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Issue 4, 2013
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Steric hindrance effect on thermoresponsive behaviors of pyrrolidone-based polymers

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Abstract

This paper describes the steric hindrance effect on thermoresponsive behaviors of pyrrolidone-based water-soluble polymers. Two polymers, poly[N-(1-meth-2-acryloyloxyethyl)pyrrolidone] (PMEP) and poly[N-(2-acryloyloxypropyl)pyrrolidone] (PAPP) with different pyrrolidone-based side groups were synthesized via conventional free-radical polymerization. PMEP and PAPP with approximate molecular weights (MW) and polydispersities were confirmed by gel permeation chromatography. Their thermoresponsive phase transition behaviors in aqueous media were studied using dynamic light scattering (DLS) and temperature-variation 1H NMR. The cloud points of PMEP and PAPP decreased exponentially rather than linearly with the increase in concentration. PMEP exhibited a lower cloud point than PAPP at the same mass concentration. Both PMEP and PAPP showed a solvent isotopic effect, as their cloud points in deuterium oxide (D2O) were lower than those in hydrogen oxide (H2O). We also noted that the ΔCP [CPPAPP − CPPMEP] was 5.2 °C in D2O and 4.2 °C in H2O at 20.0 mg ml−1. In addition, PAPP showed more noticeable changes in proton resonance signal intensities during the temperature elevation. The differences in thermoresponsive phase transition behaviors between PMEP and PAPP resulted from the steric hindrance effect of their side groups.

Graphical abstract: Steric hindrance effect on thermoresponsive behaviors of pyrrolidone-based polymers

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Publication details

The article was received on 21 Sep 2012, accepted on 29 Oct 2012 and first published on 19 Nov 2012


Article type: Paper
DOI: 10.1039/C2PY20773G
Polym. Chem., 2013,4, 1068-1076

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    Steric hindrance effect on thermoresponsive behaviors of pyrrolidone-based polymers

    P. Liu, L. Xiang, Q. Tan, H. Tang and H. Zhang, Polym. Chem., 2013, 4, 1068
    DOI: 10.1039/C2PY20773G

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