Page 30 - controlled drug delievery

Cont. Single unit systems

• Glass transition of polymers:

Polymers can be amorphous or crystalline

Amorphous polymers can exist in the glassy or rubbery state

G(ilmasmsyosbtialetech--a--in--s->-g--la--s-s-t-r-a-nH-s-ei-ta-ito-i-nn-g-te--m--p-.-(-T-g-)-(-l-i-mRuitbebdecrhyasitnamteobility,

• Hard &brittle) soft & flexible)

• Plasticizers decrease the polymer Tg, therefore:

i. Facilitate droplet coalescence during coating.

ii. Increase film flexibility and mechanical resistance.

iii. Increase fluid uptake by the polymer coat (in vivo) thus
increase its permeability.