Kroeger Anja, Li Xingfu, Eisenberg Adi
Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 2K6, Canada.
Langmuir. 2007 Oct 9;23(21):10732-40. doi: 10.1021/la701334r. Epub 2007 Sep 7.
The water content-dependent supramolecular structure formation of polystyrene-block-poly(acrylic acid) (PS-b-PAA) copolymer in the presence of a fourth-generation amine-terminated poly(amido amine) dendrimer (PAMAM) is investigated by dynamic light scattering, turbidity measurements, and transmission electron microscopy. The solvent system for this study is a mixture of dioxane/THF and water. A very complex turbidity profile is observed with increasing water content in the system and is explained by the presence of various aggregated structures based on strong interactions between the amine-containing dendrimers and the poly(acrylic acid) blocks of the polymer. The onset of the self-assembly of single chains of PS-b-PAA (primary structure) into single and multiple dendrimer core inverse micelles (secondary structure) is detected as very low water contents of cw < 2% wt (cwc). These micelles consist of dendrimers coated with PAA blocks, which are connected to the corresponding PS chains that form the corona. Further addition of water leads to an association of these micelles into compound multiple dendrimer core inverse micelles (tertiary structure) in the range of cw = approximately 6 to approximately 10% wt. At still higher water content, some of the acrylic acid chains of the block copolymer move from the vicinity of the dendrimer to the outside of the aggregates, resulting in a decrease in the size of the formed structures and the acquisition of progressively increasing hydrophilic character of the aggregates. Multiple dendrimer core inverse onion micelles are formed, which agglomerate into compound multiple dendrimer core inverse onion micelles at cw = approximately 12 to approximately 18% wt. Above this water content, vesicular structures are formed. The complexity is unusual for block copolymer systems and illustrates the importance of strong interactions in structure formation.
通过动态光散射、浊度测量和透射电子显微镜研究了在第四代胺端基聚（酰胺胺）树枝状大分子（PAMAM）存在下，聚苯乙烯 - 嵌段 - 聚（丙烯酸）（PS - b - PAA）共聚物的水含量依赖性超分子结构形成。本研究的溶剂体系是二氧六环/四氢呋喃和水的混合物。随着体系中水含量的增加，观察到非常复杂的浊度曲线，这可以通过基于含胺树枝状大分子与聚合物的聚（丙烯酸）嵌段之间的强相互作用而存在的各种聚集结构来解释。当水含量cw < 2% wt（cwc）非常低时，检测到PS - b - PAA单链（一级结构）自组装成单个和多个树枝状大分子核心反胶束（二级结构）。这些胶束由涂覆有PAA嵌段的树枝状大分子组成，这些PAA嵌段连接到形成冠层的相应PS链上。进一步加水会导致这些胶束在cw = 约6%至约10% wt范围内缔合形成复合多个树枝状大分子核心反胶束（三级结构）。在更高的水含量下，嵌段共聚物的一些丙烯酸链从树枝状大分子附近移动到聚集体外部，导致形成的结构尺寸减小，并使聚集体的亲水性逐渐增加。形成了多个树枝状大分子核心反洋葱状胶束，它们在cw = 约12%至约18% wt时聚集成复合多个树枝状大分子核心反洋葱状胶束。高于此水含量时，形成囊泡结构。这种复杂性在嵌段共聚物体系中是不寻常的，说明了强相互作用在结构形成中的重要性。
