Synthesis, Processing, and Characterization of Helical Polypeptide Rod–Coil Mixed Brushes

Abstract

Mixed polymer brushes of rod-type polypeptide and coiltype vinyl polymer brushes were synthesized via two sequential steps of vapor deposition surface-initiated ring-opening polymerization (SI-ROP) and surface-initiated atom transfer radical polymerization (SI-ATRP), respectively. The effect on polypeptide brushes by coil-type brushes of their surface morphology, film thickness, and orientation were investigated before and after solvent quenching processes using chloroform and acetone. Before solvent quenching, the as-grown coil-type brushes forced the polypeptide brushes to stand up from the surface, resulting in higher film thickness, but the polypeptide brushes remained randomly oriented. After solvent quenching, polypeptide brushes tended to aggregate into conical bundles with an orientation perpendicular to the substrate, but coil-type brushes restricted the free arrangement of the polypeptide brushes and lessen their upward movement. Changes in film thickness, rod orientation, morphology, and wettability were observed with increased molecular weight of the coil-type polymer in the mixed brushes.

High-Resolution Nanopatterning of Free-Standing, Self-Supported Helical Polypeptide Rod Brushes via Electron Beam Lithography

“…Vapor-deposition conditions were further optimized to prevent background contamination of the silane in unexposed areas. After the resist lift-off, PBLG brushes were grown via vapor phase SI-ROP under vacuum and elevated temperature, and the solvent quenching process was used via the procedure described by Tran et al 19 (Chart 1).…”

“…Furthermore, the grafting-from synthesis approach, that is, surface-initiated polymerization, results in high grafting density and controlled and uniform film thickness, thus, achieving enhanced self-assembly of the mixed rod−coil polymer brushes. Combining with a solvent quenching process 19 significantly reduced the annealing time compared to the thermal or solvent annealing techniques compared to block copolymer self-assembly. Further studies are required for understanding the mechanism of such attachments and finer control on these assemblies to produce patterned rod-brush structures with smaller spacings and explore their possible applications in biological simulations and electronic devices.…”

“…Our previous research has already shown the vertical alignment and self-aggregation of polypeptide brushes when placed in a mixed rod–coil brushes system. However, the poly-γ-benzyl- l -glutamate (PBLG) brushes’ self-support and free-standing capability were not examined in the same study due to a lack of nanopatterning analysis . It is worth noting that the fundamental characteristics of nanopatterned polymer brushes (NPB) are different from those of homogeneous brush layers and micropatterned brushes since the NPB’s polymer contour length now becomes comparable to pattern size. − Therefore, it was of interest to investigate helical polypeptide NPBs and gain insight into how nanostructured rod-type polymer brushes adapt to the imposition of nanoscale patterns.…”

Spontaneous Tilting Transition in Liquid-Crystalline Polymer Brushes

“…This potential application, along with others such as organic electronics, switches, and sensors, has spurred numerous experimental studies. [19][20][21][22][23][24][25][26][27][28][29] Subsequent theoretical calculations have, so far, concentrated on the simpler system of LC brushes in conventional solvents. In particular, Birshtein et al 30 examined freely-jointed chains interacting by Maier-Saupe LC interactions.…”

Organocatalyzed Living Radical Polymerization of Itaconates and Self‐Assemblies of Rod−Coil Block Copolymers

“…Rod−coil block copolymers can form unique assembly structures and found a range of applications in composites, [ 40 ] biomaterials, [ 41,42 ] and organic electronics. [ 43 ] The rod (rigid) segment studied so far includes aromatic polymers, [ 44,45 ] π‐conjugated polymers, [ 46,47 ] polypeptides, [ 48,49 ] and polyisocyanates. [ 50,51 ] Because itaconate monomers have two alkyl esters at the α‐position, itaconate polymers are rigid and can be used as rod segments in rod−coil copolymers.…”