Symmetrical polymer systems prepared using a degradable bifunctional atom transfer radical polymerization initiator: Synthesis, characterization, and cleavage
SourceJournal of Polymer Science, Part A: Polymer Chemistry
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Linear (co)polymers and dimethacrylate-end-linked polymer networks of methyl methacrylate with 2-(dimethylamino)ethyl methacrylate, cleavable in the middle of the polymer chain, either under thermolysis or alkaline hydrolysis conditions, were prepared via atom transfer radical polymerization (ATRP) using a specially designed bifunctional degradable initiator. This initiator was 2,6-pyridinediethanol di(2-bromo-2-methyl propanoate) (PyDEDBrMeP), bearing two 2-(pyridin-2-yl)ethyl ester moieties, known for their thermal and hydrolytic (alkaline conditions) lability. As a control, a more stable bifunctional ATRP initiator, 2,6-pyridinedimethanol di(2-bromo-2-methyl propanoate) (PyDMDBrMeP), was also synthesized together with the corresponding linear polymers and polymer networks prepared from it. Thermal or hydrolytic treatment of the polymers prepared using PyDEDBrMeP led to a reduction in the molecular weights of the linear polymers by a factor of two, and to the conversion of the polymer networks to soluble branched (star) structures, consistent with the expected cleavage of the initiator residue located in the middle of the polymer chain. Thermal treatment of the polymers prepared using PyDMDBrMeP did not affect their molecular weight due to the thermal stability of the (pyridin-2-yl)methyl ester group, while treatment under alkaline hydrolysis conditions resulted in complete cleavage, similar to the PyDEDBrMeP-prepared polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2342–2355. © 2017 Wiley Periodicals, Inc.