Unsworth Larry D, Tun Zin, Sheardown Heather, Brash John L
Departments of Chemical Engineering and Pathology and Molecular Medicine, McMaster University, Hamilton, ON L8S 4L7, Canada.
J Colloid Interface Sci. 2005 Jan 1;281(1):112-21. doi: 10.1016/j.jcis.2004.08.022.
Physical property studies of surfaces formed by chemisorption of polyethylene oxide (PEO) onto gold are reported. Such surfaces have potential as model materials for elucidation of the mechanism of resistance to protein adsorption by PEO surfaces. Thiolated monomethoxy poly(ethylene oxide) (PEO) was chemisorbed onto gold-coated silicon wafers under various conditions such that different surface chain densities were achieved. Chain density was varied by controlling PEO solubility (proximity to cloud-point conditions) as well as chemisorption time. Films prepared with PEO of molecular weight 750, 2000, and 5000 g/mol were studied. Chain densities determined in the dry state by ellipsometry were found to be in the range of 0.4-0.7, 0.33-0.58, and 0.12-0.30 chains/nm(2) for MW 750, 2000, and 5000 PEO, respectively. Chain density was found to decrease with increasing molecular weight and to increase as cloud-point conditions were approached. PEO-layer mass densities and chain densities were determined independently by neutron reflectometry. Under low-solubility conditions and for a 4-h chemisorption time, film mass and chain density values of 1.0 +/-0.3 g cm(-3) and 1.8 +/- 0.9 chains/nm(2) were found for MW 750 PEO, and 0.82 +/- 0.02 g cm(-3) and 0.23 +/- 0.07 chains/nm(2) for MW 5000 PEO. Ellipsometry data for these systems yielded graft densities of 0.63 +/- 0.13 and 0.30 +/- 0.02 chains/nm(2), respectively. Using the mass densities obtained from the neutron data in the ellipsometry calculations, chain densities of 0.6 +/- 0.3 and 0.25 +/- 0.02 chains/nm(2), respectively, were obtained for the MW 750 and 5000 films. The ellipsometry and neutron data for the MW 5000 system are thus in agreement within experimental error. In general, the chain-density values are much higher than those corresponding to layers of unperturbed random coil PEO ("mushrooms"), suggesting that the PEO layers are in the brush regime with the chains in an extended conformation.
报道了聚环氧乙烷（PEO）化学吸附到金表面形成的表面的物理性质研究。这类表面有潜力作为模型材料，用于阐明PEO表面抗蛋白质吸附的机制。巯基化单甲氧基聚（环氧乙烷）（PEO）在各种条件下化学吸附到涂金的硅片上，从而实现不同的表面链密度。通过控制PEO的溶解度（接近浊点条件）以及化学吸附时间来改变链密度。研究了用分子量为750、2000和5000 g/mol的PEO制备的薄膜。通过椭偏仪测定的干燥状态下的链密度，对于分子量为750、2000和5000的PEO，分别在0.4 - 0.7、0.33 - 0.58和0.12 - 0.30链/nm²范围内。发现链密度随分子量增加而降低，并随着接近浊点条件而增加。通过中子反射法独立测定了PEO层的质量密度和链密度。在低溶解度条件下且化学吸附时间为4小时时，对于分子量为750的PEO，薄膜质量和链密度值分别为1.0±0.3 g/cm³和1.8±0.9链/nm²，对于分子量为5000的PEO，分别为0.82±0.02 g/cm³和0.23±0.07链/nm²。这些体系的椭偏仪数据分别给出了接枝密度为0.63±0.13和0.30±0.02链/nm²。在椭偏仪计算中使用从中子数据获得的质量密度，对于分子量为750和5000的薄膜，分别得到链密度为0.6±0.3和0.25±0.02链/nm²。因此，分子量为5000体系的椭偏仪和中子数据在实验误差范围内是一致的。一般来说，链密度值远高于对应于未受干扰的无规线团PEO（“蘑菇”）层的值，这表明PEO层处于刷状区域，链呈伸展构象。
