What is a gel

Almdal K, Dyre J, Hvidt S, Kramer O (1993) What is a gel Makromol Chem Macromol Symp 76 49-51... 

What is a common electrode pair used to determine the pH of a gel at any point ... 

This cross-linked polymer is a gel that has interesting physical properties. You may explore some of them by forming your material into a ball and then seeing what happens when you carefully tip it in the palm of your hand. If a long column of polymer forms, jerk it abruptly and record the result. Be creative and test the properties of the gel in other ways ... 

Alkaline batteries (Fig. 19.12) are the power source in television remote controls, many toys, and personal stereos. These are often classified by their electrical potential and shape and size, such as the round AA or AAA 1.5-volt batteries or the rectangular 9-volt batteries. The anode of an alkaline battery is a gel that contains zinc in contact with a potassium hydroxide solution. The presence of the hydroxide ion is what gives these batteries their name. The cathode is a mixture of manganese(IV) oxide and graphite. The reactions are... 

When introducing the subject of liquid crystals, the first and most important question to be answered is, What is a liquid crystal Unlike the more well-known varieties of soft matter, such as polymers or gels, liquid crystals are often something of a mystery to the nonspecialist, although a simple definition can be made for the wide variety of materials that can exhibit liquid crystalline properties. 

C°ii, builds up. For proteins, a gel layer (Michaels, 1968a) may often be developed on the UF membrane surface when C°i is high enough to be Qgei, leading to what is called gel polarization (Figure 6.3.26(a)) ... 

Self-Test 6.14B Ethanol trapped in a gel is another common camping fuel. What mass of ethanol must be burned to supply 350. kj as heat The thermochemical equation for the combustion of ethanol is... 

Amorphous silica, with pore sizes in the range 1-10 nm is a common support for base catalysts, whilst more structured pore sizes can be made by what is known as the sol-gel method. In this method a micelle is... 

The fact that the initial setting process for magnesium oxychloride cements takes place without observable formation of either the 5 1 8 or the 3 1 8 phase is important. It indicates that formation of an amorphous gel structure occurs as the first step, and that crystallization is a secondary event which takes place from what is effectively a supersaturated solution (Urwongse Sorrell, 1980a). This implies that crystallization is likely to be extremely dependent upon the precise conditions of cementition, including temperature, MgO reactivity, heat build-up during reaction and purity of the components in the original cement mixture. 

It did not give rise to phase separation or precipitation. Similar behavior was observed when other types of polysaccharides were examined [53,54]. By now all the commercially important polysaccharides have been applied to the fabrication of hybrid silica nanocomposites in accordance with Scheme 3.2. What is more, various proteins have been entrapped in silica by the same means. In all instances the THEOS demonstrated good biocompatibility with biopolymers, even though its amount in formulations was sometimes up to 60 wt%. Biopolymer solutions after the precursor admixing remained homogeneous to the point of transition into a gel state. 

One also sees that at room temperature the two peaks of the quadru-pole split pattern are different in intensity. This difference disappears at 77°K. It is an example of what is known as the Gordanskii effect 10) and is caused by the fact that the amplitude of vibration is different, parallel to the surface and normal to the surface, so that the effective resonant fraction is different for the two halves of the quadrupole splitting. This effect has been extensively studied by the Russians. In a recent paper, Suzdalev and others report a study of tin in the surface of silica gel 18), They put calcium ions in the surface of silica gel, then replaced them with divalent tin by ion exchange. The result was a mixture of stannous and stannic ions, and of course, the use of the Mossbauer effect made it possible to determine accurately the relative amounts of the two. They studied the amplitude of vibration of the two kinds of atoms and found, for example, for the stannous ions, the r.m.s. amplitude of vibration parallel to the surface was 0.07 A., and the r.m.s. amplitude of vibration perpendicular to the surface was about twice as great—about 0.13 A. Karasev and others have also worked on the chemistry of adsorbed... 

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