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Herein, we simultaneously prepared borax-crosslinked starch-based hydrogels with enhanced mechanical properties and self-healing ability via a simple one-pot method. The focus of this work is to study the effects of the amylose/amylopectin ratio of starch on the grafting reactions and the performance of the resulting borax-crosslinked hydrogels. An increase in the amylose/ amylopectin ratio increased the gel fraction and grafting ratio but decreased the swelling ratio and pore diameter. Compared with hydrogels prepared from low-amylose starches, hydrogels prepared from high-amylose starches showed pronouncedly increased network strength, and the maximum storage modulus increased by 8.54 times because unbranched amylose offered more hydroxyl groups to form dynamic borate ester bonds with borate ions and intermolecular hydrogen bonds, leading to an enhanced crosslink density. In addition, all the hydrogels exhibited a uniformly interconnected network structure. Furthermore, owing to the dynamic borate ester bonds and hydrogen bonds, the hydrogel exhibited excellent recovery behavior under continuous step strain, and it also showed thermal responsiveness. [ABSTRACT FROM AUTHOR]

The synthesis of biobased polyesters based on 2,5-bis(hydroxymethyl)furan (BHMF) is challenging due to the limited stability of this interesting furanic monomer. In this work, a series of BHMF-based polyesters were produced via a green and efficient bulk polymerization process, by using either an enzyme (iCALB) or a commercially available catalyst (DBTO). The polymerization methods were compared and shown to both be successful, with values up to 14 000 g mol−1. The number of methylene units in the aliphatic comonomer was varied from 2 to 8, and the influence of this on the thermal behavior and stability of the polymers was investigated. The degree of crystallinity of compression molded discs was found to be in the range from 13 to 27%, and the contact angles were determined to be in the region from 63 to 73°, confirming that these polyesters are hydrophilic. An oscillatory shear rheology investigation demonstrated significant differences between the melt behavior of the BHMF-based polyesters, ranging from a Newtonian liquid to a shear thinning material with a 3 orders of magnitude higher complex viscosity. A clear inversely proportional correlation between the low-frequency complex viscosity and the number of methylene units in the aliphatic segment was observed. Finally, a biodegradability test revealed that the synthesized BHMF-based polyesters had a biodegradable character over time, wherein different biodegradation rates were observed related to the length of aliphatic segments in the repeating units. The sustainability of both synthesis routes was analyzed based on atom economy (AE), reaction mass efficiency (RME), E-factor and EcoScale. This work emphasizes that renewable BHMF-based polyesters can be produced via a solvent-free and sustainable process, which show biodegradable behavior and that their thermal and rheological properties can be tailored by varying the number of methylene groups in the aliphatic unit. [ABSTRACT FROM AUTHOR]

Despite rapid advancements in the development of triboelectric nanogenerators (TENG), mechanical defects generated during their working condition limit the service lifetime of these devices. Polyester-based vitrimers can offer a solution to solve this issue via their dynamic bond exchange reactions. However, they often require high temperatures and a long time to crosslink, rendering them not useful for large-scale TENG fabrication. To solve these issues, a self-healable vitrimer-based triboelectric nanogenerator (VITENG) is developed based on diacrylate poly(dimethylsiloxane) (AA-PDMS) via a fast thiol-Michael reaction. By including 2,3-dihydroxypropyl methacrylate (DHPMA), hydroxy end dangling side chains are generated in the matrix, which increase the PDMS network's flexibility and transesterification efficiency. Efficient transesterification occurs on the abundant dynamic ß-hydroxy ester bonds in the PDMS network, resulting in 100% efficient mechanical damage repair. The VITENG demonstrates a good performance with an output voltage of 135 V under a load of 10 N, demonstrating the potential for mechanical energy harvesters with long lifetimes and high design flexibility. [ABSTRACT FROM AUTHOR]