Investigation of a dual set of driving forces (hydrophobic + electrostatic) for the two-step fabrication of defined block copolymer micelles

Exploring the construction of multicompartmental micelles by halogen bonding of complementary macromolecules

An approach to the construction of multicompartmental micelles, using halogen bonding between complementary macromolecules, is described. The design involves a sequential assembly protocol, in which the initial compartments are formed by interpolymer halogen bonding, followed by the collapse of a second, hydrophobic compartment upon transfer to aqueous solvent. Triblock terpolymers incorporating a halogen bond accepting segment have been synthesized. Transmission electron microscopy was used to characterize multicompartmental assemblies generated from these terpolymers in the presence of a halogen bond donor-functionalized polystyrene derivative.

Multicompartment micelles from pH-responsive miktoarm star block terpolymers

We describe the synthesis of pH-responsive miktoarm star block terpolymers mu-[polystyrene][poly(ethylene oxide)][poly(2-(dimethylamino)ethyl acrylate)] (mu-SODA) using a combination of two successive living anionic polymerizations and one reversible addition-fragmentation chain-transfer polymerization. Poly[2-(dimethylamino)ethyl acrylate] (PDMAEA) is a weak polybase that is hydrophilic at low pH and hydrophobic at high pH because of the protonation of the dimethylamino functional group with decreasing pH. In addition, our results suggest that PDMAEA is immiscible with polystyrene (PS), a feature that is desirable for the formation of multicompartment micelles. Using a combination of dynamic light scattering and cryogenic transmission electron microscopy, we demonstrate that mu-SODA micelles formed in water evolve from mixed corona (PEO + PDMAEA corona; PS core) and predominantly spherical micelles to multicompartment (PEO corona; PS + PDMAEA core) micelles with increasing pH.

Synthesis and micellar self-assembly of ternary hydrophilic-lipophilic-fluorophilic block copolymers with a linear PEO chain

Linear amphiphilic diblock and ternary triblock copolymers were synthesized by the RAFT method in two successive steps using a poly(ethylene oxide) (PEO) macrochain transfer agent, butyl or 2-ethylhexyl acrylate, and 1H,1H,2H,2H-perfluorodecyl acrylate. The diblock and the triblock copolymers, which consist of a hydrophilic, a lipophilic, and a short fluorophilic block, self-assemble in water into spherical micellar aggregates. Imaging by cryogenic transmission electron microscopy (cryo-TEM) revealed that the micellar cores of the aggregates made from these "triphilic" copolymers can undergo local phase separation to form a unique ultrastructure. In these multicompartment micelles, it appears that extended nonspherical domains, presumably made of nanocrystallites of the fluorocarbon block, are embedded in the hydrocarbon matrix forming the spherical micellar core. This novel internal structure of a micellar core is attributed to the mutual incompatibility of the fluorocarbon and hydrocarbon side chains in combination with the tendency of the used fluorocarbon acrylate monomer to undergo side-chain crystallization.