Ester Functional Epoxide Monomers for Random and Gradient Poly(ethylene glycol) Polyelectrolytes with Multiple Carboxylic Acid Moieties

Abstract

The tailormade ester functional epoxides, methyl 4,5epoxypentenoate (MEP) and t butyl 4,5-epoxypentenoate ( t BEP), were synthesized in good overall yields (60−65%) in short reaction sequences. Both MEP and t BEP were investigated as comonomers in the statistical copolymerization with ethylene oxide (EO) via the monomer-activated anionic ring-opening polymerization (MAROP), using triisobutyl-aluminum as a catalyst. Homopolymers and a series of copolymers of EO with varied molar contents of MEP and t BEP (0.6−31.3 mol %) were prepared, possessing molecular weights up to 11,800 g mol −1 . Surprisingly, in situ 1 H NMR kinetics studies revealed an ideally random copolymer microstructure for EO/MEP copolymers (r EO = 0.99, r MEP = 1.0) via MAROP for the first time. t BEP was found to be a less reactive comonomer, yielding gradient polyether structures (r EO = 2.9, r t BEP = 0.35). After polymerization, the ester-protecting groups were fully cleaved under basic or acidic conditions, respectively, resulting in either random or gradient distribution of carboxyl moieties. MTT assays demonstrated good biocompatibility of the novel carboxylic acid functional poly(ethylene glycol) (PEG) copolymers. The thermal properties of the copolymers were investigated via differential scanning calorimetry, showing the highly flexible nature of the PEG-based polyelectrolytes after deprotection. The liberated carboxylic acid groups were addressed with Ca 2+ cations, resulting in cross-linked polymer networks.

Designing Cooperative Hydrogen Bonding in Polyethers with Carboxylic Acid Pendants

“…According to the Fox equation, a T g of 14 °C was estimated on the basis of the equimolar mixture of PEO ( T g of −76.6 °C) and PAA ( T g of 101 °C). Similarly, Frey and co-workers recently reported the T g of ester-functionalized polyethers, including methyl 4,5-epoxypentenoate and t -butyl 4,5-epoxypentenoate, to be 41 and −25 °C, respectively …”

“…Similarly, Frey and co-workers recently reported the T g of ester-functionalized polyethers, including methyl 4,5-epoxypentenoate and t-butyl 4,5-epoxypentenoate, to be 41 and −25 °C, respectively. 33 Self-Association in the Aqueous PGA Solution. An aqueous solution of PGA retained a highly negative charge with a ζ-potential value of −44.3 mV at pH 7 because of the deprotonation of all of the carboxylic acids in the pendant groups of the PGA under neutral conditions (Figure S15).…”

Divergent Synthesis of Biocompatible Nearly Monodisperse Multi‐Functional Poly(ethylene glycol) Periodic Copolymers

“…[ 51,52 ] However toxicity increases when different functionalities such as alkyl chains or ionic groups are attached in the PEG copolymers. [ 31 ] Therefore, to understand the cytotoxicity of the current copolymers, MTT assay (cell viability tests) was performed for PEG‐1A (linear) and PEG‐4 (corresponding Star) using L929 cells. In this study, polymer solutions of different concentrations (100, 50, 25, 12.5, and 6.25 µg mL −1 ) were used and the results were compared with untreated cells.…”

“…[28,29] Further secondary amine and ester groups in the PEG chains can be introduced via anionic ROP of aminal and ester-protected epoxides respectively and followed by a post-polymer deprotection. [30,31] For ATRP and RAFT, PEG based ATRP initiators and PEG based CTAs are used respectively to prepare targeted copolymers. [32][33][34][35] In almost all cases, copolymers of PEG are reported with a dispersity of 1.1-1.5, which is a typical of living radical polymerizations.…”

Facile Synthesis of Poly(ethylene oxide)-Based Self-Healable Dynamic Triblock Copolymer Hydrogels

“…PEO-based hydrogels are particularly desirable for biomedical applications owing to their non-toxicity, low immunogenicity, and thus excellent biocompatibility. In synthetic approaches toward PEO-based polyethers, A blocks can be readily prepared by employing diverse functional monomers − or post-polymerization modifications. − In this context, the abundance of available epoxide monomers can provide a wide range of functionality that can be further modified to achieve the desired physical and chemical properties for targeted applications. ,,, Alternatively, post-polymerization modification can be an ideal strategy for evaluating various functional groups across a single polymer with an identical degree of polymerization and molecular weight distribution. ,− Moreover, post-polymerization modification provides the synthesis of polymers with pendant groups through bypassing the limitations of direct polymerization. In view of these benefits, the post-polymerization modification is receiving significant interest to produce well-defined polymers with tailorable properties.…”