Poly(amine-co-ester)s by Binary Organocatalytic Ring-Opening Polymerization of N-Boc-1,4-oxazepan-7-one: Synthesis, Characterization, and Self-Assembly

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Abstract

Binary organocatalytic ring-opening polymerization (ROP) of N-Boc-1,4-oxazepan-7-one (OxPBoc) is proposed as a versatile method to generate metal-free poly(amine-co-ester)s and the corresponding biodegradable polycationic homo/block (co)polymers. Optimization experiments with different organocatalysts, including 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), DBU/1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylthiourea (TU1), and phosphazene/thiourea, revealed that t-Bu-P4/TU1 leads to a fast and controlled/living ROP with benzyl alcohol (BnOH) as an initiator and thus allows the formation of well-defined poly(amine-co-ester)s with high molecular mass (Mn,SEC up to 38.8 kg mol−1) and narrow dispersity. Well-defined poly(N-Boc-1,4-oxazepan-7-one)-based diblock copolymers were also synthesized successfully via the controlled/living ROP, regardless of whether hydrophilic poly(ethylene glycol) (PEG) or hydrophobic polycaprolactone (PCL) was used as a macroinitiator. After treatment with trifluoroacetic acid, the corresponding water-soluble polycationic homopolymer, as well as the hydrophilic (PEG-based copolymer) and amphiphilic (PCL-based copolymer) polycationic diblock copolymers, was obtained. Dynamic light scattering in water and transmission electron microscopy analyses revealed that both polycationic copolymers self-assembled spontaneously to nanostructures; the hydrophilic block copolymer formed spherical nanoparticles, while the amphiphilic one formed rod-shaped nanoparticles.
Original languageEnglish (US)
Pages (from-to)223-232
Number of pages10
JournalMacromolecules
Volume53
Issue number1
DOIs
StatePublished - Dec 27 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors thank Dr. Saibal Bhaumik for his help with the TEM measurements. The research reported in this publication was supported by King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia.

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