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Author Topic: Help with Polymer Chemistry Question?  (Read 552 times)

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shady6121

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Help with Polymer Chemistry Question?
« on: November 29, 2012, 10:59:14 PM »

1.   We discussed how polymer linking and structure contribute to its properties. How would you expect the density, elasticity, and rigidity of a polymer that is branched to compare to one that is linear?                                                                    
    My answer: Branched polymers feature a primary chain of atoms with additional, diverging chains. For this reason, a branched polymer is typically stronger and denser than a linear polymer. Branched polymers with erratic chains, however, can be weaker than their linear counterparts. Branched polymers also tend to be more elastic and less rigid. This is because of the altered intermolecular forces between polymer chains that are branched rather than linear.

I'm confused though since initially I thought linear is stronger and more dense? I'm not sure at all.
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Arkcon

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Re: Help with Polymer Chemistry Question?
« Reply #1 on: November 30, 2012, 02:16:04 AM »

My answer: Branched polymers feature a primary chain of atoms with additional, diverging chains. For this reason, a branched polymer is typically stronger and denser than a linear polymer.l.

Why did you say this?  Most of the rest of your answer:

Quote
Branched polymers with erratic chains, however, can be weaker than their linear counterparts. Branched polymers also tend to be more elastic and less rigid. This is because of the altered intermolecular forces between polymer chains that are branched rather than linear.

Doesn't support the initial statement at all.  Can you use what you know about intermolecular forces, and compare them to the two (maybe three in your explanation) classes of polymers, and make a guess as to the properties you're interested in?  Maybe by making a table to keep all the information straight?
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fledarmus

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Re: Help with Polymer Chemistry Question?
« Reply #2 on: November 30, 2012, 07:03:25 AM »

Try this - make some chemical models of straight chain hydrocarbons and pack them together. Then make some chemical models of branched chain hydrocarbons and stack them together. Which one would have the stronger intermolecular forces? Remember that Van der Waal's forces are related to the total surface area of the molecules that can come into contact.
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