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Issue 14, 2012
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Dynamic self-aggregation behavior of a PNIPAM-based nonlinear multihydrophilic block copolymer revealed by two-dimensional correlation spectroscopy

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Abstract

IR spectroscopy in combination with the perturbation correlation moving window (PCMW) technique and 2D correlation spectroscopy (2DCOS) is employed to elucidate the dynamic self-aggregation behavior of a novel miktoarm star PNIPAM-based multihydrophilic block copolymer, poly(N-isopropylacrylamide)2–[poly(N-vinylpyrrolidone)-b-poly(acrylic acid)]2 ((PNIPAM)2–(PVP-b-PAA)2). At pH = 8, (PNIPAM)2–(PVP-b-PAA)2 tends to self-assemble into micelles with PNIPAM in the core and ionized PAA segments in the shell during heating. IR investigation shows that the AA segments exhibit a similar “phase transition” behavior to the PNIPAM segments, which can be ascribed to the indirect influence through the drastic content changes of water molecules along with the hydrophilic-to-hydrophobic transformation of PNIPAM segments. Boltzmann fitting and PCMW easily determine the transition temperature to be ca. 33 °C and the transition temperature range to be 29.5–35 °C. Moreover, 2DCOS discerns a sequential group motion from PNIPAM to PVP and PAA segments. It is concluded that the three polymeric segments have relatively independent phase behavior during the formation of PNIPAM-core micelles, and the chain conformation adjustment induced by hydrophilic-to-hydrophobic transformation of PNIPAM segments should be the driving force of the whole self-aggregation process. The dynamic self-aggregation process we proposed can be further confirmed by dynamic laser scattering (DLS) and zeta potential measurements.

Graphical abstract: Dynamic self-aggregation behavior of a PNIPAM-based nonlinear multihydrophilic block copolymer revealed by two-dimensional correlation spectroscopy

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Publication details

The article was received on 07 Oct 2011, accepted on 22 Dec 2011 and first published on 29 Feb 2012


Article type: Paper
DOI: 10.1039/C2SM06908C
Citation: Soft Matter, 2012,8, 3980-3987
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    Dynamic self-aggregation behavior of a PNIPAM-based nonlinear multihydrophilic block copolymer revealed by two-dimensional correlation spectroscopy

    S. Sun, W. Zhang, W. Zhang, P. Wu and X. Zhu, Soft Matter, 2012, 8, 3980
    DOI: 10.1039/C2SM06908C

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