Chung Peter C, Glynos Emmanouil, Sakellariou Georgios, Green Peter F
Department of Materials Science and Engineering, Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States.
Department of Chemistry, University of Athens, Panepistimiopolis, Zografou, 15771, Athens Greece.
ACS Macro Lett. 2016 Apr 19;5(4):439-443. doi: 10.1021/acsmacrolett.5b00944. Epub 2016 Mar 15.
We show evidence of thickness-dependent elastic mechanical moduli that are associated largely with the effects of architecture (topology) and the overall shape of the macromolecule. Atomic force microscopy (AFM) based nanoindentation experiments were performed on linear chain polystyrene (LPS) and star-shaped polystyrene (SPS) macromolecules of varying functionalities (number of arms, ) and molecular weights per arm . The out-of-plane elastic moduli () increased with decreasing film thickness, , for less than a threshold film thickness, . For SPS with ≤ 64 and > 9 kg/mol, the dependencies of () on were virtually identical for the linear chains. Notably, however, for SPS with = 64 and = 9 kg/mol (SPS-9k-64), the was over 50% larger than that of the other polymers. These observations are rationalized in terms of the structure of the polymer for high and sufficiently small and not in terms of the influence of interfacial interactions.
我们展示了与大分子的结构（拓扑结构）和整体形状的影响密切相关的厚度依赖性弹性力学模量的证据。基于原子力显微镜（AFM）的纳米压痕实验是针对具有不同官能度（臂数）和每条臂分子量的线性链聚苯乙烯（LPS）和星形聚苯乙烯（SPS）大分子进行的。对于小于临界膜厚度的情况，面外弹性模量随膜厚度的减小而增加。对于臂数≤64且每条臂分子量>9 kg/mol的SPS，线性链的弹性模量对膜厚度的依赖性实际上是相同的。然而，值得注意的是，对于臂数 = 64且每条臂分子量 = 9 kg/mol的SPS（SPS - 9k - 64），其弹性模量比其他聚合物大50%以上。这些观察结果根据聚合物在高官能度和足够小的膜厚度下的结构得到了合理的解释，而不是基于界面相互作用的影响。
