Signal Conditioning of the conductive Polymer?
The first step would be to determine what the magnitude of the resistance change is going to be in your application. You'll want to check whether that change is linear or highly nonlinear over the range of operation, and determine how much accuracy and resolution you're going to need. You'll also need to determine any additional constraints, such as how much voltage and/or current you can apply to the material.

Once you have that kind of information, you can start to think about how to convert the resistance change into a voltage signal you can measure.