Porphyrin tripod as a monomeric building block for guest-induced reversible supramolecular polymerisation

Reversible supramolecular polymerisation and depolymerisation of biomacromolecules are common and fundamental phenomena in biological systems, which can be controlled by the selective modification of biomacromolecules through molecular recognition. Herein, a porphyrin tripod (DPZnT) connected through a triazole bridge was prepared as a monomeric building block for guest-induced supramolecular polymerisation. Although the lone pair electrons in triazolic nitrogen potentially bind to the zinc porphyrin units through axial ligation, the intrinsic steric hindrance suppressed the coordination of the triazole bridge to the porphyrin unit in DPZnT. Therefore, DPZnT formed spherical nanoparticles through π-π interactions. The addition of 1,3,5-tris(pyridine-4-yl)benzene (Py3B) caused the guest-induced fibrous supramolecular polymerisation of DPZnT by forming a 1:1 host-guest complex, which was further assembled into a fibrous polymer. Furthermore, addition of Cl− to DPZnT induced the transformation of spherical nanoparticles to fibrous supramolecular polymers. The fibrous supramolecular polymers of DPZnT obtained by adding Py3B or Cl− were depolymerised to their original spherical particles after adding Cu(ClO4)2 or AgNO3, respectively.

Fibrous Polymer-Based Composites Obtained by Electrospinning for Bone Tissue Engineering

Currently, the significantly developing fields of tissue engineering related to the fabrication of polymer-based materials that possess microenvironments suitable to provide cell attachment and promote cell differentiation and proliferation involve various materials and approaches. Biomimicking approach in tissue engineering is aimed at the development of a highly biocompatible and bioactive material that would most accurately imitate the structural features of the native extracellular matrix consisting of specially arranged fibrous constructions. For this reason, the present research is devoted to the discussion of promising fibrous materials for bone tissue regeneration obtained by electrospinning techniques. In this brief review, we focus on the recently presented natural and synthetic polymers, as well as their combinations with each other and with bioactive inorganic incorporations in order to form composite electrospun scaffolds. The application of several electrospinning techniques in relation to a number of polymers is touched upon. Additionally, the efficiency of nanofibrous composite materials intended for use in bone tissue engineering is discussed based on biological activity and physiochemical characteristics.

Methods of mechanical treatment of machine parts made of fibrous polymer composite materials (Review)

The growing volumes of production of mechanical engineering products made of fibrous polymer composite materials can be explained with the possibility of producing products of relatively small mass with specified physical and mechanical, thermophysical, dielectric and many other properties, which allows them to be highly competitive in comparison with products made of metals and their alloys. The results of a review of the main defects that arise during the machining of machine parts made of fibrous polymer composite materials, as well as ways to prevent their occurrence and improve the quality of the treated surfaces are presented and discussed. Based on the analysis of the information presented, it was concluded that increasing the efficiency of mechanical treatment of machine parts made of fibrous polymer composite materials and ensuring the durability of such parts was possible due to an integrated approach to the development of a technological process of mechanical treatment, taking into account individual characteristics of various types of fibrous polymer composite materials.

The Tool’s Optimum Geometry Research for Obtaining Apertures in Semi-Cured Polymer Composite Materials

The composite materials features and characteristic defects in the obtaining apertures by machining are considered. A new method for forming apertures in fibrous polymer composite materials is proposed. The optimal shape of a tool for piercing holes is determined. The profiles of the pointed part of the tool are compared using numerical modeling.

Numerical Modeling of Tribological Characteristics of Fibrous Polymer Composite Materials

The paper presents a numerical simulation of the contact interaction of fibrous polymer composite materials in a finite element ANSYS package and studies the friction coefficients for cells with wear of 0%, 25%, 50% and 75%. To predict the coefficient of friction of composites it was proposed to use the method of mechanics of composite materials – the method of local approximation. With the help of numerical simulation, the fields of distribution of normal stresses and contact stresses in the contact zone were obtained and the corresponding conclusions were drawn

On the sensitivity of large precision space structures of high-modulus fibrous polymer composite materials to microdynamical effects

The paper considers the problem of sensitivity of large precision space structures made of high-modulus fibrous polymer composite materials to external and internal microdynamic effects. This problem is related to the extent of structure forming elements, as well as to an abrupt increase in the elastic modulus of the material when passing the threshold of low stresses. It is found that under low loading in the orbital flight conditions the calculated values of the elastic modulus of large precision space structures made of high-modulus fibrous polymer composite materials may be higher than the real ones by more than 20 times, which must be taken into account in the calculations. Possible ways to reduce the sensitivity of such space structures made of high-modulus fibrous polymer composite materials to external and internal microdynamic effects are shown.