Temperature, pH, and ionic strength induced changes of the swelling behavior of PNIPAM-poly(allylacetic acid) copolymer microgels
Temperature, pH, and ionic strength induced changes of the swelling behavior of PNIPAM-poly(allylacetic acid) copolymer microgels
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DOI：
10.1021/la702996p
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发表时间：
2008-06-17
期刊：
影响因子：
3.9
通讯作者：
Hellweg, T.
中科院分区：
文献类型：
--
作者：
Karg, Matthias;Pastoriza-Santos, Isabel;Hellweg, T.
由N-异丙基丙烯酰胺（NIPAM）制成的胶体微凝胶的体积相转变已被充分研究，并且已知转变温度可受共聚影响。采用简单的自由基聚合方法合成了一系列不同烯丙基乙酸含量的N-异丙基丙烯酰胺-烯丙基乙酸共聚物。利用动态光散射（DLS）研究了这些颗粒的温敏行为。通过采用透射电子显微镜（TEM）和zeta电位测量进行进一步表征。TEM观察揭示了共聚物颗粒的近似球形形状和低多分散性。此外，测得的zeta电位提供了有关相对表面电荷的信息。由于这些共聚物是更敏感的外部刺激，如pH值和离子强度比他们的纯PNIPAM同行，体积相变进行了研究，在两个不同的pH值和各种盐浓度。对于AAA含量最高的共聚物微凝胶，在pH 10时，体积相变温度显着向更高的值移动。对于较高的AAA含量，pH从8到10的变化可以引起半径变化高达100 nm，使颗粒作为pH控制的致动器很有趣。
The volume phase transition of colloidal microgels made of N-isopropylacrylamide (NIPAM) is well-studied and it is known that the transition temperature can be influenced by copolymerization. A series of poly(N-isopropylacrylamide-co-allylacetic acid) copolymers with different contents of allylacetic acid (AAA) was synthesized by means of a simple radical polymerization approach. The thermoresponsive behavior of these particles was studied using dynamic light scattering (DLS). Further characterization was done by employing transmission electron microscopy (TEM) and zeta potential measurements. TEM observations reveal the approximately spherical shape and low polydispersity of the copolymer particles. In addition, the measured zeta potentials provide information about the relative surface charge. Since these copolymers are much more sensitive to external stimuli such as pH and ionic strength than their pure PNIPAM counterparts, the volume phase transition was investigated at two different pH values and various salt concentrations. At pH 10 for the copolymer microgels with the highest AAA content, a significant shift of the volume phase transition temperature toward higher values is found. For higher AAA content, a change in pH from 8 to 10 can induce a change in radius of up to 100 nm making the particles interesting as pH controlled actuators.