Thermal degradation of poly(2,2-dialkyl-3-hydroxypropionic acid). 1. Living depolymerization

Abstract

Poly(2,2-dialkyl-3-hydroxypropionic acid)s (usually prepared by living anionic polymerization of the corresponding 2,2-dialkyl-3-propiolactone) thermally degrade by two independent mechanisms depending on the state of the carboxylate group at the termination end of the polymer chain. When the carboxylate is deprotonated (X = Li+, Na+, K+, Cs+, R4N+, or R4P+) the polymer degrades predominantly by reverse polymerization. This paper concentrates on the reverse polymerization mechanism for polymer degradation. Reverse polymerization is dependent on the nucleophilicity of the terminal carboxylate group. This is demonstrated by the effect of the terminal counterion on the rate of degradation. Furthermore, reverse polymerization is shown to be a "living depolymerization". By living depolymerization we mean that all polymer chains degrade simultaneously from the living ends of the chains. Kinetics, change in MW distributions, and degradation of block copolymers are consistent with a living depolymerization.

The use of the trellis‐6 thrombectomy device in the management of acute limb ischemia due to native vessel occlusion: Challenges, tips, and limitations

“…The expanded region of 1 H NMR spectra in range of methyl group protons of acetate and crotonate terminal groups illustrates the activity of the carboxylates, bearing respective cations, in α‐deprotonation degradation. An increase of carboxylate activity was noticed for alkali metal salts (lithium, potassium and cesium, respectively) with increasing cation radius, which correlates to our previous data11 as well as “living” depolymerization of polypivalolactone via an anionic mechanism 30–32. Regarding salts of bivalent metals (calcium, magnesium and zinc), it was found that their activity was much lower in comparison to salts of monovalent metals.…”

Polymer Distribution Change During Irreversible Depolymerization by Chain‐End Scission

“…Note that in the chain-end depolymerization experiments, the severed monomer is not included in the polymer population, [1,2,6] and N Ã (r) does not include monomers severed from chain ends. On the other hand, however, the total distribution that includes monomers will also be shown in some of the illustrative calculations later.…”

“…The living depolymerization has been investigated experimentally, [1,2] and is expected to be a fruitful research area both from the academic and industrial point of view. Although the ideal living polymerization leads to the Poisson distribution that is extremely narrow for large polymers, the broadening of the MWD may occur such as by slow exchange reactions [3,4] even when the activity at the chain end is not lost.…”

Synthesis and cationic ring-opening polymerization of mono- and bifunctional spiro orthoesters containing ester groups and depolymerization of the obtained polymers: An approach to chemical recycling for polyesters as a model system

“…Among a few methods of recycling of polymeric materials such as thermal and material recyclings, chemical recycling is the most important and essential, because it can recover original monomers by depolymerization. Several works on depolymerization have been reported concerning poly(methyl methacrylate), 2 poly(saccaride), 3 poly(chloroacetaldehyde), 4 poly(2,2-dialkyl-3-hydroxypropionic acid), 5 and poly(-caprolactone). 6 Spiro orthoesters (SOEs, 1) undergo cationic polymerization at high temperature (Ͼ100°C) via a double ring-opening process to give poly(ether esters) (2) as illustrated in Scheme 1.…”