By far the easiest solution would be to put the data.frame's into a list where you create them. However, assuming you have a character list of object names:
list_df = lapply(list_object_names, get)
where you could construct you list like this (example for 10 objects):
list_object_names = sprintf("data_frame%s", 1:10)
or get all the objects in your current workspace into a list:
list_df = lapply(ls(), get)
names(list_df) = ls()
