Polylactide/poly(butylene adipate-co-terephthalate)/rare earth complexes as biodegradable light conversion agricultural films

Dicyanopyridine derivatives: One-pot preparation, ACQ-to-AIE transformation, light-conversion quality and photostability

Low cost and strong fluorescence emission are two important guarantees for luminogens used as light conversion agents. By one-pot multicomponent approach and inexpensive starting materials, three dicyanopyridine (DP) derivatives named as DCP (2-amino-6-methoxy-4-phenylpyridine-3,5-dicarbonitrile), DCO (2-amino-6-methoxy-4-(4-methoxyphenyl) pyridine-3,5-dicarbonitrile) and DCC (2-amino-4-(4-cyanophenyl)-6-methoxypyridine-3,5-dicarbonitrile) were designed and synthesized. Meanwhile, the ACQ-to-AIE transformation was successfully realized by altering substituent groups rather than traditional rotor-stator theory. Based on crystal analysis and theoretical calculations, the ACQ-to-AIE transformation is attributed to the tunable stacking modes and intermolecular weak interactions. Owing to matched fluorescence emission, low lost, high yield, and AIE activity, DCC is used as light conversion agents and doped in EVA matrix. The light conversion quality confirms that DCC can not only convert ultraviolet light, but also significantly improve the transmittance of 25 %/40 % EVA, whose photosynthetic photon flux density at 400-500 nm and 600-700 nm increased to 30.67 %/30.21 % and 25.37 %/37.82 % of the blank film, respectively. After 20 h of UV irradiation (365 nm, 40 W), the fluorescence intensities of DCC films can maintain 92 % of the initial values, indicating good photostability in the doping films. This work not only provides an excellent and low-cost light conversion agent, but also has important significance for ACQ-to-AIE transformation of luminogens.

UV-barrier poly(lactic acid) film with light-stabilized Eu complexes as filler

The poor UV shielding property of PLA limit it further applications on food packaging. The rare-earth complex Eu(DBM)3phen converts absorbed ultraviolet (UV) light to red light, which inspires the development of new UV shielding materials. However, this complex has low photostability and decomposes easily under UV irradiation. Thus, we prepared a long-lasting rare-earth complex transluminant Eu(DBM)2(BP-2)phen by introducing BP-2 into Eu(DBM)3phen, and blended it with PLA to obtain PLA/Eu(DBM)2(BP-2)phen composite films. The test results showed that the complex could reduce the UV transmittance of PLA films by emitting luminescence and heat. The UV transmittance of the composite film with 0.5 % mass fraction decreased from 87.4 % to 7.7 %, compared to pure PLA films, and remained at 11.6 % after 12 days of UV aging. The film had long-lasting UV shielding performance, good transparency and mechanical properties. Finally, In the storage experiments of flaxseed oil, the P/E25 film effectively retarded the oxidation process of the oil.

Modified Composite Biodegradable Mulch for Crop Growth and Sustainable Agriculture

Using biodegradable films as a substitute for conventional polyolefin films has emerged as a crucial technology to combat agricultural white pollution. To address the shortcomings in the tensile strength, water vapor barrier properties, and degradation period of PBAT-based biodegradable films, this investigation aimed to create a composite film that could improve the diverse properties of PBAT films. To achieve this, a PBAT/PLA-PPC-PTLA ternary blend system was introduced in the study. The system effectively fused PBAT with PLA and PPC, as evidenced by electron microscopy tests showing no apparent defects on the surface and cross-section of the blended film. The developed ternary blend system resulted in a 58.62% improvement in tensile strength, a 70.33% enhancement in water vapor barrier properties, and a 30-day extension of the functional period compared to pure PBAT biodegradable films. Field experiments on corn crops demonstrated that the modified biodegradable film is more suitable for agricultural production, as it improved thermal insulation and moisture retention, leading to a 5.45% increase in corn yield, approaching the yield of traditional polyolefin films.

