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应用大规模分子动力学方法, 模拟了锥形探头在非晶态聚合物薄膜表面的滑动摩擦过程, 研究了摩擦导致的聚合物薄膜表层微观结构改变, 以及探头与基体间黏着作用、滑动速度和分子链长度对基体表层微观结构改变的影响. 当探头与基体之间为黏着作用时, 摩擦导致基体表面滑痕区域的键取向沿滑动方向重新取向, 导致表层分子链回转半径沿滑动方向伸长, 并且这些表层微观结构的改变程度随滑动速度的减小而增大. 在摩擦导致结构改变的过程中, 链端单体和链中单体的贡献作用不同, 形成了不同的分子链拉伸变形机制. 当样本缠结度较大或探头滑动速度较小时, 相比于链中单体, 探头对链端单体的拖曳作用使更多分子链发生拉伸变形. 研究还发现, 在探头与聚合物薄膜系统中, 使薄膜表层微观结构发生改变是摩擦能量耗散的重要途径.The sliding friction between a rigid tip and an amorphous polymer film is studied using large scale molecular dynamics simulation. We focus on the changes of surface microstructure on the polymer film caused by friction, and study the effects of the interaction between tip and substrate, the sliding speed and the molecular chain length on the change of surface microstructure. When there is an adhesive force between tip and substrate, the bond reorientation caused by friction occurs in the sliding region of polymer substrate, and radius of gyration of the molecular chains on the surface layer of polymer substrate elongates along the sliding direction. Moreover, the extent of surface microstructure changes increases with the decrease of sliding speed. During the process of microstructure changes caused by friction, the chain loops and chain ends make different contributions, leading to different deformation mechanisms of molecular chain. The drag action between the tip and chain end monomers plays a more important role in making molecular chains deformation, when the degree of entanglement of polymer substrate becomes greater or when the sliding speed of tip becomes lower. Our results also show that change of surface microstructure is a key mode of friction energy dissipation in this tip and polymer film tribology system.
[1] Chen L, Yang B P, Zhang J Y 2014 J. Adhes. Sci. Technol. 28 1725
[2] Liu Y M, Sinha S K 2013 Wear 300 44
[3] Chen G L, Zheng X, Huang J, Si X L, Chen Z L, Xue F, Massey S 2013 Chin. Phys. B 22 115206
[4] Balzer B N, Micciulla S, Dodoo S, Zerball M, Gallei M, Rehahn M, von Klitzing R, Hugel T 2013 Acs. Appl. Mater. Inter. 5 6300
[5] Zhang Z H, Li H P, Han K 2013 Acta Phys. Sin. 62 158701 (in Chinese) [张兆慧, 李海鹏, 韩奎 2013 62 158701]
[6] Zhang Z H, Han K, Cao J, Wang F, Yang L J 2012 Acta Phys. Sin. 61 028701 (in Chinese) [张兆慧, 韩奎, 曹娟, 王帆, 杨丽娟 2012 61 028701]
[7] Maeda N, Chen N H, Tirrell M, Israelachvili J N 2002 Science 297 379
[8] Chen N H, Maeda N, Tirrell M, Israelachvili J 2005 Macromolecules 38 3491
[9] Ghorbal A, Ben Brahim A 2013 Polym. Test. 32 1174
[10] Dai L, Satyanarayana M N, Sinha S K, Tan V B C 2011 Langmuir 27 14861
[11] Dai L, Satyanarayana N, Sinha S K, Tan V B C 2013 Tribol. Int. 60 53
[12] Yew Y K, Minn M, Sinha S K, Tan V B C 2011 Langmuir 27 5891
[13] Solar M, Meyer H, Gauthier C 2013 Eur. Phys. J. E 36 29
[14] Solar M, Meyer H, Gauthier C, Fond C, Benzerara O, Schirrer R, Baschnagel J 2012 Phys. Rev. E 85 021808
[15] Solar M, Meyer H, Gauthier C, Benzerara O, Schirrer R, Baschnagel J 2011 Wear 271 2751
[16] Everaers R, Sukumaran S K, Grest G S, Svaneborg C, Sivasubramanian A, Kremer K 2004 Science 303 823
[17] Plimpton S 1995 J. Comput. Phys. 117 1
[18] Bucaille J L, Gauthier C, Felder E, Schirrer R 2006 Wear 260 803
[19] Tocha E, Schoenherr H, Vancso J 2009 Soft Matter 5 1489
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[1] Chen L, Yang B P, Zhang J Y 2014 J. Adhes. Sci. Technol. 28 1725
[2] Liu Y M, Sinha S K 2013 Wear 300 44
[3] Chen G L, Zheng X, Huang J, Si X L, Chen Z L, Xue F, Massey S 2013 Chin. Phys. B 22 115206
[4] Balzer B N, Micciulla S, Dodoo S, Zerball M, Gallei M, Rehahn M, von Klitzing R, Hugel T 2013 Acs. Appl. Mater. Inter. 5 6300
[5] Zhang Z H, Li H P, Han K 2013 Acta Phys. Sin. 62 158701 (in Chinese) [张兆慧, 李海鹏, 韩奎 2013 62 158701]
[6] Zhang Z H, Han K, Cao J, Wang F, Yang L J 2012 Acta Phys. Sin. 61 028701 (in Chinese) [张兆慧, 韩奎, 曹娟, 王帆, 杨丽娟 2012 61 028701]
[7] Maeda N, Chen N H, Tirrell M, Israelachvili J N 2002 Science 297 379
[8] Chen N H, Maeda N, Tirrell M, Israelachvili J 2005 Macromolecules 38 3491
[9] Ghorbal A, Ben Brahim A 2013 Polym. Test. 32 1174
[10] Dai L, Satyanarayana M N, Sinha S K, Tan V B C 2011 Langmuir 27 14861
[11] Dai L, Satyanarayana N, Sinha S K, Tan V B C 2013 Tribol. Int. 60 53
[12] Yew Y K, Minn M, Sinha S K, Tan V B C 2011 Langmuir 27 5891
[13] Solar M, Meyer H, Gauthier C 2013 Eur. Phys. J. E 36 29
[14] Solar M, Meyer H, Gauthier C, Fond C, Benzerara O, Schirrer R, Baschnagel J 2012 Phys. Rev. E 85 021808
[15] Solar M, Meyer H, Gauthier C, Benzerara O, Schirrer R, Baschnagel J 2011 Wear 271 2751
[16] Everaers R, Sukumaran S K, Grest G S, Svaneborg C, Sivasubramanian A, Kremer K 2004 Science 303 823
[17] Plimpton S 1995 J. Comput. Phys. 117 1
[18] Bucaille J L, Gauthier C, Felder E, Schirrer R 2006 Wear 260 803
[19] Tocha E, Schoenherr H, Vancso J 2009 Soft Matter 5 1489
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