Nonionic Cellulose Ether Research Articles

Surface modification of hydroxyapatite to avoid bacterial adhesion

Hydroxyapatite was surface-modified by adsorption of nonionic polymers carrying phosphate groups as anchoring groups. A combination of alcohol ethoxylate and alkyl phosphate was also used. The possibility of interfering with early microbial colonization on apatite, mimicking the tooth surface, was investigated using radiolabelledStreptococcus mutans as model bacteria. The polymers, a nonionic cellulose ether and an EO/PO block copolymer based on polyglycerol as starting alcohol, were effective in buffer but gave only limited reduction of bacterial adhesion when the apatite had been pretreated with saliva. A 1∶1 molar mixture of alcohol ethoxylate and alkyl phosphate was effective both with and without saliva, however. Studies with14C-labeled compounds, as well as microelectrophoresis experiments, indicate that an unsymmetrical double layer is formed on the apatite surface with predominantly alkyl phosphate in the inner layer and with alcohol ethoxylate pointing towards the water phase.

Phase behavior of a nonionic cellulose ether in nonaqueous solution

Phase behavior of a nonionic cellulose ether in nonaqueous solution

An Explanation of the Rheological Behaviour of Mixed Aqueous Solutions of Anionic and Non-Ionic Cellulose Ethers

An Explanation of the Rheological Behaviour of Mixed Aqueous Solutions of Anionic and Non-Ionic Cellulose Ethers

Modulation of bacterial binding to salivary pellicle by treatment with hydrophilizing compounds

Two hydrophilizing agents, a branched polyethylene glycol derivative and a non-ionic cellulose ether (EHEC) bind to buffer-treated hydroxyapatite and prevent attachment of Streptococcus mutans. EHEC gives a more efficient surface modification, presumably due to a more complete surface coverage. Neither of the 2 hydrophilizing agents were effective on hydroxyapatite which had been pre-treated with saliva. In a small clinical trial, EHEC was found to be moderately effective in preventing plaque formation.

Thermal gelation of nonionic cellulose ethers and ionic surfactants in water

A novel gel-forming system which shows an anomalous temperature dependence is reported. The system consists of a nonionic cellulose ether and an ionic surfactant in water (the effect is particularly strong for ethyl (hydroxyethyl)cellulose [EHEC]). When the system is heated (typically to 40–50°C), it undergoes a transformation from a low-viscous solution to a clear and stiff gel. The unusual behaviour is reversible and an apparently unlimited number of temperature cycles can be performed without loss of the gelling capability. The rheological properties were characterized by steady-flow and dynamic viscosity measurements, and it is found that the gel has many features in common with weak polymer gels. The cellulose ether could either be relatively hydrophobic (methyl-, hydroxypropyl- and ethyl(hydroxyethyl)cellulose), or contain a small number of long alkyl groups (e.g.,‘hydrophobically modified’ hydroxyethylcellulose). The mechanism behind the formation of this novel type of gel is discussed in terms of cooperative binding of the ionic surfactants to the EHEC polymer, leading to small micelle-like aggregates. These may act as a cross-links between hydrophobic segments in different polymer chains, giving rise to extended and rigid polymer networks. Moreover, we have found that the interaction has a reverse temperature dependence — an increase in temperature leads to a higher degree of surfactant binding — which thus may explain the temperature anomaly in the gelling process.

Viscosity Profiles of Printing Thickeners at High Shear Rates and Their Use in Predicting Paste Flow in Screen Printing

Apparent viscosities of various natural and synthetic printing thickeners were measured at shear rates from 0.05 to 7000 s-1. Log viscosity-log shear rate plots (viscosity profiles) were curves, not straight lines as generally believed. Nonlinear regression equations were computed and required significant second or third order terms or both to fit the data. The slopes and shapes (or curvature) of the profiles were distinctly different for synthetic copolymers, for nonionic cellulose or starch ethers, and for anionic polysaccharides (either carboxylmethyl cellulose or sodium alginate). The interaction efforts on both apparent viscosity and slope of viscosity profiles of such variables as pH, temperature, concentration of thickener and added electrolyte, thickener composition, and molecular weight were estimated by analysis of variance. The appearance of prints made with different thickeners was compared visually, photometrically, and microscopically. Prints with optimum sharpness of mark, levelness, and penetrations were obtained from pastes whose profiles, even with widely different shapes, all intersected at the same shear rate and apparent viscosity. The concentrations of each thickener required for optimum paste spread and appearance could be calculated from the slope of the viscosity profiles and from the estimated change in viscosity with concentration.

Nonionic polymer surfactants

AbstractNonionic water‐soluble polymeric surfactants have been prepared by addition of long‐chain n‐alkyl epoxides to nonionic cellulose ethers. The polymers exhibit properties which can be explained by interchain association. The relationship between hydrocarbon‐modifier carbon number and the onset of association follows a linear relation analogous to those observed for monomeric nonionic surfactants.

Influence of electrolytes on the hydration of methylcellulose in solution.

Abstract Light-scattering techniques were used to obtain weight-average molecular weights for three grades of methylcellulose in water. On addition of electrolyte to the polymer solutions the molecular weight was not found to alter but the root-mean-square end-to-end length decreased. This contrasts with the results of Neely (1963). The exponent α of the Mark-Houwink viscosity equation was also found to decrease in the presence of electrolyte. Two stages of polymer dehydration are suggested for non-ionic cellulose ether derivatives.