Copolymers of N,N-dimethylacrylamide and acrylamide

DETAILED DESCRIPTION The copolymers of acrylamide and N,N-dimethylacrylamide of the present invention may be represented by the formula ##STR1## where m and n are whole numbers such that the weight:weight ratio of NNDMA to AM ranges from greater than 10:90 to about 95:5, Z is a number such that the viscosity (1% w/w solution in deionized water, Brookfield LVF viscometer, Spindle 2, 60 rpm) of the copolymer is at least about 55 centipoise (cP), and indicates that the distribution of NNDMA and AM in the polymer chain is random.
These copolymers are useful for the production of the hydrolyzed copolymers of this invention.
It is preferred that the NNDMA:AM ratio range from about 1:3 to about 3:1.
It is also preferred that the value of Z be such that a 1.
0% solution of the polymer in deionized water have a viscosity, as measured on a Brookfield LVF viscometer, spindle No.
2 at 60 rpm, of at least 100 cp at 21.
degree.
C.
Another aspect of this invention is the partially hydrolyzed derivatives of NNDMA:AM copolymers.
Degree of hydrolysis ranging from about 5% to about 65% is included within the scope of this invention, by which is meant that about 5% to 65% of the amide groups in the original copolymers are hydrolyzed to carboxyl groups.
Included within the scope of this invention are partially hydrolyzed copolymers of Formula I where the NNDMA:AM ratio ranges from greater than 5:95 to about 95:5 and Z is such that a 1.
0% solution of the hydrolyzed polymer in deionized water has a viscosity, as measured on a Brookfield LVF viscometer, spindle No.
4 at 60 rpm, of at least 1000 cP at 21.
degree.
C.
It is preferred that hydrolysis range from 10% to 25%.
Most preferred is 25% hydrolysis.
Another aspect of this invention is a composition for enhanced oil recovery which comprises an effective amount of a partially hydrolyzed copolymer of Formula I where the NNDMA:AM ratio ranges from greater than 5:95 to about 95:5 and an aqueous medium therefor.
Such a composition is effective when the viscosity of the composition ranges from 1