Fluorine Enriched Melt Blown Fibers from Polymer Blends of. Poly(butylene terephthalate) and A Fluorinated Multiblock Copolyester

Transcription

1 Supporting Information Fluorine Enriched Melt Blown Fibers from Polymer Blends of Poly(butylene terephthalate) and A Fluorinated Multiblock Copolyester Zaifei Wang, Christopher W. Macosko, Frank S. Bates * Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN * Address correspondence to: bates1@umn.edu. S-1

2 The thermal properties of,, and / blends are shown in Figure S1. Both the T g and T m are insensitive to the blend miscibility and compositions. Heat flow (w/g), Endo up.5 w/g a. b. /_1 c. /_3 d. /_5 e. /_1 f. f e d c T g T m b a -5 a Temperature ( C) Figure S1. DSC analysis of,, and / blends. The data shows the features of the second heating scans at 1 C. The rheological properties were characterized at 24 C with a strain-controlled ARES rheometer (TA Instrument) equipped with a 25 mm parallel-plate fixture. As to and, dynamic strain sweeps were first performed to determine the linear viscoelastic region. Then, dynamic frequency sweeps were employed to measure the complex viscosity (η*) and dynamic elastic modulus (G ) and loss modulus (G ) as a function of frequency (1 ω 1 rad/s) (5 % strain). Steady shear tests were carried out for / blends (.1 shear rate 1 s -1 ). As shown in Figure S2 (b), G ~ ω 1.7 and G ~ ω 1 indicate liquid behaviors of both and at 24 C. In addition, the complex viscosity (η * ) of nearly equals to that of, approximately 1 Pa s, which is appropriate for melt blowing. Therefore, the melt blowing experiments were performed at 24 C. Figure S3 shows the shear rate dependence of the blends viscosities. S-2

3 1 3 (a) (b) η* (Pa s) G' & G'' (Pa) G'' ~ ω 1 G' ~ ω 1.7 G' G'' G' G'' ω (rad/s) ω (rad/s) Figure S2. Rheological properties of and. (a) Complex viscosity (η*); (b) elastic modulus (G ) and viscosity modulus (G ) at 24 C. 1 3 viscosity (Pa s) T = 24 C /_1 /_3 /_5 /_ shear rate (s -1 ) Figure S3. Steady shear results of / blends at 24 C. Figure S4 shows the ATR-IR spectra of,, and / blends. The C=O vibration in pure located at 177 cm -1 is attributed to the crystalline carbonyl group. 1 If there are dipole-dipole interactions between the C=O and CF 2 groups in the blends, the C=O peak would be expected to shift to lower frequency. However, there are negligible shifts of the C=O peaks in / blends, as demonstrated by the second derivatives of the spectra in S-3

4 Figure S4(b). Moreover, there is no noticeable broadening associating with the C=O peaks. Therefore, we conclude that there are no, or extremely weak, specific interactions Normalized Absorbance (a) /_1 /_1 2 nd Derivative. -.1 (b) /_1 /_ Wavenumber (cm -1 ) Wavenumber (cm -1 ) Figure S4. Representative ATR-IR analysis of,, and their blends: (a) normalized IR spectra and (b) the corresponding 2 nd derivatives. Table S1 exemplifies the calculation of the solubility parameter (δ) using the groupcontribution theory. Through the calculation we obtained δ = 11.7 (cal/cm 3 ).5, δ = 9.96 (cal/cm 3 ).5. The value of δ agrees well with other publications. 2-4 δ is calculated to be 1.24 (cal/cm 3 ).5 which is larger than the critical value of δ ( δ critical =.1 (cal/cm 3 ).5 ) suggested by Coleman for miscible binary blends. 5 Therefore, is predicted to be immiscible with, which is consistent with the SEM observations. S-4

5 Table S1. An example of calculating the solubility parameter (δ) of using the groupcontribution method. Group unit E h (J/mol) unit V (cm 3 /mol) δ ((cal/cm 3 ).5 ) phenylene ester methylene E h, total δ = = Vtotal 11.2 a. E h = cohesive energy b. The values of E h and V are obtained from Krevelen, D. W. 6 The effect of concentration on blend morphology is shown in Figure S5. The drop size stayed fairly constant but their number increased. S-5

6 Figure S5. Representative SEM images of / blends with a composition of (a) ϕ = 1 wt%; (b) ϕ = 3 wt%; (c) ϕ = 5 wt%; (d) ϕ = 1 wt%. The samples were prepared by microtoming the blends at -6 C. SEM micrographs were captured using a backscattered electron detector. To investigate the effects of thermal annealing the /_1 blend was annealed quiescently at 24 C for 8 min. Figure S6. Representative SEM images showing the morphology of (a) /_1 (ϕ = 1 %) blend, (b) /_1 annealed at 24 C for 8 min,. All samples were cryo-fractured in LN2. S-6

