Jemili Nouha, Fauquignon Martin, Grau Etienne, Fatin-Rouge Nicolas, Dole François, Chapel Jean-Paul, Essafi Wafa, Schatz Christophe
Laboratoire Matériaux, Traitement et Analyse, Institut National de Recherche et d'Analyse Physico-Chimique, Pôle Technologique de Sidi Thabet, 2020 Sidi Thabet, Tunisia.
Université de Tunis El Manar, Faculté des Sciences de Tunis, 2092 Tunis, Tunisia.
Polymers (Basel). 2022 Jun 14;14(12):2404. doi: 10.3390/polym14122404.
In this work the electrostatic complexation of two strong polyelectrolytes (PEs) was studied, the hydrophilic and positively charged poly (diallyldimethylammonium chloride) (PDADMAC) and the hydrophobic and negatively charged poly (styrene-co-sodium styrene sulfonate) (P(St-co-SSNa)), which was prepared at different sulfonation rates. The latter is known to adopt a pearl necklace conformation in solution for intermediate sulfonation rates, suggesting that a fraction of the P(St-co-SSNa) charges might be trapped in these hydrophobic domains; thus making them unavailable for complexation. The set of complementary techniques (DLS, zetametry, ITC, binding experiment with a cationic and metachromatic dye) used in this work highlighted that this was not the case and that all anionic charges of P(St-co-SSNa) were in fact available for complexation either with the polycationic PDADMAC or the monocationic o-toluidine blue dye. Only minor differences were observed between these techniques, consistently showing a complexation stoichiometry close to 1:1 at the charge equivalence for the different P(St-co-SSNa) compositions. A key result emphasizing that (i) the strength of the electrostatic interaction overcomes the hydrophobic effect responsible for pearl formation, and (ii) the efficiency of complexation does not depend significantly on differences in charge density between PDADMAC and P(St-co-SSNa), highlighting that PE chains can undergo conformational rearrangements favoring the juxtaposition of segments of opposite charge. Finally, these data have shown that the formation of colloidal PECs, such as PDADMAC and P(St-co-SSNa), occurs in two distinct steps with the formation of small primary complex particles (<50 nm) by pairing of opposite charges (exothermic step) followed by their aggregation within finite-size clusters (endothermic step). This observation is in agreement with the previously described mechanism of PEC particle formation from strongly interacting systems containing a hydrophobic PE.
在这项工作中，研究了两种强聚电解质（PEs）的静电络合作用，即亲水性带正电荷的聚二烯丙基二甲基氯化铵（PDADMAC）和疏水性带负电荷的聚（苯乙烯 - 共 - 苯乙烯磺酸钠）（P(St - co - SSNa)），后者是在不同磺化速率下制备的。已知后者在溶液中对于中等磺化速率会呈现珍珠项链构象，这表明P(St - co - SSNa)的一部分电荷可能被困在这些疏水区域中；从而使其无法用于络合。这项工作中使用的一系列互补技术（动态光散射（DLS）、zeta电位测定、等温滴定量热法（ITC）、与阳离子和变色染料的结合实验）表明情况并非如此，实际上P(St - co - SSNa)的所有阴离子电荷都可用于与聚阳离子PDADMAC或单阳离子邻甲苯胺蓝染料络合。在这些技术之间仅观察到微小差异，一致显示在不同P(St - co - SSNa)组成的电荷当量下，络合化学计量比接近1:1。一个关键结果强调：（i）静电相互作用的强度克服了导致珍珠形成的疏水效应，（ii）络合效率并不显著取决于PDADMAC和P(St - co - SSNa)之间电荷密度的差异，突出表明PE链可以进行构象重排，有利于相反电荷片段的并置。最后，这些数据表明，诸如PDADMAC和P(St - co - SSNa)之类的胶体聚电解质复合物（PEC）的形成分两个不同步骤进行，首先通过相反电荷配对形成小的初级复合颗粒（<50 nm）（放热步骤），然后它们在有限尺寸的聚集体中聚集（吸热步骤）。这一观察结果与先前描述的由含有疏水PE的强相互作用体系形成PEC颗粒的机制一致。
