Fluorescence Study on the Dynamics and Structure of Polymer Chain I. Intramacromolecular Photo-crosslinking Reaction of a Polymer Containing Anthryl and Eosinyl Moieties in Dilute Solution

Abstract

ABSTRACT:A photo-crosslinkable polymer with pendant anthryl and eosinyl m01etJes attached to its side chains was synthesized. Dilute DMF (N,N-dimethyl formamide) solutions of the polymer were UV-irradiated to induce intramacromolecular photo-crosslinking reaction under degassed conditions. Decrease in anthryl moiety based on photo-dimerization between anthryl moieties during the UV-irradiation was evaluated from the change in absorption spectra. Change in the dimensions of the polymer coil induced by the reaction was studied by GPC. Parameters for polymer chain dynamics were studied in the course of the intramacromolecular crosslinking reaction resulting in shrinkage of the polymer coil. The time-conversion curve of the photodimerization between anthryl moieties showed that the photo-crosslinking reaction consists of two stages. The mobility of polymer chain segments decreased gradually in the initial stage and deceases rapidly in the later stage. Radius of gyration of the polymer coil and the rotational mobility of side chain decreased rapidly only in the later stage. Three possible models for the reaction are discussed in order to explain the results. The short range reaction model is most suitable model for the intramacromolecular crosslinking reaction. In the initial stage crosslinks are formed between nearest-neighbor side chains; in the later stage shrinkage of the polymer coil occurs due to formation of crosslinks between far-apart side chains which remained unreacted in the initial stage.

Fluorescence Study on Dynamics and Structure of Polymer Chain II. Dependence of Intra-macromolecular Photo-crosslinking Reaction of Polymers with Anthryl and Eosinyl Moieties on Number of Crosslinkable Side Chains

“…Benzyl 9-anthracenecarboxylate (BA) as the model compound for the photo-crosslinkable anthryl side chain and 2' ,4' ,5', 7'-tetrabromofluorescein benzylester sodiumsalt (benzyl eosinate) as the model compound for the eosinyl side chain as the emissive probe were prepared as previously reported. 14 Figure 1 represents the chemical structures of the sample polymers and the model compounds.…”

“…The intensity of irradiation light, I 0 , was determined as 2.9 x 10-7 einstein · s -l cm -z. Spectroscopic and GPC measurements were carried out as reported previously. 14 All obtained data were stored and analyzed by a personal computer (NEC PC-9801) with program softwares prepared at our laboratory.…”

“…14 The second-order plot for the photo-dimerization of benzyl 9-anthracenecarboxylate (BA), on the assumption of proportionality of the concentration of excited state BA to that of ground state BA, failed to give a straight line because of the large absorbance.…”

“…Since the photo-dimerization of anthryl moiety, used in our work, proceeds via a sandwich excimer state within a very short lifetime ( < 20 ns ), the photo-dimerization reaction is also a diffusion-controlled reaction. In the previous work, 14 a photo-crosslinkable polymer containing anthryl and eosinyl moieties was synthesized and we discussed intra-macromolecular photo-crosslinking reactions on the basis of dimensions and dynamics of the polymer chain. The emission probe method was used since it can be regarded as the best tool for characterizing the mobility and dynamical aspects of the polymer chains in the course of such photo-reactions.…”

“…The emission probe method was used since it can be regarded as the best tool for characterizing the mobility and dynamical aspects of the polymer chains in the course of such photo-reactions. 15 In the previous work, 14 we found out that the intramacromolecular photo-crosslinking reaction of the polymer was divided into two stages from the view points of changes in dimensions and dynamics of the polymer chain. However the effect of the density of crosslinkable side chains on the reaction kinetics was not clear.…”