pH对接枝磺化碱木质素聚合物吸附特征的影响

Influence of pH on the Adsorption Characteristics of Sulfonated Alkali Lignin-based Polymers

采用动态光散射技术、透射电镜等表征了接枝磺化碱木质素聚合物(SBAL)在不同pH条件下的溶液行为,结果表明随着pH的增加,SBAL分子中的亲水官能团磺酸基、羧基和酚羟基逐步解离,分子链由卷曲变得伸展.利用频率-耗散联用型石英晶体微天平和静电逐层自组装技术,借助紫外光谱、原子力显微镜等表征了不同pH条件下SBAL在固/液界面上的吸附特征,结果发现随着pH由3增加到12,SBAL在金片和石英玻片上的吸附量先减小后增大,pH=9时吸附量最小.随着pH的增加,SBAL的吸附特征由刚性变得柔软,吸附构型呈现由致密到松散再到致密的变化趋势,吸附构象在酸性、中性和碱性条件下依次为mushroom结构、pancake结构和高分子刷,在中性和酸性条件下SBAL与聚二烯丙基二甲基氯化铵之间的作用力以阳离子-π相互作用为主,吸附强度较弱,而在强碱条件下以静电作用为主,吸附强度较大.

The solution behaviors of sulfonated alkali lignin-based polymers （SBAL） at different pH values were investigated by means of dynamic light scattering and transmission electron microscopy （TEM）.The results indicated that with the increase of pH,the hydrophilic functional groups of SBAL：sulfonic,carboxyl and phenolic hydroxyl groups were ionized gradually.With the increase of pH,the molecular configuration of SBAL changed from coil chain to extended chain.Moreover,the adsorption characteristics of SBAL on solid/liquid interface at different pH values were determined using a quartz crystal microbalance with dissipation monitoring （QCM-D） and electrostatic layer-by-layer self-assembly,as well as UV-Vis spectroscopy and atomic force microscopy （AFM）.The results showed that with the pH increased from 3 to 12,the adsorption amount of SBAL on gold plate and quartz slide decreased at first and then increased,the lowest amount was at pH=9.The adsorption configuration changed from rigid to soft,tight to loose and then tight again.The adsorption conformations of SBAL on gold plate and quartz slide with poly（diallyldimethylammonium chloride） （PDAC） showed mushroom-like structure,pancake-like structure and polymer brushes in the acidic,neutral and alkaline conditions,respectively.Cation-π interaction was the main driving force between SBAL and PDAC in the acidic and neutral conditions and the adsorption strength was weak.However,electrostatic interaction played an important role between SBAL and PDAC in the alkaline condition and the adsorption strength was strong.