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Aggregation behavior of doubly thermoresponsive polysulfobetaine‑b‑poly(N‑isopropylacrylamide) diblock copolymers

: Vishnevetskaya, Natalya S.; Hildebrand, Viet; Niebuur, Bart-Jan; Grillo, Isabelle; Filippov, Sergey K.; Laschewsky, André; Müller-Buschbaum, Peter; Papadakis, Christine M.


Macromolecules 49 (2016), No.17, pp.6655-6668
ISSN: 0024-9297
ISSN: 1520-5835
Deutsche Forschungsgemeinschaft DFG
Journal Article
Fraunhofer IAP ()
block copolymer; multiresponsive polymer; micelle; schizophrenic aggregation; LCST; UCST

A 2-fold thermoresponsive diblock copolymer PSPP430-b-PNIPAM200 consisting of a zwitterionic polysulfobetaine (PSPP) block and a nonionic poly(N-isopropylacrylamide) (PNIPAM) block is prepared by successive RAFT polymerizations. In aqueous solution, the corresponding homopolymers PSPP and PNIPAM feature both upper and lower critical solution temperature (UCST and LCST) behavior, respectively. The diblock copolymer exhibits thermally induced schizophrenic aggregation behavior in aqueous solutions. Moreover, the ion sensitivity of the cloud point of the zwitterionic PSPP block to both the ionic strength and the nature of the salt offers the possibility to create switchable systems which respond sensitively to changes of the temperature and of the electrolyte type and concentra tion. The diblock copolymer solutions in D2O are investigated by means of turbidimetry and small-angle neutron scattering (SANS) with respect to the phase behavior and the self-assembled structures in dependence on temperature and electrolyte content. Marked differences of the aggregation below the UCST-type and above the LCST-type transition are observed. The addition of a small amount of NaBr (0.004 M) does not affect the overall behavior, and only the UCST-type transition and aggregate structures are slightly altered, reflecting the well-known ion sensitivity of the zwitterionic PSPP block.