Interplay between gelation and phase separation in aqueous solutions of methylcellulose and hydroxypropylmethylcellulose. 2012

J Patrick A Fairclough, and Hao Yu, and Oscar Kelly, and Anthony J Ryan, and Robert L Sammler, and Michael Radler
Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, U.K.

Thermally induced gelation in aqueous solutions of methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC) has been studied by rheological, optical microscopy, and turbidimetry measurements. The structural and mechanical properties of these hydrogels are dominated by the interplay between phase separation and gelation. In MC solutions, phase separation takes place almost simultaneously with gelation. An increase in the storage modulus is coupled to the appearance of a bicontinuous structure upon heating. However, a thermal gap exists between phase separation and gelation in the case of HPMC solutions. The storage modulus shows a dramatic decrease during phase separation and then rises in the subsequent gelation. A macroporous structure forms in the gels via "viscoelastic phase separation" linked to "double phase separation".

UI MeSH Term Description Entries
D008747 Methylcellulose Methylester of cellulose. Methylcellulose is used as an emulsifying and suspending agent in cosmetics, pharmaceutics and the chemical industry. It is used therapeutically as a bulk laxative. BFL,Celevac,Cellothyl,Cellulone,Citrucel,Cologel,Dacryolarmes,Methocel,Methyl Cellulose,Muciplasma,Cellulose, Methyl
D005782 Gels Colloids with a solid continuous phase and liquid as the dispersed phase; gels may be unstable when, due to temperature or other cause, the solid phase liquefies; the resulting colloid is called a sol.
D012212 Rheology The study of the deformation and flow of matter, usually liquids or fluids, and of the plastic flow of solids. The concept covers consistency, dilatancy, liquefaction, resistance to flow, shearing, thixotrophy, and VISCOSITY. Flowmetry,Velocimetry,Velocimetries
D012996 Solutions The homogeneous mixtures formed by the mixing of a solid, liquid, or gaseous substance (solute) with a liquid (the solvent), from which the dissolved substances can be recovered by physical processes. (From Grant & Hackh's Chemical Dictionary, 5th ed) Solution
D013816 Thermodynamics A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed) Thermodynamic
D014867 Water A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Hydrogen Oxide
D015394 Molecular Structure The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds. Structure, Molecular,Molecular Structures,Structures, Molecular
D065347 Hypromellose Derivatives Polymeric compounds that contain repeating units of hydroxypropyl methylcellulose. The properties of hypromellose polymers can vary greatly and are defined by their molecular weight, the percentage of hydroxyl groups, the percentage of hydroxypropyl groups, and viscosity measurements. They are found a broad variety of commercial products such as FOOD ADDITIVES; EXCIPIENTS; and LUBRICANTS. HPMC 2910,HPMC-K-100 M,Hydroxypropyl Methylcellulose,Hydroxypropylmethylcellulose,Hypromellose,K-8515,K8515,MHPC Polymer,Methocel E,Methoxyhydroxypropylcellulose,Methyl Hydroxypropyl Cellulose,Methyl-hydroxypropyl-cellulose,Derivative, Hypromellose,Derivatives, Hypromellose,HPMC K 100 M,HPMCK100 M,Hypromellose Derivative,K 8515

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