Supramolecular Polypseudorotaxanes Composed of Star-Shaped Porphyrin-Cored Poly(-caprolactone) and -Cyclodextrin

Star-shaped porphyrin-cored poly(-caprolactone) (SPPCL) was synthesized using a tetrahydroxyethyl-terminated porphyrin as a core initiator and stannous octoate as a catalyst in bulk at 120 °C. The molecular weight of as-synthesized polymer could be adjusted linearly by controlling the molar ratio of -caprolactone to porphyrin core initiator, and the molecular weight distribution was reasonably narrow. Supramolecular polypseudorotaxanes were prepared by inclusion complexation of SPPCL with -cyclodextrin (-CD) and thoroughly characterized by means of FT-IR, 1H NMR, 13C CP/MAS NMR, DSC, TGA, and WAXD. The results demonstrated that the porphyrin-cored polypseudorotaxanes formed through -CD molecules threading onto the branch chains of star-shaped SPPCL polymers, and they had a channel-type crystalline structure. Meanwhile, the original crystallization of SPPCL polymers within the polypseudorotaxanes was completely suppressed in the -CD cavities. Moreover, inclusion complexation between SPPCL and -CD enhanced the thermal stability of both the guest SPPCL polymers and the host -CD. Furthermore, both the SPPCL polymers and the polypseudorotaxanes showed similar fluorescent and UV-vis spectra compared with porphyrin core initiator. Consequently, this will not only provide potentially porphyrin-cored poly(-caprolactone) and its polypseudorotaxanes for photodynamic therapy but also improve the compatibility between poly(-caprolactone) and peptide drugs for drug delivery.