Lei Wang,Zhen-Zhen Li,Gong-Ji Chen,Mi-Zhuan Li,Yan Cheng,Zhong-Xiu Chen
The activity of lipase was inhibited or promoted by different macromolecular colloids, but the underlined general rules were not clear. In this paper, lipase activity was systematically analyzed in different macromolecular media. The detailed factors that affect the enzyme activity were extracted for quantification. Three functions, including viscosity, the crowding effect, and soft interactions, were established to describe the macromolecular medium effect. The medium parameter based on the Huggins constant and Kramer constant was able to characterize the quality of the macromolecular media. A multivariate nonlinear regression model was proposed for the correlation or prediction between three groups of factors and enzyme activity, and a crowding enzyme factor CCef was proposed. This study pioneered the qualification and prediction of the multiple factors that affect the enzyme activity in complex media. It is also significant for scientifically predicting the efficacy of functional macromolecules related to healthy food and the formulation of dietary fibers.
Dynamic covalet networks, exemplified by Vitrimers, hold significant promise for sustainable polymers due to their reprocessability and mechanical robustness. However, their susceptibility to creep deformation under sustained stress, driven by dynamic bond mobility, limits practical utility. We report a multiphase Vitrimer elastomer based on transesterification. Two distinct carboxylic acid cross-linkers containing dynamic β-hydroxy ester bonds were highly cross-linked into epoxidized natural rubber (ENR). Dithiodibenzoic acid (DS) bearing benzene rings first undergoes preferential aggregation via π–π interactions and thermally cross-links with epoxy groups to form a rigid hard phase, thereby restricting chain slippage and rearrangement at service temperatures to enhance creep resistance. Concurrently, 3,3′-dithiodipropionic acid (DD) establishes a soft phase with epoxy groups in the matrix, while preserving the material’s reprocessability. Stress relaxation and creep tests reveal that the hard domains/regions within the heterogeneous network structure impede segmental relaxation at relatively low temperatures, thereby enhancing the material’s creep resistance. At elevated reprocessing temperatures, however, these hard domains maintain dynamic bond exchange and segmental mobility, while the soft phase facilitates material reprocessability. This work establishes a scalable design framework for Vitrimers that synergistically enhances creep resistance and recyclability, addressing critical demands for durable yet sustainable engineering materials.
Zaizheng Sun,Jinming Liu,Haiming Chen,Dongsheng Mao
With the in-depth exploration of extreme environments in polar, mountainous areas, and outer space, the demand for ultralow temperature resistant adhesives is increasing. However, for most adhesives used, represented by epoxy and acrylic resins, this is almost impossible due to their extensive intermolecular interaction and rigid three-dimensional (3D) network structure. Herein, an adhesive with a well-designed hard–soft phase separation structure has been developed in this work, which exhibits excellent bonding strength and debonding performance when bonded to metals (stainless steel and aluminum) and nonmetallic materials (polycarbonate) at −80 °C. The bonding strength and debonding energy with stainless steel reached 35.7 MPa and 61.16 kN/m, respectively, which is 5 times higher than those reported in the literature. Moreover, the adhesive exhibits good stability after 10 cycles of rapid cooling and heating between −196–50 °C. Finally, the mechanism behind the excellent bonding was verified, which stems from the strong polarity of the hard segments and the hardening of the soft segments.
危险品化学品经营许可证（带存储）