Trickily designed copolyesters degraded in both land and sea - confirmed by the successful capture of degradation end product CO2

In vivo and in vitro degradation and biological toxicity studies of polyesters with varying degradation rates

The fragmentation of biodegradable plastics into "degradable particles" is an essential step during their degradation process. Investigating their in vivo degradation behaviors and toxicity differing from microplastics holds significant implications. In this study, we selected biodegradable polyesters with distinct degradation rates-polyglycolic acid (PGA) and its copolymer poly(butylene succinate-co-glycolate) (PBSG)-alongside non-biodegradable polyethylene terephthalate (PET) as a control. Using combined in vitro simulations and animal experiments, we assessed their degradation in simulated body fluid (SBF), simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and toxicity effects on rat body weight and multiple organs (heart, liver, spleen, stomach, lung, kidney, colon, brain). Results showed PET exhibited negligible degradation and the highest biotoxicity. After 18 weeks, PGA demonstrated degradation rates of 53.28 % (SBF), 96.35 % (SGF), and 76.14 % (SIF), while PBSG degraded at 7.98 %, 10.28 %, and 10.42 %, respectively. Biodegradable plastics caused no significant toxicity at low doses. However, high doses induced weight loss, tissue necrosis and inflammation in rats. Notably, PGA-with the fastest degradation-showed the weakest physiological toxicity. These findings highlight the important relationship between the degradation rate of biodegradable plastics and their biotoxicity, and can guide the development of new materials to balance environmental benefits and minimized health risks.

Biodegradability of bioplastics in different aquatic environments: A systematic review

Bioplastics were first introduced as environmentally friendly materials, with properties similar to those of conventional plastics. A bioplastic is defined as biodegradable if it can be decomposed into carbon dioxide under aerobic degradation, or methane and CO2 under anaerobic conditions, inorganic compounds, and new cellular biomass, by the action of naturally occurring microorganisms. This definition however does not provide any information on the environmental conditions, timescale and extent at which decomposition processes should occur. With regard to the aquatic environment, recognized standards have been established to assess the ability of plastics to undergo biodegradation; however, these standards fail to provide clear targets to be met to allow labelling of a bioplastic as biodegradable. Moreover, these standards grant the user an extensive leeway in the choice of process parameters. For these reasons, the comparison of results deriving from different studies is challenging. The authors analysed and discussed the degree of biodegradability of a series of biodegradable bioplastics in aquatic environments (both fresh and salt water) using the results obtained in the laboratory and from on-site testing in the context of different research studies. Biochemical Oxygen Demand (BOD), CO2 evolution, surface erosion and weight loss were the main parameters used by researchers to describe the percentage of biodegradation. The results showed a large variability both in weight loss and BOD, even when evaluating the same type of bioplastics. This confirms the need for a reference range of values to be established with regard to parameters applied in defining the biodegradability of bioplastics.

All-natural environmentally degradable poly (butylene terephthalate-co-caprolactone): A theoretical and experimental study of its degradation properties and mechanisms

The design and production of materials with excellent mechanical properties and biodegradability face significant challenges. Poly (butylene terephthalate-co-caprolactone) copolyesters (PBTCL) is obtained by modifying the engineering plastic polybutylene terephthalate (PBT) with a simple one-pot process using readily biodegradable ε-caprolactone (ε-CL). The material has mechanical properties comparable to those of commercial biodegradable copolyester PBAT. Besides, this copolyester exhibited remarkable degradability in natural environments such as soil and ocean, for example, PBTCL1.91 lost >40 % of its weight after 6 months of immersion in the Bohai Sea. The effect and diversity of specific microorganisms acting on degradation in the ocean were analyzed by 16 s rDNA gene sequencing. Theoretical calculations such as Fukui function and DFT, and experimental studies on water-soluble intermediates and residual matrixes produced after degradation, confirmed that the insertion CL units not only act as active sites themselves susceptible to hydrolysis reactions, but also promote the reactivity of ester bonds between aromatic segments. This work provides insight for the development of novel materials with high performance and environmental degradability.

Fluorescence tracing the degradation process of biodegradable PBAT: Visualization and high sensitivity

Biodegradable plastics have emerged as a potential solution to the mounting plastic pollution crisis. However, current methods for evaluating the degradation of these plastics are limited in detecting structural changes rapidly and accurately, particularly for PBAT, which contains worrying benzene rings. Inspired by the fact that the aggregation of conjugated groups can endow polymers with intrinsic fluorescence, this work found that PBAT emits a bright blue-green fluoresces under UV irradiation. More importantly, we pioneered a degradation evaluation approach to track the degradation process of PBAT via fluorescence. A blue shift of fluorescence wavelength as the thickness and molecular weight of PBAT film decreased during degradation in an alkali solution was observed. Additionally, the fluorescence intensity of the degradation solution increased gradually as the degradation progressed, and was found to be exponentially correlated with the concentration of benzene ring-containing degradation products following filtration with the correlation coefficient is up to 0.999. This study proposes a promising new strategy for monitoring the degradation process with visualization and high sensitivity.

Study on composting and seawater degradation properties of diethylene glycol-modified poly(butylene succinate) copolyesters

The marine pollution caused by traditional plastics is becoming increasingly serious, and the fundamental way to solve this problem is to look for plastic substitutes that can degrade in the marine environment. Herein, a series of high-molecular-weight poly(butylene succinate-co-diethylene glycol succinate) (PBDS) was obtained by the introduction of low-cost diethylene glycol (DEG) into the main chain of poly(butylene succinate) (PBS), which aimed to obtain the materials that can be degraded both in compost and seawater. The research showed that the increase in the DEG content reduced the crystallinity of the copolyester, which led to the decrease in mechanical strength and thermal properties of the copolyester to a certain extent. Meanwhile, the increase in hydrophilicity and the decrease in crystallinity improved the degradation rate of the material. Compared with PBS, PBDS exhibited not only a faster composting degradation rate but also a faster degradation rate in seawater.