Synthesis of Oppositely Charged Block Copolymers of Poly(ethylene glycol) via Reversible Addition−Fragmentation Chain Transfer Radical Polymerization and Characterization of Their Polyion Complex Micelles in Water

Abstract

Diblock copolymers consisting of a water-soluble nonionic block and either an anionic or cationic block were prepared from sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) or (3-(methacryloylamino)propyl)trimethylammonium chloride (MAPTAC) via reversible addition-fragmentation chain transfer (RAFT)controlled radical polymerization using poly(ethylene glycol) (PEG)-based chain transfer agent (PEG-CTA) in water. The RAFT polymerization proceeded in a living fashion, as suggested by the observation that the numberaverage molecular weight (M n ) increased linearly with the monomer conversion (up to conversions of 30% for MAPTAC and 50% for AMPS), whereas the polydispersity (M w /M n ) remained nearly constant (M w /M n < 1.05 for MAPTAC and <1.2 for AMPS) independent of the conversion. The mixing of aqueous solutions of the oppositely charged diblock copolymers, PEG-b-PAMPS and PEG-b-PMAPTAC, led to the spontaneous formation of polyion complex (PIC) micelles. The PIC micelles were characterized by 1 H NMR spin-spin relaxation time, static light scattering (SLS), dynamic light scattering (DLS), and scanning electron microscopy (SEM) techniques. The hydrodynamic size of the micelle depended on the mixing ratio of PEG-b-PAMPS and PEG-b-PMAPTAC with the size maximizing at the mixing ratio of stoichiometric charge neutralization. The mixing of the oppositely charged diblock copolymers with shorter charged blocks formed a core-shell PIC micelle. In contrast, a complicated aggregate was formed from a pair of longer blocks. The exact structure of the aggregate is still an open question, but it is speculated to be a multicore intermicellar aggregate on the basis of various characterization data.

Anionic multiblock core cross-linked star copolymers via RAFT polymerization

“…14 In order to diversify its functionality and optimise its physical properties, AMPS ® is often polymerized with other comonomers such as acrylic acid, 1 acrylamide, N,N-dimethylacrylamide, 15 sodium 3acrylamido-3-methylbutanoate, 16 or poly(ethylene glycol). 17 For example, diblock copolymers of PAMPS-b-PAMBA with low dispersity values were successfully obtained in water within 12 hours by Sumerlin et al…”

Frit inlet field-flow fractionation techniques for the characterization of polyion complex self-assemblies

“…FI-AsFlFFF hyphenated with online MALS and DLS also gave access to the Rg/Rh ratio, indicating the morphology of the nano-object. PICs in the literature have been observed to exhibit Rg/Rh ratios over a very wide range, from 0.3 to 1.3, depending on the more or less defined core-shell morphology and the density of the core [3,7,8,[62][63][64][65][66][67]. The values found in this work suggest objects with a dense core for those close to 0.3-0.4 or homogeneous spherical ones for Rg/Rh close to 0.7-0.8 [18,68].…”

Hollow nanoparticles prepared from pH‐responsive template polymer micelles

“…4‐Cyanopentanoic acid dithiobenzoate (CPD),22 PEG‐based chain transfer agent (PEG‐CPD, M n (NMR) = 2.37 × 10 3 , M w / M n = 1.02),23 and sodium 6‐(acrylamido)hexanoate (AaH)24 were synthesized according to previously reported methods. APTAC (75% in water; Aldrich) was passed through alkaline alumina columns to remove the inhibitor.…”