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A Remarkably Large Phase‐Transition Effect in a Random Copolymer of Oligo(ethylene glycol) Methyl Ether Methacrylate (OEGMA) 500 Induced by the Photochemistry of the 2‐(Hydroxyimino)aldehyde Group
Author(s) -
D’Acunzo Francesca,
Santis Serena,
Masci Giancarlo,
Nardi Martina,
Renzi Polyssena,
Sobolev Anatoly Petrovich
Publication year - 2019
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201900200
Subject(s) - copolymer , polymer chemistry , chemistry , ethylene glycol , dynamic light scattering , methacrylate , photochemistry , polymer , aldehyde , materials science , organic chemistry , nanoparticle , catalysis , nanotechnology
The effect of UV irradiation on the cloud points (CP) of aqueous solutions of a random 1:1 copolymer of oligo(ethylene glycol) methyl ether methacrylate (OEGMA 500 ) and a 2‐(hydroxyimino)aldehyde (HIA) functionalized methacrylate is presented. CPs are determined by visible spectroscopy and dynamic light scattering (DLS). 1 H and 13 C NMR experiments are carried out in D 2 O and DMSO‐ d 6 on the polymer and on an HIA‐functionalized model of the photoresponsive repeat unit. UV‐irradiated solutions exhibit an unprecedented increase of the phase‐separation temperature for an OEGMA photoresponsive copolymer (10–22 °C, depending on concentration and irradiation conditions). Phase separation is reversible with little hysteresis. With both pristine and irradiated polymer solutions, aggregate dimensions are <10 nm (DLS) at room temperature. Aggregates of >100 nm form at the CP and gradually grow as temperature increases, whereas the light‐induced processes of the repeat unit model in DMSO‐ d 6 are well identified (e.g., oxime E / Z isomerization and Norrish‐Yang cyclization of the aldehyde moiety), it is not straightforward to extrapolate such behavior to the polymeric solution in water. The remarkably large phototriggered thermal effect in the present work motivates further investigations on the solvent‐dependent photochemistry of HIA as a promising functional group for the synthesis of multi‐stimuli responsive materials.