Thermal, mechanical, and topographical evaluation of nonstoichiometric α-cyclodextrin/poly(ε-caprolactone) pseudorotaxane nucleated poly(ε-caprolactone) composite films

Figure S1. Fourier transform infrared spectra (FTIR) of PpRs between PCL and αCD obtained from multiple batches (suffixes 1 and 2 correspond to batches with 3 (A), 6 (B), and 12(C) % coverage by α-CD. With increasing coverage by α-CD (C > B > A), hydroxyl group (at 3350 cm-1) peaks become more prominent. The results were consistent across the batches (A1 vs A2; B1 vs B2; and C1 vs C2) for all –OH groups. Likewise, with increasing coverage by α-CD, concomitant decreases in the prominent carbonyl peak of PCL observed at ~1725 cm-1 was observed (C > B > A). Also, similar to hydroxyl groups, similar peak intensities were observed across the batches (A1 vs A2; B1 vs B2; and C1 vs C2). Control samples are not shown here as the purpose is to elucidate the differences in FTIR spectra of PpRs and similarities between the batches.

Fig S2: Non-isothermal differential scanning calorimetric analyses of the PCL/α-CD PpRs obtained from the first cooling (A) and second heating cycles (B) between the temperatures 20 to 80 °C. In general, sharp endo- and exotherms are observed in the cooling and heating cycles, respectively, for the PpRs compared to neat PCL. In addition, higher crystallization temperatures observed for the PpRs also indicate faster crystallizability.

Figure S3. Weight vs temperature (A) and first derivative plots (B) obtained from the thermogravimetric analyses (TGA) of neat PCL and PpRs between 25 and 550 °C. Neat PCL shows a single step-degradation at ~410 ° C, whereas the PpRs show a two-step degradation that can be ascribed to the degradation of α-CD (340–350 °C) and PCL (410–415 ° C). Higher temperatures observed for the α-CD degradation, compared to the degradation temperatures reported for neat uncomplexed α-CD (270 to 300 ° C), demonstrates the presence of PpRs, rather than the physical mixtures.

Figure S4. Weight vs temperature and first derivative thermograms of PCL and 10% PpR-nucleated composite films obtained from TGA analyses. Both degradation thermograms and first derivative plots demonstrate a single degradation pattern for neat PCL and some PpRs (PpR-3 and PpR-6), with the degradation of α-CD coinciding with the degradation of PCL. In PpR-12, a two step-degradation was observed with a unique, distinguishable peak at 350 ° C clearly demonstrates the presence of intact PpR in this composite.

Figure S5. Wide angle X-ray Diffraction analyses (WAXD) of the neat PCL and PCL/α-CD PpRs. Neat PCL showed two crystalline peaks at 2θ = 22 and 24° ascribed to (110) and (200) reflections of the orthorhombic crystal structure. PpRs, in addition to characteristic PCL peaks at 2θ = 22 and 24°, showed characteristic channel structure of the α-CDs via the peak at 2θ = 20°. With increasing coverage of PCL chains by α-CDs (PpR-3 > PpR-6, PpR-12), the peak intensity of the channel structure intensifies, while simultaneously, the intensity of the (110) crystalline PCL reflection decreases.

Figure S6. Wide-angle X-ray diffractograms of PCL and pseudorotaxane-nucleated PCL composite films. Neat PCL showed characteristic reflections at 22 and 24° 2θ corresponding to (110) and (200) reflections. Similarly, composites containing PpR-12 as nucleant or PpR-6 at higher loading (20%) showed a faint signal at 2θ = 20° indicating the presence of intact PpRs in the composite films. Even though this signal was absent in composites containing low stoichiometric PpR-3 (both 10 and 20%), and PpR-6 at 10%, shifts in the PCL peaks (2θ = 22 and 24°), also indicates the possibility of the presence of PpRs in these composite films.

Figure S7. Non-isothermal DSC thermograms obtained from the first cooling (a) and the second heating (b) cycles of PCL and PpR-nucleated PCL composite films. Neat PCL composites show a broad endotherm at 32.2 ± 0.2 °C (ΔHc =68.0 ± 3.5 J/g), whereas PpR-nucleated composites showed more narrow crystallization exotherms with higher crystallization temperatures. In addition, with the exception of neat PCL and PpR3 containing composites, two broad overlapping exothermic events with unique peaks were observed upon cooling in the remaining composites indicating the possibility of two different phases (PCL and PpRs) in the composites.

Figure S8. Relative crystallinity values obtained from the isothermal DSC thermograms of PCL and pseudorotaxane-nucleated PCL composite films at various temperatures (40, 42, 44, and 46 ° C). At all studied crystallization temperatures (40, 42, 44, and 46 ° C), t1/2 s of the PpR-nucleated composites were shorter than the neat PCL film, indicating rapid crystallizability of these composites. In addition, at crystallization temperatures closer to the melting temperature (46 ° C) retardation in crystallization was observed for all the composites. Even at this temperature, t1/2 of the PpR-nucleated composites were shorter compared to neat PCL films, which showed t1/2 of ~20 min.

Figure S9. Avrami plots obtained from the isothermal DSC thermograms of PCL and pseudorotaxane-nucleated PCL composite films at various temperatures (40, 42, 44, and 46 °C). From the Avrami plots, Avrami index (n) and rate constants were obtained for the composites, which showed low n values for the neat PCL films with concomitant higher n values for the PpR-nucleated composites, indicating crystal formation in 3-dimensions.

Figure S10. Representative surface roughness average profiles and quantitative analyses of surface roughness profiles of neat PCL and PCL/pseudo-rotaxane composite films obtained from atomic force microscopy (AFM). (A) Neat PCL, (B) 10% PpR-3, (C) 20% PpR-3, (D) 10% PpR-6, (E) 20% PpR-6, (F) 10% PpR-12, (G) 20% PpR-12.

Fig S11. Representative stress–strain plots of neat PCL, 10% PpR-3, 10% PpR-6 and 10% PpR-12 nucleated PCL composites.

Table S1. Synthesized PpRs, their relative Wide angle XRD intensities, and PCL composite films nucleated by PpRs via solution and casting techniques.

Table S2. Melting and cooling temperatures and enthalpies of the neat PCL and PpR- nucleated composites obtained from the non-isothermal differential scanning calorimetric analyses.

Table S3. Avrami constants and half-crystallization times (t_1/2) of neat PCL and PpR-nucleated PCL films observed by isothermal DSC.