Spectroscopic Investigation of Polypeptide Plane Brushes

Vlasova, E. N.; Волчек, Б. З.; Tarasenko, I. I.; Vlasov, G. P.

doi:10.1002/masy.201000130

Cited by 3 publications

(4 citation statements)

References 10 publications

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“…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.…”

Section: Introductionmentioning

confidence: 99%

“…Using an Alexander-de Gennes type calculation, Halperin and Williams , demonstrated how LC brushes could be used to control the alignment of a liquid-crystalline solvent, an important issue for LC display technology. This potential application, along with others such as organic electronics, switches, and sensors, has spurred numerous experimental studies. − …”

Section: Introductionmentioning

confidence: 99%

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Spontaneous Tilting Transition in Liquid-Crystalline Polymer Brushes

2019

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The equilibrium phase behavior of main-chain liquid-crystalline polymer brushes in good solvent is investigated using self-consistent field theory. The calculation assumes semi-dilute brushes, where the grafting density is sufficient to cause overlap among the polymers but low enough to allow the solvent to be treated implicitly. The polymers are modeled as semi-flexible worm-like chains with Maier-Saupe interactions. Previous calculations based on freely-jointed chains have predicted that extended brushes collapse into folded nematic brushes, as the liquid-crystalline interaction strength is increased. For the more sophisticated model of worm-like chains, which penalizes hairpin folds, we find that extended brushes become unstable with respect to tilting prior to the onset of folding. This implies that the brushes spontaneously collapse by a symmetry-breaking transition, where the chains tilt rather than fold.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spontaneous Tilting Transition in Liquid-Crystalline Polymer Brushes

2019

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“…Thus, under the transmission mode, when the IR-beam went through the samples and interacted with PBLG brushes, only the active electric field components of the transition dipole moments of the amide bonds parallel to the substrate were measured . Then, the dichroic ratio D of amide I over amide II adsorption can give a qualitative assessment of the average orientation of α-helical rod. − The decrease in D value is related to higher average tilt angle of the α-helical rods with respect to the substrate. The trend of decreasing D value from sample I to IV implied an increase in average tilt angle which was consistent with the increase in film thickness mentioned previously (Figures and A).…”

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confidence: 99%

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

2018

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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.

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“…A key challenge underlying the rational design of smart surfaces based on polypeptide brushes is characterization of the organization of the brushes. In past studies, the out-of-plane orientations of PBLG chains were characterized by Fourier transform infrared (FTIR) spectroscopy, − which provides average molecular orientations of the grafted chains, and atomic force microscopy (AFM), , which probes mesoscale surface topography. While these past studies provided important insights in brush organization, they also highlight the limitations of FTIR and AFM methods.…”

Section: Introductionmentioning

confidence: 99%

Using Liquid Crystals to Probe the Organization of Helical Polypeptide Brushes Induced by Solvent Pretreatment

et al. 2021

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Grafted polymer brushes form the basis of a versatile class of surfaces with properties that can be tailored via choice of the chemical functional groups or architecture of the grafted polymers. Here, we explore how treatment by solvents can program the organization of homopolymer brushes comprising helical poly(γ-benzyl-Lglutamate) (PBLG) and how the orientational behavior of liquid crystals (LCs) contacted with the brushes can provide fresh insights into brush organization. We treated PBLG brushes with either good (chloroform) or poor (acetone) solvents to form collapsed or teepee-like grafted polymer organizations, respectively. When supported on PBLG brushes with thicknesses [determined by atomic force microscopy (AFM)] of 50 nm, we found that collapsed and teepee-like brushes induced planar (parallel to surface) and homeotropic (perpendicular to surface) orientations of nematic LCs, respectively. By preparing solvent-pretreated brushes with a range of thicknesses (12−140 nm), and by combining insights based on AFM, Fourier-transform infrared spectroscopy and LCs, we found that a continuous change in tilt of the LC is accompanied by a continuous change in tilt of the PBLG chains, as influenced by the teepee-like organization. The role of PBLG chain orientation in dictating the LC orientation was confirmed by additional experiments in which PBLG brushes were thermally denatured. Finally, when using mixed solvents (mixtures of chloroform and acetone) to manipulate the PBLG brush organization, we observed LCs to exhibit patterned orientations on the micrometer scale, consistent with patterned orientations of the PBLG chains imprinted by droplets formed during the mixed solvent drying process. Overall, these results expand our understanding of the range of PBLG brush organizations that can be induced by solvent pretreatment and demonstrate the utility of LCs for imaging PBLG chain orientation within brushes.

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Spectroscopic Investigation of Polypeptide Plane Brushes

Cited by 3 publications

References 10 publications

Spontaneous Tilting Transition in Liquid-Crystalline Polymer Brushes

Spontaneous Tilting Transition in Liquid-Crystalline Polymer Brushes

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

Using Liquid Crystals to Probe the Organization of Helical Polypeptide Brushes Induced by Solvent Pretreatment

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