Porous network mechanical properties

When the size of a material is reduced to the nanoscale, their physical and chemical properties are dramatically changed. The separated nanostructure of polymer composites is expected to bring important improvements for polymer electronics because the size reduction of materials increases the contact surface area and lowers the interfacial impedance between the electrode and the electrolyte, and decreases the transport pathways for both electrons and ions (Shi et al., 2015). In addition, the mechanical properties for strain accommodation as well as the flexibility will be improved. A variety of nanostructures of polymer composites have been developed including zero-dimensional nanoparticles, one-dimensional nanowires/rods/belts, two-dimensional nanosheets/plates, and three-dimensional porous frameworks/networks. 

In this technique water-polymer emulsion is formed which is thermodynamically unstable. At low gelation temperature, nanoscale fibers network is formed, whereas high gelation temperature leads to the formation of platelet-like structure. Uniform nanofiber can be produced as the cooling rate is increased. Polymer concentration has a significant effect on the nanofiber properties, as polymer concentration is increased porosity of fiber decreased and mechanical properties of fiber are increased. The final product obtained is mainly porous in nature but due to controlling the key parameters we can obtain a fibrous structure (Figure 9.29). The key parameters involved are as follows [36]. 

Finally, the remarkable mechanical properties and reinforcing potential, renew-ability, biobased nature, biodegradability and unique nanostructured porous network of BC make it a perfect candidate for polymer and hybrid nanocomposites development. In this sense, extensive research has been carried on the design of innovative BC nanocomposite materials with improved and functional properties, by combination with several natural and synthetic polymers as well as inorganic nanophases, for a wide range of biomedical and technological applications. This will be the object of the two coming sections. 

Cai et al. [203] prepared a porous scaffold using bacterial cellulose and poly-3-hydroxybutyrate-co-4-hydroxybutyrate (P(3HB-co-4HB)) with a trifluoroacetic acid as a co-solvent, and by freeze-drying the solution to remove the co-solvent. They determined that the scaffold presented a three-dimensional network with improved mechanical properties over P (3HB-co-4HB) alone. 

Porous matrices are often used to reconstruct connective tissues because they allow the formation of complex extracellular matrix networks responsible for the tissue s mechanical properties and the fusion of the implant with the host s tissue. Pore sizes in the range of 30 to 300 /um are the most common. Smaller pore sizes provide more surface area per volume of matrix however, pores less than 30 /u.m will not allow seeding or ingrowth of the host s tissue into the matrix. 

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