PRES LUNAM, Université du Maine, IMMM UMR CNRS 6283, Département PCI, Avenue Olivier Messiaen, 72085 Le Mans Cedex 09, France.
J Phys Chem B. 2012 Jun 28;116(25):7560-5. doi: 10.1021/jp3012377. Epub 2012 Jun 14.
The ionization behavior of an amphiphilic diblock copolymer poly(n-butyl acrylate(50%)-stat-acrylic acid(50%))(100)-block-poly(acrylic acid)(100) (P(nBA(50%)-stat-AA(50%))(100)-b-PAA(100), DH50) and of its equivalent triblock copolymer P(nBA(50%)-stat-AA(50%))(100)-b-PAA(200)-b-P(nBA(50%)-stat-AA(50%))(100) (TH50) were studied by potentiometric titration either in pure water or in 0.5 M NaCl. These polymers consist of a hydrophilic acidic block (PAA) connected to a hydrophobic block, P(nBA(50%)-stat-AA(50%))(100), whose hydrophobic character has been mitigated by copolymerization with hydrophilic units. We show that all AA units, even those in the hydrophobic block could be ionized. However, the AA units within the hydrophobic block were less acidic than those in the hydrophilic block, resulting in the preferential ionization of the latter block. The preferential ionization of PAA over that of P(nBA(50%)-stat-AA(50%))(100) was stronger at higher ionic strength. Remarkably, the covalent bonds between the PAA and P(nBA(50%)-stat-AA(50%))(100) blocks in the diblock or the triblock did not affect the ionization of each block, although the self-association of the block copolymers into spherical aggregates modified the environment of the PAA blocks compared to when PAA was molecularly dispersed.
两亲性嵌段共聚物聚（n- 丁基丙烯酰胺（50%）- 嵌段- 丙烯酸（50%））（100）- 嵌段- 聚（丙烯酸）（100）（P（nBA（50%）-stat-AA（50%））（100）-b-PAA（100），DH50）及其等摩尔的三嵌段共聚物聚（n- 丁基丙烯酰胺（50%）- 嵌段- 丙烯酸（50%））（100）-b-PAA（200）-b- 聚（n- 丁基丙烯酰胺（50%）- 嵌段- 丙烯酸（50%））（100）（TH50）在纯水中或 0.5 M NaCl 中通过电位滴定法研究了其离子化行为。这些聚合物由亲水酸性嵌段（PAA）与疏水性嵌段 P（nBA（50%）-stat-AA（50%））（100）连接而成，后者的疏水性通过与亲水性单元共聚而得到缓解。我们表明，所有 AA 单元，即使是在疏水性嵌段中的 AA 单元，都可以离子化。然而，在疏水性嵌段中的 AA 单元的酸性比在亲水性嵌段中的酸性低，导致后者的优先离子化。在较高的离子强度下，PAA 相对于 P（nBA（50%）-stat-AA（50%））（100）的优先离子化更强。值得注意的是，嵌段共聚物中二嵌段或三嵌段中 PAA 与 P（nBA（50%）-stat-AA（50%））（100）之间的共价键并未影响每个嵌段的离子化，尽管嵌段共聚物自组装成球形聚集体会改变 PAA 嵌段的环境，与 PAA 分子分散时相比。
