Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida, Ueda, Nagano, 386-8567 Japan.
J Phys Chem B. 2014 Feb 27;118(8):2194-204. doi: 10.1021/jp410983x. Epub 2014 Feb 19.
Internal structures of thermosensitive microgels and their hybrid counterparts that contain Au nanoparticles are investigated by means of small-angle X-ray scattering (SAXS). Thermosensitive cationic microgels were synthesized by aqueous free radical precipitation polymerization from N-isopropylacrylamide and 3-(methacrylamino) propyltrimethylammonium chloride used as monomers. Using the microgels as templates, Au nanoparticles were synthesized in situ, using the cationic sites in the microgel to nucleate particle growth. To obtain different types of the hybrid microgels, Au nanoparticles were synthesized in the presence of the microgels by changing the reduction conditions of the precursor ions, such as temperature and species of reducing reagent. The hybrid microgels were characterized mainly by TEM and SAXS. For SAXS investigation, the hybrid microgels were analyzed in the wide q-range of 0.07 nm(-1) < q < 20 nm(-1), where q is the magnitude of the scattering vector. A quantitative description of the scattering intensities, I(q), for the nonhybrid microgels requires a sum of five components having different physical origins. An upturn increase of the forward intensity originates from the interface of microgels, obeying the Porod law, I(q) ∝ q(-4). An additional Guinier term found in q < 0.2 nm(-1) seems to arise from solidlike density fluctuation due to the inhomogeneities of chemical cross-links. The power-law behavior manifested in the low- to intermediate-q range is directly linked with the fractal nature of the swollen (coil) polymer networks and well described by the Ornstein-Zernike equation. Two interference peaks centered at q ≈ 5 nm (-1) and q ≈ 15 nm(-1) are likely to reflect inter- and intrachain correlations of pNIPAm, respectively, which are formally fitted by pseudo-Voigt equations. As for the hybrid microgels, a pronounced new contribution from the Au nanoparticles emerges, which calls for an additional scattering component describing polydisperse spheres having a homogeneous internal electron density distribution. The width of the Gaussian distribution for the radius of the Au nanoparticles evaluated from the SAXS data turns out to be consistent with those obtained with TEM observation.
采用小角 X 射线散射（SAXS）研究了含金纳米粒子的热敏性微凝胶及其杂化对应物的内部结构。热敏性阳离子微凝胶通过 N-异丙基丙烯酰胺和 3-（甲基丙烯酰胺基）丙基三甲基氯化铵作为单体的水溶液自由基沉淀聚合合成。使用微凝胶作为模板，通过改变前驱体离子的还原条件（如温度和还原剂种类），在微凝胶存在下原位合成金纳米粒子，利用微凝胶中的阳离子位来引发颗粒生长。为了获得不同类型的杂化微凝胶，通过改变前驱体离子的还原条件（如温度和还原剂种类），在微凝胶存在下原位合成金纳米粒子。通过改变还原条件（如温度和还原剂种类），在微凝胶存在下原位合成金纳米粒子。通过改变还原条件（如温度和还原剂种类），在微凝胶存在下原位合成金纳米粒子。杂化微凝胶主要通过 TEM 和 SAXS 进行表征。对于 SAXS 研究，在 0.07nm(-1)<q<20nm(-1)的宽 q 范围内分析杂化微凝胶，其中 q 是散射矢量的大小。对于非杂化微凝胶散射强度 I(q)的定量描述需要五个具有不同物理起源的分量之和。源自微凝胶界面的前向强度的上升增加遵循 Porod 定律，I(q)∝q(-4)。在 q<0.2nm(-1)范围内发现的额外 Guinier 项似乎是由于化学交联不均匀引起的固态密度涨落。在低到中等 q 范围内表现出的幂律行为与溶胀（线圈）聚合物网络的分形性质直接相关，并通过 Ornstein-Zernike 方程很好地描述。两个中心位于 q≈5nm(-1)和 q≈15nm(-1)的干涉峰可能分别反映 pNIPAm 的链间和链内相关性，这通过伪 Voigt 方程形式拟合。对于杂化微凝胶，金纳米粒子的出现引起了明显的新贡献，这需要一个额外的散射分量来描述具有均匀内部电子密度分布的多分散球体。从 SAXS 数据评估的金纳米粒子半径的高斯分布的宽度与通过 TEM 观察获得的宽度一致。
