A study of molecular diffusion in alcohol—water solution of poly-4-vinylpyridine by fluorescence quenching

Intra- and intermolecular diffusion processes in alcohol—water solutions of poly-4-vinylpyridine (PVPy) were studied by the fluorescence quenching method. It was prepared fluorescent-labelled PVPy (PVPy-F) by copolymerizing 4-vinylpyridine with anthrylmethylmethacrylate (F) (one chromophore group per 500 chain links in the copolymer). PVPy carrying both the chromophore and quenching chain links (quaternization of the pyridine residue by dimethylsulphate) (PVPy-FQ) and PVPy carrying only the quenchers (PVPy-Q).Measurement of the mean lifetime of the excited state of the anthracene group for the polymers and for the monomer analogue (F) with increasing quencher concentration and use of the Stern-Volmer relation permit determination of the constants of bimolecular collisions between the monomer quencher (Q) (4-ethyl-N-methyl pyridinium sulphate) and F, between the monomer quencher and PVPy-F and between Q and F incorporated in the same polymer chain (PVPy-FQ). The values of the diffusion constant for the system of PVPy-F and Q and for the system of PVPy-FQ are approximately two and four times respectively less than that for the monomer pair (F + Q). For the latter system, the finding indicates some hindrance to the diffusion of the chain links with each other within the coil. Nevertheless, their mobility remains high and probably microdiffusion will not limit chemical reactions of functional groups within coils and with monomer molecules.In studying the fluorescence quenching of the chromophore for PVPy-F in the presence of the polymer quencher, it was found that mutual interpenetration of the polymer coils is intensified markedly when the solution volume is filled entirely by the swelling coils.