Lecture 9 Flashcards
Temperature-responsive Polymers?
PNIPAM
A block copolymer
poloxamer
Examples of poloxamer?
A is water-soluble (Polyoxyethylene)
B is water-insoluble (Polyoxypropylene)
Uses of poloxamer?
emulsifier
gelation in poloxamer is achieved by?
A: At high solution concentration: Micelle is closely packed making the solution immobile
B: Concentrated solution is warmed making polyoxyethylene more hydrophobic = Micelle Formation
Temperature-responsive polymers?
PLGA-PEG-PLGA & PNIPAM
What happens to gel when stress is applied?
Viscosity changes upon applying stress. Turns into solution when stress is applied.
How can syneresis be decreased?
addition of electrolyte, glucose & sucrose, or by increased polymer concentration
How is polylactide & polyglycolide degraded?
Homo & co-polymer of polylactide & polyglycolide hydrolyzed into lactic acid & glycolic acid. The products eliminated by Kreb cycle in the form of Co2 & H20
5 stages:
stage 1: hydration stage 2: depolymerization stage 3: loss of mass integrity stage 4: absorption stage 5: elimination
Factors that accelerate polymer degradation?
more hydrophilic backbone hydrophilic end groups more reactive hydrolytic groups in the backbone less crystallinity more porosity smaller device size
Characteristics of PH-sensitive polymer?
pH-sensitive polymers are polyelectrolytes that bear in their structure weak acidic or basic groups that either accept or release protons in response to changes in environmental pH.
Application of PH-sensitive polymer?
The most common approach utilizes enteric polymers (enteric coating) that
resist degradation in an acidic environment and release drug in alkaline media
due to the formation of salt.
Examples of PH-sensitive polymer?
Eudragit L, Eudragit S.
