Catalyzed synthesis of crystalline linear polymer nanofibers

Abstract

Crystalline nanofibers of linear polyethylene with an ultrahigh molecular weight (6,200,000) and a diameter of 30 to 50 nanometers were formed by the polymerization of ethylene with mesoporous silica fiber-supported titanocene, with methylalumoxane as a cocatalyst. Small-angle x-ray scattering analysis indicated that the polyethylene fibers consist predominantly of extended-chain crystals. This observation indicates a potential utility of the honeycomb-like porous framework as an extruder for nanofabrication of polymeric materials.

What is claimed is:  
     
         1 . A method of manufacturing a linear polymer comprising the steps of: 
 preparing a tubular catalyst support carrying a catalyst; and    polymerizing a monomer in the presence of said tubular catalyst support, to obtain a linear polymer.    
     
     
         2 . The method according to  claim 1 , wherein the step of polymerizing is conducted in the presence of a plurality of said tubular catalyst supports.  
     
     
         3 . The method according to  claim 1 , wherein the step of polymerizing is conducted in the presence of a plurality of said tubular catalyst supports which are adjacent to each other.  
     
     
         4 . The method according to  claim 1 , wherein the step of polymerizing is conducted in the presence of a plurality of said tubular catalyst supports which are adjacent to each other, each of tubular catalyst supports has a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support, and said plurality of said tubular catalyst supports are disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports.  
     
     
         5 . The method according to  claim 1 , wherein said linear polymer is an oriented linear polymer.  
     
     
         6 . The method according to  claim 1 , wherein said tubular catalyst support comprises silica, and said silica carries said catalyst.  
     
     
         7 . The method according to claim, wherein said catalyst is a titanium catalyst.  
     
     
         8 . The method according to  claim 1 , wherein said catalyst comprises TiX 2 , wherein X represents cyclopentadienyl, derivatives of cyclopentadienyl, and analogs of cyclopentadienyl.  
     
     
         9 . The method according to  claim 1 , wherein an opening of said tubular catalyst support has a diameter of from 1 to 10 nm.  
     
     
         10 . The method according to  claim 1 , wherein said tubular catalyst support is made of zeolite.  
     
     
         11 . The method according to  claim 1 , wherein said monomer is ethylene, and said linear polymer is polyethylene.  
     
     
         12 . The method according to  claim 1 , wherein a co-catalyst, which is selected from the group consisting of alkylalumoxanes and trialkylaluminums, is used in the step of polymerizing the monomer.  
     
     
         13 . The method according to  claim 12 , wherein a ratio Al/Ti (molar ratio) of aluminum contained in said co-catalyst to titanium contained in said titanium catalyst ranges from 10 to 10,000.  
     
     
         14 . The method according to  claim 1 , wherein said linear polymer has a microfiber structure having a diameter of from 10 to 150 nm.  
     
     
         15 . The method according to  claim 1 , wherein said monomer is ethylene, and the step of polymerizing the ethylene monomer is conducted at a temperature of from 10 to 50° C., and at a pressure of from 1 to 20 atm.  
     
     
         16 . An oriented linear polymer.  
     
     
         17 . The polymer according to  claim 16 , wherein said polymer has a degree of crystallinity of 90% or more.  
     
     
         18 . The polymer according to  claim 16 , wherein said polymer has a microfiber structure having a diameter of from 10 to 150 nm.  
     
     
         19 . The polymer according to  claim 16 , wherein said polymer is free from small-angle X-ray scattering (SAXS) signals at 0.324 degrees (2θ) as measured by SAXS.  
     
     
         20 . A catalyst support for use in preparing a polymer from a monomer, comprising a tubular catalyst support carrying a catalyst.  
     
     
         21 . The support according to  claim 20 , comprising a plurality of tubular catalyst supports which are adjacent to each other.  
     
     
         22 . The support according to  claim 20 , comprising a plurality of tubular catalyst supports which are adjacent to each other, each of tubular catalyst supports has a substantially hexagonal cross-section in a direction orthogonal to a longitudinal direction of the support, and said plurality of said tubular catalyst supports are disposed in a honeycomb-like arrangement as viewed in a direction orthogonal to a longitudinal direction of the supports.  
     
     
         23 . The support according to  claim 20 , wherein said tubular catalyst support comprises silica, and said silica carries said catalyst.  
     
     
         24 . The support according to  claim 20 , wherein said catalyst is a titanium catalyst.  
     
     
         25 . The support according to  claim 20 , wherein said catalyst comprises TiX 2 , wherein X represents cyclopentadienyl, derivatives of cyclopentadienyl, and analogs of cyclopentadienyl.  
     
     
         26 . The support according to  claim 25 , wherein X is selected from the group consisting of cyclopentadienyl, pentamethylcyclopentadienyl, dimethylsilyl-bis-cyclopentadienyl, indenyl, and ethylene-bis-indenyl.  
     
     
         27 . The support according to  claim 20 , wherein an opening of said tubular catalyst support has a diameter of from 1 to 10 nm.  
     
     
         28 . The support according to  claim 20 , wherein said tubular catalyst support is made of zeolite.  
     
     
         29 . The support according to  claim 20 , wherein said support is for use in preparing polyethylene from ethylene.