Classification of Polymers in Novel Drug Delivery Systems can be classified by source, structure, polymerization method, molecular forces, and other properties.
Classification Based on Source
1) Natural Polymers:
Sourced from nature, known for biocompatibility and biodegradability.
Examples: Cellulose, chitosan, alginate, gelatin, proteins.
2) Semi-synthetic Polymers:
Derived from natural polymers with chemical modifications to enhance properties.
Examples: Carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose.
3) Synthetic Polymers:
Produced from petrochemicals, often tailored for specific drug delivery needs.
Examples: Polyvinyl alcohol, polyvinylpyrrolidone, polylactic acid, polyglycolic acid, and copolymers.
Classification Based on Structure
1) Linear Polymers:
Composed of straightforward, chain-like structures with no branches.
2) Branched Polymers:
Polymers with branched structures extending from the main chain.
3) Cross-linked or Network Polymers:
Monomeric units are interconnected in a 3D network with strong covalent bonds, often used in hydrogel formulations in NDDS.
Classification Based on Mode of Polymerization
1) Addition or Chain-growth Polymers:
Formed by successive addition of monomers in a chain reaction.
Examples: Polyethylene, polystyrene, polytetrafluoroethylene.
2) Condensation or Step-growth Polymers:
Created through stepwise intermolecular reactions, typically with the release of simple molecules like water.
Examples: Polyesters, polyamides, polyurethanes.
Classification of Polymers in Novel Drug Delivery Systems Based on Molecular Forces
1) Elastomers:
Feature weak intermolecular forces, allowing them to stretch and return to original shape.
Examples: Natural rubber, polybutadiene, polyisoprene.
2) Fibers:
Have strong intermolecular forces like hydrogen bonds, used in creating pharmaceutical sutures.
Examples: Nylon, silk, wool.
3) Thermoplastics:
Possess intermediate forces, allowing softening on heating and hardening on cooling.
Examples: Polyvinyl chloride, polyethylene, polystyrene.
4) Thermosetting Polymers:
Cannot be softened by heating once molded due to a 3D network structure.
Examples: Bakelite, melamine-formaldehyde resins.