MODIFICATION OF THE CRYSTALLIZATION KINETICS OF A MIXED BATH OF ALKANES IN THE PRESENCE OF COIL-CRYSTALLINE BLOCK-COPOLYMER MICELLES

Recent Neutron Scattering experiments by Richter et al. [1] show that the presence of coil-crystalline block copolymer (PE-PEP) micelles in a mixed alkane bath suppresses the crystallization out of solution of the long alkane component at low temperatures. Motivated by these expe riments, we study theoretically the thermodynamics and kinetics of lam ellar coil-crystalline block copolymer micelles in a bimodal solvent t o better understand the factors determining the anti-precipitation act ion of coil-crystalline block copolymers. We assume an Alexander-de Ge nnes brush model for the strongly stretched corona chains and explicit ly account for the polydispersity of the solvent chains. For the therm odynamic distribution of solvent chains in the corona, we find a predo minance of short solvent chains to long solvent chains in the corona p hase compared to the solvent bath; both with and without nematic inter actions in the corona phase. We also calculate the rate of crystalliza tion of the long solvent chains onto the micellar crystal core and fin d that the rate is sensitive to both brush and core parameters. In par ticular, we predict that to maximize the rate, both E-fold/kTN(A) and chi(n) need to be made as small as possible, where E-fold is the foldi ng energy of the crystal core chains, N-A the number of statistical se gments of the solvated corona chains and chi(n) parameterises the stre ngth of nematic interactions in the micellar corona. This leads to the surprising result that for fixed E-fold, the rate of crystallization is increased when we increase the molecular weight of the corona block s.