Bridging of poly(acetylene)s and PEG-modified poly(olefin)s through ring-opening metathesis copolymerization (ROMCP)

Abstract

Amphiphilic copolymers of highly conjugated poly(acetylene)s and poly(ethylene glycol)-functionalized perylene diimide (PEG₇₅₀–PDI)-incorporating poly(olefin)s have been synthesized via tandem cyclopolymerization and ring-opening metathesis copolymerization (ROMCP) methodologies. Both di- and tri-block copolymers were prepared from 1,6-heptadiyne and oxanorbornene imide-based cycloolefin monomers using ruthenium-based alkylidene initiators. The relative atomic weight percentages of both di- and tri-block copolymers were estimated using X-ray photoelectron spectroscopy (XPS) analysis. Photophysical properties of both copolymers have been explained based on both UV-Vis and fluorescence spectroscopic analysis shedding more light on their different stages of organization as well as the π–π stacking interactions of the PEG₇₅₀-incorporating perylene cores in aqueous solutions. Furthermore, these investigations elucidate the modulation of the photophysical properties and H-type aggregation processes of polymers in aqueous solutions that lead to the formation of PEG₇₅₀–PDI-derived amphiphiles. Copolymeric surface analysis, segmental patterns and film morphology were examined by atomic force microscopy (AFM) revealing globular or spherical morphological features enhanced by various functional groups present in the polymer bulk. In addition, the formation of these spherical morphologies was further visualized in the thin film cross-sections of both di-and tri-block polymers by scanning electron microscopy (SEM) to confirm the surface morphologies determined by AFM analysis of both polymeric materials.