Effects of Europium Complex on Thermal and Photoluminescence Properties of Polyurethane-Europium Materials

A europium complex with double bonds was synthesized with crotonic acid as the ligand and a europium ion as the center ion. Then, the obtained europium complex was added to synthesized poly(urethane-acrylate) macromonomers to prepare the bonded polyurethane-europium materials by the polymerization of the double bonds in the complex and the poly(urethane-acrylate) macromonomers. The prepared polyurethane-europium materials had high transparency, good thermal stability and good fluorescence. The storage moduli of polyurethane-europium materials are obviously higher than those of pure polyurethane. Polyurethane-europium materials exhibit bright red light with good monochromaticity. The light transmittance of the material decreases slightly with increases in the europium complex content, but the luminescence intensity gradually increases. In particular, polyurethane-europium materials possess a long luminescence lifetime, which has potential applications for optical display instruments.

Plant growth acceleration using a transparent Eu3+-painted UV-to-red conversion film

The stimulation of photosynthesis is a strategy for achieving sustainable plant production. Red light is useful for plant growth because it is absorbed by chlorophyll pigments, which initiate natural photosynthetic processes. Ultraviolet (UV)-to-red wavelength-converting materials are promising candidates for eco-friendly plant cultures that do not require electric power. In this study, transparent films equipped with a UV-to-red wavelength-converting luminophore, the Eu3+ complex, were prepared on commercially available plastic films for plant growth experiments. The present Eu3+-based films absorb UV light and exhibit strong red luminescence under sunlight. Eu3+-painted films provide significant growth acceleration with size increment and biomass production for vegetal crops and trees in a northern region. The plants cultured with Eu3+-painted films had a 1.2-fold height and 1.4-fold total body biomass than those cultures without the Eu3+ luminophores. The present film can promote the plant production in fields of agriculture and forestry.

Effects of Ligands in Rare Earth Complex on Properties, Functions, and Intelligent Behaviors of Polyurea-Urethane Composites

There is a need to create next-generation polymer composites having high property, unique function, and intelligent behaviors, such as shape memory effect (SME) and self-healing (SH) capability. Rare earth complexes can provide luminescence for polymers, and their dispersion is highly affected by ligand structures. Here, we created three different REOCs with different ligands before studying the effects of ligands on REOC dispersion in polyurea-urethane (PUU) with disulfide bonds in main chains. In addition, the effects of different REOCs on mechanical properties, luminescent functions, and intelligent behaviors of PUU composites were studied. The results showed that REOC I (Sm(TTA)3phen: TTA, thenoyltrifluoroacetone; phen, 1,10-phenanthroline) has incompatible ligands with the PUU matrix. REOC I and REOC III (Sm(BUBA)3phen: BUBA, 4-benzylurea-benzoic acid) with amine and urea groups facilitate their dispersion. It was REOC III that helped the maintenance of mechanical properties of PUU composites due to the good dispersion and the needle-like morphologies. Due to more organic ligands of REOC III, the fluorescence intensity of composite materials is reduced. The shape recovery ratio of the composite was not as good as that of pure PUU when a large amount of fillers was added. Besides, REOC I reduced the self-healing efficiency of PUU composites due to poor dispersion, and the other two REOCs increased the self-healing efficiency. The results showed that ligands in REOCs are important for their dispersion in the PUU matrix. The poor dispersion of REOC I is unbeneficial for mechanical properties and intelligent behavior. The high miscibility of REOC II (Sm(PABA)3phen: PABA, 4-aminobenzoic acid) decreases mechanical properties as well but ensures the good shape recovery ratio and self-healing efficiency. The mediate miscibility and needle-like morphology of REOC III are good for mechanical properties. The shape recovery ratio, however, was decreased.

Research Progress of Light Wavelength Conversion Materials and Their Applications in Functional Agricultural Films

