2. The strategies to incorporate AIE molecules into polymers by RDRP.

By exploiting the versatility of RDRP, AIE molecules can be facilely incorporated into the final polymer product through multiple ways to ultimately synthesize AIE-active polymers; block copolymer containing separate blocks of non-AIE monomers and AIE monomers (Scheme 1A ), surface-grafted block copolymer (Scheme 1B ), AIE monomers as crosslinkers for two block copolymers (Scheme 1C ), AIE moieties as pendent groups in block copolymer (Scheme 1D ), hyperbranched with random distribution of AIE monomers linked by non-AIE monomer backbone (Scheme 1E ), four-arm star polymer with AIE moiety as the central core (Scheme 1F ), end-functionalized AIE moiety chain extended with non-AIE monomers (Scheme 1G ), direct linkage of AIE monomers (Scheme 1H ), and unusual AIE behavior of non-AIE monomers after surface-grafted direct linkage (Scheme 1I ).
Many different combinations of monomers, initiators, linkers, and catalysts type and amount were discovered and experimented to synthesize AIE polymers since the advent of AIE discovery. A few of the more interesting reaction types as examples are listed in Table 1that incorporate AIE characteristics into the final polymeric product.
For the reaction types categorized as “RAFT” above, AIBN is typically used as the standard initiator and includes one type of RAFT agent as the chain transfer agent (CTA). Most of the polymerization reactions listed are considered to be multi-component reactions (MCRs) where more than one type of monomer is involved. For example, Entry 1 – Entry 4 (Table 1 ) involves three different monomers and is considered a random copolymer reaction, where Entry 4 shows a special case of one of the monomer block (PEG) coupled to the RAFT agent to form a macro-CTA. Entry 5 and Entry 6(Table 1 ) are considered a four-component and two-component reaction respectively. Entry 1 – Entry 6 (Table 1 ) are classified as block copolymers containing AIE monomers (Scheme 1A ). A two-component surface-initiated reaction with the RAFT agent anchored onto a solid surface (Entry 7 ,Table 1 ) allows for rapid functionalization through surface-grafted block copolymers of non-AIE and AIE monomers (Scheme 1B ). Further expansion of this concept enabled the successful synthesis of a hyperbranched polymer variant using a non-AIE vinyl-functionalized diamide as a cross-linking backbone (Entry 8, Table 1 ) to incorporate the AIE monomers as pendent groups randomly distributed across the entire polymer molecule (Scheme 1E ). Functionalization of symmetrical AIE monomers with vinyl bonds imparts cross-linking capabilities in a two-component reaction (Entry 9and Entry 10, Table 1 ) to crosslink two block copolymers made up of the other non-AIE monomer (Scheme 1C ). Similar to a hyperbranched polymer mentioned before, the incorporation of an AIE monomer as a pendent group in an MCR (Entry 11, Table 1 ) also endows the block copolymer with AIE properties (Scheme 1D ).
For all reaction types categorized as “ATRP” above, most of the examples uses AIE molecule-functionalized macro-initiator to produce the final polymeric product possessing AIE characteristics. For example, ATRP initiator core-functionalized with AIE moiety (Entry 12and Entry 13, Table 1 ) generates four-arm star polymer after polymerizing with non-AIE monomers endows it with unique AIE fluorescence properties (Scheme 1F ). Another popular choice for incorporating AIE groups into polymers is through end-functionalized AIE moieties (Entry 14 – 19, Table 1 ) with subsequent chain extension using non-AIE monomers (Scheme 1G ). Polymerizing directly vinyl-functionalized AIE monomers (Entry 20, Table 1 ) provides ease in handling the reaction via direct linkages of the AIE monomers (Scheme 1H ). Surface-initiated ATRP of AIE-inactive acrylonitrile monomers (Entry 21, Table 1 ) yielded unusual AIE fluorescence behavior in the final product without presence of any phenyl groups or aromatic rings (Scheme 1I ).
For all reaction types categorized as “Others” above, although Cu(0) polymerizations bear similarities to ATRP, they use different oxidation states of Cu and are considered different to ATRP. Similar toEntry 1 , AIE monomers are attached to the polymeric product through ionic bonding with N -containing non-AIE monomers as backbone (Entry 22, Table 1 ) to form block copolymers with the AIE moieties as pendent groups (Scheme 1D ). Similar toEntry 20 , unique designs of AIE monomers are polymerized separately (Entry 23, Table 1 ) through direct linkages (Scheme 1G ). Similar to Entry 1 – 6 , complex AIE active monomers functionalized with vinyl bonds (Entry 24, Table 1 ) allows for direct block copolymer synthesis of the AIE monomers separately (Scheme 1A ). Similar to Entry 14 – 19 , AIE end-functionalized polymers (Entry 25 and Entry 26, Table 1 ) are produced through polymerizing with non-AIE monomers (Scheme 1G ).