Functional polyphosphazene cyclomatrix microspheres (PMS) containing glucose and dodecyl moieties were utilized for physical adsorption of lipase. In this regard, Candia Rugosa lipase was immobilized onto the above microspheres through physical adsorption, which exhibited catalytic hydrolysis of glycerol triacetate as the model reaction. As observed under transmission electron microscope (TEM) and scanning electron microscope (SEM), the size of all the microspheres ranged from 400 nm to 1 μm with a mean diameter of 680 nm. Zeta potential analysis demonstrated that the microspheres were negatively charged. The influences of buffer pH, substrate concentration and temperature were also studied along with reusability. The obtained results demonstrated that the immobilized lipase on deprotected glycosylated PMS (D-GPMS) showed the best performance and possessed the highest enzymatic loading activity around 1.0884 mmol L −1 min −1 g −1 , and retained nearly 50% of its initial activity even after 10 cycles of application. Moreover, the lipase-microsphere complex displayed high pH adaptability from 7 to 9 and temperature stability above 40 °C. From the viewpoint of biocompatible PMS support, the GPMS-lipase conjugate have potential applications in field such as food, medicine and environment.
Polymeric ablative materials (PAMs) are widely used in spacecraft currently for thermal insulation. However, it is challenging to find a single filler that can improve both ablative and mechanical properties of PAMs. In this study, a new type of hybrid cross-linked polyphosphazene microspheres (PHC) is added to ethylene propylene diene monomer (EPDM) composites as a filler for the first time and its influence on the ablation, mechanical, and thermal properties of EPDM is investigated. The results show that the addition of 3 phr PHC increases the ablation performance by about 10% and enhances the mechanical properties by 20% approximately. In addition, the ablation mechanism is studied in accordance with SEM, FTIR, and Raman spectroscopy. On the one hand, PHC has the effect of catalyzing carbonization, thus increasing the rate of residual carbon; on the other hand, PHC changes the morphology of the char layer, forming a cross-linked structure containing P─O─Si bonds on the surface. The findings regarding catalyzing carbonization and the special char layer structure could guide the design of ablative materials.
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