Unprecedented Blue Intrinsic Photoluminescence from Hyperbranched and Linear Polyethylenimines: Polymer Architectures and pH‐Effects

Abstract

The intrinsic photoluminescence properties of hyperbranched polyethylenimines (PEIs) and their linear counterpart (LPEIs) have been studied in absence of any classical fluorescent probes. The comparison of the inherent fluorescence emission between hyperbranched polyethylenimines and their linear analogues demonstrates that linear polyamines are capable of producing strong intrinsic photoluminescence species having long excited lifetimes without need of having a tridimensional‐branched structure. The creation of inherently fluorescent polymeric centers from hyperbranched and linear polyethyleimines can be modulated by specific chemical modification and oxidation of amine groups as well as by adjusting the acidity of the polymer.magnified image

Fluorescence Investigations of Oxygen‐Doped Simple Amine Compared with Fluorescent PAMAM Dendrimer

“…However, in addition to PAMAM dendrimers with different endgroups, [2,5] the authors' group [5,7] reported that commercially-available poly(propyleneimine) (PPI) dendrimer and synthesized poly(ethyleneimine) (PEI) dendrimer, containing only alkyl amine units in the dendritic structure, can also emit a blue fluorescence after similar air treatment. Although some reports indicated a pH dependency, such that acidic conditions lead to a higher emission intensity than basic conditions, [2,5,6] the photoluminescence of polysiloxane coated by PAMAM dendron side chains was intensified in crowded circumstances under alkaline condition, rather than in less-crowded circumstances under acidic conditions. [4] These results imply that the more rigid, crowded dendritic structure -attributed to the interior tertiary amines -exhibits a higher fluorescence yield.…”

Luminescent Polymers Containing Unconventional Chromophores

“…Cao 等 [7] 采用二乙基三胺 与丙烯酸甲酯在不同配料比下进行反应, 获得一系列 [9] . 证明脂肪胺中的胺基是发光活性中心的更直接证 据来自 2007 年西班牙巴伦西亚大学 Stiriba 课题组 [10] 对 超支化聚乙二胺(hb-PEIs)和线性聚乙二胺(l-PEIs)发光 行为的研究. 他们比较了两种超支化聚合物和两种线性 聚合物, 分别是 hb-PEIs、 l-PEI 和端基甲基化的 图 3 用三脂肪胺作模型分子研究树枝状 PAMAM 的荧光的示意图, 树枝状大分子内部的叔胺分支点被确定为发光中心 [8] Figure 3 An illustration of the fluorescence of dentritic PAMAM using aliphatic tertiary amine as a model compound, and the N-branch points of tertiary amines inside the dentrimer are assigned to emitting centers [8] hb…”

“…Chemical structure and photoluminescence properties of the hyperbranched polyethylenimine and their linear counterpart [10] 尽管 PAMAM 发光的机理一直存在争议, 但是改善…”

Stimulus responsive fluorescent hyperbranched polymers and their applications

“…Consequently, they concluded that a compacted and crowded structure could strengthen the fluorescence of dendritic polymers. Stiriba and coworkers [79] reported a similar hyperbranched PEI to hb-P12 but end-capped with methyl groups. The PL intensity measured in methanol is also heavily pH-dependent while the difference is that the intensity of the polymer increases from  f = 0.02 to 0.1 when pH is lowered from 11 to 2, with longer from 5.3 to 8.4 ns of emission lifetime.…”