Critical behavior of the banded-unbanded spherulite transition in a mixture of ethylene carbonate with polyacrylonitrile.

We investigate the transition from unbanded to banded spherulitic growth in mixtures of ethylene carbonate with polyacrylonitrile. By carefully considering systematic errors, we show that the band spacing diverges with a power-law form showing scaling over nearly two decades. We also observe that the bands disorder as the transition point is approached. The critical exponent is nonclassical. One possible explanation is that the nonequilibrium transition is actually weakly first order (subcritical).