【作者】 王晓雯；

【导师】 张广照； 刘光明；

【作者基本信息】 中国科学技术大学 ， 物理化学， 2014， 博士

【摘要】 在本论文中,我们研究了两种聚电解质在固-液界面上的行为,主要研究内容如下：(1)利用耗散测量型石英晶体微天平(QCM-D)和表面等离子体共振仪(SPR)研究了不同带电量PDMAEMA刷构象行为的离子特异性效应。通过调节溶液pH,使PDMAEMA分别处于完全带电、部分带电和完全不带电状态。当PDMAEMA刷处于完全带电或部分带电状态时,反离子凝聚效应占主导作用,随着离子强度的增加,PDMAEMA刷逐渐塌缩。相对于一价ClO3-,二价SO42-可更加有效地诱导聚电解质刷的塌缩。当PDMAEMA刷完全不带电时,链本身处于塌缩状态,由于离子与链上极性和非极性基团间的相互作用,会使PDMAEMA刷在低盐浓度时先进一步塌缩,而后随着离子浓度升高而溶胀。(2)结合QCM-D和SPR研究了牛血清蛋白(BSA)在不同亲疏水表面吸附行为的离子特异性效应。研究表明,pH3.8时,BSA吸附量随表面疏水性增加呈非单调变化,BSA吸附表现出明显的离子特异性效应；pH7.4时,BSA吸附量随表面疏水性增加而增大,BSA吸附的离子特异性效应不明显。耗散因子变化表明BSA分子形成较为刚性的吸附层。此外,BSA吸附过程分为两个不同的动力学阶段。pH3.8时,第一阶段受蛋白与表面间相互作用主导,且无明显离子特异性效应,第二阶段受蛋白结构重排主导,离子特异性效应明显；pH7.4时,第二阶段只在较为疏水的表面上才可观察到,且两个动力学阶段都无明显的阳离子特异性效应。(3)结合嵌段聚合物刻胶法和表面引发原子转移自由基聚合制备了大面积周期在100纳米以下图案化的PDMAEMA刷,通过调节pH控制纳米图案化PDMAEMA刷构象,pH9时,PDMAEMA链不带电,导致PDMAEMA塌缩；pH4时,PDMAEMA链带正电,PDMAEMA刷处于溶胀态。利用激光共聚焦扫描显微镜、原子力显微镜和QCM-D研究了BSA在其表面的可逆吸附。在1mMNaCl (pH5.8)的溶液中,BSA可被同时吸附在图案化纳米PDMAEMA刷内部和外围,外围吸附的BSA可在1M的NaCl溶液中解吸附,但留在刷子内部的BSA使原本纳米图案尺寸增加。更多还原

【Abstract】 In this thesis, we have investigated the behavior of two types of polyelectrolytes at the solid-liquid interface. The main results are as follows:(1) We have investigated the salt effects on the conformational change of PDMAEMA chains grafted on a surface at different pH by using quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR). Poly [(2-dimethylamino) ethyl methacrylate](PDMAEMA) is completely charged, partially charged, and uncharged at pH4,7, and10, respectively. Conformational behavior of PDMAEMA brushes is governed by counterion condensation when PDMAEMA chains are completely charged or partially charged. The electrostatic repulsion between PDMAEMA chains will be screened, causing the chains to collapse. And this effect grows with the increase of ionic strength. The addition of Na2SO4induces more collapse of the grafted layer than that of NaClO3at pH4and7. The conformational behavior of PDMAEMA brushes is governed by nonelectrostatic anion adsorption when PDMAEMA chains are uncharged at pH10. Because of the Van der waals interaction between ions and nonpolar or polar moiety of the chains, PDMAEMA chains dehydrate at low ionic strength and then swell again at high ionic strength.(2) We have systematically investigated the effect of surface wettability on ion-specific adsorption of bovine serum albumin (BSA) by using quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR). The results show a nonmonotonous change of the adsorbed amount of BSA as a function of molar fraction of1-dodecanethiol (xDDT) of the self-assembled monolayer at pH3.8, while the amount of adsorbed protein gradually increases with the xDDT at pH7.4. The small changes of dissipation (△D) indicate that BSA molecules form a quite rigid protein layer on the surfaces, which results in only a slight difference in the adsorbed mass between the mass-uptake estimations from the Sauerbrey equation and the Voigt model. The difference in the adsorbed mass between QCM-D and SPR measurements is attributed to the coupled water in the protein layer. On the other hand, specific anion effect is observed in the BSA adsorption at pH3.8with the exception of the surface at xDDT of0%, but no obvious cation specificity can be observed at pH7.4. The△D-△f plots show that the BSA adsorption at pH3.8has two distinct kinetic processes. The first one dominated by the protein-surface interactions is an anionnonspecific process, whereas the second one dominated by the protein structural rearrangements is an anion-specific process. At pH7.4, the second kinetic process can only be observed at the relatively hydrophobic surfaces, and no cation specificity is observed in the first and second kinetic processes.(3) We present fabricating patterned poly(2-(dimethylamino)ethyl methacrylate)(PDMAEMA) brushes with sub-100nm features over large areas. The patterned polymer brushes are fabricated by a combination of block copolymer micelle lithography and surface-initiated atom transfer radical polymerization. The PDMAEMA brushes are neutralized and collapsed at pH9, and positively charged and swollen at pH4. The protein adsorption and desorption on the patterned PDMAEMA brushes are studied by laser scanning confocal microscopy, atomic force microscopy, and quartz crystal microbalance with dissipation. In1mM NaCl solution at pH5.8, the patterned brushes take up bovine serum albumin (BSA, isoelectric point～4.8) via electrostatic interactions. BSA adsorbs both inside the brushes and at the outer edge of the brushes. BSA at the outer edge of the brushes is released by rinsing the brushes with1M NaCl solutions at pH4and9. Part of the absorbed BSA remains trapped inside the brushes, resulting in an increase of their volume.更多还原