Poly(N-isopropylacrylamide) microparticles produced by radiation pressure of a focused laser beam: a structural analysis by confocal Raman microspectroscopy combined with a laser-trapping technique.
Poly(N-isopropylacrylamide) microparticles produced by radiation pressure of a focused laser beam: a structural analysis by confocal Raman microspectroscopy combined with a laser-trapping technique.
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DOI：
10.1021/jp044894b
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发表时间：
2005-03
期刊：
影响因子：
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通讯作者：
Yasuyuki Tsuboi;Masayuki Nishino;Tetsuya Sasaki;N. Kitamura
中科院分区：
文献类型：
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作者：
Yasuyuki Tsuboi;Masayuki Nishino;Tetsuya Sasaki;N. Kitamura
我们开发了一个与激光捕获技术相结合的共焦拉曼显微光谱系统，并将其应用于聚（N-异丙基丙烯酰胺）（PNIPA）的水溶液（H（2）O和D（2）O），这是众所周知的代表性温敏聚合物，即，螺旋态和球状态之间的相变/分离。通过将近红外（1064 nm）激光束引入显微镜，在激光束的聚焦点处产生PNIPA微粒，无论是在H（2）O和D（2）O中。利用本系统，我们首次成功地获得了PNIPA在800-3500 cm（-1）宽波数范围内的卷曲态和球状态的拉曼谱。对于D（2）O溶液（其中光热效应可以忽略，因此微粒应该是纯粹由辐射压力的影响产生的），在卷曲态、球状态和激光诱导微粒的拉曼光谱中观察到一些显著的差异。通过对这些光谱的详细分析，我们揭示了激光诱导的微粒的结构类似于球形状态。我们还讨论了辐射压力对聚合物高阶结构的影响。
We developed a confocal Raman microspectroscopy system combined with a laser trapping technique and applied it to aqueous solutions (H(2)O and D(2)O) of poly(N-isopropylacrylamide) (PNIPA), which is well-known as a representative thermo-responsive polymer, i.e., phase transition/separation between coiled and globular states. By introducing a near-infrared (1064 nm) laser beam into a microscope, PNIPA microparticles were produced at the focused spot of the laser beam, both in H(2)O and D(2)O. By using the present system, we succeeded in obtaining the Raman spectra of PNIPA in the coiled and globular states over a wide wavenumber region (800-3500 cm(-1)) for the first time. For the D(2)O solutions (in which the photothermal effect is negligible and hence the microparticles should be produced purely by the effect of radiation pressure), some significant differences were observed in the Raman spectra for the coiled state, in the globular state, and for laser induced microparticles. By analyzing these spectra in detail, we revealed that the structure of the laser-induced microparticles was analogous to that in the globular state. We also discuss the fundamental mechanism underlying the transformation of the higher order structure of a polymer by radiation pressure.