A sealant composition comprising:(a) 100 parts by weight of a silane functionalized polymer component which is prepared by reacting enough silane of the general formula R R'.sub.n SiY.sub.3-n (where n equals 0, 1 or 2 and where R is a non-hydrolyzable organic group which is capable of grafting onto the polymer, R' is a non-hydrolyzable organic group incapable of grafting onto the polymer and Y is a hydrolyzable organic group) with a polymer component to thereby functionalize the polymer component and provide a resultant sealant composition with adhesion which is resistant to deterioration in the presence of water;said polymer component comprising an A'B' block copolymer, a multiblock copolymer having at least two end blocks A and at least one midblock B, or mixtures of an A'B' block copolymer and the multiblock copolymer wherein:the A' and A blocks comprise monoalkenyl arene blocks and the B' and B blocks comprise substantially completely hydrogenated conjugated diene polymer blocks, and the average molecular weight of the A and A' blocks is greater than the minimum molecular weight needed to obtain microphase separation and domain formation of the A and A' blocks, and is less than the maximum molecular weight which would render the polymer incapable of being melt processed;the multiblock copolymer comprises a monoalkenyl arene content no more than a maximum weight percent needed to retain a modulus suitable as a sealant for the resultant composition and no less than a minimum weight percent needed to obtain the desired phase separation and the desired minimum cohesive strength for the resultant composition;(b) an amount of a midblock compatible component wherein said midblock compatible component is at a concentration to maintain the resultant composition in a plyable condition at room temperture and to maintain the glass transition temperature of the resultant composition below 10.degree. C.