Saunders Brian R
Manchester Materials Science Centre, UMIST, University of Manchester, Grosvenor Street, Manchester M1 7HS, UK.
Langmuir. 2004 May 11;20(10):3925-32. doi: 10.1021/la036390v.
This investigation presents a study of the internal structure of poly(NIPAM/xBA) microgel particles (NIPAM and BA are N-isopropylacrylamide and N,N'-methylene bisacrylamide, respectively). In this study, x is the wt % of BA used during microgel synthesis. Two values of x were used to prepare the microgels, 1 and 10. The microgel dispersions were investigated using photon correlation spectroscopy (PCS) and small-angle neutron scattering (SANS). These measurements were made as a function of temperature in the range 30-50 degrees C. Scattering maxima were observed for the microgels when the dispersion temperatures were less than their volume phase transition temperatures. The SANS data were fitted using a model which consisted of Porod and Ornstein-Zernike form factors. The analysis showed that the macroscopic hydrodynamic diameter of the microgel particles and the submicroscopic mesh size of the network are linearly related. This is the first study to demonstrate affine swelling for poly(NIPAM/xBA) microgels. Furthermore, the mesh size does not appear to be strongly affected by x. The data suggest that the swollen particles have a mostly homogeneous structure, although evidence for a thin, low segment density shell is presented. The study confirms that poly(NIPAM/xBA) microgel particles have a core-shell structure. The shell has an average thickness of approximately 20 nm for poly(NIPAM/1BA) particles which appears to be independent of temperature over the range studied. The analysis suggests that the particles contained approximately 50 vol % water at 50 degrees C. The molar mass of the poly(NIPAM/1BA) microgel particles was estimated as 6 x 10(9) g mol(-1).
本研究对聚（NIPAM/xBA）微凝胶颗粒的内部结构进行了研究（NIPAM和BA分别为N-异丙基丙烯酰胺和N,N'-亚甲基双丙烯酰胺）。在本研究中，x为微凝胶合成过程中所用BA的重量百分比。使用两个x值来制备微凝胶，分别为1和10。利用光子相关光谱法（PCS）和小角中子散射（SANS）对微凝胶分散体进行了研究。这些测量是在30至50摄氏度范围内作为温度的函数进行的。当分散温度低于其体积相变温度时，观察到微凝胶的散射最大值。SANS数据使用由Porod和Ornstein-Zernike形状因子组成的模型进行拟合。分析表明，微凝胶颗粒的宏观流体动力学直径与网络的亚微观网孔尺寸呈线性相关。这是首次证明聚（NIPAM/xBA）微凝胶具有仿射溶胀的研究。此外，网孔尺寸似乎不受x的强烈影响。数据表明，溶胀颗粒具有大致均匀的结构，尽管有证据表明存在一个薄的、链段密度低的壳层。该研究证实聚（NIPAM/xBA）微凝胶颗粒具有核壳结构。对于聚（NIPAM/1BA）颗粒，壳层的平均厚度约为20 nm，在所研究的温度范围内似乎与温度无关。分析表明，在50摄氏度时，颗粒中含有约50体积%的水。聚（NIPAM/1BA）微凝胶颗粒的摩尔质量估计为6×10⁹ g·mol⁻¹。
