Self-assembly and glass-formation in a lattice model of telechelic polymer melts: Influence of stiffness of the sticky bonds

摘要

The lattice cluster theory (LCT) for strongly interacting, self-assemblingtelechelic polymers provides a theoretical tool that enables establishing theconnections between important microscopic molecular details of self-assemblingpolymers and their bulk thermodynamics. The original LCT for self-assembly oftelechelic polymers considers a model of fully flexible linear chains [J.Dudowicz and K. F. Freed, J. Chem. Phys. \textbf{136}, 064902 (2012)], whileour recent work introduces a significant improvement to the LCT by including adescription of chain semiflexibility for the bonds within each individualtelecheic chain [W.-S. Xu and K. F. Freed, J. Chem. Phys. \textbf{143}, 024901(2015)], but the physically associative (or called "sticky") bonds between theends of the telechelics are left as fully flexible. Motivated by the ubiquitouspresence of steric constraints on the association of real telechelic polymersthat impart an additional degree of bond stiffness (or rigidity), the presentpaper further extends the LCT to permit the sticky bonds to be semiflexible butto have a stiffness differing from that within each telechelic chain. Ananalytical expression for the Helmholtz free energy is provided for this modelof linear telechelic polymer melts, and illustrative calculations demonstratethe significant influence of the stiffness of the sticky bonds on theself-assembly and thermodynamics of telechelic polymers. A brief discussion isalso provided for the impact of self-assembly on glass-formation by combiningthe LCT description for this extended model of telechelic polymers with theAdam-Gibbs relation between the structural relaxation time and theconfigurational entropy.