7 Figure S7 shows the internal morphology of single melt blown fibers. Surprisingly, there are no nanofibers embedded inside. The representative TEM image in Figure S8 further demonstrates the absence of nanofibers inside single melt blown fibers. Figure S7. Representative SEM images showing the (a) longitudinal and (b) cross-sectional morphology of the cryo-fractured melt blown /_1 fibers. SEM micrographs were captured using a backscattered detector Figure S8. A TEM image showing the cross-sectional morphology of melt blown /_1 fibers. S-7

8 The fluorine content on the fiber surfaces was characterized by XPS. Survey spectra are shown in Figure S9 and curve fitting in Figure S1. Two approaches were employed to quantify the amount of. One method uses the peak areas of the C 1s, O 1s, and F 1s signals from the XPS survey scans. Both equation (1) and (2) were used to determine the amount of on the fiber surfaces. F W F M = C C n W + W M n n M C (1) W 416b W 1 + = (2) where F = atomic concentration of fluorine (F), C = atomic concentration of carbon (C), the average number of element i present in the representative unit of. number of element i present in the representative unit of. For example, i n = i n = the average F n = 16, and = 4. M = number average molecular weight of the representative unit. W = surface weight percentage of each component. O n The second method relies on detailed fitting the C 1s envelope obtained from high-resolution XPS scans. Firstly, the curve fitting and peak deconvolution were carried out on pure melt blown fibers for reference, as shown in Figure S1. S-8

9 4 4 (a) /_1 fiber (b) /_3 fiber C 1s O 1s C 1s O 1s F 1s F 1s (c) /_5 fiber (d) /_1 fiber O 1s C 1s F 1s F 1s O 1s C 1s Figure S9. XPS survey spectra showing the photoemission areas of C 1s, O 1s, and F 1s of melt blown fibers of (a) /_1 (ϕ = 1 %); (b) /_3 (ϕ = 3 %); (c) /_5 (ϕ = 5 %); (d) /_1 (ϕ = 1 %). S-9

10 4 (a) C 1s (b) O 1s shake-up Figure S1. Line fitting analysis of (a) C 1s envelopes and (b) O 1s envelopes of pure melt blown fibers. The results of the peak deconvolution for is summarized in Table S2. The ratio of C 1, C 2, and C 3 is about 5 : 1 : 1, which is roughly consistent with the relative numbers of C 1, C 2, and C 3 (8, 2, 2) in the repeating unit of. The results also matches the analysis by Burrell et al. 7 Also, the ratio of O 1 and O 2 is close to 1 : 1. Table S2. Line fitting results of C 1s and O 1s for C 1 C 2 C 3 Shake-up O 1 O 2 BE (ev) Atom % FWHM (ev) Sensitivity Factor In order to quantify the amount of on surface, the pure was also analyzed for reference, as shown in Figure S11. S-1

11 4 (a) C 1s (b) O 1s (c) F 1s Figure S11. Line fitting analysis of (a) C 1s envelopes, (b) O 1s envelopes, and (c) F 1s envelope of. S-11

12 The C 1s envelop of is more complicated and was fitted with 7 peaks, as shown in Figure S11(a). In particular C 4 corresponds to CF 2 CHF O at 29.5 ev. 8-1 C 5 represents CF 2 CFCF 3 O and CF 2 CF 2 CF 3 at ev C 6 corresponds to O CF 2 CHF O and O CF 2 CF 2 at ev, 11 and C 7 correlates with CF The results of the peak deconvolution for is summarized in Table S3. Table S3. The line fitting results of C 1s and O 1s for. C 1 C 2 C 3 C 4 C 5 C 6 C 7 O 1 O 2 O 3 BE (ev) Atom % FWHM (ev) Sensitivity Factor The ratio of C 1, C 2, C 3, C 4, C 5, C 6, and C 7 (43.8 : 8.92 : 1.22 : 4.97 : 1.35 : 12.9 : 9.46) is slightly lower than the relative numbers of C 1, C 2, C 3, C 4, C 5, C 6, and C 7 (14 : 5 : 4 : 1 : 2 : 3 : 2) in the repeating unit of, which may be attributed to the surface segregation of the pendent perfluorinated segment. The ratio of O 1, O 2, and O 1 appears to be insensitive to the segregation of the pendent segment. Figure S12 shows the representative static contact angle measurements. S-12

13 Figure S12. Typical images demonstrating the static water contact angle measurements on (a) fiber mat, CA = 128 ± 4 ; and (b) /_5 fiber mat, CA = 155 ± 3. Figure S13 shows the influence of the concentration on both the advancing (θ A ) and receding (θ R ) contact angles. 18 θ A 16 θ R θ A & θ R ( ) W,bulk (%) Figure S13. Variation of both the advancing contact angle (θ A ) and receding contact angle (θ R ) as a function of the concentration in the bulk. S-13

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