Abstract
Amphiphilic Janus dendrimers composed of hydrophilic poly(ether-ester) (PEE) dendron and hydrophobic poly(benzyl ether) (PBE) dendron were synthesized by fragment coupling through copper catalyzed alkyne-azide cycloaddition (“click” chemistry). By varying the dendron generation and the oligo(ethylene glycol) linker between the branching units of the PEE dendron, a small library containing 14 Janus dendrimers were prepared. These Janus dendrimers were used to produce micelles and vesicles in water which were further investigated by microscopic studies. Amphiphilic linear-dendritic block copolymers (LDBCs) composed of hydrophilic PEE dendron and linear polystyrene tail were synthesized by dendron initiated atom transfer radical polymerization (ATRP). By varying the polymerization time and catalyst concentration, a series of LDBCs with different PEE generation and polystyrene chain length were prepared. These LDBCs were used to produce porous films by static breath figure technique. The hydrophilic to hydrophobic ratio and precipitation rate of the LDBCs determines the regularity of the pores. Only the first generation LDBC bearing OH surface groups with low PEE content were able to generate breath figure films. Higher generations LDBCs require water miscible cosolvent to produce porous films. Mixing the LDBCs with hydroxyl groups with homo polystyrene provides a method to fabricate monolayer porous films with controllable pore size. LDBCs were further utilized to prepare colloidal particles by cosolvent (nanoprecipitation) method. The morphology of obtained self-assembled particles was studied by electron microscopies. The morphology of these micelles depends on PEE content and its generation. The polystyrene tail is stretched in the micellar cores formed by the first and second generation LDBCs while relaxed in the third generation LDBCs when THF is used as the common solvent. The morphologies were tuned by changing the common solvent or complexing the palladium to LDBCs. Bicontinuous sponge, cubic (Im3̅m)and reversed hexagonal (HII)phases were produced.