@acer 

ok sorry my bad. of course...first think then post...

cheers

Hello and thanks for your quick answer, the solution you suggested could work for the simple problem i am adressing in this thread if diffusion in one of the layers is much quicker than in the other.

Yet, if i want to expand the model with further reaction terms in one of the layers the sequential solution of the different regions will pose a problem, which is why i really need to actually couple the PDEs and solve them together.

It is pretty similar to a multilayer heat transfer problem which was solved here:

http://www.mapleprimes.com/questions/100922-Pdsolve-Numeric-For-Multilayer-Heat-Conduction

Yet i am not sure how to transform my coordinates in my case because i only have the diffusion coefficients and nothing else...

Any ideas?

Cheers

Goon

ok it works. however it turns out that it doesnt resemble the actual behaviour because like this it yields a steady slope. the initial question is still valid (how do i couple two PDEs, that is how do i provide transient boundaries) because i want to have the contraints c(x0,t)=zeta(x0,t) but without the local derivatives beiing equal as well.

So any comments anyone, please??

Cheers

Goon

@Preben Alsholm 

thanks. pretty easy. didnt occur to me but thats quite elegant

cheers