Luminescent Polymers Containing Unconventional Chromophores

Abstract

Luminescent polymers are referred to as conjugated polymers, which are constructed by π-aromatic building blocks functioning as emitting units. But in recent years, it has been found that a few kinds of polymers only containing auxochromophores or unconventional chromophores such as aliphatic tertiary amine, carbonyl, ester, and amide demonstrate strong luminescence under proper conditions. Poly(amido amine) (PAMAM) dendrimers and hyperbranched poly(amido amine)s are the first reported and most investigated luminescent polymers containing unconventional chromophores. Lately, this kind of polymers have been extended to hyperbranched poly(amino ester)s (hb-PAEs), hyperbranched poly(ether amide)s (hb-PEAs), and polyurea dendrimers (PUREs) containing tertiary amine moieties. The luminogen of PAMAMs, hb-PAEs, hb-PEAs and PUREs is associated with the N-branched tertiary amine moiety and the oxidation of the tertiary amine is assigned to the emitting source. Meanwhile, some distinct polymers had been also reported to be luminescent. Poly[(maleic anhydride)-alt-(vinyl acetate)], polyisobutene succinic anhydrides, glycodynamer analogues of poly(acrylhydrazone)s and multiblock polymer derived by poly(trithiocarbonate) mediated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropyl-acrylamide. A common feature of these polymers is that only carbonyl and ester groups rather than tertiary amine are involved in the polymer structure. Aggregation of multiple carbonyl groups induced emission is usually adopted to explain the mechanism of the emission, and the interaction between carbonyl and phenyl groups was also used to explain the unconventional emission.

Aggregate Science: From Structures to Properties

“…In the aggregate state, however, through-space conjugation such as n→σ*, n→π*, π→π*, metal-metal, and metal-ligand interaction exists, which serves as the chromophores of clusteroluminescence. [198,[211][212][213][214][215][216] Noteworthily, these clusteroluminogens, especially nonconjugated polymeric ones, have demonstrated good biocompatibility, which is advantageous for their biological applications. [217,218] Thanks to the abundant n→π* interaction, room-temperature phosphorescence was observed occasionally in clusteroluminogens but its generation relied heavily on the morphology and ambient environment.…”

Nonconventional macromolecular luminogens with aggregation‐induced emission characteristics

“…Conventional luminogens normally contain bulky aromatic or conjugated units with remarkable conjugation in individual molecules, which ensure them emissive . Besides these traditional luminogens, more recently, the observation of intrinsic photoluminescence (PL) from nonconventional luminogens in absence of any type of proverbial chromophores, some even free of any (hetero)cyclic aromatic building blocks has been reported . Among these emerging luminophors, nonconjugated polymers with chain flexibility and structure tunability have aroused great interests because of their significant fundamental importance and promising technical applications .…”

Unexpected fluorescence from polymers containing dithio/amino-succinimides

“…4 Typically, fluorescent polymers are either intrinsically fluorescent or prepared by functionalizing with fluorophores, which usually possess conjugated structures. 6 For instance, the emission mechanism of poly(amido amine) (PAMAM) has been extensively studied in the last decade. 6 For instance, the emission mechanism of poly(amido amine) (PAMAM) has been extensively studied in the last decade.…”