Synthesis, characterization, and fluorescence of pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymer with pentaerythritol core

Novel and well‐defined pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymers were successfully achieved by combination of esterification, atom transfer radical polymerization (ATRP), divergent reaction, ring‐opening polymerization (ROP), and coupling reaction on the basis of pentaerythritol. The reaction of pentaerythritol with 2‐bromopropionyl bromide permitted ATRP of styrene (St) to form four‐arm star‐shaped polymer (PSt‐Br) 4 . The molecular weights of these polymers could be adjusted by the variation of monomer conversion. Eight‐hydroxyl star‐shaped polymer (PSt‐(OH) 2 ) 4 was produced by the divergent reaction of (PSt‐Br) 4 with diethanolamine. (PSt‐(OH) 2 ) 4 was used as the initiator for ROP of ε‐caprolactone (CL) to produce eight‐arm star‐shaped dendrimer‐like copolymer (PSt‐ b ‐(PCL) 2 ) 4 . The molecular weights of (PSt‐ b ‐(PCL) 2 ) 4 increased linearly with the increase of monomer. After the coupling reaction of hydroxyl‐terminated (PSt‐ b ‐(PCL) 2 ) 4 with 1‐pyrenebutyric acid, pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymer (PSt‐ b ‐(PCL‐pyrene) 2 ) 4 was obtained. The eight‐arm star‐shaped dendrimer‐like copolymers presented unique thermal properties and crystalline morphologies, which were different from those of linear poly(ε‐caprolactone) (PCL). Fluorescence analysis indicated that (PSt‐ b ‐(PCL‐pyrene) 2 ) 4 presented slightly stronger fluorescence intensity than 1‐pyrenebutyric acid when the pyrene concentration of them was the same. The obtained pyrene‐containing eight‐arm star‐shaped dendrimer‐like copolymer has potential applications in biological fluorescent probe, photodynamic therapy, and optoelectronic devices.