polymer dissolution - simple ppt!!

2. While low molecular substances readily undergo dissolution.
Polymers take considerable to do so . If we add a low molecular
weight substance like Nacl to water in a beaker and stir . It get
ionized Na+,cl-,ions and they are uniformly dispersed in water.
They are dissolved faster when agitated. If we add a polymer like
solid PVA (poly vinyl alcohol)to water and stir nothing will happen
for same time .Slowly the fragment swell and increase in size.
Then only diffusion takes place.
The polymer molecules are large compared to
solvent molecules .They are not in discrete form but
interpenetrated and tightly folded random coils forces like
dispersion and hydrogen bonding hold the coils and segments
together .Because of larger size coiled nature and strong possess
solvent molecules take time to established interaction with the
polymer molecule and dissolved them.

3. Different stages of polymer dissolution
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Solid polymer
added to solvent
Swollen polymer
In solvent
Solvated polymer molecules
Diffusing out of swollen mass

4. THANK YOU