Fast hydrolyzable polyesters are promising candidates as biodegradable plastics degrading to carbon dioxide, water, and biomass in the presence of oxygen in a suitable environment. The rate-determining step of biodegradation is the fragmentation of polyesters to lower mass fragments by hydrolysis, which in the second step undergo bioassimilation. Polyesters with a balance of good mechanical properties and fast hydrolyzability are urgently needed as a sustainable solution to the problem of plastic pollution and persistent microplastics when used in packaging and agricultural applications. Aromatic polyesters, such as poly(butylene terephthalate) (PBT), are mechanically strong but require harsh hydrolysis conditions, making them nonbiodegradable. The trend is mostly the opposite for aliphatic polyesters. We present in this work an aromatic polyester, a constitutional isomer of PBT [poly(1,4-benzenedimethylene succinate) (PBDMS)], and its copolymers (PB x BDM y S) in which aliphatic ester units balance the mechanical, thermal, and hydrolysis properties. PBDMS was prepared from 1,4-benzenedimethanol (BDM) and succinic acid (S) via two-step polycondensation. Its copolyesters with 1,4-butanediol (B) as a comonomer are also presented. High-molecular-weight PBDMS showed a glass-transition temperature of 6 °C and a melting temperature around 100 °C, very high thermal stability, and melt processability. The structure−property relationship of such polyesters was intensively studied, focusing on the impact of molecular composition. The stress−strain behavior of these (co-)polyesters largely depended on the content of BDM and covered a wide range from ductile to elastic to brittle materials. The films of these polyesters showed much faster hydrolysis under basic conditions, making them promising for future detailed degradation studies under different environmental conditions.
Poly(lactic-co-glycolic acid) (PLGA)
is an aliphatic
polyester that degrades under environmental conditions making it interesting
for replacing microplastic creating polyolefins in packaging and agricultural
applications. However, linear PLGA exhibits unfavorable thermomechanical
properties for use. Therefore, synthetic aspects, characterization,
and reprocessing ability of PLGA in the form of dynamic covalent networks
are studied in the present work. The dynamic covalent networks were
synthesized from short-chain four-armed star-shaped PLGA with hydroxy
end groups and 4,4′-methylene diphenyl diisocyanate as a cross-linker.
Tin octanoate was used as a catalyst to promote the associative exchange
reactions at elevated temperatures. The synthesized networks with
dynamic bonding and debonding are insoluble in common organic solvents,
have enhanced the thermomechanical properties, and have maintained
the possibility of thermal reprocessing and recycling like thermoplastics.
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