Polysarcosine (PSar), a water-soluble
polypeptoid, is gifted with
biodegradability via the random ring-opening copolymerization of sarcosine-
and alanine-N-thiocarboxyanhydrides catalyzed by
acetic acid in controlled manners. Kinetic investigation reveals the
copolymerization behavior of the two monomers. The random copolymers,
named PaS, with high molecular weights between 5.3 and 43.6 kg/mol
and tunable Ala molar fractions varying from 6 to 43% can be degraded
by porcine pancreatic elastase within 50 days under mild conditions
(pH = 8.0 at 37 °C). Both the biodegradation rate and water solubility
of PaS depend on the content of Ala residues. PaS with Ala fractions
below 43% are soluble in water, while the one with 43% Ala self-assembles
in water into nanoparticles. Moreover, PaS are noncytotoxic at the
concentration of 5 mg/mL. The biodegradability and biocompatibility
endow the Ala-containing PSar with the potential to replace poly(ethylene
glycol) as a protective shield in drug-delivery.
It is significant and challenging to use CO 2 to produce polymeric materials, especially with olefins. Here, a novel strategy named "scrambling polymerizations" is designed and performed for the copolymerization of a CO 2 -and-1,3-butadiene-derived valerolactone, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL), with ɛ-caprolactone (CL) to prepare polyesters. Anionic ring-opening polymerization of CL and conjugated addition oligomerization of EVL take place individually to form PCL and EVL oligomers, respectively. Then EVL oligomers insert into PCL by transesterification resulting in polyester P(CL-co-EVL) with a tunable topology and composition. The non-cytotoxic and degradable polyester network with elongation at break of > 600 % can be used as an elastomer. We propose a method to provide polyester elastomers from CO 2 and olefins for the first time, and expand the potential of transformation from sustainable feedstocks to polymeric materials.
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