the strong absorption capacity helps maintain cell morphology and pore elastic structure.…”