BEH.462/3. 962J Molecular Principles of Biomaterials Spring 2003 Polyion complex hydrogels Coacervates o complexation between two oppositely charged polyelectrolytes can lead to precipitation(insoluble solid phase driven by charge neutralization on hydrophobic polymers driven by macro-aggregate formation 2. coacervate formation(dense liquid phase) 3. soluble comple o mechanisms of formation Polyanion Polycation Random primary Ordered secondary 解 Complex aggregates 1. initial rapid Coulombic bonding 2. formation of new bonds/restructuring of chain distortions gregation of secondary complexes o mixing of two polyions can lead to 90% complex formation Polyelectrolytes studied as coacervates for biomaterials: Polyanions o Carboxymethylcellulose o Dextran sulfate o Carboxymethyl dextran o Pectin o Polycau chitosan(derived from crab shells) o Polyethyleneimine o Poly (4-vinyl-N-butylpyridinium) bromide o Quarternized polycations o Poly(vinylbenzyltrimethyl)ammonium hydroxide Lecture 9-polyelectrolyte hydrogels 4of17BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Polyion complex hydrogels4 Coacervates o complexation between two oppositely charged polyelectrolytes can lead to: 1. precipitation (insoluble solid phase) ƒ driven by charge neutralization on hydrophobic polymers ƒ driven by macro-aggregate formation 2. coacervate formation (dense liquid phase) 3. soluble complexes o mechanisms of formation 1. initial rapid Coulombic bonding 2. formation of new bonds/restructuring of chain distortions 3. aggregation of secondary complexes o mixing of two polyions can lead to 90% complex formation o Polyelectrolytes studied as coacervates for biomaterials:4 o Polyanions o Carboxymethylcellulose o Alginate o Dextran sulfate o Carboxymethyl dextran o Heparin o Carrageenan o Pectin o xanthan o Polycations o Chitosan (derived from crab shells) o Polyethyleneimine o Poly(4-vinyl-N-butylpyridinium) bromide o Quarternized polycations o Poly(vinylbenzyltrimethyl)ammonium hydroxide Lecture 9 – polyelectrolyte hydrogels 4 of 17