Kinetic aspects of the coil-stretch transition of polymer chains in dilutesolution under extensional flow

When linear polymer chains in dilute solution are subject to extensional fl ow, each chain in the sample experiences the coil-stretch transition at a d ifferent time. Using Brownian dynamics simulation, we have studied the dist ribution of transition times in terms of the extensional rate and the lengt h of the chains. If instead of time one characterizes the effect of the flo w by the accumulated strain, then the distribution and its moments seem to take general forms, independent of molecular weight and flow rate, containi ng some numerical, universal constants that have been evaluated from the dy namical simulation. The kinetics of the transition, expressed by the time-d ependence of the fraction of remaining coils, has also been simulated, and the results for the kinetic rate constant has been rationalized in a manner similar to that used for the transition time. The molecular individualism, characterized in this work by the distribution of transition times, is rel ated to the excess of the applied extensional rate over its critical value, which will determine the transition time and other features of the coil-st retch transition. (C) 2001 American Institute of Physics.