Amorphous Cell / Confined Layer

I am trying to simulate the interface between a particle and the polymer matrix. The main problem is that in the confined layer construction, the polymer is deformed unrealistically by the vacuum layer. Is there a way to create a cell which has the interface, but on the back end acts like an amorphus cell?

|------------------------|----------------------------------------|-------------------------------------|

| +++++++++++++++Interface+++++++++++++Polymer+++| +++  Another Polymer chain++|

|+++++++++++++++++|  C +++++++++++++++++++++++++ A | +++++++++++++++++++++++  B|

|------------------------|------------------------------------------|------------------------------------|

In other words, if a chain ends up at the point A, in a confined layer it would be forced to treat the edge of the Cell as a barrier and have to stay within its confines.  In an amorphus cell, it would wrap to point C.  What I want is a way for the chain to wrap to point B, simulating an infinite polymer matrix interacting with a single interface.

Thank you and let me know if I can clarify anything about my question,

Kaitlyn