Liquid-Phase Synthesis of Block Copolymers Containing Sequence-Ordered Segments

Abstract

Monodisperse sequence-defined oligomers have been synthesized in solution in the absence of protecting groups. These structures have been prepared stepwise using two consecutive chemoselective reactions: 1,3-dipolar cycloaddition of terminal alkynes and azides and amidification of carboxylic acids with primary amines. These oligomers were efficiently constructed on either a conventional solid support (commercial Wang resin) or tailor-made soluble polystyrene supports synthesized by atom-transfer radical polymerization. The latter approach was found to be very versatile. Indeed, well-defined soluble macromolecular supports allowed not only the synthesis and cleavage of defined oligomers (i.e., sacrificial support) but also the preparation of noncleavable block copolymers containing sequence-defined segments.

Tailored Polymer Microstructures Prepared by Atom Transfer Radical Copolymerization of Styrene and N‐substituted Maleimides

“…[11,13] Iterative synthetic approaches (e.g., solid-phase synthesis) allow the design of short sequence-defined oligomers; however these technically demanding syntheses remain unfortunately marginal in synthetic polymer science. [4,[13][14][15] Besides, one-pot polymerization processes such as step-growth or chain-growth polymerizations offer very limited options for controlling macromolecular sequences. [11] Indeed, in these conventional synthetic approaches, polymer chains are assembled in a concentrated ''soup'' of comonomers, and thus statistics govern the copolymerization processes.…”

“…[5,13,15,20,[22][23][24][25][26][27][28][29][30][31][32] In particular, a few research groups investigated sequence-regulation in chaingrowths polymerizations. For instance, the innovative approaches recently reported by the research groups of Sawamoto, [26,29,32,33] Thomas, [10,27] and Kamigaito [20,30] have to be mentioned.…”

Metal‐Catalyzed Synthesis of Alternating Copolymers

“…[11] Other unique approaches include a-olefins-alt-ethylene copolymerization using bridged C 1 -symmetric metallocenes with heterotopic coordination sites, [12] ring-opening insertion metathesis polymerization, [13] and solid or liquid-phase iterative synthesis. [14] In order to obtain alternating polymers, coordination polymerization using well-defined metal complexes has played a leading role in the last two decades. The goal of the proposed paper is the description of catalysts that allow higher order sequence control of this latter type, and create alternating macromolecular structures with advanced properties.…”

“…Site-selective coordination also seems to occur with the C 1 -symmetric pyridine-oxazoline ligand used, causing syndiotactic copolymerization as was the case in the original catalytic system containing bipyridine. [57] Nozaki et al have demonstrated that a cationic Pd(II) complex of unsymmetrical chiral bidentate phosphinephosphite, (R,S)-BINAPHOS (14), serves as an efficient catalyst for the asymmetric copolymerization of TBS with carbon ligands. Even if 2,1-insertion takes place, rapid b-hydride elimination occurs, as is common with the other phosphorus ligands, but in that case the resulting Pd-H species reinitiates the copolymerization, as was proven by MALDI-TOF mass analysis of the product copolymers.…”

Recent developments in the synthesis of sequence controlled polymers

“…Lutz and coworkers [20,80] developed solid phase synthesis using modified Wang resin in combination with orthogonal coupling reactions such as azide alkyne cycloaddi-…”