In situ kinetics of layer-by-layer assembled nonlinear-optical-active amphiphiles from dynamic surface force measurements.
In situ kinetics of layer-by-layer assembled nonlinear-optical-active amphiphiles from dynamic surface force measurements.
复制标题
通过动态表面力测量，逐层组装非线性光学活性两亲物的原位动力学。
作者：
Niña G. Caculitan;Paul H. Scudder;Analiz Rodriguez;J. Casson;Hsing;J. M. Robinson;M. Johal
报道了一类偶氮苯表面活性剂与聚阳离子聚乙烯亚胺(PEI)的合成和层层沉积。不同类型的X-偶氮-(CH2)10-SO3-表面活性剂，其中X=-NO2，-CN和-COCH3，在偶氮苯部分具有递减的吸电子强度。我们用动态表面力测量的方法研究了两亲分子在PEI上的吸附动力学。吸附暂停紫外可见光谱获得的非原位动力学数据验证了表面力计算结果。这些测量描述了动态力测量在LBL系统中跟踪吸附的第一次应用。用紫外-可见光谱、二次谐波(SHG)和单波长椭圆偏振光谱仪对薄膜进行了表征。观察到的两亲分子吸附时的蓝移表明多层膜内有H型聚集。所研究的两种表面活性剂均符合朗缪尔吸附行为，平衡吸附倍数在2 0 0 S以下，倍频结果与两亲分子超极化率的预期趋势一致。
We report the synthesis and layer-by-layer (LBL) deposition of a class of azo-benzene surfactants with the polycation poly(ethylenimine) (PEI). The different surfactants of the type X-azo-(CH2)10-SO3-, where X = -NO2, -CN, and -COCH3 in the azo-benzene moiety, have decreasing electron-withdrawing strengths. We use dynamic surface force measurements to study the in situ kinetics of adsorption of the amphiphiles onto PEI. Ex situ kinetics data obtained by adsorption-paused UV-visible spectroscopy validate the surface force results. These measurements describe the first application of dynamic force measurements to follow adsorption in LBL systems. UV-visible spectroscopy, second harmonic generation (SHG), and single-wavelength ellipsometry were also used to characterize the films. The observed blue shift upon adsorption of the amphiphiles suggests H-type aggregation within the multilayer. Two of the surfactants studied within the LBL films follow Langmuir adsorption behavior with equilibrium adsorption times under 200 s. The SHG results are consistent with the expected trends in the hyperpolarizabilities of the amphiphiles.