Improving stiffness, strength, and toughness of. poly(ω-pentadecalactone) fibers through in situ. reinforcement with a vanillic acid based

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1 Supporting information for manuscript Improving stiffness, strength, and toughness of poly(ω-pentadecalactone) fibers through in situ reinforcement with a vanillic acid based thermotropic liquid-crystalline polyester. Carolus H. R. M. Wilsens 1,*, Mark P.F. Pepels 2, Anne B. Spoelstra 2, Giuseppe Portale 3, Dietmar Auhl 1, Yogesh S. Deshmukh 1, Jules A.W. Harings 1. 1 Department of Biobased Materials, Maastricht University, P.O. Box 616, 6200MD, Maastricht, The Netherlands. 2 Laboratory of Polymer Materials, Eindhoven University of Technology, Den Dolech 2, 5600MB, Eindhoven, The Netherlands. 3 Macromolecular Chemistry & New Polymeric Materials, Zernike Institute for Advanced Materials, Nijenborgh 4, 9747 AG, Groningen, The Netherlands. *Corresponding author: karel.wilsens@maastrichtuniversity.nl

2 SEM characterization of the fiber morphology of PPDL/LCP 80/20 and 60/40 fibers. In Figure S1, the fiber morphology of the PPDL/LCP 80/20 and 60/40 fibers as observed in SEM analysis are shown. Characteristic for the PPDL/LCP 80/20 fiber morphology is that the dispersion of the LCP phase is homogenous and the fibers are uniform in shape. In contrast, for the PPDL/LCP 60/40 fibers, the fibrils are highly inhomogeneous in shape, diameter and length. Figure S1. Fiber morphology for PPDL/LCP 80/20 (A, B) and PPDL/LCP 60/40 (C, D) fibers as observed in SEM analysis. Nucleation effect of the LCP fibrils on the PPDL phase. Additional to the data supplied in the original manuscript, DSC heating and cooling experiments were performed at slow cooling rates to verify the repeatability of the nucleation effect of the LCP fibrils. In Figure S2, the DSC cooling traces obtained at a cooling rate of 1 C/min are supplied after heating the sample to 110 C. As can be seen from Figure S2, the presence of LCP fibrils in PPDL/LCP 80/20 and 60/40 fibers enhances the peak

3 crystallization temperature to 84.9 C, which is an increase of roughly 1.2 C compared to the pure PPDL material. 0.2 First DSC cooling run (10 C/min) Heat Flow (W/g) H c = 85.8 J/g T c = 84.9 C H c = 68.6 J/g T c = 84.9 C -0.8 PPDL/LCP 60/40 fiber H c = J/g PPDL/LCP 80/20 fiber T c = 83.7 C PPDL fiber Temperature ( C) Figure S2. First DSC cooling traces obtained on the as-spun fibers at a cooling rate of 1 C/min. The fibers were initially heated to 110 C and kept isothermal for 3 minutes prior to cooling back to room temperature.

4 Additional information of the L p determination from SAXS data on PPDL/LCP 80/20 fiber. Figure S3. Exemplary overview of the determination of the long-period reported in Figure 4 of the original manuscript from the 2D-SAXS patterns and their resulting Lorentz-corrected SAXS patterns. The Lorentz correction has been applied through multiplying the measured intensity distribution by a factor q 2. N.b. The dotted lines are added to guide the eye and to show the expected intensity profile at the detector grid positions.

5 Orientation parameter calculation from WAXD diffraction of PPDL/LCP fiber Figure S4 shows the obtained 2D-WAXD patterns, the corresponding polar plots and the resulting azimuthal density distribution. For pure PPDL fibers, no orientation is observed, therefore the azimuthal density distribution was constant and is not shown. The PPDL/LCP 60/40 fiber was used for determination of the LCP orientation parameter, since the LCP signal was strongest due to the highest LCP loading. From the polar plots it can be seen that the peak of the scattering signal of the LCP phase partially overlaps with the signal of the amorphous PPDL phase. This implies that any determination of the LCP orientation parameter will be affected by any orientation of the amorphous PPDL phase. However, for the PPDL/LCP 60/40 fiber, it can be seen that the amorphous PPDL phase is present as an isotropic halo in the WAXD pattern. This indicates that in the as-spun fibers, there is no orientation of the amorphous PPDL phase. Determination of the orientation parameter of the LCP phase therefore yields a value of 0.7. For comparison, pure PPDL fibers were solid-state deformed to introduce orientation in the amorphous PPDL phase. As a result of this solid-state deformation, the orientation parameter was determined, yielding a value of This data indicates that indeed the amorphous PPDL phase overlaps with the LCP phase and that any orientation of the amorphous PPDL phase results in an inaccurate determination of the LCP orientation parameter. For this reason, caution should be taken when interpreting the data in the original manuscript.

6 Figure S4. Left, 2D WAXD patterns of the as-spun PPDL/LCP 60/40 fiber, the solid-state drawn PPDL, and the as-spun pure PPDL fiber. In the middle of this Figure, the polar plots are shown after integration. On the right, the azimuthal density distribution of the PPDL/LCP 60/40 fiber and solid state deformed PPDL phase are shown after integration at the same q values.

7 SEM analysis of necked region of a yielded PPDL/LCP fiber. To identify whether debonding occurs in the PPDL/LCP fibers upon deformation, a thick PPDL/LCP 70/30 fiber (as is shown in the inset of Figure 6B) was deformed and the generated neck was cut out. Next, to prevent further deformation and the formation of crazes due to the sample preparation procedure, the neck was cut along the deformation direction using cryomicrotomy at -100 C in order to generate a smooth surface. Prior to SEM analysis, a conductive gold layer was applied by sputtering. As is visible from Figure S5, voids are running parallel to the deformation (and drawing) direction of the fiber. If these voids would be crazes induced by the deformation process itself, they would run perpendicular to the deformation direction. This indicates that the voids are likely a result of debonding in the material. Although the SEM characterization procedure does not allow us to differentiate between the LCP and the PPDL phase, we expect that the debonding occurs on or close to the PPDL/LCP interface.

8 Figure S5. SEM images of the necked region of a thick PPDL/LCP 70/30 fiber. Dark voids are observed along the deformation direction, likely as a result of debonding during deformation. N.b. The neck is placed horizontally with respect to the SEM images, thus, the voids are running parallel to the deformation and drawing direction of the fiber.