Controlled ring-opening polymerization of N-(3-tert-butoxy-3-oxopropyl) glycine derived N-carboxyanhydrides towards well-defined peptoid-based polyacids?

Polymer Chemistry Pub Date: 2021-01-05 DOI: 10.1039/D0PY01395A

Abstract

Polypeptoids bearing carboxylic acid groups on the N-substituent are useful building blocks for the construction of peptidomimetic supramolecular assemblies with stimuli-responsive properties. Towards this end, N-(3-tert-butoxy-3-oxopropyl) glycine derived N-carboxyanhydride (tBuO2Pr-NCA) has been successfully synthesized and polymerized using primary amine initiators to produce the corresponding poly(N-(3-tert-butoxy-3-oxopropyl) glycine) with molecular weights (Mn) of 5.6–59 kg mol?1 and a narrow molecular weight distribution (PDI = 1.003–1.026). The polymerization was shown to proceed in a controlled manner, evidenced by the good agreement of the experimental molecular weight (Mn) with theoretical values and narrow molecular weight distribution in a wide range of monomer-to-initiator ratios ([M]0?:?[I]0 = 25?:?1–200?:?1), the linear increase of Mn with conversion and the second-order polymerization kinetics. The cloaked carboxyl groups on the poly(N-(3-tert-butoxy-3-oxopropyl) glycine) can be readily unveiled in mild acidic conditions to yield the poly(N-(2-carboxyethyl) glycine), a structural mimic of poly(glutamic acid). The poly(N-(2-carboxyethyl) glycine) polymer is a weak polyelectrolyte whose hydrodynamic size in water can be controlled by the solution pH.

Graphical abstract: Controlled ring-opening polymerization of N-(3-tert-butoxy-3-oxopropyl) glycine derived N-carboxyanhydrides towards well-defined peptoid-based polyacids
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