The phosphorescence characteristics of naphthyl labelled poly(acrylic acid) film samples have been studied as a function of temperature, with a view to investigating the effect of matrix control on the level of triplet emission observed. Two relaxations, which serve to deactivate the excited triplet states have been detected from phosphorescence lifetime measurements: the ct (or glass) and the beta transition (which can be associated with the onset of rotation of the carboxylic acid group). Investigation of the emission from 2-benzoyl naphthalene dispersed within both an acrylic acid-methyl methacrylate copolymer and a PAA film, respectively, has revealed that the more intense, longer-lived phosphorescence results from the modified polymer. This is considered to reflect the existence of (i) hydrogen-bonding interactions induced by the presence of carboxylic acid groups which serve to form a rigid matrix and (ii) intramolecular aggregates of methyl methacrylate units which create hydrophobic-rich pockets, capable of sustaining intense phosphorescence at room temperature.