Synthesis and Crystallization of Star-Shaped Photocleavable Poly(ε-caprolactone)s

Here, we report on the synthesis and different crystallization behavior of linear- and star- PCL's containing a photocleavable linker (5-hydroxy-2-nitro benzaldehyde), modulated by photochemical switching. Basis is the attachment of a photocleavable moiety close to the star-core of a three-arm star poly(caprolactone), so that the crystallization behavior can be controlled via a photochemical stimulus. The polymerization of epsilon-caprolactone using a trivalent photocleavable initiator and stannous octanoate catalyst resulted in the synthesis of different molecular weights of star-shaped photocleavable polymers. Various techniques like H-1 NMR and ESI-TOF-MS confirmed the successful synthesis of the star-shaped polymers. Complete photocleavage is ensured via GPC, HPLC, and ESI-TOF-MS. DSC studies clearly indicated the enhancement in crystallinity after photocleavage of the star-shaped poly(epsilon-caprolactone)s. Hence, for the first time phototriggered crystallization behavior of PCL polymers is reported, where the confinement exerted by the star architecture is removed by photoirradiation. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 642-649