# Synthesis of Porous Biomimetic Composites: A Sea Urchin Skeleton Used as a Template
###### Abstract  
The paper presents an original method for the template synthesis of biomimetic porous composites using polyferophenylsiloxane (PFPS) and the skeleton of the sea urchin _Strongylocentrotus intermedius_ as a structuring template. The study aimed to form an organosilicon base of a composite with an inverted structure relative to the original structure of the sea urchin shell with a period of structure movement of about 20 \(\upmu\)m and ceramic composites fabrication with the silicate base with an average pore size distribution of about 10 \(\upmu\)m obtained by the reaction of PFPS with the inorganic base of the sea urchin test under conditions of calcination at 1000 \({}^{\circ}\)C followed by acid etching. The composition and morphology of the obtained composites were investigated by IR, XRD, XPS, EDX, and SEM techniques and by mercury porosimetry; the parameters of the porous structures depend on the selected methods of their synthesis. The proposed method is of fundamental importance for developing methods for the chemical synthesis of new biomimetics with a unique porosity architecture based on environmentally friendly natural raw materials for a vast practical application.  
biomimetic materials; ceramic composites; sea urchin skeleton; calcium silicate; polymer-organic compounds; template synthesis +
Footnote †: journal: Applied Sciences  
13 September 2021  
Multi-dimensional modeling of heterogeneous materials; dynamic models; dynamicprocesses, including the effects of molecular sieving through the pores and specific chemical interactions between the pore surface and the solute. A recent review by [PERSON] et al. [16] presents their studies that show that the characteristics of porosity (type of pores, pore size distribution, pore density, aperture) are the key factors that determine the efficiency of biomimetic membranes for various applications. Interestingly, the structural parameters of the materials are also crucial for electrochemical applications [17; 18; 19].  
These functional structures with the required transport pores are created based on template synthesis using inorganic and polymer patterns (templates) that form a porous framework [20; 21]. The sea urchin test, which is an organic-inorganic biocompatible, is of great interest as such a template. As shown in the skeletons of the sea urchins _Heterocentrotusaminidase_[22] and _Strongylocentrotus intermedius_[23], these skeletons are characterized by their complex bicontinuous porous structure, also known as stereome, which often also exhibits controlled gradients of porosity and structural change [24]. At the same time, individual skeletons based on stereomes are single crystals based on calcite containing magnesium [23; 25], which indicates the chemical activity of the inorganic base of the sea urchin skeleton when used as a raw material in chemical synthesis.  
Considering the possibilities of chemical and biochemical application of the sea urchin skeletons to create new functional materials, we investigated the chemical interaction of organosiloxans with the sea urchin skeleton as a pore-forming template for obtaining new materials with a developed porous structure. The method proposed in this work can be of fundamental importance for determining the possibility of obtaining ordered porous composite materials for a vast practical application, including technologically demanded highly porous cellular membranes or filters.