Gelation kinetics of native and acetylated konjac glucomannan (KGM) samples in the presence of alkali (sodium carbonate) was studied by dynamic viscoelastic measurements. Molecular weight and other molecular parameters of KGM were determined by static light scattering and viscosity measurements. It was found that KGM molecules were degraded during acetylation treatment, but the molecular weights of acetylated samples were almost independent of the degree of acetylation (DA) and were about a half of that of a native sample. At a fixed alkaline concentration, increasing concentration of KGM or temperature shortened the gelation time, but increasing DA delayed it. The deacetylation reaction and subsequent aggregation process of acetylated samples needed longer time than that of native sample, and acetylated samples formed finally more elastic gels. It implied that the presence of acetyl groups exerts a strong influence on gelation behavior of KGM. It was suggested that the gelation rate of acetylated KGM and native KGM, which depends on the alkaline concentration and temperature, is an important factor that determines the elastic modulus of gels. This was supported by the experimental finding that the saturated elastic modulus tends to the same value when the ratio of alkali concentration to acetylated groups was kept constant. In slower gelation processes, junction zones are more homogeneously distributed and more numerous, leading to the more elastic gels.

New fluoroalkylated oligomeric silane coupling agents containing morpholino groups were prepared by the reactions of fluoroalkanoyl peroxides with trimethoxyvinylsilane and acryloylmorpholine. The modified glass surface treated with these silane coupling agents was shown to have a strong hydrophilicity with good oil repellency, and these fluoroalkylated oligomers are applicable to new flip-flop-type silane coupling agents.

The effects of softening agents on the wetting of textiles were investigated by measuring the capillary spreading of liquid as a function of time. The values of the exponent n during phase II of the capillary spreading of softened fabrics increased in comparison with those of unsoftened fabrics owing to the adsorption of the softening agent, which made the fiber surface more hydrophobic and produced a larger advancing contact angle of the fiber to the water (&thetas; A ). Based on experiments with DTAC as a softening agent for nylon, the following quantitative relationship was found between the value of the exponent n and the advancing contact angle of water (&thetas; A ): n = (4.62 X 10 -3 )&thetas; A , -0.001. From this, reasonable advancing contact angles were also estimated for other fabrics.

Nine samples of gellan gum in the sodium form, ranging in weight-average molar mass from 3.47 x 10(4) to 1.15 x 10(5) at 40 degrees C, were investigated by static and dynamic light scattering and viscometry in 25 mM aqueous NaCl both at 40 and at 25 degrees C. The ratios of the molar mass at 25 degrees C (in the ordered state) to that at 40 degrees C (in the disordered state) were in the range of 1.99 to 2.07, supporting the scheme of the conformational transition of gellan gum between a disassociated single chain and an associated chain composed of two molecules. Focusing on the effects of polydispersity, the intrinsic viscosities, radii of gyration, and hydrodynamic radii were analyzed on the basis of unperturbed wormlike chain models. The persistence lengths were evaluated as 9.4 nm at 40 degrees C and 98 nm at 25 degrees C.