Thermosensitive spontaneous gradient copolymers with block- and gradient-like features

Abstract

Amphiphilic gradient copolymers with thermoresponsive properties were synthesized in one pot via RAFT copolymerization.

Asymmetric Copolymers: Synthesis, Properties, and Applications of Gradient and Other Partially Segregated Copolymers

“…For this purpose, xanthate‐mediated RAFT polymerization is particularly useful as xanthates provide good control over less activated monomers such as vinyl esters and vinylamides (and lactams), coupled with acceptable levels of control over more activated monomers such as acrylates and acrylamides . Numerous examples of xanthate‐mediated spontaneous gradient copolymers can be found in the literature …”

“…Similarly to block copolymers, amphiphilic gradient copolymers form a range of different nanostructures through self‐assembly in solution, the morphology of which is greatly influenced by their composition . In contrast to the abrupt change in composition of block copolymers, no discrete point exists within individual asymmetric copolymer chains separating them into two distinctly different constituent parts.…”

“…Several groups have attempted to improve the representation and classification of gradient copolymers. One approach is to display a number of simulated chains, with the probability of finding a monomer at each location determined by the monomer composition at the conversion corresponding to that location and the identity of the previous added monomer ( Figure ) . This provides information on the interchain variation as well as the distribution of alternating sequences and blocks within each chain, but still conflates conversion with chain length and is difficult to quantify numerically.…”

“…Many techniques have been used for the preparation of asymmetric copolymers, including anionic and cationic polymerizations, C1 polymerization, catalyst transfer polycondensation, catalyzed copolymerization of olefins and epoxides, ring‐opening metathesis polymerization (ROMP) and various RDRP techniques (e.g., atom transfer radical polymerization (ATRP), nitroxide‐mediated polymerization (NMP), organometallic‐mediated radical polymerization (OMRP), and reversible addition–fragmentation chain transfer (RAFT)).…”

“…Similarly, a wide range of monomers have been used, including acrylates and methacrylates, acrylamides/methacrylamides, styrenics, olefins, vinyl esters, and epoxides . Both monomers must be compatible with the chosen polymerization technique and should ideally propagate rapidly and terminate relatively slowly in order to allow long chains to be prepared while maintaining acceptable levels of termination.…”