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Ch.12 - Solids and Modern Materials

Chapter 12, Problem 72

The smectic liquid crystalline phase can be said to be more highly ordered than the nematic phase. In what sense is this true?

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Hey everyone were asked which of the following statements is true. Looking at our answer choices, it looks like we're discussing syntactic liquid crystalline phases versus the Matic phases. Now, before we look at our answer choices, let's go ahead and draw these out. Starting with our nomadic phase. Now we know that these molecules will be aligned in the same direction, but these molecules are free to roam around randomly, so this will have no periodicity. Now, comparing this to our smack tic phase, these molecules will have some periodicity and they will be aligned in the same direction and usually these molecules are arranged in layers. Now that we've drawn these out, Let's go ahead and look at our answer choices. We can go ahead and eliminate A and B. Because A and B both state that syntactic is less ordered than the pneumatic phase. And as we've drawn we can see that syntactic is more ordered than the pneumatic phase. So we can eliminate A and B. Now between C and D. D. Is going to be incorrect. And the reason why is because the ends of the molecules are not the only ones that are aligned in our syntactic phase. So our final answer here is going to be C. Syntactic liquid crystalline phases more ordered than the pneumatic face because the long directions and ends of the molecules are aligned, which is exactly what we drew out. Now, I hope that made sense. And let us know if you have any questions