基于水杨醛席夫碱锌配合物交联稳定化荧光聚合物胶束的合成及其对铜离子的荧光响应性

以S-十二烷基-S'-(α,α'-二甲基-α″-乙酸)-三硫代碳酸酯(DMAT)为链转移剂、2-羟基-5-乙烯基苯甲醛(HVB)为单体,利用可逆加成-断裂链转移自由基聚合法(RAFT)合成结构明确、数均相对分子质量可控的水杨醛聚合物(PHVB)。将PHVB直接地与单端胺基功能化聚乙二醇(m PEG-NH2)按n(—NH2group)/n(—CHO group)=0.50投料进行醛-胺缩合反应,获得接枝率为50%的两亲性接枝水杨醛席夫碱聚合物PHVB-graft-PEG。采用凝胶渗透色谱仪(GPC)和核磁共振氢谱(1H NMR)对合成的聚合物的数均相对分子质量和结构进行了确证。将PHVB-graft-PEG直接地分散于无水乙醇中,自组装形成以聚乙烯水杨醛席夫碱为核、聚乙二醇为壳的胶束,然后以所得胶束为微反应器,与Zn(OAc)2进行配位反应得到外壳为可溶性链段PEG,内核为发光水杨醛席夫碱锌配合物的PHVB-graft-PEG/Zn~(2+)交联稳定化胶束。通过紫外-可见分光光谱(UV-Vis)、荧光发射光谱(FLL)、动态光散射(DLS)和透射电子显微镜(TEM)分别对胶束的交联稳定化过程进行了表征。研究结果表明,经交联稳定化后,PHVB-graft-PEG/Zn~(2+)胶束在干燥后仍可在水和常见有机溶剂中再分散形成粒径大小约为100 nm、在约460 nm处发射出蓝光荧光的纳米粒子,并且可作为荧光传感器,在水溶液中对Cu~(2+)离子进行选择性识别,其荧光淬灭率与Cu~(2+)离子浓度(0~50μmol/L范围内)呈线性关系,最低检测下限至0.5μmol/L,而其它共存离子如Cd~(2+)、Mg~(2+)、Ni~(2+)、Pb~(2+)、Ca~(2+)、Hg~(2+)、Al3+、Mn~(2+)等对Cu~(2+)离子的荧光响应性没有干扰,即可实现对Cu~(2+)离子进行定量检测。

Synthesis of Fluorescent Cross-linked Stabilized Polymeric Micelles Based on Salicylidene Schiff Base/Zn2+ Complexes and Sensor for Cu2+ Detection

A well-defined polymer with pendant salicylaldehyde groups(PHVB) was achieved by reversible addition-fragmentation chain transfer(RAFT) polymerization with S-1-dodecyl-S'-(α,α'-dimethyl-α″-acetic acid) trithiocarbonate as the RAFT agent and a salicylaldehyde-functionalized vinyl monomer, 2-hydroxy-5-vinylbenzaldehyde(HVB) in THF at 65 ℃. The resulting well-defined polymer with pendant salicylaldehyde groups can react directly with monoamine-terminated PEG(PEG-NH₂, number-average relative molecular mass 2000 g/mL, 0.5 stoichiometric number of the —CHO group in PolyHVB) to afford an amphiphilic graft copolymer bearing a pendant salicylidene Schiff base PHVB-graft-PEG with 50% grafting density. These new polymers were characterized by GPC and ¹HNMR. Owing to the presence of hydrophilic PEG pendants, PHVB-graft-PEG is capable of self-assembling into nano-sized micelles with salicylidene Schiff base functioned cores, PEG coronas in ethanol. Coordination of the pre-assembled PHVB-graft-PEG micelles with Zn(OAc)₂ will endow the polymeric micelles with fluorescence features, and simultaneously the resulting luminescent micelles may be stabilized by ionic cross-linking in consequence of the complex reaction at the core. Thus, the luminescence properties and form of the obtained micelles were investigated by UV-Vis spectra(UV-Vis), fluorescence spectra(FLL), dynamic light scattering(DLS), transmission electron microscopy(TEM) .After removing ethanol by drying, the resultant Zn²⁺ coordinated particles can be re-dispersed readily in water or common organic solvent to form a micellar solution, which display blue fluorescence with maximum emission peak around 460 nm, indicating the same aggregate size(nearly 100 nm) as before re-dispersion. The obtained luminescent nanoparticles can be used as a highly selective fluorescent probe for Cu²⁺ ion over other metal ions such as Cd^{2 +}, Mg²⁺, Ni²⁺, Pb²⁺, Ca²⁺, Hg²⁺, Al³⁺, Mn²⁺ in aqueous solution, and exhibit a linear range of 0~50 μmol/L and detection limit of 0.05 μmol/L Cu²⁺, respectively.