Departamento de Física, ICEx, Universidade Federal de Minas Gerais, CEP 30123-970, Belo Horizonte, Brazil.
Langmuir. 2010 Jan 19;26(2):648-54. doi: 10.1021/la902240d.
Self-assembled monolayers, bilayers, and other structures of mixed phosphonic acids were investigated using atomic force microscopy. Octadecylphosphonic acid (OPA, 18 carbon atoms in the alkyl chain) was mixed in solution, with different ratios, with octylphosphonic acid (OcPA, 8 carbon atoms in the alkyl chain) and deposited onto mica substrates. Self-assembled monolayers were formed, with no evidence of phase separation, from pure OPA up to 5:10 OPA/OcPA ratio (despite the large alkyl chain length difference). It was found that water plays a crucial role in the morphology of the self-assembled structures and their time evolution. The formation of bilayers instead of monolayers (OcPA-type behavior) is dominant for high water content (both in solution and/or the atmosphere). Mechanical and thermal resistance tests were performed on mixed and pure samples and revealed different properties that can be correlated to their composition.
使用原子力显微镜研究了混合膦酸的自组装单层、双层和其他结构。十八烷膦酸（OPA，烷基链中有 18 个碳原子）与辛烷膦酸（OcPA，烷基链中有 8 个碳原子）在溶液中以不同比例混合，并沉积在云母基底上。尽管烷基链长度差异很大，但自组装单层在纯 OPA 中直至 5:10 OPA/OcPA 比例范围内没有出现相分离的证据。研究发现，水在自组装结构的形态及其时间演化中起着至关重要的作用。对于高含水量（无论是在溶液中还是在大气中），双层的形成（OcPA 型行为）而不是单层的形成占据主导地位。对混合和纯样品进行了机械和热阻测试，揭示了不同的性能，这些性能可以与其组成相关联。
