Disclosed are devices and methods to synthesize polynucleotides and libraries of polynucleotides such as libraries of oligonucleotides. In exemplary embodiments, the device includes a support having a plurality of features. Each feature contains a plurality of oligonucleotides. Within each feature, each of the plurality of oligonucleotides includes an identical predetermined subunit sequence of X nucleosides and a degenerate sequence of Y nucleosides. A predetermined combination of a subset of the features can be used to produce a polynucleotide having a predetermined sequence of Z nucleosides.