Graft copolymers containing ionomer units

A process for preparing a graft copolymer containing cationic moieties and having the structural formula:

• wherein R and R′ are independently selected from the group consisting of hydrogen and a C1 to C4 alkyl group, Z is selected from the group consisting of nitrogen and phosphorous, R1 and R2 are the same or different alkyl radicals containing 1 to 4 carbon atoms, R3 is a direct link or an organic radical containing 1 to 6 carbon atoms, X is a halogen, and PL is a polymer chain segment derived from at least one anionically polymerized monomer, the process comprising the steps of:
• a) polymerizing one or a mixture of anionically polymerizable monomers under anionic polymerization conditions using, as a polymerizaton initiator, a compound having the formula R1R2ZR3—Li to form a polymer having the structure R1R2Z R3—PL, wherein R1, R2, Z, R3 and PL are as previously defined;
• and
• b) reacting said polymer under onium salt-forming conditions with a copolymer containing polymerized monomer units in the polymer chain having the structure:
• wherein R and R′ are as previously defined.