Reactive spreading activation energy

There are mechanisms by which a gradient of surface concentration is formed and maintained even when all the surface is in contact with the solu-lion. A gradient is formed when certain parts of the surface adsorb more rapidly than other parts the solute accedes to the surface at these locations and then spreads to the rest of the surface. This process is likely when the surface is heterogeneous and contains reactive regions with a low activation energy for adsorption (Birnholtz et at, 1984). It can also be determined by porosity as molecules confined in pores have a greater chance of being sorbed (Aharoni et al., 1989). 

Temperature has a greater influence on the ri and V2 values of ionic copolymerizations than in free-radical copolymerization because of the greater spread of activation energies for the propagation reactions involving ions. There is no general trend observable and the monomer reactivity ratios may increase or decrease with temperature in the isobutylene-styrene copolymerization ri increases by a factor of 1.5 and V2 increases by a factor of 3 when going from —94°C to —30°C... 

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