Chen Tongquan, Lu Yanping, Chen Tianyou, Zhang Xinghong, Du Binyang
MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science & Engineering, Zhejiang University, Hangzhou 310027, China.
Phys Chem Chem Phys. 2014 Mar 28;16(12):5536-44. doi: 10.1039/c3cp54535k. Epub 2014 Feb 5.
The effects of concentration, relative block length and environmental temperature as well as the surface chemical and wetting properties of solid substrates on the adsorption behaviors and mechanisms of a series of pentablock terpolymer poly(N-isopropylacrylamide)x-poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20-poly(N-isopropylacrylamide)x (PNIPAmx-PEO20-PPO70-PEO20-PNIPAmx or PNIPAmx-P123-PNIPAmx) with x of 10, 63 and 97 on gold were studied by using a quartz crystal microbalance (QCM) technique. It was found that increasing the solution concentration did not alter the adsorption mechanism of thickness growth mode but increase the adsorption amount of PNIPAm97-P123-PNIPAm97 on a bare gold substrate at 20 °C. Increasing the length x of PNIPAm block decreased the adsorption rate constant and shifted the adsorption mechanism from the densification adsorption process for PNIPAm10-P123-PNIPAm10 to the thickness growth mode for PNIPAm63-P123-PNIPAm63 and PNIPAm97-P123-PNIPAm97 on bare (unmodified) gold substrate at 20 °C. The adsorption mechanisms of PNIPAm97-P123-PNIPAm97 at 20 °C on the hydrophobic and hydrophilic gold surfaces were the thickness growth mode and densification adsorption process, respectively. A complex adsorption behavior with large adsorption amounts was observed at the lower critical solution temperature (LCST) of PNIPAm block, i.e. 34.7 °C, for the adsorption of PNIPAm97-P123-PNIPAm97 not only on hydrophobic gold substrates but also on hydrophilic gold substrates. The adsorption mechanism of PNIPAm97-P123-PNIPAm97 micelles at 45 °C was the densification adsorption process regardless of the surface wetting and chemical properties of gold substrate. Overall, the adsorption behavior and mechanism of PNIPAmx-P123-PNIPAmx pentablock terpolymers were mainly determined by the interactions of the pentablock terpolymers with different chain conformations in dilute aqueous solutions at various temperatures and the gold substrates with surface wetting and chemical properties.
采用石英晶体微天平（QCM）技术研究了浓度、相对嵌段长度、环境温度以及固体基质的表面化学和润湿性质对一系列五嵌段三元共聚物聚（N-异丙基丙烯酰胺）x-聚（环氧乙烷）20-聚（环氧丙烷）70-聚（环氧乙烷）20-聚（N-异丙基丙烯酰胺）x（PNIPAmx-PEO20-PPO70-PEO20-PNIPAmx或PNIPAmx-P123-PNIPAmx，其中x为10、63和97）在金表面吸附行为和吸附机理的影响。研究发现，提高溶液浓度不会改变厚度增长模式的吸附机理，但会增加20℃时PNIPAm97-P123-PNIPAm97在裸金基底上的吸附量。增加PNIPAm嵌段的长度x会降低吸附速率常数，并使吸附机理从PNIPAm10-P123-PNIPAm10的致密化吸附过程转变为20℃时PNIPAm63-P123-PNIPAm63和PNIPAm97-P123-PNIPAm97在裸（未改性）金基底上的厚度增长模式。20℃时，PNIPAm97-P123-PNIPAm97在疏水和亲水金表面的吸附机理分别为厚度增长模式和致密化吸附过程。在PNIPAm嵌段的较低临界溶液温度（LCST）即34.7℃时，观察到PNIPAm97-P123-PNIPAm97不仅在疏水金基底上而且在亲水金基底上吸附时具有大量吸附的复杂吸附行为。45℃时，PNIPAm97-P123-PNIPAm97胶束的吸附机理为致密化吸附过程，与金基底的表面润湿和化学性质无关。总体而言，PNIPAmx-P123-PNIPAmx五嵌段三元共聚物的吸附行为和机理主要由五嵌段三元共聚物在不同温度下稀水溶液中不同链构象与具有表面润湿和化学性质的金基底之间的相互作用决定。
