Four types of polyvinyl alcohol (PVA)/iodine complex films were made using different boric acid treatments to prepare polarizing films having high durability under humid and warm atmospheres and to identify the effects of the boric acid treatment method on the formation of the PVA/iodine polarizing film. The four types of films were a PVA iodinated film(I), a PVA film that was iodinated and then treated with boric acid(I-B), a PVA film that was treated with boric acid and then iodinated(B-I), and a PVA film that was simultaneously treated with iodine and boric acid(I+B). The concentrations of I(2)/KI were 0.03, 0.05, and 0.07 mol/L, and the concentrations of boric acid were 0.1, 0.3, and 0.5 mol/L. Comparing four type films treated with 0.05 mol/L I(2)/KI and 0.5 mol/L boric acid, the conformation of PVA/iodine complexes for I-B film were larger than the others. The degrees of polarization (rho) of all of the films increased to very high levels (99.9%dagger). The durability of I-B was superior to B-I or I+B, and the change in the q was below 5% because the boric acid treated after iodine treatment reduced the molecular mobility of the PVA/iodine complex chains through intracrosslinking, so that the PVA/iodine complex could not easily collapse. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123:672-681, 2012