Synthesis and characterization of new photoswitchable azobenzene-containing poly(ε-caprolactones)

Abstract

A novel and efficient strategy in obtaining series of mono-and bi-armed azobenzene-containing poly(3-caprolactone)s is described, starting from a commercially available azobenzene dye via azide/alkyne-"click"-reactions. The attachment of alkyne-telechelic poly(3-caprolactone)s (1 kDa and 3 kDa), followed by chromatographic separation, allowed the attachment of either one or two PCl-chains to either side of the azobenzene-dye. The resulting mono-and bi-armed photo-switchable polymers are fully characterized by 2D-NMR techniques and show a high thermal stability. Additionally liquid chromatography at critical conditions (LCCC) coupled to ESI-TOF allowed us to prove the presence of either one or two polymer chains affixed onto the central azobenzene dye.

Multidimensional Mass Spectrometry of Synthetic Polymers and Advanced Materials

“…In LCCC, the entropic and enthalpic terms in the distribution equilibrium between the stationary and mobile phases are equal; as a consequence, all chains with the same repeat unit have identical retention times and are eluted according to their end groups . With block copolymers, critical conditions can be adjusted for one of the blocks, resulting in fractionation by the size of the other block, which acts as one of the end groups . The critical conditions are determined by a series of LC experiments using different mobile‐phase compositions .…”

“…This process is laborious, and the critical conditions established by such means may be valid only for short chain lengths (within <5000 Da) . These issues have prevented LCCC‐MS from becoming a broadly used analytical technique and limited its applications to very complex end‐group distributions that are difficult to derive by other methods …”

Mehrdimensionale Massenspektrometrie von synthetischen Polymeren und modernen Materialien

“…Bei der LCCC sind Entropie‐ und Enthalpieterm im Verteilungsgleichgewicht zwischen stationärer und mobiler Phase gleich; darum haben alle Ketten mit der gleichen Wiederholungseinheit die gleiche Retentionszeit und werden entsprechend ihren Endgruppen eluiert . Bei Blockcopolymeren können die kritischen Bedingungen für einen der Blöcke eingestellt werden, was zur Fraktionierung entsprechend der Größe des anderen Blocks führt, der als eine der Endgruppen fungiert . Die kritischen Bedingungen werden mithilfe von LC‐Experimenten ermittelt, die sich in der Zusammensetzung der mobilen Phase unterscheiden .…”

“…Dieser Prozess ist aufwendig, und die so ermittelten kritischen Bedingungen gelten möglicherweise nur bei kurzen Kettenlängen (<5000 Da) . Diese Aspekte haben verhindert, dass sich die LCCC‐MS zu einer breit angewendeten Analysenmethode entwickelt hat, und ihre Anwendung auf sehr komplexe Endgruppenverteilungen beschränkt, die mit anderen Methoden schwer abzuleiten sind …”

Rare earth complexes using azobenzene-containing poly(aryl ether)s with different absorption wavelengths as macromolecular ligands: synthesis, characterization, fluorescence properties and fabrication of fluorescent holographic micropatterns

“…Azobenzene-containing polymers (azo-polymers) have attracted much attention due to their potential application in optical data storage, photochemical switches, photodeformation materials and nonlinear optical materials. [1][2][3][4][5][6][7][8] One of the attractive phenomena is that surface relief gratings (SRGs) can be formed directly on the lms of azo-polymers by exposing the lms to two interfering laser beams due to the reversible photoisomerization and photoinduced anisotropy of the azobenzene groups. 9,10 The SRGs are stable below the glass transition temperatures (T g s) of the polymers and can be removed by heating the polymers above their T g s or can be erased optically.…”