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ABSTRACT Charge transport in poly(3-alkylthiophene)s (P3AT)s is closely linked to the nanoscale organization of crystallites. Block copolymer morphologies provide an ideal platform to study crystallization as the chain ends are tethered at a known interface in a well-defined geometry. The impact of soft versus hard confinement on P3EHT crystallization was studied using poly(3-(2′-ethyl)hexylthiophene) (P3EHT) containing diblocks with both rubbery poly(methyl acrylate) (PMA) and glassy polystyrene (PS) blocks. Here, P3EHT's lower melting point relative to the commonly studied poly(3-hexylthiophene) (P3HT) facilitated its confined crystallization and makes it an ideal model system. While transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) revealed well-ordered lamellar morphologies both in the melt and post-crystallization for both sets of diblocks, the glassy blocks inhibit confined crystallization of P3EHT relative to rubbery matrix blocks. Analysis of aligned diblocks by both SAXS and wide angle X-ray scattering (WAXS) revealed that the P3EHT chain axis aligns perpendicular to domain interfaces, allowing preferential growth of the alkyl-chain and π-π stacking directions parallel to lamellae. Finally, it was shown that following diblock self-assembly in the melt, crystallite growth drives expansion of microdomains to match the P3EHT contour length. It was concluded that P3EHT chains adopted an extended conformation within confined crystallites due to the rigid nature of polythiophenes relative to flexible chain crystalline polymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 205-215 [ABSTRACT FROM AUTHOR]

Tunability of polymer surface properties depends cruciallyon boththe chemical composition of the polymer and the physics of the chains(e.g., surface segregation, chain shape, etc.). Polypeptoids, whichare non-natural biomimetic polymers based on an N-substituted glycinebackbone, provide a flexible model system in which monomer sequence,chain shape, and self-assembled structure can easily be controlledto understand their influence on surface properties. We demonstratethe influence of the amount and sequence of hydrophobic monomers ina predominantly hydrophilic peptoid chain on the surface propertiesof a hybrid block copolymer, poly(peptoid-b-styrene).Just three fluorinated groups in peptoid sequences consisting of upto 45 hydrophilic monomers in length were needed to lower the surfaceenergy of the peptoid and allow for its maximal surface segregation.Positioning these fluorinated groups in the middle of a chain as opposedto the chain ends resulted in a change in chain conformation at thesurface as evidenced by near-edge X-ray absorption fine structurespectroscopy (NEXAFS). Surface reconstruction of polymers containingonly three fluorinated monomers occurred within seconds but couldbe slowed by an order of magnitude when five fluorinated monomerswere incorporated. [ABSTRACT FROM AUTHOR]

Block copolymers with tunable compositions offer theability todirectly control the interaction strength between the two blocks andtherefore polymer properties. The miscibility of an A–B blockcopolymer can be increased by introducing B or B-like comonomers intothe A block, and literature has shown that both the amount and thedistribution of these comonomers affect the compatibility of the twoblocks. Sequence-defined block copolymers in which one can exactlycontrol the composition and comonomer distribution provide a uniqueopportunity to control the overall strength of segregation. Here,sequence-defined block copolymers have been synthesized via azide–alkynecoupling using polystyrene and sequence-specific polypeptoids (N-substitutedglycines) with 2-methoxyethyl side chains. These polystyrene-polypeptoidblock copolymers readily self-assemble into hexagonally packed andlamellar morphologies. N-(2-phenylethyl)glycine residues,which have a styrene-like side chain, were introduced throughout thepolypeptoid block to increase the compatibility with the polystyreneblock. As the compatibility increased, the strength of segregationand therefore the block copolymer order–disorder transitionsdecreased. The polystyrene–polypeptoid block copolymers providea tunable platform for further studies on the effect of compositionand sequence design on self-assembly and block copolymer properties. [ABSTRACT FROM AUTHOR]