Local Polarity and Microviscosity of the Interior of Dendritic Polyethylene Amphiphiles

From the temperature dependent steady-state and time-resolved fluorescence studies of coumarin 153 (C153) in dendritic polyethylene (DPE)-poly(oligo(ethylene gylcol) methacrylate) (POEGMA) unimolecular micelles, the polarity and microviscosity of the microenvironments of DPE POEGMA were obtained. The analysis of the steady-state emission suggested that C153 sensed a more polar microenvironment in dendrimer polyethylene (dPE)-POEGMA than that in hyperbranched polyethylene (hPE)-POEGMA. It is found that the microviscosity around C153 in DPE-POEGMA micelle could be predicted from the measured reorientational time, which was observed to decrease with increasing temperature, and that local friction experienced by C153 in dPE-POEGMA decreases faster than in hPE POEGMA with the increase of temperature, although both have similar local friction ranges.