Synthesis and characterization of thermo-responsive polypeptoid bottlebrushes

Abstract

Linear polypeptoid macromonomers with controlled chain length and composition were prepared by norbornene methylamine-initiated copolymerization of N-ethyl N-carboxyanhydride (Et-NCA) and Nbutyl N-carboxyanhydride (Bu-NCA). Polypeptoid bottlebrush copolymers with varying backbone length and side chain composition were subsequently synthesized using the grafting-through method via the ring-opening metathesis polymerization (ROMP) of norbornenyl-terminated poly(N-ethyl glycine)-ranpoly(N-butyl glycine) macromonomers. The bottlebrush copolypeptoids are thermally responsive with a cloud point transition in aqueous solution similar to the linear macromonomers. In contrast to the linear macromonomers, the cloud point transition of the bottlebrush copolypeptoids is strongly dependent on the thermal history of the solution. Freshly prepared aqueous solutions of the bottlebrush copolypeptoids do not exhibit any notable cloud point transition, whereas the solutions that have been thermally annealed at high temperature exhibit sharp and reversible cloud point transition. Intriguingly, upon inorganic salt addition, the aqueous solutions of the bottlebrush copolypeptoids exhibit normal cloud point transition which is independent of the solution thermal history. It was suggested that the thermal annealing and the presence of a salt facilitated the conformational reorganization of the bottlebrush copolypeptoids to favor hydrophobic collapse and intermolecular aggregation, resulting in a cloud point transition.

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…[290], polylactate groups [291,292,293], polypeptide chains [294], polyacrylate or substituted polystyrene chains [295], nitroxide groups [296], fluorescent groups [297], a perfluorooctyl group [298], perfluorocarboxylic acid groups [299], and a fullerene-carbene adduct [300]; (2) norbornene in the presence of Fe 3 O 4 nanoparticles [301]; (3) norbornenes in the presence of an allylated lanthanide salen complex [302]; (4) norbornyl-acac-like systems complexed to terbium [303] or to an iridium-pyrazolone complex (e.g. 71) [304];…”

Polypeptoid polymers: Synthesis, characterization, and properties

“…[19] Bottlebrush copolymers comprised of the linear P(NEG-r-NBG) random copolypeptoid sidechains were obtained by ROMP of the norbornene-terminated P(NEG-r-NBG) macromonomer ( Figure 5). [71] The polypeptoid bottlebrush copolymers also exhibited cloud point transition in aqueous solution similarly to the linear macromonomers.…”

“…[71] Freshly prepared aque- proline) copolymer can be hydrolytically degraded into the respective amino acids under highly acidic conditions (6N HCl, 1208C, 24 h). [82] We have found that polysarcosine also completely degraded into the blocks with higher content of the sarcosine at the N-terminus.…”

Post polymer modification of polyethylenimine with citrate esters: selectivity and hydrophobicity

“…While these terms provide a great framework for understanding and explaining certain experimental observations, a more quantitative approach is frequently desired. 1,2 Given universal interest in "hydrophobic" surfaces, 2,3 monomers, 4-6 micelles, 7 polymers, 8,9 peptides, 10 proteins, 11 molecules, 12 solvents, 13 and drugs, 14 comparing one system to another is often necessary.…”