Polymers useful for associating therewith oligonucleotides and for delivering the oligonucleotides into a cell, conjugates comprising these polymers and an oligonucleotide associated therewith, and compositions comprising same are provided. Also provided are uses of these conjugates in, for example, gene therapy, and particularly gene silencing. The disclosed polymers feature a PGA backbone, and amine-terminated pendant groups attached to at least 40% of the backbone units, and optionally further comprise alkyl pendant groups and/or other nitrogen-containing pendant groups attached to other one or more portions of the backbone units. The disclosed polymers can be cross-linked or can form a part of a block-copolymer.
