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End-group functionalization of poly(2-oxazoline)s using methyl bromoacetate as initiator followed by direct amidation

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Abstract
Poly(2-alkyl/aryl-2-oxazoline)s (PAOx) are an alluring class of polymers for many applications due to the broad chemical diversity that is accessible for these polymers by simply changing the initiator, terminating agent and the monomer(s) used in their synthesis. Additional functionalities (that are not compatible with the cationic ring-opening polymerization) can be introduced to the polymers via orthogonal post-polymerization modifications. In this work, we expand this chemical diversity and demonstrate an easy and straightforward way to introduce a wide variety of functional end-groups to the PAOx, by making use of methyl bromoacetate (MeBrAc) as a functional initiator. A kinetic study for the polymerization of 2-ethyl-2-oxazoline (EtOx) in acetonitrile (CH3CN) at 140 degrees C revealed relatively slow initiation and slower polymerization than the commonly used initiator, methyl tosylate (MeOTs). Nonetheless, well-defined polymers could be obtained with MeBrAc as initiator, yielding polymers with near-quantitative methyl ester end-group functionality. Next, the post-polymerization modification of the methyl ester end-group with different amines was explored by introducing a range of functionalities, i.e. hydroxyl, amino, allyl and propargyl end-groups. The lower critical solution temperature (LCST) behavior of the resulting poly(2-ethyl-2-oxazoline)s was found to vary substantially in function of the end-group introduced, whereby the hydroxyl group resulted in a large reduction of the cloud point transition temperature of poly(2-ethyl-2-oxazoline), ascribed to hydrogen bonding with the polymer amide groups. In conclusion, this paper describes an easy and fast modular approach for the preparation of end-group functionalized PAOx.
Keywords
RING-OPENING POLYMERIZATION, CHEMISTRY, 2-METHYL-2-OXAZOLINE, POLYOXAZOLINES, Poly(2-oxazoline)s, End-group functionalization, Amidation, Methyl, bromoacetate, Kinetics

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MLA
Podevyn, Annelore, et al. “End-Group Functionalization of Poly(2-Oxazoline)s Using Methyl Bromoacetate as Initiator Followed by Direct Amidation.” EUROPEAN POLYMER JOURNAL, vol. 120, 2019.
APA
Podevyn, A., Arys, K., Retamero De La Rosa, V., Glassner, M., & Hoogenboom, R. (2019). End-group functionalization of poly(2-oxazoline)s using methyl bromoacetate as initiator followed by direct amidation. EUROPEAN POLYMER JOURNAL, 120.
Chicago author-date
Podevyn, Annelore, Koen Arys, Victor Retamero De La Rosa, Mathias Glassner, and Richard Hoogenboom. 2019. “End-Group Functionalization of Poly(2-Oxazoline)s Using Methyl Bromoacetate as Initiator Followed by Direct Amidation.” EUROPEAN POLYMER JOURNAL 120.
Chicago author-date (all authors)
Podevyn, Annelore, Koen Arys, Victor Retamero De La Rosa, Mathias Glassner, and Richard Hoogenboom. 2019. “End-Group Functionalization of Poly(2-Oxazoline)s Using Methyl Bromoacetate as Initiator Followed by Direct Amidation.” EUROPEAN POLYMER JOURNAL 120.
Vancouver
1.
Podevyn A, Arys K, Retamero De La Rosa V, Glassner M, Hoogenboom R. End-group functionalization of poly(2-oxazoline)s using methyl bromoacetate as initiator followed by direct amidation. EUROPEAN POLYMER JOURNAL. 2019;120.
IEEE
[1]
A. Podevyn, K. Arys, V. Retamero De La Rosa, M. Glassner, and R. Hoogenboom, “End-group functionalization of poly(2-oxazoline)s using methyl bromoacetate as initiator followed by direct amidation,” EUROPEAN POLYMER JOURNAL, vol. 120, 2019.
@article{8658214,
  abstract     = {Poly(2-alkyl/aryl-2-oxazoline)s (PAOx) are an alluring class of polymers for many applications due to the broad chemical diversity that is accessible for these polymers by simply changing the initiator, terminating agent and the monomer(s) used in their synthesis. Additional functionalities (that are not compatible with the cationic ring-opening polymerization) can be introduced to the polymers via orthogonal post-polymerization modifications. In this work, we expand this chemical diversity and demonstrate an easy and straightforward way to introduce a wide variety of functional end-groups to the PAOx, by making use of methyl bromoacetate (MeBrAc) as a functional initiator. A kinetic study for the polymerization of 2-ethyl-2-oxazoline (EtOx) in acetonitrile (CH3CN) at 140 degrees C revealed relatively slow initiation and slower polymerization than the commonly used initiator, methyl tosylate (MeOTs). Nonetheless, well-defined polymers could be obtained with MeBrAc as initiator, yielding polymers with near-quantitative methyl ester end-group functionality. Next, the post-polymerization modification of the methyl ester end-group with different amines was explored by introducing a range of functionalities, i.e. hydroxyl, amino, allyl and propargyl end-groups. The lower critical solution temperature (LCST) behavior of the resulting poly(2-ethyl-2-oxazoline)s was found to vary substantially in function of the end-group introduced, whereby the hydroxyl group resulted in a large reduction of the cloud point transition temperature of poly(2-ethyl-2-oxazoline), ascribed to hydrogen bonding with the polymer amide groups. In conclusion, this paper describes an easy and fast modular approach for the preparation of end-group functionalized PAOx.},
  articleno    = {109273},
  author       = {Podevyn, Annelore and Arys, Koen and Retamero De La Rosa, Victor and Glassner, Mathias and Hoogenboom, Richard},
  issn         = {0014-3057},
  journal      = {EUROPEAN POLYMER JOURNAL},
  keywords     = {RING-OPENING POLYMERIZATION,CHEMISTRY,2-METHYL-2-OXAZOLINE,POLYOXAZOLINES,Poly(2-oxazoline)s,End-group functionalization,Amidation,Methyl,bromoacetate,Kinetics},
  language     = {eng},
  pages        = {9},
  title        = {End-group functionalization of poly(2-oxazoline)s using methyl bromoacetate as initiator followed by direct amidation},
  url          = {http://dx.doi.org/10.1016/j.eurpolymj.2019.109273},
  volume       = {120},
  year         = {2019},
}

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