Lignins have three precursors: p-coumaryl alcohol, coiferyl alcohol, and sinapyl alcohol [1,23]. The polymerization of these three primary monomers results in formation of structural units in lignin: p-hydroxyphenyl (H), guaiacyl (G), and syringyl, respectively . Approximately, 90% of SKL units are G units [1,23]. HKL units contain both G and S units. FTIR spectroscopy, according to Popescu et al. is an important tool for structural characterization between hardwood and softwood samples . Figure 1 shows FTIR spectra of the lignin powders. The hydroxyl region of the spectra (3000 cm−1–3700 cm−1) shows that SKL-F4 had the highest amount of hydroxyl groups available. A distinctive difference between HKLs and SKLs is the ratio of the peaks at 1130 cm−1 and 1030 cm−1: in softwoods 1130 cm1 < 1030 cm−1 and in hardwoods 1130 cm−1 > 1030 cm−1. The peak at 1030–1035 cm−1 is allocated to Aromatic C–H in plane deformation, where amount of G units are higher than S units, this region is also allocated to C–O deformation in primary alcohols, and C = O stretch (unconjugated) [26,27]. Peaks at the wavenumber range of 1266–1270 cm−1 are associated with G ring vibrations and as shown in Fig. 2, they are not present in HKL samples. Twin peak at 855 cm−1 and 815 cm−1 is assigned to softwoods and single peak at 835 cm−1 to hardwoods . The presence of more methoxyl groups attached to the aromatic rings in HKLs (S unit) inhibits formation of 5–5 or dibenzodioxocin linkages , where for SKLs β-O-4 linkages are more predominant. Differences in the available functional groups might affect stacking of the molecules and affect size of the ordered domains in the samples. To calculate the size of the ordered domains, XRD analysis was acquired. Figure 2 shows XRD patterns of the three fractions of HKLs, three fractions of SKLs and HP-L powder samples. For each sample, peak fitting was performed for four different refinements: PearsonVII, Pseudo-Vigot, Lorentzian, and Gaussian. Gaussian character was predominant in overall peak shape for softwood samples and Lorentzian character was predominant in hardwood samples and HP-L. After fitting the curves, the maximum diffraction angel was determined for each sample. The average peak for hardwoods is located at 2θ = 21.2 ± 0.15 deg and for softwood it is located at 2θ = 19.35 ± 0.18 deg (Table 1 shows the values for each sample). Kubo et al. reported the diffraction angel of 22.7 deg for hardwood acetic acid lignin  and Ansari and Gaikar reported 2θ = 22.37 deg for lignin from sugar mill . Such differences could be caused by the difference in the lignin type. The Scherrer's equation is usually used for calculating the mean size of the ordered domains (crystallite): , where d is the mean size of the ordered domains, B = dimensionless shape factor (value of 0.9 is used [28,29]), λ = X-ray wavelength (0.154 nm for Cu K-α), and β = full width at half maximum (FWHM) . To measure the FWHM, instrumental broadening effect should be subtracted from the data. Table 1 shows the results of calculated mean size of the ordered domains (“d” in Scherrer's equation) for lignins. Among SKLs, the fraction 4 had the highest size of the ordered domains. According to literature, SKL-F4 has fiber forming ability by electrospinning method . Among HKLs, the unfractionated sample (HKL) had the highest size of the ordered domains. However, because unfractionated sample is composed of different sized molecules in its structure (higher polydispersity index), when spinning parameters were adjusted for one portion of the molecular weight (e.g., viscosity of the solution), the other portions were not spinnable. In other words, although some fiber formation was observed in electrospinning, spraying also occurred. Therefore, SKL-F4 was selected for nanofiber production via electrospinning and further analysis of the nanofibers.