Two-Dimensional Controlled Syntheses of Polypeptide Molecular Brushes via N -Carboxyanhydride Ring-Opening Polymerization and Ring-Opening Metathesis Polymerization

Fan, Jingwei [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States]; Borguet, Yannick P. [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States]; Su, Lu [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States] (ORCID:000000018207756X); Nguyen, Tan P. [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States]; Wang, Hai [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States]; He, Xun [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States]; Zou, Jiong [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States]; Wooley, Karen L. [Departments of Chemistry,
Chemical Engineering, Materials Science and Engineering, and Laboratory
for Synthetic-Biologic Interactions, Texas A&M University, P.O. Box 30012, 3255 TAMU, College Station, Texas 77842, United States] (ORCID:000000034086384X)

doi:10.1021/acsmacrolett.7b00603

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 ( t BuO 2 Pr-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 ( M n ) 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 ( M n ) 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 M n 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.

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