hyrogels Flashcards
What are hydrogels?
Hydrogels are crosslinked polymeric systems that absorb water, forming a network structure. They can be natural (like gelatin) or synthetic.
Name some examples of natural hydrogels.
Cellulose, starch, alginate, chitin, collagen, and gelatin.
What are homopolymers and copolymers in the context of hydrogels?
Homopolymers are made from one type of monomer, while copolymers are made from two or more different monomers in various arrangements (random, block, alternating).
How are hydrogels produced?
Hydrogels are produced by polymerizing monomers with crosslinking agents or by forming networks from existing polymers with a crosslinking agent.
What are the types of crosslinks in hydrogels?
Chemical (strong covalent bonds), ionic (pH-dependent), and physical (weak hydrogen bonds, affected by pH and temperature).
Describe the two main classifications of hydrogels.
Chemical or neutral hydrogels are pH/temperature-independent, while physical or reversible hydrogels respond to environmental changes like pH or temperature.
What role does pore size play in hydrogels?
Pore size determines water absorption and affects the diffusion of solutes through the hydrogel, which is influenced by polymer composition and crosslink density.
What factors affect diffusion in hydrogels?
- Solute concentration
- solute size
- degree of swelling
- molecular weight between crosslinks
- crystallinity
- pore size.
What is the restriction coefficient in hydrogel diffusion?
A measure of solute diffusion;
if
𝐾𝑟<1K r
<1, diffusion occurs, while if
𝐾𝑟>1Kr
>1, diffusion is restricted.
How does tortuosity affect solute diffusion in hydrogels?
Tortuosity refers to the complexity of the diffusion path. Higher tortuosity means a more twisted path, slowing diffusion.
What is complexation in hydrogels?
A process where hydrogels form hydrogen bonds, allowing them to swell or shrink in response to pH changes, making them pH-responsive.
How do pH-responsive hydrogels work in drug delivery?
They swell at higher pH levels (e.g., in the intestine) to release the drug, but stay compact at low pH (e.g., in the stomach) to protect it.
What is modulated drug delivery in hydrogels?
Delivery that can be “switched” on or off by changing conditions, such as temperature, which alters the hydrogel’s swelling and drug release rate.
Give an example of a temperature-responsive hydrogel.
Poly(isopropyl acrylamide) (PIPAAm), which swells at lower temperatures to release the drug and shrinks at higher temperatures to stop release.
What are neutral hydrogels?
Crosslinked hydrogels with a predetermined shape and size, typically made from polymer precursors in a mold.
