Polyethylene copolymers having a particular comonomer distribution

1. A polyethylene copolymer, wherein the copolymer has a comonomer partitioning tendency (ζ) of greater than 1.4, wherein the copolymer has a melt index ratio (flow index (I 21 ) as measured in accordance with ASTM D1238/melt index (I 2 ) as measured in accordance with ASTM D1238) ranging from about 15 to about 50, and wherein the comonomer partitioning tendency is defined by equation (1) and measures a proclivity of the polyethylene copolymer to have comonomer in high molecular weight chains;

ξ

=

C

⁢

⁢

P

⁢

⁢

I

P

⁢

⁢

D

⁢

⁢

I

×

C

⁢

⁢

D

⁢

⁢

I

(

1

)

wherein

CPI is a comonomer partitioning index (χ w /χ n ) wherein χ w =ΣN i (M i C i ) 2 /ΣN i (M i C i ) and χ n =ΣN i (M i C i )/ΣN i ;

PDI is a polydispersity index (M w /M n );

CDI is a comonomer dispersity index (C w+1 /C w ) wherein C w =ΣN i M i C i /ΣN i M i and C w+1 =ΣN i M i C i 2 /ΣN i M i C i ;

M i =molecular weight of a copolymer;

N i =number of copolymers having molecular weight M i ;

C i =weight fraction of comonomer in a copolymer;

M w =weight average molecular weight of the copolymer;

M n =number average molecular weight of the copolymer; and

C w =average weight fraction of comonomer in the copolymer.

2. A copolymer according to claim 1 , wherein the comonomer is one or more comonomers containing 3 to 16 carbon atoms.

3. A copolymer according to claim 1 , wherein the copolymer has a melt index (I 2 ) ranging from about 0.2 to about 20.

4. A copolymer according to claim 1 , wherein the copolymer has a density ranging from about 0.87 g/cm 3 to about 0.97 g/cm 3 .

5. A copolymer according to claim 1 , wherein the copolymer has a polydispersity index (M w /M n ) ranging from about 1.5 to about 20.