First-order wetting transition at finite contact angle

The wetting of a polymer brush by a melt of similar chains can have a window of complete wetting with a classical allophobic wetting transition at low grafting density ¿ and an autophobic one at high ¿. However, when the melt chains are much longer than the brush chains, the contact angle ¿ goes through a nonzero minimum where ¿¿/¿¿ has a jump. A self-consistent-field analysis and experimental observations indicate a double-well disjoining pressure curve, consistent with a first-order wetting transition at finite ¿. The metastable contact angle can become zero.