You mean "some of the conduction electrons move to the far end of the cooper rod leaving the near end of the cooper rod depleted in electrons and thus with an unbalanced positive charge"?
The plastic rod is negatively charged. The electrons have negative charge. When the plastic rod is brought close to the cooper, it repels the free electrons of the cooper and they move as far as possible. So the part of the cooper rod which is close to the plastic becomes positive. That part is attracted by the negative plastic rod, and the far end is repelled, but with less force, as it is farther. (The electrons pushed away are attracted to the positive charge remained at the close end, but that force is smaller then that of the plastic rod).
ehild