Synthesis of Poly(n-butyl acrylate)-block-poly(acrylic acid) Diblock Copolymers by ATRP and Their Micellization in Water

Abstract

Amphiphilic diblock copolymers, poly(n-butyl acrylate)-block-poly(acrylic acid) (PnBA-PAA), with narrow molecular weight distribution (PDI ≤ 1.07) were prepared by atom transfer radical polymerization (ATRP) of n-butyl acrylate and tert-butyl acrylate (tBA), followed by selective acidolysis of the PtBA block. These polymers possess a soft PnBA hydrophobic block with a constant chain length of 90−100 monomer units and pH- and ionic strength-sensitive hydrophilic PAA block with DPPAA = 33−300 AA monomer units. They were expected to form stimuli-responsive micelles. The block copolymers with DPPAA ≥ 100 are directly soluble in water at pH > 4.7. Pyrene steady-state fluorescence spectroscopy and fluorescence correlation spectroscopy (FCS) studies indicate the existence of a very low critical micelle concentration (cmc ∼ 10-8 mol/L). The number-average hydrodynamic radii of the micelles, as determined by FCS, range from 28 to 55 nm, depending on the PAA block length. FCS data indicate that micellar sizes significantly decrease upon dilution for salt-free systems. This is attributed to a dynamic, but kinetically controlled, behavior of these self-assembled nanostructures. In saline solutions the micellar sizes remain constant above the “apparent” cmc (cmc*), which is attributed to slower dynamics of unimer exchange between micelles.

Tandem mass spectrometry of poly(methacrylic acid) oligomers produced by negative mode electrospray ionization

“…Hydrogels, i.e., weakly cross-linked hydrophilic polymers, obtained after copolymerization of polyethylene glycol (PEG) with methacrylic acid were recently demonstrated to be efficient absorbents of uranyl ions [2]. On the other hand, the ability of amphiphilic PMAA-based block copolymers to self-assemble and produce dynamic micelles sensitive to different stimuli was shown to highly depend on the balance between hydrophobic and hydrophilic segments [3][4][5][6]. Since the performance of such copolymer materials is closely associated to structurally related parameters, unambiguous characterization of their microstructure is a crucial analytical issue.…”

Amphiphilic Ionic Perylenediimides: Structures, Self-Assembly Studies and Biomedical Applications

“…Because of the well-defined structures, amphiphilic ionic molecules (AIMs) are studied widely in the field of AIS. Various nanostructures are obtained by the self-assembly of AIMs and the relationship between the morphologies and parameters was discovered by theoretical studies [1][2][3][4][5][6][7][8]. AIMs are designed and fabricated to form various nanostructures such as helical fibres, nanotubes, nanospheres and so on [9][10][11][12].…”

Poly(ethylene oxide)-block-poly(n-butyl acrylate)-block-poly(acrylic acid) triblock terpolymers with highly asymmetric hydrophilic blocks: synthesis and aqueous solution properties

“…of triuoroacetic acid with respect to the tBA units according to a procedure known to preserve the PnBA groups. 18,19 We found that for the complete hydrolysis of PtBA, the reaction time (Table 1) has to be extended as compared to other reported protocols.…”

“…18 Theoretical calculations show that the cmc values of PnBA-PAA block copolymers dramatically decrease with the increase of the molar mass of PnBA. 20 It is noteworthy that the micellization of such copolymers is considered to be a kinetically controlled process.…”