Chemical Concept Demonstrated: Cross-linking between polymer chains
|The poly(vinyl alcohol) and borax solution are vigorously mixed together in a cup.
A polymer "slime" is produced.
Poly(vinyl alcohol) is an addition polymer with an average molecular weight of about 100,000 daltons. Borax reacts with water to form a B4O72+/HB4O7- buffer solution with a pH of about 9. The borate ions form hydrogen bonds to the -OH groups on the PVA backbone that weakly cross-link this polymer. Cross-links either weaker or stronger than this would produce materials with very different properties.