## 4 Morphology of Electrospun PCL Blends and Composites  
In most cases, the electrospinningning of PCL with other polymers or electrospun fibers has more of an advantage over pure electrospun PCL. The addition of another filler or electrospun polymer and fiber incorporated has been reported to improve the properties of PCL. [PERSON] et al. [45] investigated the production of nano hydroxyapatite/poly(caprolactone) composites for tissue engineering applications. In the absence of hydroxyapatite nanoparticles, PCL nanofibers fabricated at lower concentration (viz 7.5% (w/v)) had beads, while those produced at higher concentration (viz 12.5% (w/v)) were bead-less fibers with submicron dimensions. The addition of _n_HA resulted in bead-less fibers without agglomerates, with the fibers thicker than those of PCL nanofibers. The development of electrospun 3D PCL/chitosan core-shell structure as scaffolds was studied for tissue engineering usage [46]. The composite was fabricated by utilizing coaxial electrospinningning technique, whereby PCL was used as a core and chitosan as shell layer. The authors reported on bead-less and continuous core-shell micro/nano fibers. SEM images further showed that the scaffolds were biocompatible, which suggested that the PCL/chitosan will be a suitable candidate for scaffold in tissue engineering applications. Table 2 summarizes some selective morphologies of PCL/blends and its composites for medical applications.  
\begin{table}
\begin{tabular}{l l l} \hline \hline
**Solvent System** & **Morphological Results** & **Refs.** \\ \hline
1:1 tetrahydrofuran (THF)/_N_,N_-dimethylformamide (DMF) (w/w) at concentration of 15 wt\% & SEM images of PCL fibers showed a smooth bead-less & [39] \\ \hline
1,1,3,3,3-hexahtoro-2-propanol to a concentration (10\% w/vol) & Anchoring of individual PCL fibers was confirmed by optical microscopy images of the fibers before and after manipulations. & [40] \\ \hline
15 wt\% of PCL dissolved in N,N-dimethylformamide (DMF) and dichloromethane (DCM) solvent mixture at 70:30 ratio: DMF-DCM & PCL mat with an average diameter of \(-1.5\) μm were obtained. & [41] \\ \hline PCL was electrospun with good solvents such as chloroform (CF), dichloromethane (DCM), tetrahydrofuran (THF) and formic acid (FA) were used with poor solvent dimethylsulfoxide (DMSO) & Porous structure consist of bead-free fibers having average diameters of 1470 to 2270 nm was obtained using 12.5\% v/v PCL in CF/DMSO & [42] \\ \hline PCL pellets was dissolved in a solvent mixture of chloroform and dimethylformamide (7:3 v\(\times\)) & Aligned and randomly oriented PCL nanofibers were collected with different collectors & [43] \\ \hline PCL was dissolved in \(N\),N_-dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), chloroform (CF) and dimethylsulfoxide (DMSO) & When NMP, AC and DMF were employed as the solvents for PCL electrospinningning, PCL fibers showed smaller fiber diameters than those of DCM, CF and THF & [44] \\ \hline PCL was dissolved in acetic acid & Optical microscopy images showed coarse features of the fibers. A 17 wt\% concentration showed large beads with diameters of about 15 μm randomly spread. An increase in concentration (viz 19 wt) resulted in large beads only & [37] \\ \hline  & Finer fibers were obtained for formic acid/acetic acid (FA/AA) and formic acid/acetone (FA/A) for electrospinningning of PCL & Finer fibers were obtained for formic acid/acetate acid (FA/AA) and formic acid/acetone solvent system. Optimum conditions for PCL nanofibers electrospinning were produced for 70:30 FA/AA solvent ratio with 15\% PCL concentration & [38] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Selective solvent systems and morphologies of electrospinningning of PCL.