This paper investigates the porphyrin de-aggregation in a set of guest-host films, prepared by spin coating, in a series of poly(n-alkyl methacrylate)s matrices. UV-Vis optical absorbance and steady-state photoluminescence spectroscopy in association with the fluorescence lifetime imaging technique (FLIM) helped to characterize the film blends. All the PnMA matrices de-aggregated the porphyrin molecules. The size of the PnMA n-alkyl side group influenced the porphyrin de-aggregation level. FLIM images showed that porphyrin aggregates in spin-coated PnMA/porphyrin films also presented a ring shape. The presence of the PnMA host matrix improved the film structure and produced porphyrin rings with different types of porphyrin building blocks. Each building block corresponded to a different kind of porphyrin aggregation. The FLIM images evidenced that porphyrin aggregates were radially distributed, and that the most aggregated porphyrin molecules tended to accommodate in the inner part of the porphyrin ring, while the monomers were preferentially located in the outer part of the ring. (C) 2016 Elsevier Ltd. All rights reserved.