Thompson R B, Rasmussen K Ø, Lookman T
Theoretical Division, Los Alamos National Laboratory, New Mexico 87545, USA.
J Chem Phys. 2004 Feb 22;120(8):3990-6. doi: 10.1063/1.1643899.
We study the linear elastic response of multiblock copolymer melts in the lamellar phase, where the molecules are composed of tethered symmetric AB diblock copolymers. We use a self-consistent field theory method, and introduce a real space approach to calculate the tensile and shear moduli as a function of block number. The former is found to be in qualitative agreement with experiment. We find that the increase in bridging fraction with block number, that follows the increase in modulus, is not responsible for the increase in modulus. It is demonstrated that the change in modulus is due to an increase in mixing of repulsive A and B monomers. Under extension, this increase originates from a widening of the interface, and more molecules pulled free of the interface. Under compression, only the second of these two processes acts to increase the modulus.
我们研究了层状相中多嵌段共聚物熔体的线性弹性响应，其中分子由相连的对称AB二嵌段共聚物组成。我们采用自洽场理论方法，并引入实空间方法来计算拉伸模量和剪切模量作为嵌段数的函数。发现前者与实验结果在定性上相符。我们发现，随着嵌段数增加，桥接分数的增加伴随着模量的增加，但模量的增加并非由桥接分数的增加所致。结果表明，模量的变化是由于排斥性A和B单体的混合增加。在拉伸时，这种增加源于界面的加宽以及更多分子从界面中脱离。在压缩时，这两个过程中只有第二个过程起到增加模量的作用。
