In order to allow for free movement of electrons, graphitic carbon materials have a tendency of sharing crystalline domain (Fitzer & Köchling, 1992) for increased conductivity (Walker, P. L., 1973). In the study carried out by (Novoselov, et al.; Bazaroz & Nikolaev, 1989; Liu et al., 2004; Harfanist et al., 2004; Coleman et al., 2006), the use of graphitic carbon in several applications including the next generation electronics, composite materials (Coleman et al., 2006; Chen, I.-H., Chen, C.-Y., & Wang, 2010), activated carbon fibers, fuel cells (Wang, Zhao, & Niu, 2007; Marta, et al, 2008), sensors and batteries (Besenhard, 1999; Hess, Lebraud & Levasseur, 1997) are studied extensively. By using simple and inexpensive fabrication techniques, the process of obtaining graphitic carbon structures in nanoadittives has made this area of study more attractive.
Miniaturized structures and also chemically forced graphitization of bulk carbon materials has been on study for a long time. (Oya & Otani 1979; Oya & Marsh 1982) studied chemical methods of catalization which include combining metal additives in the starting materials. This can be semi-graphitic or pyrolyzed non-graphitic carbon or a carbonizable polymer precursor. Inspite of these additives leading to a higher amount of crystalline domain in the ensuing carbons, there is a limit to the industrial usage of this materials due to the excess remaining of unwanted metal components. Exploration of physical catalysis (templating) by filling polymer precursor in secluded areas e.g. pores of a host structure (Kruk, et al. 2007) or their deposition over silicon surfaces (Yang, et al. 2005) has been studied as an effective way of getting more graphitic domains. There is however limited freedom in the designing of such devices such the template since it has a pre-defined geometry. To solve these problems, it is advisable to use carbon templating materials as nanoadditives to polymer precursors which gives room for fabrication of devices and design as well as yielding graphitic carbon that need no additional purification. Due to increased ordering of carbon atoms, a wide range of application have been investigated (Zussman, et al. 2005) in the properties (Mechanical, electrochemical, electrochemical and electrical) of Carbon Nano Tubes (CNT) polymer composites. These properties rely on several factors such as distribution of CNTs in the matrix of polymers, shapes, size, orientation, CNT polymer interaction, volume fraction and the extend of dispersion among others(Fitzer & Köchling, 1992)
Functionalization offers the ability of anchoring binding sites to their surfaces as well as formation of specific CNTs groups. New binding sites are likely to have a reaction with many chemicals which happens provided the binding energy is high and the reactant is selective. Occasionally, site selectivity in binding on functionalized CNTs is particularly of importance to bio-polymer oriented applications and plays a major role in key-lock mechanisms (Coleman et al, 2006) In order to retain the original properties of CNTs non-covalent functionalization methods have to better fit. This will involve surfactants adsorption polymers and their combination (Besenhard, 1999). For effective stabilization, polymers have to conform in order to get better peculiarities of CNTs based composites.
Adsorbing polymers should be full be well matched with tissues containing the composite locations for efficient biopolymer intended applications. In market today, synthetic polymers do not meet the requirements above thus resulting to the extensive use of biopolymers. As a result, nucleic acids, polypeptides , proteins and polysaccharides are used as substitutes(Hess,& Levasseur, 1997). The relation between amino acids (nucleotides) and the CNTs functionalize their surface through embedding of a specific functional group (Wang, Zhao & Niu, 2007). The CNTs, do not belong to the biopolymer-based stabilization class inspite of their renowned utility as sensors (Ōya & Ōtani, 1979).
Electrospinning is an effective and commonly used technique for the fabrication of thin mats of polymer nanofibers (Kruk et al, 2007). According to Maitra et al. (2011), it is the most effective way of fabricating single, suspended CNTs composite nanofibers which are integrated with a polymeric micro-electro-mechanical system (MEMS) platform. Such platforms structures have the ability to produce carbon nanowires of electrical conductivity anchored on, graphitic content and integrated with the underlying carbon micro-structure. In their review on polymer nanofibers by electrospinning and their applications in nanocomposites (Huang, et al. 2003), conclude that different polymers have dissimilar spinnable thickness ranges and therefore, the solution viscosity cannot serve as a controlling parameter in such cases. Electrospinning is therefore recognized as an competent technique for fabrication of polymer nanofibers.
After shrinking the diameters of polymer fiber materials from micrometers (e.g. 10–100 mm) to submicrons or nanometers (e.g. 10_10_3–100_10_3 mm),several features like elasticity in surface functionalities, large surface area to volume ratio (which for a nanofiber can be about 103 times that of a microfiber) and superior mechanical performance (e.g. tensile strength and stiffness)are realized when compared with other known material forms. These properties make the polymer nanofibers the most favorable choice for many applications. A number of processing techniques such as phase separation , template synthesis, drawing , electrospinning and self-assembly etc. have recently been used to prepare polymer nanofibers(Yang et al, 2005). The drawing process can be compared to in the fiber industry's dry spinning, where one-by-one long single nanofibers can be made. However, the only materials that can be made into nanofibers through drawing are only viscoelastic materials that can undergo tough deformations and still remain solid enough to bear the stresses developed during pulling (Fujihara, 2003).
