title: Impact of chain microstructure on solution and thin film self-assembly of PCHD-based semi-flexible/flexible diblock copolymers.
abstract: Self-assembly of semi-flexible/flexible block copolymers in a selective solvent is examined using a set of diblock copolymers where the chain microstructure of the semi-flexible block is manipulated in order to tune chain stiffness. Conceptually, the reduced conformational space of the semi-flexible block is anticipated to alter the way the chains pack, potentially changing the structure of self-assembled aggregates in comparison to flexible diblock copolymer analogs. Semi-flexible/flexible diblock copolymers comprised of poly(styrene)-block-poly(1,3-cyclohexadiene) (PS-b-PCHD) having systematic changes in chain microstructure, as captured by the ratio of 1,4/1,2-linkages between cyclohexenyl repeat units, and molecular weight of the PCHD blocks were synthesized using anionic polymerization. These diblocks were dissolved in tetrahydrofuran (THF), which is a preferential solvent for PS, and the structures formed were examined using laser light scattering and complementary imaging techniques. Results show that PS-b-PCHD copolymers with a chain microstructure of 90% 1,4/10% 1,2 linkages between cyclohexenyl repeat units (referred to simply as 90/10) are able to micellize, forming spherical structures, while diblocks of 70/30 and 50/50 1,4-to-1,2 ratios remain as single chains and ill-defined aggregates, respectively, when dissolved in THF. With inferences drawn from simple structural models, we speculate that this self-assembly behavior arises due to the change in the chain configuration with increasing content of 1,2-links in the backbone. This renders the chain with higher 1,2 content incapable of swelling in response to solvent and unable to pack into well-defined self-assembled structures.
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, TN 37996, USA.
authors.forename: Kamlesh
authors.initials: K
authors.lastname: Bornani
authors.forename: Xu
authors.initials: X
authors.lastname: Wang
authors.forename: Jesse L
authors.initials: JL
authors.lastname: Davis
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wang
authors.forename: Weiyu
authors.initials: W
authors.lastname: Wang
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Hinestrosa
authors.forename: Jimmy W
authors.initials: JW
authors.lastname: Mays
authors.forename: S Michael
authors.initials: SM
authors.lastname: Kilbey