SANS and DLS Study of Tacticity Effects on Hydrophobicity and Phase Separation of Poly(N‑isopropylacrylamide)

The tacticity effect on phase separation process of poly(N-isopropylacrylamide) (PNiPAM) aqueous solutions was investigated by dynamic light scattering (DLS) and small angle neutron scattering (SANS) measurements. SANS measurement revealed that hydrophobicity of PNiPAM consisting of meso- and racemo...

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Bibliographic Details
Published inMacromolecules Vol. 46; no. 15; pp. 6225 - 6232
Main Authors Nishi, Kengo, Hiroi, Takashi, Hashimoto, Kei, Fujii, Kenta, Han, Young-Soo, Kim, Tae-Hwan, Katsumoto, Yukiteru, Shibayama, Mitsuhiro
Format Journal Article
LanguageEnglish
Published Washington, DC American Chemical Society 13.08.2013
Subjects
Applied sciences
Exact sciences and technology
Organic polymers
Physicochemistry of polymers
Properties and characterization
Solution and gel properties
Structure effect
Hydrodynamic radius
Hydrophilic lipophilic balance
Phase separation
Concentration effect
Temperature effect
Aqueous solution
Experimental study
Acrylamide derivative polymer
Mechanism
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Summary:The tacticity effect on phase separation process of poly(N-isopropylacrylamide) (PNiPAM) aqueous solutions was investigated by dynamic light scattering (DLS) and small angle neutron scattering (SANS) measurements. SANS measurement revealed that hydrophobicity of PNiPAM consisting of meso- and racemo-isomers increased with increasing the meso-content. This result is in accordance with the result of the previous experimental and simulation study on NiPAM dimers (DNiPAM) and trimers (TNiPAM) [ Katsumoto Y ; J. Phys. Chem. B 2010, 114, 13312−13318 , and Autieri E. ; J. Phys. Chem. B 2011, 115, 5827–5839 ]; i.e., meso-diad is more hydrophobic than racemo-diad. In addition, a series of scattering experiments revealed that the ratio of meso-diad does not affect the static structure or the shrinking behavior of a single chain, but strongly affects the aggregation behavior. The PNiPAMs with low meso-content suddenly associate around the phase separation temperature, while that of the high meso-content gradually aggregate with increasing temperature. We propose that phase transition behavior of PNiPAM aqueous solutions can be controlled by changing the stereoregularity of the polymer chain.
ISSN:0024-9297
1520-5835
DOI:10.1021/ma401349v