Ligand graft functionalized substrates

1. An article comprising a porous thermoplastic substrate and extending from the surfaces thereof free-radically grafted biguanide ligand groups to form a free-radically-grafted substrate, wherein the free-radically grafted substrate is of the formula: Substrate˜(M ligand ) m , where Substrate represents the thermoplastic substrate, M ligand represents a polymerized grafted ethylenically unsaturated monomer having pendant biguanide ligand groups, and m is at least two;

wherein said pendent biguanide ligands groups are selected from one or more of the formula:

wherein

R 2 is an arylene or alkylene and a is at least one and wherein the grafted ligand groups comprise the reaction product of a free-radically grafted electrophilic functional group and a ligand compound:

wherein

each R 4 is individually H, alkyl or aryl,

each R 6 is individually alkylene or arylene,

c may be zero or an integer from 1 to 500, and

d is zero or 1, with the proviso that when d is zero, then c is 1 to 500.

2. The article of claim 1 , further comprising free-radically grafted quaternary ammonium groups on the surface of the substrate.

3. The article of claim 1 , wherein the porous substrate is selected from a porous membrane, porous non-woven web, or porous fiber.

4. The article of claim 1 , wherein the grafted biguanide ligand groups comprise the reaction product of (a) a first free-radically grafted electrophilic functional group comprising an epoxy group, an isocyanato group, or an azlactone group with (b) a ligand compound:

wherein

each R 4 is individually H, alkyl or aryl,

each R 6 is individually alkylene or arylene,

c may be zero or an integer from 1 to 500, and

d is zero or 1, with the proviso that when d is zero, then c is 1 to 500.

5. An article of claim 1 comprising a porous base substrate having interstitial and outer surfaces; and grafted ligand groups extending from the surfaces of the porous base substrate, wherein the grafted ligand groups comprise the reaction product of a free-radically grafted electrophilic functional group and a ligand compound:

wherein

each R 4 is individually H, alkyl or aryl,

each R 6 is individually alkylene or arylene,

c may be zero or an integer from 1 to 500, and

d is zero or 1, with the proviso that when d is zero, then c is 1 to 500.

6. The article of claim 5 , wherein the free-radically grafted electrophilic functional group is selected from (i) an epoxy group or a ring-opened epoxy linkage group, (ii) an azlactone group or a ring-opened azlactone linkage group, or (iii) an isocyanato group.

7. The article of claim 5 , further comprising free-radically grafted ionic or hydrophilic groups.

8. The article of claim 7 , wherein the free-radically grafted ionic groups are grafted quaternary ammonium groups.

9. The article of claim 5 , wherein the porous base substrate is microporous.

10. The article of claim 5 , wherein the article further comprises free-radically grafted hydrophilic groups.

11. The article of claim 5 , wherein the porous base substrate comprises a porous membrane, a porous nonwoven web, or a porous fiber.

12. The article of claim 5 , wherein the free-radically grafted ligand groups comprise the reaction product of (a) a first grafted electrophilic functional group comprising an epoxy group, an isocyanato group, or an azlactone group with (b) a ligand compound:

wherein

each R 4 is individually H, alkyl or aryl,

each R 6 is individually alkylene or arylene,

c may be zero or an integer from 1 to 500, and

d is zero or 1, with the proviso that when d is zero, then c is 1 to 500.

13. A method of preparing a ligand functional substrate of claim 1 comprising:

1) providing a thermoplastic polymer substrate;

2) free-radically grafting a functional group to the surface of the substrate to produce a substrate having a grafted electrophilic functional groups extending from the surface(s) thereof; and

3) reacting the grafted electrophilic functional groups with biguanide ligand groups to produce a substrate having grafted biguanide ligand groups extending from the surface(s) of the substrate.

14. The method of claim 13 , comprising the steps of:

a) providing a porous thermoplastic polymer base substrate;

b) imbibing the porous thermoplastic polymer base substrate with a first solution to form an imbibed porous base substrate, the first solution comprising at least one grafting monomer having (a) a free-radically polymerizable group and (b) an additional electrophilic functional group;

c) exposing the imbibed porous base substrate to a controlled amount of electron beam radiation so as to form a first functionalized substrate having free-radically grafted electrophilic functional groups;

d) reacting the functionalized substrate having grafted electrophilic functional groups with a ligand compound:

wherein

each R 4 is individually H, alkyl or aryl,

each R 6 is individually alkylene or arylene,

c may be zero or an integer from 1 to 500, and

d is zero or 1, with the proviso that when d is zero, then c is 1 to 500.

15. The method of claim 14 , wherein the imbibing solution further comprises a second grafting monomer having (a) a free-radically polymerizable group and (b) an ionic group or a hydrophilic group.

16. The method of claim 15 , further comprising the steps of:

imbibing the first functionalized substrate with a second solution to form a first imbibed functionalized substrate, the second solution comprising at second grafting monomer having (a) a free-radically polymerizable group and (b) a second quaternary ammonium group, and

exposing the first imbibed functionalized substrate to a controlled amount of electron beam radiation so as to form a second functionalized substrate comprising free-radically grafted quaternary ammonium groups attached to the surfaces of the porous base substrate.

17. The method of claim 13 , wherein the biguanide ligand groups are one or more of the formula:

wherein

R 2 is an arylene or alkylene and a is at least one.