The AIEE effect and two-photon absorption (TPA) enhancement induced by polymerization: synthesis of a monomer with ICT and AIE effects and its homopolymer by ATRP and a study of their photophysical properties

A monomer including pyrazoline and l,8-naphthalimide moieties and its homopolymer were prepared by atom transfer radical polymerization (ATRP). The emission of the monomer can be tuned by choosing solvents with different polarities or aggregation-induced emission (AIE). The rotation of the fluorophore of the homopolymer was further limited by both the side chain and the flexible main chain, resulting in emission enhancement in strong polar solution and aggregation-induced emission enhancement (AIEE) characteristics. More interestingly, compared to that of the monomer, the two-photon absorption (TPA) property of the homopolymer is much more enhanced both in toluene and aggregates. This is attributed to the amplification effect of the polymer chain. This may become a new and promising method with which to prepare TPA polymers.