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Factors Effecting Polymer Flexibility
Name: Ehsan
Status: student
Grade: 9-12
Country: Turkey
Date: Summer 2011
Question:
What are the factors involved in determining the flexibility in polymers?
Replies:
Ehsan,
As you can imagine, there are several variables that control polymer
bulk flexibility.
The polymer chain becomes more flexible with: higher freedom of
rotation around main chain bonds - so no double bonds, no bulky side
groups that inhibit main-chain bond rotation, no cross-links, etc.
Polymer chain motion is enhanced in the presence of a lot of free
voluble (in which the bonds can rotate into) - so short side-chains
that inhibit chain interaction by literally pushing other chains
away, stereoirregularity that inhibits high crystallinity, low
polarity functional groups that only interact by London Forces, etc.
The bulk flexibility is increased when there are fewer entanglements
between chains, so that the chains are free to reptate - so high
molecular weights that tend to entangle is no good, but low
molecular weights that tend to crystallize is also not good.
Then there are additives. Small molecules that act as plasticizers
increase free volume. Inorganic solids can act as fillers and
inhibit motion across the filler space.
There is a lot here, so you may have to study all these different aspects.
Dr. Roberto Ma. Gregorius, Assoc. Prof.
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Update: June 2012
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