以超支化聚乙烯亚胺为构筑基元、以卤键为推动力制备了可以选择性吸附带有负电荷小分子的层层组装多层膜. 为了将超支化聚乙烯亚胺引入多层膜体系中, 我们首先制备了接枝有卤键给体分子-碘全氟苯的超支化聚乙烯亚胺(BPEI-I). 然后将BPEI-I和含有卤键受体的聚(4-乙烯吡啶)(PVPy)在四氢呋喃和三氯甲烷的混合溶剂中组装成膜, 并用紫外可见光谱、AFM和XPS对膜的组装过程、形貌、厚度和推动力进行了表征. 制备得到的BPEI-I和PVPy多层膜可以吸附含有负电荷的2-蒽甲酸钠小分子, 而对有类似结构但带有正电荷的溴化-N-(2-蒽甲基)吡啶盐却没有吸附作用. 这种选择性吸附能力主要得益于包覆在多层膜中的超支化聚乙烯亚胺基元的正电荷空腔和由卤键构筑的弱极性微环境. 本文的研究为制备选择性吸附薄膜提供了一种新的思路, 在传感、富集分离和微接触印刷等领域都有潜在应用价值.

A multilayer film that could selectively adsorb negatively charged molecules through layer-by-layer assembly of modified hyperbranched poly(ethylene imine) (BPEI) and poly(vinyl pyridine) (PVPy) via halogen bonding has been fabricated. To build up the film via halogen bonding, the BPEI modified with a donor of halogen bonding (BPEI-I) was firstly prepared by introducing the iodo-tetrafluorophenoxy group into the BPEI through a series of reactions. The BPEI-I was purified by dialysis and precipitation and the structure was determined by ¹H NMR. The BPEI-I could be layer-by-layer assembled with PVPy in the mixture solvents of tetrahydrofuran and chloroform. The UV-Vis spectrum was used to monitor the assembly process, which indicated that the assembly process was uniform. AFM was employed to observe the morphology and estimate the thickness of the resulting films, both of which confirmed the successful fabrication of the BPEI-I and PVPy multilayer. The driving force of the assembly was verified by XPS. The variation of the bonding energy of the N 1s and I 3d in the multilayer proved the halogen bonding between BPEI-I and PVPy. To demonstrate the selective adsorption, sodium anthracene-2-carboxylate (SAC) and 1-(anthracen-2-ylmethyl)pyridin-1-ium bromide (APB) was utilized as the probes, which resembled in the structure whereas had opposite charges. The adsorption was studied by UV-Vis spectra, which exhibited that the negatively charged SAC could be adsorbed by the BPEI-I/PVPy films, but the positively charged APB could not. In order to improve the stability of the film, as-prepared BPEI-I/PVPy films were further crosslinked by 1,3-dibromopropane. The resulting film still could selectively adsorb the small molecule with negative charge and moreover possessed higher stability. The ability of the BPEI-I/PVPy film to selectively adsorb negatively charged molecules could be attributed to halogen bonding, which provided the neutral environments, and the BPEI units, which offered the positive charged cavity to contain the objects. Such multilayer films could be potentially useful in the fields of biosensor, separation and micro-contact printing.