Preparation of well-defined 2D-lenticular aggregates by self-assembly of PNIPAM-b-PVDF amphiphilic diblock copolymers in solution

PNIPAM-b-PVDF (poly(N-isopropylacrylamide)-b-poly(vinylidene fluoride)) amphiphilic block copolymers (BCPs) were synthesized via RAFT polymerization from PNIPAM macromolecular chain transfer agents (macro-CTAs). PNIPAM was used as it is one of the few hydrophilic polymers soluble in dimethyl carbonate (DMC) and which can be synthesized using a xanthate CTA with relatively good control. The polymerizations were conducted at 73 °C in DMC using two PNIPAM macro-CTAs of different molar masses and targeting various DPs for the PVDF block. The RAFT polymerization of VDF resulted in relatively well-defined BCPs (Đ ≤ 1.50). These amphiphilic BCPs were able to self-assemble into various morphologies such as spherical, crumpled, lamellar and lenticular 2D aggregates by changing the common solvent or the self-assembly protocol. The size of the aggregates could be controlled by varying the DP of the PVDF block. The polymers were characterized by 1H and 19F NMR, SEC, TGA and DSC, and the assembled structures were studied by TEM, SEM and AFM. The thermosensitive behavior of the 2D lenticular aggregates was also examined.