Role of the Polymer Microstructure in Controlling Colloidal and Thermo-Responsive Properties of Nano-Objects Prepared...

After having demonstrated their potential in biomedical applications, thermo-responsive block copolymers that are able to self-assemble into nano-objects in response to temperature modifications are becoming more and more appealing in other sectors, such as the oil and gas and lubricant fields. Reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly has been demonstrated as a valuable strategy for producing nano-objects from modular block copolymers in non-polar media, required for the mentioned applications. Although the influence of the nature and size of the thermo-responsive block of these copolymers on the properties of the nano-objects is extensively studied in the literature, the role of the solvophilic block is often neglected. In this work, we elucidate the role of the main microstructural parameters, including those of the solvophilic portion, of block copolymers produced by RAFT polymerization in the hydrocarbon blend decane/toluene 50:50 v/v on the thermo-responsive behavior and colloidal properties of the resulting nano-objects. Two long-aliphatic chain monomers were employed for the synthesis of four macromolecular chain transfer agents (macroCTAs), with increasing solvophilicity according to the number of units (n) or length of the alkyl side chain (q). Subsequently, the macroCTAs were chain-extended with different repeating units of di(ethylene glycol) methyl ether methacrylate (p), leading to copolymers that are able to self-assemble below a critical temperature. We show that this cloud point can be tuned by acting on n, p, and q. On the other hand, the colloidal stability, expressed in terms of area of the particle covered by each solvophilic segment, is only a function of n and q, which provides a way for controlling the size distribution of the nano-objects and to decouple it from the cloud point.