Arginine-Functional Methacrylic Block Copolymer Nanoparticles: Synthesis, Characterization, and Adsorption onto a Model Planar Substrate.

Recently, we reported the synthesis of a hydrophilic aldehyde-functional methacrylic polymer (Angew. Chem., 2021, 60, 12032-12037). Herein we demonstrate that such polymers can be reacted with arginine in aqueous solution to produce arginine-functional methacrylic polymers without recourse to protecting group chemistry. Careful control of the solution pH is essential to ensure regioselective imine bond formation; subsequent reductive amination leads to a hydrolytically stable amide linkage. This new protocol was used to prepare a series of arginine-functionalized diblock copolymer nanoparticles of varying size via polymerization-induced self-assembly in aqueous media. Adsorption of these cationic nanoparticles onto silica was monitored using a quartz crystal microbalance. Strong electrostatic adsorption occurred at pH 7 (Γ = 14.7 mg m-2), whereas much weaker adsorption occurred at pH 3 (Γ = 1.9 mg m-2). These findings were corroborated by electron microscopy, which indicated a surface coverage of 42% at pH 7 but only 5% at pH 3.

Synthesis and Characterization of Charge-Stabilized Poly(4-hydroxybutyl acrylate) Latex by RAFT Aqueous Dispersion Polymerization: A New Precursor for Reverse Sequence Polymerization-Induced Self-Assembly.

The reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 4-hydroxybutyl acrylate (HBA) is conducted using a water-soluble RAFT agent bearing a carboxylic acid group. This confers charge stabilization when such syntheses are conducted at pH 8, which leads to the formation of polydisperse anionic PHBA latex particles of approximately 200 nm diameter. The weakly hydrophobic nature of the PHBA chains confers stimulus-responsive behavior on such latexes, which are characterized by transmission electron microscopy, dynamic light scattering, aqueous electrophoresis, and 1H NMR spectroscopy. Addition of a suitable water-miscible hydrophilic monomer such as 2-(N-(acryloyloxy)ethyl pyrrolidone) (NAEP) leads to in situ molecular dissolution of the PHBA latex, with subsequent RAFT polymerization leading to the formation of sterically stabilized PHBA-PNAEP diblock copolymer nanoparticles of approximately 57 nm diameter. Such formulations constitute a new approach to reverse sequence polymerization-induced self-assembly, whereby the hydrophobic block is prepared first in aqueous media.