Department of Wood Science and Forest Products and T. Brooks Forest Products Center, Virginia Tech, Blacksburg, VA 24061, USA.
ACS Appl Mater Interfaces. 2009 Mar;1(3):559-66. doi: 10.1021/am800119q.
Surface chemistry of wood is based on the exposed surface that is the combination of the intact and cut cellular wall material. It is inherently complex and changes with processing history. Modification of wood surfaces through noncovalent attachment of amine containing water soluble polyelectrolytes provides a path to create functional surfaces in a controlled manner. Adsorption of polyethylenimine (PEI) and polydiallydimethylammonium chloride (PDDA) to wood was quantified as a function of solution conditions (pH and ionic strength). Polycation adsorption was maximized under basic pH without the addition of electrolyte. Added salt either had marginal influence or decreased adsorption of polycation, indicating interactions are strongly influenced by Coulombic forces. PEI adsorption could be modeled by both a Langmuir and Freundlich equations, although the wood surface is known to be heterogeneous. After adsorption of polycations, layer-by-layer assembled films were created on the wood surface. Layered films masked ultrastructural features of the cell wall, while leaving the microscale features of wood (cut lumen walls and openings) evident. These findings revealed for the first time that nanoscale films on wood can be deposited without changing the microscopic and macroscopic texture. Functionalized wood surfaces created by nanoscale films may have a future role in adhesives systems for wood composites, wood protection, and creating new functional features on wood.
木材的表面化学性质基于暴露的表面，它是完整和切割细胞壁材料的组合。它本质上是复杂的，并随着加工历史而变化。通过非共价附着含胺的水溶性聚电解质来修饰木材表面，为以可控的方式创造功能表面提供了一条途径。聚乙烯亚胺 (PEI) 和聚二烯丙基二甲基氯化铵 (PDDA) 在木材上的吸附作为溶液条件 (pH 值和离子强度) 的函数进行了定量。在没有添加电解质的情况下，在碱性 pH 值下，聚阳离子的吸附达到最大值。添加的盐要么影响不大，要么降低聚阳离子的吸附，这表明相互作用受库仑力的强烈影响。PEI 的吸附可以通过 Langmuir 和 Freundlich 方程来建模，尽管众所周知，木材表面是不均匀的。在吸附聚阳离子后，在木材表面上形成了层层组装的薄膜。层状薄膜掩盖了细胞壁的超微结构特征，同时使木材的微尺度特征（切割腔壁和开口）明显。这些发现首次揭示了纳米级薄膜可以在不改变微观和宏观纹理的情况下沉积在木材上。通过纳米级薄膜制备的功能化木材表面可能在木材复合材料的胶粘剂系统、木材保护以及在木材上创造新的功能特征方面具有未来的作用。
