Luminescent Polymers Containing Unconventional Chromophores

發光聚合物一般是由具有大π電子系統的共軛基元作為發光單元,通過共價鍵連接而成的高分子.近年來,研究者發現:另一類僅含有脂肪胺、羰基、酯基、酰胺等傳統意義上的助色團的聚合物在適當條件下也能發射強的熒光.樹枝狀聚酰胺胺(PAMAM)和超支化聚酰胺胺(hb-PAMAM)是最早和最廣泛被研究的含非典型性熒光生色團的聚合物.最近,這類聚合物被擴展到含有叔胺基元的聚氨酯、聚醚酰胺、聚脲體系.這些體系的生色團被認定為其結構中的叔胺基元,叔胺的氧化是熒光產生的根源.同時,也有文獻報道馬來酸酐與醋酸乙烯酯交替共聚物、異丁烯與順丁烯二酸酐共聚物、聚多糖動態高分子、聚酰腙以及通過RAFT試劑制備的含聚三硫碳酸酯的多嵌段共聚物等也可以發射熒光.這些聚合物的一個共同特點是結構中不含叔胺基元,而僅含羰基和酯基,其發光機理通常用多個羰基聚集效應或羰基和苯環之間的相互作用來解釋. Luminescent polymers are referred to as conjugated polymers, which are constructed by pi-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.