Dendritic effects on photophysical and fluorescence properties of coumarin functionalized dendrigraft polybutadiene

A series of multicoumarin-functionalized dendrigraft polybutadienes with linear-comb or star-comb topology were synthesized from generation 0 to 3 (LGn and SGn respectively, n = 0–3) to investigate the dendritic effects on photophysical and fluorescence properties. From the results of SEC-TALLS, SEC and ubbelohde viscometer, the polymer architecture converted from one- or two-dimensional structure to a flexible branched structure, then advanced into a compact structure; meanwhile, the LGn exhibited a relatively looser structure than its SGn analog did. Hypsochromic shifts of the absorption and emission maxima, as well as signal amplifications were observed for both LG3 and SG3, suggesting that encapsulation effect occurred at the third generation resulting from the compact architecture. The fluorescence quantum yield (ΦF) was in the order of LG1 (8.1%) > SG1 (6.4%) > LG2 (5.0%) > SG2 (4.6%) > LG3 (2.3%) > SG3 (2.0%) > SG0 (1.1%) > LG0 (0.7%), indicating that the flexible branched polymer matrix could enhance the fluorescence properties due to the synergistic combination of inter-/intra-molecular fluorescence quenching. Also, the fluorescence properties of polymer with linear-comb architecture were always better than those of star-comb counterpart due to its looser architecture.