To establish a sustainable material production system and preserve the Earth’s environment, “biomass plastics” that are made from renewable biomass instead of petroleum and “biodegradable plastics” ...that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment are desirable products. This miniature review describes a series of studies on microbial polyesters and polysaccharide ester derivatives, including the synthesis of novel polymers, development of new processing techniques for high-performance films and fibers, elucidation of the relationship between structure and properties using synchrotron radiation, and control of the rate of enzymatic degradation.To establish a sustainable material production system and preserve the Earth’s environment, “biomass plastics” that are made from renewable biomass instead of petroleum and “biodegradable plastics” that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment are desirable products. This miniature review describes a series of studies on microbial polyesters and polysaccharide ester derivatives, including the synthesis of novel polymers, development of new processing techniques for high-performance films and fibers, elucidation of the relationship between structure and properties using synchrotron radiation, and control of the rate of enzymatic degradation.
The nonlinear characteristics of avalanche photodiodes (APDs) inhibit their performance in high-speed communication systems, thereby limiting their widespread application as optical detectors. ...Existing theoretical models have not fully elucidated complex phenomena encountered in actual device structures. In this study, actual APD structures exhibiting lower linearity than their ideal counterparts were revealed. Simulation analysis and physical inference based on GaN APDs reveal that electrode size is a noteworthy factor influencing response linearity. This discovery expands the nonlinear theory of APDs, suggesting that APD linearity can be enhanced by suppressing the electrode size effect. A physical model was developed to explain this phenomenon, which is attributed to charge accumulation at the edge of the contact layer. Therefore, we proposed an improved APD design that incorporates an additional gap layer and a buffer layer to stabilize the internal gain under high-current-density conditions, thereby enhancing linearity. Our improved APD design increases the linear threshold for optical input power by 4.46 times. This study not only refines the theoretical model for APD linearity but also opens new pathways for improving the linearity of high-speed optoelectronic detectors.
The thermal properties and crystallization kinetics of Curdlan propionate, a type of bio-based plastic and β-1,3-glucan derivative, were investigated. Melt-spun fibers were also prepared, and the ...fiber formation mechanism and internal structure were analyzed. The decrease curve in molecular weight suggests that the thermal degradation of Curdlan propionate likely proceeds by random scission. Polarized light microscopy of the isothermal crystallization process showed Curdlan propionate forms a spherulite-like morphology, which is unusual among polysaccharides with a rigid backbone chain. By optimizing the melt spinning conditions, it was found that it is possible to spin with good spinnability using a no plasticizer. The crystallization rate of Curdlan propionate was significantly different between the isothermal crystallization process and the melt spinning process. There was a positive correlation between the take-up speed, crystallinity, and the tensile strength of the fiber. A highly ordered structural model of the fiber was suggested from wide-angle x-ray diffraction results and other measurements.
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•Spherulite like-structure was observed, which is unusual for polysaccharides.•It was clarified that the thermal decomposition behavior was random decomposition.•Curdlan propionate fibers were prepared continuously without using plasticizers.•The spinning rate, crystallinity, and mechanical properties were directly proportional.
•Biodegradable polyesters were selected to produce microbeads as alternatives to conventional microbeads.•Manufactured polyester microbeads have comparable compression strengths to those of commonly ...used microbeads.•PBSA and P(3HB) microbeads have good biodegradability under marine conditions.
The conventional microbeads in cosmetics and personal care products comprise non-biodegradable plastics, which pollute the marine environment. In the present study, we used a simple melt-homogenizing method to manufacture microbeads from four biodegradable polyesters, i.e., poly(butylene succinate) (PBS), poly(butylene succinate adipate) (PBSA), poly(lactic acid) (PLA), and poly(R)-3-hydroxybutyrate (P(3HB)). We then determined the morphology, compression properties, and biodegradability of each polyester. The microbeads ranged in size from 25 to 200 μm, were almost spherical, and had smooth surfaces, as verified by scanning electron microscopy (SEM). The single microbeads were subjected to compression tests because their mechanical properties are correlated to their sensory performance. The compression strengths of the four plastic microbeads, which were comparable to those of commonly used microbeads such as polyethylene and polypropylene, were widely distributed. In particular, the PBSA and P(3HB) microbeads were readily biodegradable, as evaluated by enzymatic degradation and sea water degradation tests, indicating their potential as alternatives to conventional microbeads.
Paramylon, which is a β-(1,3)-D-glucan photosynthesized by Euglena, was chemically modified by esterification. Various paramylon triesters with different alkyl chain lengths (carbon numbers 2–12) ...were successfully prepared. All of the paramylon triesters have higher thermal degradation temperatures than that of neat paramylon. Moreover, it was found that the paramylon triesters with C2–C6 alkyl chains are crystalline polymers with melting temperatures from 281 °C to 114 °C, and those with C8–C12 alkyl chains are amorphous polymers, confirmed by both DSC and X-ray diffraction analysis. Paramylon triesters with C3–C12 alkyl chains could shape self-sustaining films by both solvent-casting and melt-quench methods with high optical transmittance and sufficient tensile strength or elongation at break. Thermal and mechanical properties of paramylon triesters can be controlled freely from hard to soft by substituted acyl length. In the cases of the crystalline paramylon triesters, highly oriented and crystallized films could be fabricated by the thermally stretched method, and their tensile strengths have been obviously improved. Well-oriented X-ray fiber diagrams of the stretched and crystallized films suggest that all of the paramylon triesters have rare 5-fold helix conformation of molecular chains in crystal.
