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研究了多孔硅胶在改性前后不同的壁面特征对纳米通道润湿性的影响规律。采用非平衡分子动力学方法研究了水分子在改性前羟基化及改性后不同链长硅烷化壁面的纳米通道内密度、速度的分布状况,并分析了氢键的径向分布函数。结果表明:羟基化壁面通道的固液界面处流体出现高密度层,几乎无速度滑移,流体密度最大值为1.24g/cm~3,滑移速度仅为0.056?/ps;链长为C_4、C_8、C_(12)的硅烷化壁面通道的固液界面处水的密度分别为1.18g/cm~3、1.12g/cm~3、1.01g/cm~3,滑移速度分别为0.402?/ps、1.211?/ps、1.810?/ps;随烷基链长的增加,固液界面处水的密度接近纯水的密度1.0g/cm~3,固液界面处出现了速度滑移;羟基化通道壁面由于较强的固液相互作用势呈强亲水性;改性后的硅烷化壁面呈疏水性,并随改性层烷基链长度的增加而增强,且固液界面处出现“滑移效应”;羟基化通道壁面与水分子存在较强的氢键作用,而改性后硅烷化通道壁面与水分子无氢键的形成,改性层烷基链长的增加减弱了两者的相互作用势,进一步揭示了其疏水机理。
The influence of different wall features of porous silica gel on the wettability of nanochannels before and after modification was studied. The unbalanced molecular dynamics method was used to study the distribution of density and velocity of the nanochannels on the silanized wall with different chain lengths after hydroxylation and modification of water molecules. The radial distribution function of hydrogen bonds was also analyzed. The results show that there is a high density layer at the solid - liquid interface of hydroxylation wall channel with almost no velocity slip, the maximum density of fluid is 1.24g / cm ~ 3, the slip velocity is only 0.056? / Ps, the chain length is C_4 The density of water in the silanization wall channel of C_8, C_8 and C_ (12) were 1.18g / cm ~ 3, 1.12g / cm ~ 3 and 1.01g / cm ~ 3, respectively. The slip velocities were 0.402 ~ /ps,1.211?/ps,1.810?/ps. With the increase of alkyl chain length, the density of water near the solid-liquid interface is close to the density of pure water of 1.0g / cm ~ 3, and the velocity slip occurs at the solid-liquid interface. The hydroxylation channel wall is strongly hydrophilic due to strong solid-liquid interaction potential. The modified silanization wall is hydrophobic and increases with the increase of the alkyl chain length of the modified layer, and appears at the solid-liquid interface “Slip effect ”; hydroxylation channel wall and water molecules have strong hydrogen bonding, and the modified silanization channel wall and water molecules without hydrogen bond formation, modified layer alkyl chain length increases weaken The interaction between the two potential, further reveals its hydrophobic mechanism.