{HEAD ~ The polyelectrolytes} can become {TAIL ~ cross} linked and unable to undergo further transitions in porosity 
{ HEAD ~ The polyelectrolytes } can become { TAIL ~ cross } linked and unable to undergo further transitions in porosity
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH