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Simultaneous covalent and noncovalent hybrid polymerizations

Science  29 Jan 2016:
Vol. 351, Issue 6272, pp. 497-502
DOI: 10.1126/science.aad4091

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Doubling down on polymerization

In biology, structural polymers such as cytoskeletal fibers assemble from covalently polymerized monomers through weaker supramolecular interactions such as hydrogen bonds. Yu et al. report the synthesis of cylindrical fibers when three monomers react, two covalently and one in a supramolecular fashion. When the reaction proceeded stepwise, lower-molecular-weight flat tapes formed instead, which suggests that supramolecular interactions helped to catalyze the covalent polymerization.

Science, this issue p. 497

Abstract

Covalent and supramolecular polymers are two distinct forms of soft matter, composed of long chains of covalently and noncovalently linked structural units, respectively. We report a hybrid system formed by simultaneous covalent and supramolecular polymerizations of monomers. The process yields cylindrical fibers of uniform diameter that contain covalent and supramolecular compartments, a morphology not observed when the two polymers are formed independently. The covalent polymer has a rigid aromatic imine backbone with helicoidal conformation, and its alkylated peptide side chains are structurally identical to the monomer molecules of supramolecular polymers. In the hybrid system, covalent chains grow to higher average molar mass relative to chains formed via the same polymerization in the absence of a supramolecular compartment. The supramolecular compartments can be reversibly removed and re-formed to reconstitute the hybrid structure, suggesting soft materials with novel delivery or repair functions.

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