Electrospinning Nanofibers Using M-Poss and Polycaprolactone - Report Example

of Electrospinning Nanofibers Using M-POSS and Polycaprolactone (PCL) in 1 Acetone:Chloroform Solution Abstract: Electrospinning is an already known technology in generating nanofibers with a wide range of diameter. This technology uses electric fields to drive the spinning process of polymers and solvents in producing the fibers. Various kinds of fibers are produced from different combinations of polymers and solvents used for diverse applications which include clothing, separation membranes, tissue engineering, filters, bioengineering, microfluidic devices, electronics, composite material reinforcements and many more. The morphology and compatibility of the polymers and the solvents used in this technology is very vital as the output fibers are greatly dependent on them. Methacryl POSS (M-POSS) and Polycaprolactone (PCL) are just one of the few polymers explored in the production of electrospun nanofibers. Solvents tried in various combinations and proportions are also tested to produce an output most suited for certain applications. M-POSS and PCL has been tried both individually and also combined together with other chemicals in the presences of different solvents in search for the fibers that would yield best results. This paper explores the M-POSS:PCL nanofiber electrospinning in the presence of chloroform:acetone solvent in 1:1 proportion. The output for the process is discovered to be fully developed and can compete with other methods ready to be used in various applications. Introduction: Electrospinning is a technique utilizing electric force to generate fibers with diameters ranging from nanometer to micrometer sizes coming from combinations of polymers and solvents. Fibers produced have characteristics that are dependent on the solvents and polymers used that would best qualify for vast functionalities and varied applications (Tungrapa, et al). Basically, electrospinning requires polymer solution that would be injected through a needle placed at a certain proximity of a grounded target. This needle is maintained at a critical voltage to create charge imbalance overcoming the surface tension of the polymer fibers. This would create an electrically charged jet. The grounded target is composed of a rotating mandrel for collection of polymeric fibers. (Rai, et al). Figure 1. General Schematic Representation of Electrospinning The electrospun fibers produced are widely used in various ways and continuous research has been done to create an output suited for use. Applications of the polymer nanofibers produced through electrospinning can be summarized below (Huang, et al): Fig. 2. Potential applications of electrospun polymer nanofibers. The properties of electrospun nanofibers are greatly affected by various parameters such as temperature, humidity, voltage applied, electrospinning solvent and the polymer characteristics. The morphology of the produced fibers are greatly affected by the solvents and the polymer being dissolved in the process (Qian, et al). Different kinds of solvents contribute various surface tensions. But not all solvents with lower surface tension automatically become compatible with electrospinning (Huang, et al). Generally, solvent properties considered include boiling point, dielectric constant, surface tension, conductivity, viscosity and many more. These parameters can cause the formation of bead like structures in electrospun fibers (Qian, et al). For successful electrospinning process, it is vital to choose the appropriate solvent system that would readily dissolve the polymer being used (Haroosh, et al). Polycaprolactone PCL or Polycaprolactone with molecular weight of 80 000g/mol Polycaprolactone is a tested candidate for electrospinning process. It has been observed that the polymer exudes the presence of nucleation growth of small and high oriented fibers (Reneker, et al).The polymer can be spun directly into fibers of small diameter. Polycaprolactone has been successfully used for tissue engineering proving its biocompatibility with the body as the fibers from the polymer can be dissolved leaving room for cell growth in pure form inside the body (Montero, G.A. et al). PCL is a biodegradable polyester that is soluble in solvents such as dichloromethane, tetrahydrofuran, ethyl acetate, chloroform, hexafluoroisopropanol and acetone (Hadcist). Electrospinning fibers from Polycaprolactone with compatible polymers at a certain ratio can be prepared from solutions of chloroform and acetone. As tried with a polymer polyactide, the resulting fiber rendered suitable microfibers. Electrospun fibers scanned in micrographs reveal samples with smooth surface with high content of polycaprolactone (Valle, et al). Acetone has been tried to be a non-toxic sustainable solvent that particularly works with polycaprolactone and other bi-compatible polymers. PCL dissolved in acetone based solvent in the electrospinning process is observed to be effective, less hazardous, and can be a sustainable solvent for the application. The morphology of the fibers produced however maybe affected by various parameters such as flowrate, voltage, distance, and the proportions of polymers and solvents used. These factors can affect the output diameter of the fibers and they can be interplayed for optimum diameter output fiber diameters suited for certain applications (Bosworth and Downes). M-POSS M-POSS or Methacryl POSS with a molecular formula of (C7H11O2)n(SiO1.5)n and molecular weight of 1433- 2150 and density of 1.20 g/ml is considered a hybrid molecular compound with a core of inorganic silsequioxane and the corners attached with methacrylate groups. It is colorless oil with low viscosity. It is soluble in solvents such as THF, chloroform, acetone, acetonitrile and ethanol (“MA0735”). Electrospinning technique has been used with POSS and its copolymers into uniform and bead-free fibers observed using Atomic Force Microscope (AFM) and ToF-SIMS. As observed, results indicate that the electrospun nanofibers were covered with POSS moieties suggesting that the surface of the fiber is structurally composed on ordered POSSs. POSS polymers have excellent thermal and mechanical properties composed of a silica cage. The corner groups have tunable chemical reactivity which makes them good building blocks for excellent and superior performing polymers that can be applicable for aerospace, electronic, and biological applications (Xue, Y. et al). POSS based polymer materials have the smallest nanofillers that can be good for high temperature composites, light emitting dots, coatings and even rheological modifiers that can be applicable for cosmetic formation (“Nanocomposites”). Formation of nanocomposite naonofibers through electrospinning of POSS/Polymer solution with 15 wt-% of CA in acetone/DMAC results to homogenous nanofibers with dispersed POSS at submicrometric level confirmed through TEM analysis. Figure 3. POSS/Polymer Nanofiber Electrspinning results The morphology of the output nanofibers would show that the fiber length has uniform diameter, and oriented fibers are bonded strongly by electrostatic crossing. The spindled local fibers of the film are also high with POSS content (Cozza). M-POSS:PCL Synthesis of an inorganic-organic nanohybrids of PCL grafted into POSS nanofillers is possible. The coordination-insertion of the ring opening of PCL is initiated by the amine groups which are carried by the nanofillers catalyzed by tin-2-ethylhexanoate (Sn(oct)2). The covalent grafting of PCL with POSS is confirmed through H-NMR. POSS-PCL nanohybrids are successfully synthesized. The polymerization is well controlled and the covalent bonding can be made evident through H-NMR and FTIR analysis. As PCL is known to be miscible with large variety of polymers, the future for POSS-PCL nanohybrids can be performed in variety of matrices and solvents (Goffin, et al.). Polymers containing POSS composites that can be prepared through grafting or through co-polymerisation are said to have good dispersing ability than pure polymers. Some of the other special characteristics include low-dielectric, high mechanical strength, and superior thermal stability (Xue., et al). PCL on the other hand is considered as bioresorbable polymer that has been successfully processed through electrospinning that are best applied in tissue engineering and biomedical researches (Montero, et al). Acetone:Chloroform Chloroform-acetone mixtures are common solvents used in many of the electrospinning procedures for various combinations of polymers to yield nanofibers with distinct characteristics. They have been tried in various proportions in search for the best fiber results for specific applications. Mixtures of chloroform and acetone with corresponding weight percentage of polymers have been successfully assayed. The parameters for electrospinning are optimized to obtain the fibers with average diameters accurate obtained through TEM micrographs. SEM micrographs are also used to show the surface characteristics of fibers produced when the other parameters in electrospinning were interplayed such as the distance of between the target and the tip of syringe, optimized voltage, flow rate and others keeping the solvent and polymer unchanged (del Valle, et al). Electrospinning polymers have used various proportions of chloroform and acetone and tested with other combinations of solvents to optimize the process. Chloroform is proven to be a suitable solvent for both polymers of PLA and PCL where it has produced consistent fibers (Diller, et al). Acetone is also a proven non toxic and sustainable solvent that is also very compatible with PCL. Dissolved PCL in acetone during electrospinning is observed to result to trends with altering parameters that can be used as well with other polymer/solvent systems (Bosworth and Downes). Acetone and chloroform has been tried with certain polymers such as PLA with PCL (Haroosh, et al), Polymethyl methacrylate or PMMA (Qian, et al)., Polycaprolactone (Montero, et al). , Cellulose acetate (Tungrapa, et al)., Polycaprolactone and polyactide (del Valle), POSS-PMMA (Xue et al) and many more. Other possible applications can be summarized on the Table 1 (“Table 1”). Table 1 List of useful biomedical materials and solvents for electrospinning. Materialsa) Solvent Natural polymers Phospholipids (Lecithin) Chloroform/DMF Synthetic polymers PCL DCM/methanol PHBV Chloroform/DMF PLCL Acetone PLCL DCM PLLA-DLA Chloroform PEG-b-PLA Chloroform Blended PLA/PCL Chloroform Composites PDLA/HA Chloroform PCL/CaCO3 Chloroform/methanol PCL/CaCO3 DCM/DMF PCL/HA DCM/DMF PLLA/HA Chloroform Gelatin/HA HFIP PCL/collagen/HA HFIP Collagen/HA HFIP Gelatin/siloxane Acetic acid/ethyl acetate/water PLLA/MWNTs/HA 1,4-dioxane/DCM PLGA/HA DCM/water Read More