Rubbing-Induced Molecular Alignment on a Rubbed Alkyl-Branched Polyimide Film

Huang, Jung Y.; Li, J. S.; Chen, S. H.

doi:10.1080/10587259508031017

Cited by 4 publications

(2 citation statements)

References 15 publications

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“…However, the fibers in the gels are randomly intertwined and they lack the mechanical integrity for stretching (in contrast to the case of polymer gels). In the case of polymer films, rubbing is a technique used for aligning the molecules . Rubbing-induced molecular alignment has been studied in the case of thin polystyrene films, liquid crystals and other polymers.…”

Section: Resultsmentioning

confidence: 99%

Influence of Double Hydrogen Bonds and Alkyl Chains on the Gelation of Nonchiral Polyurethane Model Compounds: Sheets, Eaves Trough, Tubes and Oriented Fibers

2009

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We describe the gelation, upon self-assembly of a series of nonchiral molecules, resulting in tubular morphology of the fibers. These are biscarbamates, which are model compounds for polyurethanes with two hydrogen bonding groups separated by a (CH(2))(6) spacer and symmetrically substituted with alkyl chains on either side varying in length from C(6) to C(18). Upon gelation, these molecules form a sheet initially. The sheets then tend to wrap, leading to tubules. Those with partial wrapping resemble eaves troughs. With the predominant growth along the hydrogen bonding direction, the energy of interaction between the molecules along this direction would be more dominant than just the van der Waals interaction in the other two, leading to asymmetry of interaction in the sheet. We rationalize such tube formation in this case on the basis of the theories [Schnur, J. M.; Ratna, B. R.; Selinger, J. V.; Singh, A.; Jyothi, G.; Easwaran, K. R. K. Science, 1994, 264, 945. Schnur, J. M. Science, 1993, 262, 166. McKierman, R. L.; Heintz, A. M.; Hsu, S. L.; Gido, S. P.; Penelle, J. Polym. Mater. Sci. Eng. 2001, 84, 416.] which were developed for amphiphilic mono and bilayers, which state that these bilayers are not at their minimal energy when they are flat, and prefer a bent state. The gelation behavior of this series with double hydrogen bond is compared with the monocarbamates with a single hydrogen bonding motif [Moniruzzaman, M.; Sundararajan, P. R. Langmuir 2005, 21, 3802.]. We attribute the tendency toward both gelation and crystallization in some cases to the competing contributions of the hydrogen bond and van der Waals interactions between the long alkyl side chains. Oriented fibers for X-ray diffraction were obtained by simply using a magnetic stir bar during gelation. It is also found that the solvents that gel with diureas [van Esch, J.; Kellogg, R. M.; Feringa, B. L. Tetrahedron Lett. 1997, 38, 281] also form gels with biscarbamates. While the biscarbamates with even number of CH(2) groups in the side chain form short fibers, one with (CH(2))(9) side group formed long fibers characteristic of organo gels. In addition, when this odd side chain biscarbamate was mixed with one having a (CH(2))(8) side group, the gelation led to long fibers, following the sergeant and soldier principle.

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Section: Resultsmentioning

confidence: 99%

Influence of Double Hydrogen Bonds and Alkyl Chains on the Gelation of Nonchiral Polyurethane Model Compounds: Sheets, Eaves Trough, Tubes and Oriented Fibers

2009

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“…We note that the above conclusions are not surprising in light of past studies of sheared films of synthetic polymer films (e.g., polystyrene or polyimide). Past studies have established that (i) AFM can be used to measure anisotropic topography on these surfaces − and (ii) the anisotropic topographical structure does not define the dominant interactions between the liquid crystal and surface that dictate the orientation of the liquid crystal. − Instead, oriented polymer chains and molecular-level interactions are generally believed to dictate the orientations of liquid crystals on sheared polymer surfaces. − For example, nematic 5CB orients across the “scratches” on films of sheared polystyrene. − …”

Section: Resultsmentioning

confidence: 99%

Manipulation of the Orientational Response of Liquid Crystals to Proteins Specifically Bound to Covalently Immobilized and Mechanically Sheared Films of Functionalized Bovine Serum Albumin

Kim

Abbott

2002

Langmuir

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This paper reports on the orientational behavior of thermotropic liquid crystals supported on films of biotinylated bovine serum albumin (BSA) that are covalently immobilized on the surface of glass substrates using (3-aminopropyl)triethoxysilane (APES) and disuccinimidyl suberate (DSS). The films of biotinylated BSA are mechanically sheared and then immersed into aqueous solutions of anti-biotin immunoglobulin G (IgG) prior to contact with nematic phases of 4-cyano-4′-pentylbiphenyl (5CB). Using ellipsometry, we found the capacity of the films of biotinylated BSA to bind anti-biotin IgG to be unchanged upon shearing with a polyester cloth. In contrast, we determined the orientational response of nematic phases of 5CB to the presence of bound anti-biotin IgG to be a strong function of the normal pressure applied during shearing, as well as the magnitude of the lateral displacement of the film of biotinylated BSA when in contact with the surface of the polyester cloth. The shear rate, however, appears to have little influence on the response of the liquid crystal to bound IgG. These results demonstrate that it is possible to manipulate the response (sensitivity) of liquid crystals to IgG specifically bound to sheared films of functionalized BSA by changing the manner of shearing of the films of BSA without changing the capacity of the films to bind IgG. We also report a characterization of the nanometer-scale topography of mechanically sheared films of biotinylated BSA using atomic force microscopy (AFM).

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Control of liquid crystal pretilt angles by chemical derivatization reaction of polyvinyl alcohol films

West

2004

Liquid Crystals

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Rubbing-Induced Molecular Alignment on a Rubbed Alkyl-Branched Polyimide Film

Cited by 4 publications

References 15 publications

Influence of Double Hydrogen Bonds and Alkyl Chains on the Gelation of Nonchiral Polyurethane Model Compounds: Sheets, Eaves Trough, Tubes and Oriented Fibers

Influence of Double Hydrogen Bonds and Alkyl Chains on the Gelation of Nonchiral Polyurethane Model Compounds: Sheets, Eaves Trough, Tubes and Oriented Fibers

Manipulation of the Orientational Response of Liquid Crystals to Proteins Specifically Bound to Covalently Immobilized and Mechanically Sheared Films of Functionalized Bovine Serum Albumin

Control of liquid crystal pretilt angles by chemical derivatization reaction of polyvinyl alcohol films

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