A copolymeric polyphosphite is described: wherein each R1 through R5 can be the same or different and independently selected from the group consisting of C12-20 alkyl, C12-22 alkenyl, C12-40 cycloalkyl, C12-40-cycloalkenyl, C12-20 alkyl glycol ethers and A-OH and B—OH are different end-capping groups and independently selected from the group consisting of C2-40 alkylene, C7-40 cycloalkylene, C3-20 alkyl glycol ethers, C3-40 alkyl lactone, and —R7—N(R8)—R9—; wherein R7 and through R9 are independently selected from the group C1-20 alkyl, C2-22 alkenyl, C6-40 cycloalkyl, C7-40 cycloalkylene and H; m and n are integers from 1 to 100 inclusive, with various provisos.