We have measured the time dependence of interface formation between two polymers, below their critical temperature for phase separation, using the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$${(}^3$He${,}^4$He${)}^1$H nuclear reaction as a direct profiling technique. We find that the width of the interface initially increases with time as ${\mathit{t}}^{\mathrm{\alpha }}$, where the exponent α=0.34±0.06 is significantly lower than its value of 0.5 for free diffusion.

• Received 3 November 1989

DOI:https://doi.org/10.1103/PhysRevLett.64.1119