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Issue 18, 2011
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Effect of polyethylene glycol (PEG) length on the association properties of temperature-sensitive amphiphilic triblock copolymers (PNIPAAMm-b-PEGn-b-PNIPAAMm) in aqueous solution

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Abstract

Effects of temperature on the association behavior in aqueous solutions of a series of thermosensitive poly(N-isopropylacrylamide)-block-poly(ethylene glycol)-block-poly(N-isopropylacrylamide) triblock copolymers (PNIPAAMm-b-PEGn-b-PNIPAAMm) with the length of the PNIPAAM block fixed (m ≈ 67) and with different lengths of the PEG block (n = 23, 34, 77, and 165) have been studied with the aid of turbidity, dynamic light scattering (DLS), and Monte Carlo simulations. The turbidity results show that the sharp transition to high turbidity values is shifted to higher temperatures when the length of the PEG spacer is increased from 23 to 77, whereas no transition is observed for the longest PEG block. These findings are consistent with the DLS results, which suggest the formation of large association structures at temperatures well above the cloud point. The simulation results indicate that a long PEG-block portion separating the PNIPAAM blocks in the triblock copolymer reduces the tendency of the polymer forming interchain associations at elevated temperatures. Simulation shows that for a long PEG spacer, the copolymer moiety is rather extended even at high temperatures, whereas for copolymers with a short PEG length the thermoresponsive block copolymer undergoes a transition from an extended to a compact conformation.

Graphical abstract: Effect of polyethylene glycol (PEG) length on the association properties of temperature-sensitive amphiphilic triblock copolymers (PNIPAAMm-b-PEGn-b-PNIPAAMm) in aqueous solution

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Publication details

The article was received on 15 Apr 2011, accepted on 17 Jun 2011 and first published on 19 Jul 2011


Article type: Paper
DOI: 10.1039/C1SM05679D
Soft Matter, 2011,7, 8111-8119

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    Effect of polyethylene glycol (PEG) length on the association properties of temperature-sensitive amphiphilic triblock copolymers (PNIPAAMm-b-PEGn-b-PNIPAAMm) in aqueous solution

    A. Maleki, K. Zhu, R. Pamies, R. R. Schmidt, A. Kjøniksen, G. Karlsson, J. G. Hernández Cifre, J. García de la Torre and B. Nyström, Soft Matter, 2011, 7, 8111
    DOI: 10.1039/C1SM05679D

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