Multicolor emission of nonaromatic linear polysiloxanes based on local conjugation chains

Nonaromatic luminophores with aggregation-induced emission and multicolor emission have drawn great attention; however, a linear polymer with multicolor emission remains a huge challenge. Herein, two kinds of linear polysiloxanes (LPSi-1 and LPSi-2) were obtained through a one-pot transesterification method. Surprisingly, both LPSi-1 and LPSi-2 can emit multicolor fluorescence by altering the excitation wavelengths. In particular, LPSi-1 exhibited strong multicolor fluorescence from blue, cyan, green to red. Theoretical calculations and transmission electron microscopy unraveled that the phenomenon can be attributed to the local conjugation chain formed by silicon-oxygen (Si-O) bond linking carbonyl (C 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 O) and vinyl (C C) groups. Interestingly, the longer the local conjugation in the main chain is, the more conducive to its multicolor fluorescence. So, a new emission mechanism, namely “local conjugation enhanced multicolor emission” can be proposed. Moreover, LPSi-1 also exhibited multiple stimuli-responsive properties towards Fe³⁺, pH and organic solvents with different polarities. This work offers a new strategy to design and synthesise nonaromatic linear polymers with multicolor emission.