Graft Terpolymers
Definition and meaning of Graft Terpolymers in chemistry.
Graft terpolymers are graft copolymers built from three chemically distinct monomers: a polymer backbone made from one monomer, onto which side chains composed of two other monomers are covalently attached at intervals along the chain.
In more detail
They are usually made by free-radical grafting: an initiator (often ceric ammonium nitrate or potassium persulfate) generates radical sites on the backbone, and the two branch monomers then copolymerize outward from those sites as pendant chains. This lets chemists combine the bulk properties of the backbone, such as the biodegradability and low cost of a natural polysaccharide, with functional groups from the synthetic branch monomers, such as carboxylic acid or amide groups that impart water absorption, ion exchange, or flocculation behavior. Because the branch composition can be tuned independently of the backbone, graft terpolymers offer more control over properties than simple two-monomer graft copolymers.
Key facts
| Field | Organic Chemistry |
|---|---|
| Structure | one-monomer backbone with grafted branches of two other monomers |
| Typical Initiators | ceric ammonium nitrate (CAN), potassium persulfate |
| Common Backbones | starch, cellulose, chitosan |
Starch-graft-poly(acrylamide-co-acrylic acid) is made by using ceric ammonium nitrate to generate radical sites on starch, then copolymerizing acrylamide and acrylic acid as grafted branches; the product is used as a biodegradable superabsorbent polymer in diapers and soil-moisture retention.
Frequently asked questions
How is a graft terpolymer different from a graft copolymer?
A graft copolymer involves only two monomers (one backbone, one branch monomer), while a graft terpolymer involves three distinct monomers, usually one backbone monomer plus two comonomers copolymerized together as the grafted branch.
Why use a graft terpolymer instead of a simple synthetic polymer?
Grafting synthetic monomers onto a natural backbone combines the backbone's biodegradability and low cost with functional properties, like superabsorbency or metal-ion binding, contributed by the synthetic branches.