Use of a dye-labeled ethylene-butene copolymer as a tracer in laser scanning confocal fluorescence microscopy studies of thermoplastic olefins

A benzothioxanthene-labeled ethylene-butene rubber has been synthesized and tested as a potential fluorescent tracer for the impact modifier (IM) phas e in laser scanning confocal fluorescence microscopy (LSCFM) studies of the rmoplastic olefin (TPO) morphology. The amino-functional Hostasol Yellow de rivative HY-DP reacts with maleated EBR-28 to give a good labeling yield (c a. 70%) and a dye concentration of 0.051 mmol/g, when the maleated rubber i s first refluxed over molecular sieves and the reaction purged with N-2. Wi thout pretreatment of the rubber and N-2 purging, a lower labeling yield (0 .036 mmol dye/g) is obtained and the labeled product tends to undergo cross linking at 240 degreesC and subsequent dye detachment when the crosslinked gel is hydrolyzed. LSCFM studies reveal HY-labeled EBR to be completely mis cible and evenly dispersed in the unlabeled EBR-9 of model TPO blends. More over, the HY-labeled EBR provides good fluorescence contrast between the IM droplets and the PP matrix in the TPO blend PP/EBR (80/20) (w/w) + 3 wt % labeled polymer with respect to EBR. Imaging of IM droplets down to 40 mum below the film surface of this blend has been demonstrated. (C) 2000 John W iley & Sons, Inc.