As new fluorescent materials, light wavelength conversion materials (light conversion agents) have attracted increasing attention from scientific researchers and agricultural materials companies due to their potential advantages in efficiently utilizing solar energy and increasing crop yield. According to the material properties, the light conversion agents can be divided into fluorescent dyes, organic rare-earth complexes, and inorganic rare-earth complexes. The current researches indicates that the fluorescent dyes have relatively high production costs, poor light stability, difficult degradation processes, and easily cause pollution to the ecological environment. The organic rare-earth complexes have short luminescence times, high production costs, and suffer from rapid decreases in luminescence intensity. Compared with fluorescent dyes and organic rare-earth complexes, although rare-earth inorganic complexes have high luminous efficiency, stable chemical properties, and better spectral matching performance, the existing inorganic light conversion agents have relatively poor dispersibility in agricultural films. According to the research on light conversion agents at home and abroad in recent years, this paper first introduces the three common light conversion agents, namely fluorescent dyes, organic rare-earth complexes, and inorganic rare-earth complexes, as well as their uses in agricultural films and their mechanisms of light conversion. At the same time, the preparation methods, advantages, disadvantages, and existing problems of various light conversion agents are classified and explained. Finally, we predict the development trends for light conversion agents in the future by considering six aspects, namely efficiency, cost, compatibility with greenhouse films, light matching, and light transmittance, in order to provide a reference for the preparation of stable and efficient light conversion agent materials.

Green Production of Biodegradable Mulch Films for Effective Weed Control

Biodegradable mulch films are supposed to be a prospective substitute for poly(ethylene)-based mulch films in the field of sustainable agriculture. Among them, weeding mulch films play significant roles. However, the large-scale production of weeding mulch films through the traditional high-temperature film blowing process would often cause serious pollution due to the diffusion of herbicides in the surroundings. Herein, a green and facile coating approach is developed to produce biodegradable weeding mulch films. In our strategy, a herbicide was added into a poly(vinyl alcohol) aqueous solution with dopamine in it. After the subsequent low-temperature coating procedure on a biodegradable poly(butylene adipate-co-terephthalate)/poly(lactic acid) film, effective weeding mulch films were obtained. The morphology, structure, and mechanical property test results revealed the robustness and stability of the coating, and the pot experiments clearly demonstrated the effective weed suppression ability of the obtained weeding films. Evidently, this strategy to produce biodegradable weeding mulch films is green and facile, exhibiting great prospects in the large-scale production of weeding mulch films and other functional biodegradable mulch films.

One-Step Synthesis of Eu3+-Modified Cellulose Acetate Film and Light Conversion Mechanism

A CA-Eu(III) complex was synthesized by the coordination reaction of cellulose acetate (CA) and Eu³⁺ to obtain a CA-Eu light conversion film. This product was then doped with Tb(III) to sensitize the luminescence of Eu³⁺, which could functionalize the CA film. FTIR and XPS showed that the oxygen atoms in C=O, C-O (O=C-O), and O-H were involved in the complexation with Eu³⁺ and formed a Eu-O bond. SEM revealed that Eu³⁺ filled in the pores of the CA film. By changing the experimental conditions, the best fluorescence performance was obtained at the CA: Eu³⁺ ratio of 3:1 with a reaction time of 65 min. The energy transfer between Tb³⁺-Eu³⁺ could be realized by doping Tb³⁺ to enhance the luminescence of Eu³⁺. The best fluorescence performance of the CA-Eu-Tb light conversion film was at a Eu³⁺:Tb³⁺ ratio of 3:1. Compared with the CA film, the light conversion film has high transparency, high tensile strength, and good flexibility. It can convert the ultraviolet light harmful to plants into red light that is beneficial to photosynthesis. This offers high efficiency and environmental protection in the field of agricultural films.

Chemical Recycling of End-of-Life Poly(lactide) via Zinc-Catalyzed Depolymerization and Polymerization

The chemical recycling of poly(lactide) was investigated based on depolymerization and polymerization processes. Using methanol as depolymerization reagent and zinc salts as catalyst, poly(lactide) was depolymerized to methyl lactate applying microwave heating. An excellent performance was observed for zinc(II) acetate with turnover frequencies of up to 45000 h-1. In a second step the monomer methyl lactate was converted to (pre)poly(lactide) in the presence of catalytic amounts of zinc salts. Here zinc(II) triflate revealed excellent performance for the polymerization process (yield: 91 %, Mn ∼8970 g/mol). Moreover, the (pre)poly(lactide) was depolymerized to lactide, the industrial relevant molecule for accessing high molecular weight poly(lactide), using zinc(II) acetate as catalyst.

