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Counterintuitive photomodulation of the thermal phase transition of Poly(methoxy diethylene glycol acrylate) in aqueous solution by trans-cis isomerization of copolymerized azobenzenes

 
: Miasnikova, A.; Benítez-Montoya, C.A.; Laschewsky, A.

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Macromolecular chemistry and physics 214 (2013), Nr.13, S.1504-1514
ISSN: 1022-1352
Englisch
Zeitschriftenaufsatz
Fraunhofer IAP ()

Abstract
The non-ionic monomer (methoxy diethylene glycol) acrylate is copolymerized with its azo-dye-functionalized acrylate analogue using reversible addition-fragmentation chain transfer (RAFT) polymerization. Copolymerization is increasingly difficult with increasing amounts of the azo-dye-bearing monomer. The resulting water-soluble polymers are thermosensitive, exhibiting lower critical solution temperature (LCST) behavior, which can be modulated by the photoinduced trans-cis isomerization of the dye. While already small contents of the hydrophobic azobenzene group reduce the phase-transition temperatures of the copolymers strongly, photoisomerization of the apolar trans-state to the more-polar cis-state has only a small effect, and decreases rather than increases the cloud points. The incorporation of hydrophobic azobenzene moieties into thermoresponsive poly(methoxy diethylene glycol acrylate) (PMDEGA) decreases its cloud point in water markedly. However, against intuiti on and common wisdom, photoisomerization of the apolar trans-state to the more-polar cis-state decreases rather than increases the cloud point.

: http://publica.fraunhofer.de/dokumente/N-254636.html