ADHESION AT THE SOLID-ELASTOMER INTERFACE - INFLUENCE OF THE INTERFACIAL CHAINS
ADHESION AT THE SOLID-ELASTOMER INTERFACE - INFLUENCE OF THE INTERFACIAL CHAINS
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DOI：
10.1021/ma00126a021
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发表时间：
1995-10-23
期刊：
影响因子：
5.5
通讯作者：
TIRRELL, M
中科院分区：
文献类型：
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作者：
DERUELLE, M;LEGER, L;TIRRELL, M
我们研究了交联聚二甲基硅氧烷（PDMS）弹性体透镜与单分散PDMS接枝层覆盖的硅片接触时的粘附性。通过对接枝链进行单独修饰，考察了接枝链的分子量和表面密度对接枝链粘附力的影响。我们使用的机械测试是JKR方法，它测量晶圆片和透镜之间的接触面积半径a作为所施加载荷P的函数的变化。该技术给出了界面粘附能或应变能释放率G对裂纹扩展速度v的依赖关系。我们修改了通常用于在恒定、施加位移下工作的设备，以努力在尽可能低的载荷和变形下获得数据。记录a和P作为时间的函数，可以确定G作为V的函数，速度低至5 nm/s。我们的结果表明，即使在最低速度范围内，G仍然依赖于V。如果我们将应变能释放率的低速值作为附着能G(0)，我们发现G(0)受到接枝层的强烈影响，并且明显受接枝层链穿透网络的能力的支配。我们测量的粘附能总是高于只考虑PDMS表面能的预期。从熔融状态接枝的层在一定分子量范围内，其中接枝链具有其未受干扰的尺寸，与从一定溶液浓度接枝高分子量聚合物产生的相同厚度的层相比，表现出较少的粘附增强，这导致当溶液接枝层干燥时接枝链的结构被压缩。似乎有一个接枝层的厚度最适合在透镜和晶圆之间产生附着力增强。通过改变网络的性质，我们已经表明弹性体的结构在决定粘附能方面起着重要作用。
We have studied the adhesion between an elastomeric lens of cross-linked poly(dimethylsiloxane) (PDMS) brought into contact with a silicon wafer covered by a grafted layer of monodisperse PDMS. The influence on the adhesion of the molecular weight and the surface density of the grafted chains was examined by modifying them independently. The mechanical test we used was the JKR method, which measures the variation of the radius of the contact area, a, between the wafer and the lens as a function of P, the load applied. This technique gives the dependence of the interfacial adhesion energy, or strain energy release rate, G, on the crack propagation speed, V. We modified the apparatus commonly used to operate at constant, imposed displacement in an effort to obtain data at the lowest possible loads and deformations. Recording of a and P as a function of time enabled the determination of G as a function of V down to speeds as low as 5 nm/s. Our results show that G still depends on V, even in the lowest range of speeds. If we refer to the low-velocity values of strain energy release rate as adhesion energies, G(0), we find that G(0) is affected strongly by the grafted layer and apparently governed by the ability of the chains from the grafted layer to penetrate the network. The adhesion energies we measure are invariably higher than that expected from accounting for only the surface energy of PDMS. Layers grafted from the melt state over a range of molecular weights, where the grafted chains have their unperturbed dimensions, show less adhesion enhancement than do layers of the same thickness produced by grafting high molecular weight polymers from a range of solution concentrations, which results in compressed configurations of the grafted chains when the solution grafted layers are dried. There appears to be a thickness for the grafted layers which is optimum in generating adhesion enhancement between the lens and the wafer. By modifying the nature of the network, we have shown that the structure of the elastomer plays an important role in determining the adhesion energy.