Polymerization-pH tailored RAFT-mediated polymerization-induced self-assembly for ice recrystallization inhibiting the investigation

Abstract

RAFT-mediated polymerization-induced self-assembly (RAFT-PISA) has been undergoing fast development currently, promoting research toward more diverse morphologies and more cutting-edge applications. Herein, we demonstrate a polymerization-pH tailored RAFT-PISA (pH-PISA) process, which can conveniently harvest abundant nano/micro-scale morphologies using popular monomers N,N-dimethylacrylamide (DMAA) and diacetone acrylamide (DAAM). The process proceeded through ordinary RAFT dispersion polymerization in an aqueous medium but under different pH conditions. With the use of pH-sensitive bi-carboxylic acid-capped trithiocarbonate as the chain transfer agent (CTA), it was found that the PISA of propagating amphiphilic ABA triblock copolymers was highly affected by the different ionization of the CTA. When the polymerization pH was adjusted to 2.5, an especially wide spectrum of morphologies was detected, including spheres, worms, lamellae, single or double-head tadpoles, vesicle strings and large spheres with surface protrusions. However, the diversity in morphology gradually declined when the polymerization pH was increased to 6 or 8. Diverse structures with same monomer compositions provide an ideal model to explore the influence of particle morphology on ice recrystallization inhibition (IRI) activities. The variations in mean largest grain sizes (MLGS) and growth rates of a single ice crystal were related to packing parameters (P), bridging the interface geometry of the packing of amphiphilic molecules and ice-controlling activities.