A novel polymer comprising a reaction product obtained by reacting an organosilane compound with a boron compound. The polymer comprises a reaction product obtained by reacting (a) an aminated silane compound represented by the formula R4-n—Si—(OR′)n (wherein R represents an aminated organic group; R′ represents methyl, ethyl, or propyl; and n is an integer of 1-3) with (b) at least one boron compound selected from the group consisting of H3BO3 and B2O3, the amount of the ingredient (b) being 0.02 mol or larger per mol of the ingredient (a).