The present invention relates to improved methods for the preparation of nucleic acids. More particularly, conventional solid supports used for nucleic acid synthesis are derivatized with activators having pKas within the 4 to 7 range. Preferentially, CPG-based solid supports are reacted with trialkoxysilanes containing an activator moiety such as pyridine. During each deblocking step of the nucleic acid synthesis cycle, bound pyridiniums are generated, yielding a weak acidic medium spreads throughout the solid support. The bound activators efficiently activate the phosphoramidite reagents towards coupling with 5'-hydroxynucleosides bound to the solid supports, thus eliminating or supplementing external deliveries of activator during the coupling steps.