The design and synthesis of closed-loop
recyclable polymers is
a promising solution to address the large negative effects of plastic
pollution problem and massive economic loss associated with single-use
plastics. We demonstrate that ring-opening polymerization (ROP) of
6-alkyl-substituted morpholine-2,5-dione (MDs) leads to closed-loop
recyclable aliphatic poly(ester-amide)s (PEAs) with tunable mechanical
properties. The controlled ROP of these MDs was achieved using benzyl
alcohol as an initiator and DBU/TU as a catalyst, affording various
PEA homo- and copolymers with different molar masses and compositions.
All these PEAs are amorphous and thermally stable with T
d,5% values in the range of 267–292 °C. Their
glass transition temperatures (T
g) are
in the range of 58–142 °C, being affected by the structure
of pendent alkyl groups, the hydrogen bonding between amide groups,
and the composition of copolymers. Tensile tests revealed that the
structure of pendent alkyl groups exerts a significant effect on the
mechanical property of PEAs, and they are brittle (n-butyl or cyclohexyl substituted) or ductile (n-hexyl
or n-octyl substituted) plastics. In addition, the
mechanical properties of PEAs could be finely adjusted by the copolymerization
of different MD monomers. Of importance, both homopolymers and copolymers
of these PEAs could be thermally depolymerized by sublimation to recover
the corresponding monomers in high purity and efficiency. Given their
good and adjustable thermal/mechanical properties, and excellent recyclability,
these PEAs show promise as new close-loop recyclable polymers.
Transcytosis-based active transport of cancer nanomedicine has shown great promise for enhancing its tumor extravasation and infiltration and antitumor activity, but how the key nanoproperties of nanomedicine, particularly particle size, influence the transcytosis remains unknown. Herein, we used a transcytosis-inducing polymer, poly[2-(N-oxide-N,Ndiethylamino)ethyl methacrylate] (OPDEA), and fabricated stable OPDEA-based micelles with different sizes (30, 70, and 140 nm in diameter) from its amphiphilic block copolymer, OPDEA-blockpolystyrene (OPDEA-PS). The study of the micelle size effects on cell transcytosis, tumor extravasation, and infiltration showed that the smallest micelles (30 nm) had the fastest transcytosis and, thus, the most efficient tumor extravasation and infiltration. So, the 7ethyl-10-hydroxyl camptothecin (SN38)-conjugated OPDEA micelles of 30 nm had much enhanced antitumor activity compared with the 140 nm micelles. These results are instructive for the design of active cancer nanomedicine.
Five eight-membered cyclic(ester-amide)s (M1-M5) were synthesized from phthalic anhydride and β-amino alcohols by sequential nucleophilic addition and intramolecular esterification. The organocatalytic ring-opening polymerization (ROP) of these monomers with 1,5,7-triazabicyclo[4.4.0]-dec-5-ene (TBD)...
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