Ligand grafted substrates

1. A ligand-functional substrate comprising a free radical reaction product of:

a) a substrate having a crosslinked copolymer coating thereon, wherein the coating is derived from a copolymer comprising photoinitiator-functional monomer units, hydrophilic monomer units and crosslinkable monomer units; and

b) a monomer mixture comprising ligand-functional monomer units;

wherein the substrate is selected from porous membranes, porous woven and nonwoven webs, and porous fibers.

2. The ligand-functional substrate of claim 1 wherein the hydrophilic monomer units of the copolymer comprise one or more of poly(oxyalkylene) (meth)acryloyl monomer units, (meth)acrylamide monomer units, vinyl amide monomer units, and hydroxyalkyl(meth)acryloyl monomer units.

3. The ligand-functional substrate of claim 1 , wherein the copolymer is derived from monomer units having a crosslinkable functional groups of the formula:

wherein

X 1 is —O— or —NR 1 —,

R 1 is H or C 1 -C 4 alkyl;

R 2 is a single bond or a (hetero)hydrocarbyl linking group;

A is an reactive functional group that is reactive with a crosslinking compound or is self-crosslinking; and

x is 0 or 1.

4. The ligand-functional substrate of claim 3 wherein A is an amine reactive functional group and is selected from carboxyl, oxazolinyl, azlactone, acetyl, acetonyl, acetoacetyl, ester, isocyanato, epoxy, aziridinyl, acyl halide, and cyclic anhydride groups.

5. The ligand-functional substrate of claim 4 , wherein the copolymer is crosslinked by an amine functional crosslinking compound of the formula:

(HNR 1 ) r —R 4 —(FG) q ,

where R 1 is H or C 1 -C 4 alkyl,

R 4 is a (hetero)hydrocarbyl group;

FG is a functional group that is a) reactive toward the functional group of the copolymer, or b) self-crosslinking, and subscripts r and q are at least one.

6. The ligand-functional substrate of claim 5 wherein FG is —NHR 1 , where R 1 is H or C 1 -C 4 alkyl.

7. The ligand-functional substrate of claim 6 wherein the crosslinking compound is a polyamine of the formula

R 4 (NHR 1 ) m , wherein

R 4 is a (hetero)alkylene group;

R 1 is H or C 1 -C 4 alkyl, and at least one R 1 is H, and m is at least two.

8. The ligand-functional substrate of claim 1 , wherein the crosslinked copolymer is derived from monomer units having crosslinkable functional groups that are self crosslinkable and are derived from monomers selected from alkenyl or (meth)acryloyl silanes, hydroxymethyl(meth)acrylamides and alkoxymethyl(meth)acrylamides.

9. The ligand-functional substrate of claim 1 wherein the ligand functional monomers are of the formula:

Z 1 —Y 2 —X 1 —CO—CR 1 ═CH 2 , or

Z 1 —Y 2 —CR 1 ═CH 2

wherein X 1 is —O— or —NR 1 —,

R 1 is H or C 1 -C 4 alkyl,

Y 2 is a linking group selected from a single bond or a (hetero)hydrocarbyl divalent group;

Z 1 is a ligand functional group that binds biological species by ionic, covalent, hydrophobic, and biological affinity interactions.

10. The ligand-functional substrate of claim 9 wherein Z 1 is selected from (1) an acidic group or a salt thereof, (2) an amino group or a salt thereof, (3) a guanidine or biguanide group or a salt thereof, (4) an azlactone group or a precursor to the azlactone group, (5) a glycidyl group, (6) a biological affinity ligand group, (7) a hydrophobic interaction group, (8) an isocyanate group, or (9) a combination thereof.

11. The ligand-functional substrate of claim 1 , wherein the ligand-functional monomers are of the formulas:

wherein

R 1 is H or C 1 -C 4 alkyl;

R 2 is a (hetero)hydrocarbyl group;

each R 3 is independently H or C 1 -C 4 alkyl;

R 4 is H, C 1 -C 12 alkyl or —N(R 3 ) 2 ;

R 7 is H or hydrocarbyl;

X 1 is —O— or —NR 3 —,

e is 0 or 1, and

d is 1 or 2.

12. The ligand-functional substrate of claim 1 wherein the copolymer, prior to crosslinking, is of the formula:

-(M PI ) k -(M Hydrophil ) l -(M FG ) m -(M other) i -, where

(M PI ) k are photoinitiator functional monomer units having “k” polymerized monomer units, where k is at least one

(M Hydrophil ) l are hydrophilic monomer units having “1” polymerized monomer units,

(M FG ) m are monomer units having crosslinkable functional groups and having “m” polymerized monomer units, and

(M other ) i are other monomer units, having “i” polymerized monomer units, where “i” may be zero.

13. The ligand-functional substrate of claim 12 wherein

M PI comprises 0.5 to 25 wt. % of the monomer units;

M Hydrophil comprises 35 to 97.5 wt. % of the monomer units;

M FG comprises 2-40 wt. % of the monomer units;

M other comprises 0-20 wt % of the monomer units,

based on 100 wt % total monomers.

14. The ligand-functional substrate of claim 5 wherein stoichiometry between the amine groups of the crosslinker and the reactive functional groups of the copolymer is 0.1:1 to 1:1.

15. The ligand-functional substrate of claim 1 wherein the photoinitiator-functional monomer units are from monomers of the formula:

where;

X 1 is —O— or —NR 1 ,

R 1 is independently H or C 1 -C 4 alkyl;

R 6 is a divalent (hetero)hydrocarbyl linking group connecting the (meth)acryloyl group with the photoinitiator group; and

PI is a α-cleavage photoinitiator group.

16. A method of selectively binding and removing biological materials from biological samples comprising the step of contacting a biological sample with the ligand-functionalized substrate of claim 1 .

17. A filter element comprising one or more layers of the ligand functional substrate of claim 1 .

18. A filter cartridge comprising the filter element of claim 17 .

19. The ligand-functional substrate of claim 9 wherein Z 1 is selected from a primary amino group, secondary amino group, tertiary amino group, or quaternary ammonium group.

20. The ligand-functional substrate of claim 9 wherein the ligand functional monomers are of the formula:

N(R 5 ) u —Y 2 —X 1 —(CO)—CR 1 ═CH 2

wherein X 1 is —O— or —NR 1 —, and R 1 is H or C 1 -C 4 alkyl;

each R 5 is independently hydrogen, alkyl, hydroxyalkyl, aminoalkyl, aryl, or aralkyl subscript u is 2.