A theoretical reasoning on why coordination catalysts supported on mesoporous supports produce HDPE crystalline nanofibers but not iPP crystalline nanofibers

Document Type: Original research

Author

Department of Polymer Engineering, Shiraz Branch, Islamic Azad University, Shiraz, P.O. Box: 71993-3, Iran

Abstract

Since 1999, when Takuzo Aida proposed the preparation of high density polyethylene (HDPE) crystalline nanofibers through polymerization of ethylene by a Cp2 TiCl2 /MCM-41 catalyst, many researchers have published various papers on different aspects of the idea. The published researches show that the endeavors to polymerize other types of alpha olefins, especially propylene, to obtain polyolefins with crystalline nanofiberous morphology have not been successful and no one has reported such morphology for them. In the present article, a possible reason behind these observations is proposed. Comparing the direction of the growth of HDPE chains and isotactic polypropylene (iPP) helices to become appropriate for making polymer crystals shows that HDPE chains are able to form crystal unit cells without concerning upward or downward chain growth direction, while the growth direction of adjacent iPP chains might be responsible for unsuccessful synthesis of crystalline iPP nanofibers in confined channels of the mesoporous catalysts. iPP helices can crystallize beside each other only in the form of anticline isochiral helices.

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  1. Ye Z, Zhu S, Wang W-J, Alsyouri H, Lin YS (2003) Morphological and mechanical properties of nascent polyethylene fibers produced via ethyl­ene extrusion polymerization with a metallocene catalyst supported on MCM-41 particles. J Polym Sci Pol Phys 41: 2433-2443
  2. Kageyama K, Tamazawa JI, Aida T (1999) Ex­trusion polymerization: Catalyzed synthesis of crystalline linear polyethylene nanofibers within a mesoporous Silica. Science 285: 2113-2115
  3. Dong X, Wang L, Wang W, Yu H, Wang J, Chen T, Zhou Z (2005) Preparation of nano-polyethyl­ene fibers and floccules using MCM-41 supported metallocene catalytic system under atmospheric pressure. Eur Polym J 41: 797-803
  4. Dong X, Wang L, Jiang G, Zhou Z, Sun T, Yu H, Wang W (2005) MCM-41 and SBA-15 sup­ported Cp2ZrCl2 catalysts for the preparation of nano-polyethylene fibers via in situ ethylene ex­trusion polymerization J Mol Catal A Chem 240: 239-244
  5. Dong X, Wang L, Zhou J, Yu H, Sun T (2006) Preparation of nano-polyethylene fibers using TiCl4/MCM-41 catalytic system. Catal Commun 7: 1-5
  6. Semsarzadeh MA, Aghili A (2008) Novel prepa­ration of polyethylene from nano-extrusion po­lymerization inside the nanochannels of MCM- 41/MgCl2/TiCl4 catalysts. J Macromol Sci A 45: 680-686
  7. Dong X, Wang L, Wang J, Zhou J, Sun T (2006) Evidence of nanoconfinement effects of MCM-41 on propylene polymerization catalyzed by MCM- 41 supported metallocene catalyst in the presence and absence of β-Cyclodextrin. J Phys Chem B 110: 9100-9104
  8. Delmon B, Yates JT (2005) Studies in surface science and technology, Elsevier, Vol. 158, 1443- 1443
  9. Lotz B, Wittmann JC, Lovinger AJ (1996) Struc­ture and morphology of poly(propylenes): A mo­lecular analysis. Polymer 37: 4979-4992
  10. Sperling LH (2006) Introduction to physical polymer science. 4th ed, John Wiley and Sons, 254-254
  11. Androsch R, Di Lorenzo ML, Schick C, Wun­derlich B (2010) Mesophases in polyethylene, polypropylene, and poly(1-butene). Polymer 51: 4639-4662
  12. Elias H-G, Mulhaupt R (2016) Plastics, General Survey, 1. Definition, molecular structure and properties. In: Ullmann's polymers and plastics: Products and processes, 7th ed., Wiley-VCH, Hamburg, 3-149
  13. Nekoomanesh M, Nejabat GR, Arabi H, Emami M (2009) A comment on "preparation of nano-polyethylene fibers using TiCl4/MCM-41 cata­lytic system". Catal Commun 10: 859-860
  14. Nejabat GR, Nekoomanesh M, Arabi H, Emami M, Aghaei-Nieat M (2010) Preparation of poly­ethylene nano-fibres using rod-like MCM-41/ TiCl4/MgCl2/THF bi-supported Ziegler-Natta catalytic system. Iran Polym J 19: 79-87
  15. Dong X, Wang L, Wang W, Jiang G, Chen Y, Zhao Z, Wang J (2005) Preparation of nano-polyethylene fibers and floccules by extrusion polymerization under atmospheric pressure using the SBA-15-supported Cp2ZrCl2 catalytic system. Macromol Mater Eng 290: 31–37
  16. Ahmadi E, Mohamadnia Z, Rahimi S, Armanmehr MH, Heydari MH, Razmjoo M (2016) Phillips catalysts synthesized over various silica supports: Characterization and their catalytic evaluation in ethylene polymerization. Polyolefins J 3: 23-36