{'fraction_non_alphanumeric': 0.015863689776733254, 'fraction_numerical': 0.0, 'mean_word_length': 5.426415094339623, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
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

A photo-crosslinkable polymer with pendant anthryl and eosinyl moieties 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.