Effective Control against Broadleaf Weed Species Provided by Biodegradable PBAT/PLA Mulch Film Embedded with the Herbicide 2-Methyl-4-Chlorophenoxyacetic Acid (MCPA)

Biodegradable mulches are considered a promising alternative to polyethylene-based, nonbiodegradable mulch for sustainable agriculture. In the present study, a bioactive 2-methyl-4- cholorophenoxyacetic acid/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (MCPA-PHBV) conjugate blended with biodegradable poly(butylene adipate-co-terephthalate/polylactide (PBAT/PLA) was developed and used as mulch under controlled condition greenhouse pot experiment with fava bean (Vicia faba) as the nontarget crop species. The objectives were to examine the effectiveness of sustained-release of MCPA herbicide from biodegradable mulch for broadleaf weed suppression and to assess any adverse effects of the herbicide on the nontarget species (fava bean). The energy-dispersive X-ray spectroscopy analysis (EDS) suggests that a substantial quantity of the herbicide was released from the biodegradable mulch which effectively killed the broadleaf weed species even at 1% MCPA concentration. However, the higher concentrations of the herbicide adversely affected several physiological parameters of fava bean growth and development. Stomatal conductance decreased, while leaf temperature subsequently rose (at MCPA concentrations 5, 7.5, and 10%). The quantum yield of the Photosystem II (PSII) indicates that the photosynthetic efficiency was also restricted at concentrations 7.5% and 10%. Evidently, this slow-release herbicide system worked efficiently for broadleaf weed control but at higher concentrations, resulted in adverse physiological effects on the nontarget crop species. This study has demonstrated that biodegradable mulches containing MCPA herbicide are able to effectively inhibit the growth of broad leaf weed species and may be of potential importance in a wide variety of horticultural and agricultural applications.

Ruthenium-Catalyzed Hydrogenative Degradation of End-of-Life Poly(lactide) to Produce 1,2-Propanediol as Platform Chemical

The chemical recycling of end-of-life polymers can add some value to a future circular economy. In this regard, the hydrogenative degradation of end-of-life PLA was investigated to produce 1,2-propanediol as product, which is a useful building block in polymer chemistry. In more detail, the commercially available Ru-MACHO-BH complex was applied as catalyst to degrade end-of-life PLA efficiently to 1,2-propanediol under mild conditions. After investigations of the reaction conditions a set of end-of-life PLA goods were subjected to degradation.

Tin(ii) 2-ethylhexanoate catalysed methanolysis of end-of-life poly(lactide)

The depolymerisation of end-of-life poly(lactide) (PLA) goods was studied as part of the chemical recycling of PLA.

Exploring polylactide/poly(butylene adipate-co-terephthalate)/rare earth complexes biodegradable light conversion agricultural films

In this work, rare earth europium was combined with different organic ligands to obtain two kinds of rare earth conversion agents, Eu(DBM)₄CPC and Eu(TTA)₃(TPPO)₂. Two kinds of conversion films were successfully prepared by combining them with polylactide and poly(butylene adipate-co-terephthalate). Results showed that the film has excellent light conversion ability and high color purity, and rare earth complexes improved melt flowing property and decreased melt viscosity of blend. At the same time, the elongation at break of the film increased greatly, which could up to 595.0/460.9% in the both machine direction (MD) and transverse direction (TD). The results of GPC show that rare earth complexes can make main chain of PLA scission, which causes rapid molecular weight reduction, and the effect of Eu(DBM)₄CPC on the molecular weight of PLA was more significant than Eu(TTA)₃(TPPO)₂. SEM shows that the complicity of PLA and PBAT has been improved, the dispersed phase of the blend is more uniform. DSC shows that both rare earth complexes can improve the crystallization capacity of PLA. And with the addition of cetylpyridinium chloride could improve the compatibility of rare earth complexes and polymer materials, the light transmittance and hydrophilicity of the film also increased obviously.

Highly efficient metal(iii) porphyrin and salen complexes for the polymerization of rac-lactide under ambient conditions

Metal(iii) complexes supported by porphyrin and salen ligands were highly efficient for rac-lactide polymerization at room temperature giving isotactic-enriched PLA.