(551g) Thermodynamic Mixing Rules for Block-Random Copolymers | AIChE

(551g) Thermodynamic Mixing Rules for Block-Random Copolymers


Calopiz, M. C. - Presenter, Rochester Institute of Technology
Padmanabhan, P. - Presenter, Rochester Institute of Technology
Kim, J. M., Auburn University
Ste. Marie, J., Rochester Institute of Technology
Mangibayev, K., Rochester Institute of Technology
Beckingham, B., Auburn University
Block copolymer chemistry is typically selected based on the targeted morphology and desired Flory-Huggins interaction parameters. Chemistry limits the range of temperatures of operability. In addition, the only free design parameter is the degree of polymerization which limits the range of domain spacings. Instead, we show that one can systematically and continuously change the effective Flory-Huggins parameter χeff by replacing one of the blocks with a statistically random block comprised of two monomers. This strategy of introducing block-randomness is useful only when the thermodynamic mixing rules to determine the effective parameter χeff are known prior to synthesis. In this work, we utilize both computational and experimental approaches to interrogate the thermodynamic mixing rules for obtaining the effective parameter χeff for the block-random copolymer using the parameter χ between pure blocks and composition of the random block predicted by regular solution theory. The order-disorder temperatures are identified in simulation and experiment which establishes χeff, and its relation to the composition of the random block is established. In experiment, symmetric polyisoprene-poly(isoprene-r-styrene) block-random copolymers are used as the model system and composition is varied. Computational simulations are carried out using a bead-spring model for representing the synthesized copolymers, and the effect of composition and degree of polymerization are established.