Microbeads find widespread usage in personal care items and cosmetics, serving as exfoliants or scrubbing agents. Their micro-scale size poses challenges in effective drainage capture and given their ...origin from non-biodegradable oil-based plastics, this contributes substantially to marine pollution. In this study, microbeads were prepared by a simple yet scalable melt homogenization method using four types of polyhydroxyalkanoates (PHA), namely poly(R)-3-hydroxybutyrate (P(3HB)), poly(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate (P(3HB-co-3HV)), poly(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate (P(3HB-co-3HHx)) and poly(R)-3-hydroxybutyrate-co-(R)-4-hydroxyvalerate (P(3HB-co-4HB)). Microbeads with different surface smoothness, compressive strength (6.2-13.3 MPa) and diameter (from 1 ~ 150 μm) could be produced. The microbeads were subjected to a comprehensive degradation analysis using three techniques: enzymatic, Biochemical Oxygen Demand (BOD) evaluations, and in situ degradation tests in the deep-sea off Misaki Port in the northern Pacific Ocean (depth of 757 m). Qualitatively, results from enzymatic and in situ degradation demonstrated significant degradation within one week and five months, respectively. Quantitatively, BOD findings indicated that all PHA microbeads degraded similarly to cellulose (~ 85% biodegradability in 25 days). In conclusion, PHA microbeads from this study exhibit promising potential as alternatives to conventional non-biodegradable microbeads.
α-1,3-glucan is a linear homopolymer produced through the enzymatic polymerization of sucrose using recombinant glucosyl transferase J (GtfJ) enzyme. Two series of α-1,3-glucan short- and long-chain ...mixed esters, namely α-1,3-glucan acetate hexanoate and α-1,3-glucan propionate hexanoate, with different ratios of short to long sidechains were synthesized via heterogeneous chemical esterification. α-1,3-glucan propionate hexanoate, with a stable crystalline structure, had a significantly higher melting temperature than α-1,3-glucan acetate hexanoate. Melt-spun fibers of both series of esters were successfully prepared at lower temperatures than those required for conventional α-1,3-glucan homo esters, without decreases in molecular weights. The tensile strength of melt-spun fibers increased as the proportion of the short sidechain increased, reaching 367 MPa (ratio of acetate to hexanoate groups of 2.2:0.8), which was much higher than α-1,3-glucan tripropionate with a tensile strength of 115 MPa. X-ray diffraction analyses indicate that this high tensile strength is due to the high orientation of the molecular chains.
Reversible elastic films of biobased and biodegradable poly(R)-3-hydroxybutyrate-co-4-hydroxybutyrate P(3HB-co-4HB) were prepared by uniaxial drawing procedures. Mechanical properties and highly ...ordered film structures were investigated by tensile testing and both static-state and in situ wide-angle X-ray diffraction and small-angle X-ray scattering with synchrotron radiation during stretching and relaxing. Despite the crystalline nature of the polymers, the elongation at break of these films was greater than 1500%. Reversible elasticity was achieved after the first 10 times of uniaxial stretching. X-ray measurement results indicated that on stretching, β-form molecular chains with a planar zigzag conformation were introduced from molecular chains with random coils in the amorphous regions between α-form lamellar crystals. Notably, the orientation of the α-form lamellar crystals increased after relaxation of the molecular chains with a planar zigzag conformation (β-form) between the lamellar crystals (α-form). Reversible elastic properties were regenerated by a planar zigzag conformation between the lamellar crystals, the extension of molecular chains in lamellar crystals by the rotation of molecular conformation, and changes in the degree of orientation of the lamellar crystals.
Curdlan, a β-1,3-glucan polysaccharide, produced by microorganisms, was used as a raw material to synthesize a completely substituted Curdlan mixed ester, Curdlan acetate propionate (CDAcPr). The ...degree of propionylation was changed (0.4–2.8), and the resulting thermal and crystal properties were analyzed using DSC and wide-angle X-ray diffraction (WAXD). Results showed that CDAcPr had a single T g at all degrees of propionylation, indicating that the acyl groups were randomly distributed in its molecular chains rather than a physical blend of homoesters. Further, unlike typical mixed esters, CDAcPr also showed melting points ranging from 293 to 231 °C, with several samples showing multiple melting peaks. WAXD results suggested that CDAcPr underwent cocrystallization observed in certain copolymers, exhibiting isodimorphism. The crystal structure and melting point of CDAcPr could be controlled by changing the degree of propionylation. Such structural control greatly expanded the possibilities of biomass-based plastics derived from polysaccharides.
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