PRECIPITATION OF POLYELECTROLYTES BY SALTS
PRECIPITATION OF POLYELECTROLYTES BY SALTS
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DOI：
10.1002/pol.1962.1205616312
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发表时间：
1962-01-01
影响因子：
3.4
通讯作者：
IMAI, N
中科院分区：
文献类型：
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作者：
IKEGAMI, A;IMAI, N
研究了在不同条件下聚丙烯酸的加成盐沉淀。PAA通过四正丁基氢氧化铵中和至各种电离度α。在不同的聚合物浓度Cp、温度T和α下测定了发生沉淀的最小盐浓度C ε。分别通过电导率、折射率和粘度测量来估计与聚离子结合的阳离子的量、离子水合的变化以及C ïs附近的聚合物膨胀。结果表明，存在两种沉淀类型：L型沉淀，在高α时，由于阳离子与多聚离子结合而发生，C型沉淀与多聚离子无关，在低α时，除了大离子的盐外，还出现H型沉淀。降水的这种分类也可以用C_（10）-T关系来证明;在L型中，C_（10）几乎与T无关，而在H型中，C_（10）随T而增加。在中间α-值时，在沉淀中发现盐离子的明显特异性;在α = 0.25时，Mg 2+出现H型，而Ba 2+或Ca 2+出现L型，尽管所有这些二价阳离子与聚离子的结合程度相同。这是由于聚离子-阳离子复合物的水合作用的差异。在L-型中，阳离子结合的形成，例如作为盐桥，使聚合物疏水，而在H型中，高浓度的盐离子通过改变水分子的排列使聚合物溶液不稳定。
Precipitation of poly(acrylic acid) by added salts has been investigated under various conditions. The PAA was neutralized to various degrees of ionization α by tetra‐n‐butyl ammonium hydroxide. The minimum salt concentrationC̄sat which precipitation occurs was determined at various polymer concentrationCp, temperatureT, and α. The amount of bound cations to polyions, the change in ion hydration, and the polymer expansion nearC̄swere estimated by conductance, refractive index, and viscosity measurements, respectively. It is concluded that there are two kinds of precipitation; TheLtype which satisfies the relationC̄s≐ αCpand occurs at high α due to cation binding to the polyions, and theHtype in whichC̄sis independent ofCpand which appears at low α with salts other than those having large ions. This classification of the precipitation is justified also by theC̄s–Trelation; in theLtype,C̄sis nearly independent ofT, and in theHtypeC̄sincreases withT. At intermediate α‐values pronounced specificities of salt ions are found in the precipitation; at α = 0.25, with Mg2+theHtype appears, while with Ba2+or Ca2+theLtype appears, although all of these divalent cations are bound to polyions to the same degree. This is due to the difference in the hydration of the polyion‐cation complexes. In theL‐type the formation of cation bindings, such as salt bridge, makes the polymer hydrophobic, while in theHtype highly concentrated salt ions render the polymer solution unstable by changing the arrangement of the water molecule.