# Tag Info

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Sodium polyacrylate is an example of a super-absorbing polymer. It is a cross-linked (network) polymer that contains sodium atoms. It absorbs water by a process called osmosis. When the (sodium-containing) polymer is placed in contact with water, there is a tendency for the sodium to distribute equally between the network and the water. That means, some of ...

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Liquid crystals are usually rigid rod-like molecules that tend to show some degree of intermolecular order even when notionally liquids (there is a good summary on Wikipedia). This happens because the rigid polarisable parts of the molecules can have relatively strong directional interactions even in the liquid phase. Some of the structures they form can ...

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What's wrong with water? Or (diethyl) ether? Stand back and think about what makes things hydrogen-bonded, or not.

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Pyridinium hydrochloride and methyl benzoate are both soluble in methanol and thus will be washed through the filter leaving behind clean cholesteryl benzoate. If you don't use the methanol the solid you produce will be impure and sticky; the methyl benzoate and pyridinium hydrochloride will not pass through the filter but will bind to the product crystals.. ...

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Liquid crystal displays work by using liquid crystals where the direction of alignment of the molecules in a plane rotates as you go from layer to layer. Usually this is done with twisted nematic crystals, however cholesteric LCs can also be used to achieve similar effects (I don't think smectic LCs are useful here as they don't align). To create a liquid ...

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As the molecular weight increases (more halogens or carbon atoms), so does the electron density and consequently the van-der-waals forces(dispersion forces) between the molecules rises. These forces increase intermolecular attraction and therefore increase the boiling point. T^his is valid in case of most other organic compounds' homologous series, not just ...

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I think I remember that episode. Basically, crystals of water in kerosene were not a problem during the whole flight (at minus thirty something) but crystals were too sticky when the temperature raised to -20°C and prevented the fuel to go to the engines just a few millimeters before entering the "warming cell" which was supposed to prevent any such blockage....

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Assuming you already have the optical setup built around, aiming for the least amount of expensive chemicals, you may try semicrystalline extruded polymers, e.g. polyethylene foils, or PET bottles. The «trick» is that you do not melt them, but that you reach just the glass transition temperature ($T_g$) which is below melting. Here, crystalline parts in the ...

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If, as noted in the comments, you do not open the bottle, the process should basically be repeatable, as longer as the container does not crack. Additionally, the freezing may destroy certain larger things that do not tolerate ice crystals, such as yeast cells, if any are present.

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As example, Skoog / Leary's principles in instrumental analysis contained a section about DSC in the chapter of thermoanalysis. Your university library likely has some of them or other books about the topic, too. Then, beside monitoring glas transitions, melting, decomposition (while heating) or solidification / crystallisation (while cooling) I suggest to ...

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This seems to be a very specific case. I would say that you should start with a standard Ni electroplating solution and see the result. You could then adjust the parameters of your plating operation and the concentrations of the additives in the solution. However, I have a bigger concern. How stable is your liquid crystal template under applied potential in ...

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The main influence on resonant frequency of a crystal is mechanical: the mass of the crystal and the restoring force of elasticity cause the crystal to vibrate at a specific frequency when disturbed. To fine-tune the crystal, bits may be chemically or abrasively removed or the mass may be increased slightly by rubbing with graphite. That said, crystal ...

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The answer would be clear when we know the mechanism why sodium polyacrylate absorbs water: Mechanism It consists of a set of polymeric chains that are parallel to each other and regularly linked to each other by cross-linking agents, thus forming a network. When water comes into contact with one of these chains, it is drawn into the molecule by ...

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LCs materials are dielectric. But they are not perfect insulators and have some non-zero conductivity, allowing a leakage current to flow, slowly discharging the capacitor. This is caused by mobile ions in the liquid crystal and inside the polyimide layer [2]. Infact a liquid crystal cell can be modeled electrically as this circuit: Rl ...

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