Issue calculating absolute difference of a attribute value between adjacent polygons and assigning to shared polyline boundary.

Question

Hi everyone. I need some help with a GIS task! I have a layer of geology polygons each with various attributes such as chemical reactivity and rheology. The polygons (single layer) are separated by a single polyline boundary derived from the polygons. I need to calculate the absolute difference between like attributes  (i.e., rheology, chemical reactivity) across the polyline and assign these values to a field associated with the polyline. The point of this is to map the contacts of highest reactivity and/or rheology contrasts. This needs to be calculated across all contacts between polygons in the layer, not just those in the image below. Has anyone done this before, or have a potential solution? This is an approach used in prospectivity modelling. I have tried various methods and come up short of a answer.

JDawwg · Accepted Answer

Just some other points on this. Step 3 is not necessary, whereas when completing step 4, the 'keep relationships' box must be checked.