ma7b01323_si_001.pdf (386.32 kB)
Confined Crystallization within Cylindrical P3EHT Block Copolymer Microdomains
journal contribution
posted on 2017-08-09, 14:18 authored by Emily
C. Davidson, Rachel A. SegalmanConfinement
of crystallites within block copolymer microdomains
is a promising approach to study conjugated polymer crystallization
due to interfacial chain tethering and defined geometries. The nanoscale
organization of crystallites is often critical to determining the
charge transport properties of conjugated polymers. Here, a poly(3-(2′-ethyl)hexylthiophene)-block-poly(methyl acrylate) (P3EHT-b-PMA)
system is leveraged to study the impact of confinement within cylindrical
microdomains. The crystalline P3EHT permits accessible melting temperatures
and robust formation of traditional microphase-separated morphologies,
while the rubbery PMA allows the local deformations required to permit
P3EHT crystallization. Crystallites form with chains perpendicular
to the diblock interface, causing domain expansion; TEM reveals that
this is accommodated in the cylindrical geometry via local deformation.
Complementary SAXS/WAXS of aligned diblocks shows preferential orientation
of the alkyl chain stacks down domains. Furthermore, cylindrically
confined P3EHT demonstrates a smaller window of thermal control over
crystalline perfection via isothermal crystallization conditions than
homopolymer P3EHT or block copolymer P3EHT in lamellar confinement.
This work demonstrates that postcrystallization annealing is an alternative
route to generating uniformly high quality crystallites in cylindrically
confined P3EHT. These results are important for considering routes
to optimizing and controlling crystallinity in nanoscale confined
geometries.