Controlled Polymerization of Ethyl Glyoxylate Using Alkyllithium and Alkoxide Initiators

Abstract

The synthesis of poly(ethyl glyoxylate)s (PEtGs) by anionic polymerization was explored. PEtGs are a subclass of stimuli-responsive self-immolative polymers with promising properties for applications as coatings, sensors, and drug delivery vehicles. In this report, a new purification procedure for the preparation of highly pure ethyl glyoxylate (EtG), suitable for anionic 2 polymerization reactions, and the first successful examples of controlled polymerization of EtG are described. n-BuLi, PhLi, and t-BuLi were employed as initiators under different experimental conditions and their behavior was examined using NMR spectroscopy, size exclusion chromatography, and thermal analysis to develop an optimized procedure. As functional alkoxide initiators, propargyl alkoxide was employed in optimization studies and poly(ethylene glycol) (PEG) dialkoxide was utilized for the direct synthesis of PEtG-PEG-PEtG copolymers. The new polymerization method revealed many features of controlled polymerization reactions, yielding PEtGs with predictable molar masses and relatively low dispersity values. Supporting Information. Calculations for end-group analysis; pictures of EtG distillation setup; 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectra; and SEC data for purified polymers (pdf).

Dynamic pH responsivity of triazole-based self-immolative linkers

“… 8 These unique qualities have inspired numerous studies into the development of self-immolative linkers for the controlled release of small molecules 9 and, more recently, for constructing self-immolative polymers that undergo complete head-to-tail depolymerisation upon trigger cleavage. 10 …”

The Plastics Sunset and the Bio-Plastics Sunrise

“…Polyglyoxylates represent a recently introduced class of self-immolating polymers, capable to depolymerize upon the cleavage of a stimuli-responsive end-cap from the polymer terminus, with promising properties for applications as coatings, sensors, tissue engineering, and drug delivery. These new materials are particularly attractive as the component monomers can be derived not only from petroleum-based sources, but also from renewable resources [15,16].…”

“…These new materials are particularly attractive as the component monomers can be derived not only from petroleum-based sources, but also from renewable resources [15,16].…”

Amine-Catalyzed Chain Polymerization of Ethyl Glyoxylate from Alcohol and Thiol Initiators

“…However, Gillies and coworkers have recently demonstrated controlled polymerization of EtG using alkyllithiums and alkoxides as anionic initiators. 20 While the amine-catalyzed polymerization of EtG has been described as an anionic polymerization, a more likely hypothesis is that initiation occurs by the activation of trace hydroxy-functional initiating species, water or glyoxylate hydrate (ethyl 2,2-dihydroxyacetate), by hydrogen bonding with triethylamine, followed by addition of the activated oxygen to the monomer carbonyl group. Activation of alcohols for addition to carbonyl double bonds by hydrogen bonding with amines, without formation of free alkoxide, has previously been used in a range of organocatalyzed ring-opening polymerizations.…”

“…Polymers that can be easily depolymerized or otherwise broken down or upcycled into useful molecules have potential applications in the formation of porous or patterned materials, − drug delivery agents, ,− biodegradable plastics, , and stimuli-responsive materials. , While a number of different polyesters and less easily degradable polyamides have been widely commercialized, a number of polymers with more labile backbone linkages, including acetals, ,,− orthoesters, pyrophosphates, and N , O -acetals, have been reported.…”