Relaxation processes and polymeric chain interpenetration in a PMMA-Cz/ MEH-PPV blend studied by fluorescence spectroscopy

Abstract

Miscibility and energy transfer processes of a blend containing 0.1 % of Poly[2-methoxy-5-(2-ethylhexyloxy)- 1,4-phenylenevinylene] (MEH-PPV) in a matrix of poly(methyl-methacrylate) containing 1% of attached carbazolyl groups (PMMA-Cz) were studied by fluorescence spectroscopy and microscopy techniques. From SEM micrographs, a uniform surface is found. The images on the cryogenic fracture of the blend does not show domains, although from fluorescence optical microscopy domains of MEH-PPV of about 30 μm in the PMMA-Cz matrix were observed, indicating the immiscibility of the blend components. By steady-state and time-resolved fluorescence spectroscopies measured at room temperature and at 77 K, it was found that there is an important non-radiative energy transfer occurring by Forster mechanism and due to that, there must be an interpenetration degree between polymeric chains specially at room temperature, which is evidence for miscibility. This can be inferred also by temperature-dependent fluorescence spectroscopy, which informs about relaxation processes occurring in the blend and also reveals the occurrence of an interface effect that is characteristic of miscible components.