title: Morphologies of ABC triblock terpolymer melts containing poly(cyclohexadiene): effects of conformational asymmetry.
abstract: We have synthesized linear ABC triblock terpolymers containing poly(1,3-cyclohexadiene), PCHD, as an end block and characterized their morphologies in the melt. Specifically, we have studied terpolymers containing polystyrene (PS), polybutadiene (PB), and polyisoprene (PI) as the other blocks. Systematically varying the ratio of 1,2- /1,4-microstructures of poly(1,3-cyclohexadiene), we have studied the effects of conformational asymmetry among the three blocks on the morphologies using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and self-consistent field theory (SCFT) performed with PolySwift++. Our work reveals that the triblock terpolymer melts containing a high percentage of 1,2-microstructures in the PCHD block are disordered at 110 °C for all the samples, independent of sequence and volume fraction of the blocks. In contrast, the triblock terpolymer melts containing a high percentage of 1,4-microstructure form regular morphologies known from the literature. The accuracy of the SCFT calculations depends on calculating the χ parameters that quantify the repulsive interactions between different monomers. Simulations using χ values obtained from solubility parameters and group contribution methods are unable to reproduce the morphologies as seen in the experiments. However, SCFT calculations accounting for the enhancement of the χ parameter with an increase in the conformational asymmetry lead to an excellent agreement between theory and experiments. These results highlight the importance of conformational asymmetry in tuning the χ parameter and, in turn, morphologies in block copolymers.
authors.affiliation: National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA. kumarr@ornl.gov
authors.forename: Rajeev
authors.initials: R
authors.lastname: Kumar
authors.forename: Scott W
authors.initials: SW
authors.lastname: Sides
authors.forename: Monojoy
authors.initials: M
authors.lastname: Goswami
authors.forename: Bobby G
authors.initials: BG
authors.lastname: Sumpter
authors.forename: Kunlun
authors.initials: K
authors.lastname: Hong
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Wu
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Russell
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Gido
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Misichronis
authors.forename: Sofia
authors.initials: S
authors.lastname: Rangou
authors.forename: Apostolos
authors.initials: A
authors.lastname: Avgeropoulos
authors.forename: Thodoris
authors.initials: T
authors.lastname: Tsoukatos
authors.forename: Nikos
authors.initials: N
authors.lastname: Hadjichristidis
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Beyer
authors.forename: Jimmy W
authors.initials: JW
authors.lastname: Mays