Amphiphilic tetraethylene glycol methacrylate-perfluoroalkyl acrylate block and random copolymers: Synthesis and self-assembling in water solution

Amphiphilic block and random copolymers with perfluoroalkyl segments can efficiently provide self-assembled polymeric nanostructures[1], including micelles, vesicles, and nanogels, in water and organic solvents, via the intermolecular association or intramolecular self-folding of the copolymer chains[2]. These nanomaterials may display anti-biofouling properties against proteins, cells and organisms[3]. Moreover, perfluoroalkyl polymers have several attractive features: the polymers are immiscible with both water and common organic solvents, yet have selective interactions with fluorinated compounds resulting in unique association and molecular recognition. Focusing on these features we have synthesized block and random copolymers of tetraethylene glycol methyl ether methacrylate (PEGMA) and 2-(perfluorohexyl)ethyl acrylate (FA). Owing to the controlled ATRP reaction, the molecular weight, composition and sequence of the amphiphilic block and random copolymers could be tuned in a predictable way. In this contribution copolymers with PEGMA:FA ratios 70:30 and 90:10 are reported. The philic/phobic balance directly affected the self-assembling behaviour in bulk and in solution. Above a critical concentration in water (0.5 g/L), the copolymer chains are characterized by a bimodal size distribution (Fig.1, left), comprised of nanometer and submicrometer structures. While the larger structures were due to self-assembled, intermolecular aggregates, the smaller ones were attributed to single, intramolecular folded chains. Moreover, we found a sharp thermal transition depending on the copolymer composition (Fig.1, right). Above the transition temperature, one almost monodisperse stable phase existed, with size increasing from ~500 nm to ~1500 nm with copolymer concentration from 0.5 g/L to 5 g/L. Heating and cooling cycles showed the complete reversibility of these copolymer systems. The narrow size distributions accomplished for both copolymers above the thermal transition are ascribed to the formation of intriguing thermoresponsive polymersomes with homogeneous size.