A nanoporous membrane is used to make nanofibers of hollow (a tubule) or shape solid (a fibril) in the template synthesis. This method's important feature is that fibrils of different raw materials such as semiconductors, electronically conducting polymers, metals, and carbons as well as nanometer tubules and can be fabricated. Otherwise, the method does not allow for the making of one-by-one continuous nanofibers(Hohman et al, 2001). The phase separation includes gelation , dissolution, freezing, extraction using a different solvent, and drying resulting in a nanoscale porous foam which takes a longer period of time to do the solid polymer to nano-porous foam transfer. The method in which pre-existing components arrange themselves into preferred patterns and functions individuals is known as the self-assembly which just like the phase separation, is slow in continuous polymer nanofibers processing (Demir et al, 2002).Therefore, the electrospinning process is the only method which can be further developed for mass production of one-by-one continuous nanofibers from various polymers.
Polylactide (PLA) is a biopolymer that is broadly used in engineering, the medical and agricultural sectors (La & Morreale, 2011; Vroman & Tighzert, 2009). It is advantageous in that it can be processed in a similar manner to the commodity polymers using process such as compression, injections, extrusion and blow molding (Rhim, 2013; Liao et al. 2011). It also has some negative attributes to its properties that include slow biodegradation, poor elongation, extremely brittle and has limited gas barrier properties. This has led to many researches being carried out in order to combine PLA with different polymers (poly[(ethylene oxide), (e-caprolactone), (butyl acrylate)] among others) so as to eliminate these disadvantages. Although PLA blends have good physical properties and are biodegradable (Kemala, 2012), there are thermodynamically incompatible thus limiting the scope of their applications. In process of trying to achieve interfacial localization, Wu et al. has used the technique of functionalization at the expense of decreased mechanical strength. Factors such as kinetics (viscosity ratios between polymers), enthalpic interaction between polymers are key to localization of solids (Robeson, 2007). The research carried out by Agwuncha et al. (2015), concludes that PLA can be blended with other biopolymers in order to achieve good elongation of composites.
Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic used in sheet form as shatter-resistant or a lightweight substitute for soda-lime glass. It can also be used as a casting resin as well as in inks and coatings (Deitzel & U.S. Army Research Laboratory, 2001). Although it is not a well-known silica-based glass, PMMA has often been referred to as acrylic glass. Chemically, it is referred to as the synthetic polymer of methyl methacrylate. It is an economical substitute for polycarbonate (PC) when tremendous strength is not needed. In addition, PMMA does not contain bisphenol-A subunits that are commonly found in polycarbonates( Larrondo & St, J, 1981). It is often used thanks to its low cost, easy handling and processing, and moderate properties (Fertala, Han,& Ko, 2001). Non-modified PMMA is brittle when loaded, particularly under an impact force, and is likely to get scratches than the common inorganic glasses, but modified PMMA can achieve high impact and scratch resistance. Thanks to the Polymethyl methacrylate (PMMA), nanofibers have recently found many attractive applications mainly due to their high surface area to volume ratio (Awad, A., Bashier, S. A., & Halim, S. F. 2014). The carbon black has not been used earlier in the preparation of electro spun PMMA nanofibers in literature (Méndez et al. 2002). (Qian et al. 2010) showcased a study in which PMMA was selected as the solute and processed into nanofibers by electrospinning. Due to properties like molecular weight, boiling points and molecular structure different morphologies were observed . (Piperno et al. 2006), arranged a series of nanofibers with various wt.% of PMMA to acetone and then they characterized the PMMA nanofibers on the basis of their chemical composition and morphology (Li et al, 2007). Their results showed that an increase in the PMMA concentration lead to disappearance of beads and there was an increase in the nanofibers homogeneity. In addition, the same chemical composition of the PMMA compound was presented by the nanofibers.
The electrospinning process effortlessly adds to the particles of materials such as metal oxides, pigments, and many other particles into the produced nanofibers(Hajra, Mehta, & Chase, 2003). Fibers free of beads can be formed as a result of addition of filler materials into a polymer solution, it was deduced (Zussman et al. 2002). A common polymer additive known as carbon black is used for reinforcement and for its low cost and availability as well as its capability of enhancing the polymeric compounds’ properties (Lawandy et al. 2009). PMMA is an vital commercial plastic, which is used extensively in many sectors such as in lighting, signs, aircraft glazing, architecture, transportation and merchandising (Pan & Chen, 2009).
When polymers are dissolved in volatile solvents, the solutions is said to be spinned. Spin coating therefore a preferred method for thin, uniform films to flat substrates application (Flack, 1984). Excess amount of polymer solutions are placed on top of substrates which are then rotated at high speeds in an angular velocity so as to spread the fluid by centrifugal force therefore reducing the fluid thickness. Rotation continues with the fluid spinning off the substrate edges until the required film thickness is attained. The volatile solvent allows for simultaneous evaporation.
Casting is one of the methods used in the preparation of good and quality polymer films (Hass, 1963). In this method, the polymer which is the host together with inorganic salts are dissolved into suitable solvents e.g. methanol and distilled water. The solvent is then allowed to evaporate at room temperature thus obtain a polymer electrolyte film (ISSSID, 1988).
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