INTERMOLECULAR NONRADIATIVE ENERGY-TRANSFER - EFFECT OF SPACER LENGTH CARRYING DONOR AND ACCEPTOR FLUOROPHORES IN WATER-SOLUBLE COPOLYMERS OF POLY[N-(2-HYDROXYPROPYL)METHACRYLAMIDE]

Copolymers of monomers containing donor (carbazole) and acceptor (dansyl) fluorophores with N-(2-hydroxypropyl)methacrylamide (HPMA) with ''low'' and ''high'' contents of the fluorophores were prepared. At any given fluorophore concentration, the efficiency of nonradiative energy transfer (NET) is always higher for polymers with a lower content of fluorophore labels. At higher concentrations of fluorophore, the mutual interpenetration of the polymer coils reduces this difference. Copolymers of HPMA containing donor and acceptor fluorophores attached to the end of ''short'' and ''long'' side chains were synthesized. Increase in NET between copolymers carrying fluorophores at the end of the aliphatic ''long'' spacer was interpreted as due to hydrophobic interaction of long methylene side chains. The fluorescence quantum yield of carbazole fluorophores in the model compound and in copolymers are discussed in terms of solvent polarity and the polarity of the polymer microenvironment.