Conductometric and light scattering studies on the complexation between cationic polyelectrolyte nanogel and anionic polyion.
Conductometric and light scattering studies on the complexation between cationic polyelectrolyte nanogel and anionic polyion.
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DOI：
10.1021/la1037519
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发表时间：
2011-01
期刊：
影响因子：
--
通讯作者：
Ryo Doi;E. Kokufuta
中科院分区：
文献类型：
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作者：
Ryo Doi;E. Kokufuta
本工作的目的是提供一个基本的了解水的1：1化学计量的双金属络合物（SPEC）在水中的低分子量盐的情况下。我们研究了线性聚阴离子聚乙烯醇硫酸钾（KPVS）与阳离子纳米凝胶（CPENG）在无盐水溶液（pH 3和25 °C）中的络合作用，该阳离子纳米凝胶由N-异丙基丙烯酰胺和1-乙烯基咪唑的轻度交联共聚物组成，作为阴离子与阳离子基团的摩尔混合比（Mmr）的函数。为了比较，还研究了KPVS与聚（二烯丙基二甲基氯化铵）（PDDA）的络合，这是胶体滴定中的标准反应。动态光散射（DLS）相结合的浊度和电导测量。当KPVS加入到CPENG或PDDA溶液中时，当Mmr =1时，浊度曲线突然升高，电导曲线出现突变，表明形成了SPE，当Mmr ≤ 1时，形成的络合物均为水分散性的，因此用DLS表征了络合物的组成。DLS数据的CONTIN分析显示，（i）Mmr的增加导致纳米凝胶复合物颗粒的流体动力学半径（R（h））的减小，但（ii）PDDA复合物的R（h）在Mmr < 0.8时保持不变。考虑到这些因素，我们讨论了随机模型（RM）和全有或全无模型（AONM）在复杂地层中的电导测量结果。结果发现，KPVS和PDDA在每个Mmr下产生水分散性SPEC颗粒，伴随着络合物对抗衡离子（K（+）和Cl（-））的吸收。该吸收量约为反离子化学计量释放量的7%。在纳米凝胶系统中，在Mmr < 0.2时观察到抗衡离子的完全释放，此时一个或两个KPVS链与CPENG颗粒结合，但进一步的KPVS结合导致约20%的抗衡离子吸收以维持电中性。因此，我们认为，对水的吸收成为一个关键因素，以了解水的SPEC颗粒。
This work aims to provide a basic understanding of the water dispersibility of a 1:1 stoichiometric polyelectrolyte complex (SPEC) in water in the absence of low-molecular-weight salts. We studied the complexation of a linear polyanion, potassium poly(vinyl alcohol sulfate) (KPVS), with a cationic polyelectrolyte nanogel (CPENG) composed of a lightly cross-linked copolymer of N-isopropylacrylamide and 1-vinylimidazole, in an aqueous salt-free solution (pH 3 and 25 °C), as a function of the molar mixing ratio (Mmr) of anionic to cationic groups. Also studied for comparison was the complexation of KPVS with poly(diallyldimethylammonium chloride) (PDDA), which is a standard reaction in colloid titration. Turbidimetric and conductometric measurements were used in combination of dynamic light scattering (DLS). An abrupt increase of turbidity curve and a break of conductivity curve were observed at Mmr =1 when KPVS was added to the CPENG or PDDA solution, indicating the formation of SPEC. All the complexes formed at Mmr ≤ 1 were water-dispersible and hence characterized by DLS. The CONTIN analysis of DLS data showed that (i) an increase of Mmr causes a decrease of the hydrodynamic radius (R(h)) of the nanogel complex particle but (ii) the R(h) of the PDDA complex remains unchanged at Mmr < 0.8. Taking these into account, we discussed the conductometric results in terms of the random model (RM) and all-or-none model (AONM) in polyelectrolyte complex formations. It was found that KPVS and PDDA yield a water-dispersible SPEC particle at each Mmr, accompanying the uptake of counterions (K(+) and Cl(-)) by the complex. This uptake amount was about 7% of the stoichiometric release of the counterions. In the nanogel system, a complete release of the counterions was observed at Mmr < 0.2 at which one or two KPVS chains were bound to a CPENG particle, but further KPVS binding led to about 20% of the counterion uptake to maintain electroneutrality. Thus, we suggest that the counterion uptake becomes a key factor to understand the water dispersibility of SPEC particles.