Composition effects on the air-polymer surface tension in random block copolymers

For lithographic applications, A-b-(B-r-C) copolymers are a promising route for designing defect-free structures with a specified pitch size since the microphase separation can be decoupled from the air-polymer interface. Here we use Polystyrene (PS) as the A block and modified-PGMA (Poly(Glycidyl methacrylate)) as the B and C blocks. Chemistries of B and C are chosen in such a way that air-polymer surface tension for PS is between that of B and C. For perpendicular lamellae, the surface tension of A should be balanced by the surface tension of B-r-C by varying the relative ratio of B to C. One simplified approach for predicting this ratio is to assume that the surface tension of B-r-C is linear function of composition. Here we probe this assumption using all atom MD simulations. An understanding of how composition affects surface tension allows for informed design and reduction of the synthetic burden of A-b-(B-r-C) copolymers.