Araya-Hermosilla Esteban, Catalán-Toledo José, Muñoz-Suescun Fabián, Oyarzun-Ampuero Felipe, Raffa Patrizio, Polgar Lorenzo Massimo, Picchioni Francesco, Moreno-Villoslada Ignacio
Department of Chemical Engineering-Product Technology, University of Groningen , Nijenborgh 4, NL-9747 AG Groningen, The Netherlands.
Instituto de Ciencias Químicas, Facultad de Ciencias, Universidad Austral de Chile , Casilla 567, 5090000 Valdivia, Chile.
J Phys Chem B. 2018 Feb 8;122(5):1747-1755. doi: 10.1021/acs.jpcb.7b11254. Epub 2018 Jan 29.
Amphiphilic aromatic polymers have been synthesized by grafting aliphatic polyketones with 4-(aminomethyl)benzoic acid at different molar ratios via the Paal-Knorr reaction. The resulting polymers, showing diketone conversion degree of 16%, 37%, 53%, and 69%, have been complexed with the redox-active 2,3,5-triphenyl-2H-tetrazolium chloride, a precursor molecule with which aromatic-aromatic interactions are held. Upon addition of ascorbic acid to the complexes, in situ reduction of the tetrazolium salt produced 1,3,5-triphenylformazan nanoparticles stabilized by the amphiphilic polymers. The stabilized nanoparticles display highly negative zeta potential [-(35-70) mV] and hydrodynamic diameters in the submicron range (100-400 nm). Nonaromatic polyelectrolytes or hydrophilic aromatic copolymers showing low linear aromatic density and high linear charge density such as acrylate/maleate and sulfonate/maleate-containing polymers were unable to stabilize formazan nanoparticles synthesized by the same method. The copolymers studied here bear uncharged nonaromatic comonomers (unreacted diketone units) as well as charged aromatic comonomers, which furnish amphiphilia. Thus, the linear aromatic density and the maximum linear charge density have the same value for each copolymer, and the hydrophilic/hydrophobic balance varies with the diketone conversion degree. The amphiphilia of the copolymers allows the stabilization of the nanoparticles, even with the copolymers showing a low linear aromatic density. The method of nanoparticle synthesis constitutes a simple, cheap, and green method for the production of switchable totally organic, redox-active, pH-sensitive nanoparticles that can be reversibly turned into macroprecipitates upon pH changing.
通过Paal-Knorr反应，以不同摩尔比将4-(氨甲基)苯甲酸接枝到脂肪族聚酮上，合成了两亲性芳香族聚合物。所得聚合物的二酮转化率分别为16%、37%、53%和69%，它们与氧化还原活性的2,3,5-三苯基-2H-四唑氯化物络合，该前体分子可形成芳香-芳香相互作用。向络合物中加入抗坏血酸后，四唑盐原位还原生成了由两亲性聚合物稳定的1,3,5-三苯基甲臜纳米颗粒。稳定后的纳米颗粒显示出高度负的zeta电位[-(35-70) mV]，流体动力学直径在亚微米范围内(100-400 nm)。非芳香族聚电解质或亲水性芳香族共聚物，如含丙烯酸酯/马来酸酯和磺酸盐/马来酸酯的聚合物，其线性芳香密度低且线性电荷密度高，无法稳定通过相同方法合成的甲臜纳米颗粒。本文研究的共聚物含有不带电的非芳香族共聚单体(未反应的二酮单元)以及带电芳香族共聚单体，从而提供两亲性。因此，每种共聚物的线性芳香密度和最大线性电荷密度具有相同的值，亲水/疏水平衡随二酮转化率而变化。共聚物的两亲性使得纳米颗粒得以稳定，即使是线性芳香密度较低的共聚物。纳米颗粒的合成方法是一种简单、廉价且绿色的方法，用于生产可切换的全有机、氧化还原活性、pH敏感的纳米颗粒，这些纳米颗粒在pH变化时可可逆地转变为大沉淀物。
