Synthesis of Poly(<i>n</i>-butyl acrylate)-<i>block</i>-poly(acrylic acid) Diblock
Copolymers by ATRP and Their Micellization in Water
Olivier Colombani
Markus Ruppel
Frank Schubert
Heiko Zettl
Dmitry V. Pergushov
Axel H. E. Müller
10.1021/ma0609578.s001
https://acs.figshare.com/articles/journal_contribution/Synthesis_of_Poly_i_n_i_butyl_acrylate_i_block_i_poly_acrylic_acid_Diblock_Copolymers_by_ATRP_and_Their_Micellization_in_Water/3002275
Amphiphilic diblock copolymers, poly(<i>n</i>-butyl acrylate)-<i>block</i>-poly(acrylic acid) (P<i>n</i>BA-PAA), with
narrow molecular weight distribution (PDI ≤ 1.07) were prepared by atom transfer radical polymerization (ATRP)
of <i>n</i>-butyl acrylate and <i>tert</i>-butyl acrylate (<i>t</i>BA), followed by selective acidolysis of the P<i>t</i>BA block. These polymers
possess a soft P<i>n</i>BA hydrophobic block with a constant chain length of 90−100 monomer units and pH- and
ionic strength-sensitive hydrophilic PAA block with DP<sub>PAA</sub> = 33−300 AA monomer units. They were expected
to form stimuli-responsive micelles. The block copolymers with DP<sub>PAA</sub> ≥ 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<sup>-8</sup> 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.
2007-06-12 00:00:00
micellar sizes
fluorescence correlation spectroscopy
monomer
cmc
acid
micelle
WaterAmphiphilic diblock copolymers
DPPAA
PAA block length
pH
FCS
ATRP
PDI
acrylate