Molecular association by the radiation pressure of a focused laser beam: Fluorescence characterization of pyrene-labeled PNIPAM
Molecular association by the radiation pressure of a focused laser beam: Fluorescence characterization of pyrene-labeled PNIPAM
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DOI：
10.1021/ja963830e
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发表时间：
1997-03-19
影响因子：
15
通讯作者：
Miyashita, T
中科院分区：
文献类型：
--
作者：
Hofkens, J;Hotta, J;Miyashita, T
最近，我们报道了聚（N-异丙基丙烯酰胺）（PNIPAM）在水溶液中的非常新颖且有趣的激光诱导行为。 1-3 通过显微镜照射 1064 nm 的 CW 激光束，通过 H2O 的振动泛音带进行吸收，并在焦点处局部加热溶液。结果，引发聚合物的相变，导致聚合物的卷曲到球状转变。 4-9 同时，由于瑞利粒子上的洛伦兹力，聚焦激光束对分子聚集体施加辐射力，10-12 产生单个微粒。为了清楚地证明辐射力对聚合物溶液中分子组装的作用，我们进行了两个不同的实验。在第一个实验中，我们成功地在 PNIPAM 的 D2O 溶液中形成了微粒，由于泛音带的红移，不会引起光热温度升高。 1, 2 在第二个实验中，研究了含有十二烷基硫酸钠 (SDS) 的聚 (N-异丙基丙烯酰胺-co-N-十八烷基丙烯酰胺) 水溶液。已知 SDS 与十八烷基链的相互作用会产生部分带负电荷的聚合物链。由于静电斥力，即使温度升高，聚合物链通常也不会崩溃。然而，当将聚焦红外激光束施加到溶液上时，可以看到颗粒形成。 3 从这些实验中，我们得出结论，通过辐射压力进行分子组装是一种相当普遍的现象。
Recently, we have reported quite novel and interesting laser induced behavior of poly (N-isopropylacrylamide)(PNIPAM) in aqueous solutions. 1-3 Irradiation via a microscope by a CW laser beam of 1064 nm gives absorption through the vibrational overtone band of H2O and locally heats up the solution at the focal spot. As a result, the phase transition of the polymer is induced, leading to the coil to globule transition of the polymer. 4-9 Simultaneously, the focused laser beam exerts radiation force upon the molecular aggregates, due to the Lorentz force upon Rayleigh particles, 10-12 resulting in a single microparticle.In order to demonstrate clearly the role of the radiation force upon molecular assembling in the polymer solution, we have carried out two different experiments. In the first experiment we have succeeded in forming a microparticle in a D2O solution of PNIPAM where photothermal temperature elevation is not induced because of the red shift of the overtone band. 1, 2 In a second experiment, an aqueous solution of poly (N-isopropylacrylamide-co-N-octadecylacrylamide) containing sodium dodecylsulfate (SDS) was investigated. The interaction of SDS with the octadecyl chains is known to result in partially negative charged polymer chains. Due to the electrostatic repulsion the collapse of the polymer chains is normally not realized even by temperature elevation. However, particle formation could be seen when a focused IR laser beam was applied on the solution. 3 From these experiments we have concluded that molecular assembly by radiation pressure is a quite general phenomenon.