ma1c01125_si_001.pdf (1.37 MB)
Download fileUsing Liquid Crystals to Probe the Organization of Helical Polypeptide Brushes Induced by Solvent Pretreatment
journal contribution
posted on 30.08.2021, 07:29 authored by Michael Tsuei, Hai Tran, Sangchul Roh, Christopher K. Ober, Nicholas L. AbbottGrafted
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-l-glutamate) (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.
History
Usage metrics
Read the peer-reviewed publication
Categories
Keywords
transform infrared spectroscopytailored via choiceprovide fresh insightscombining insights basedchemical functional groupsatomic force microscopypblg brush organizationsusing mixed solventsusing liquid crystalspblg chains imprintedpblg chain orientationtreated pblg brushesexhibit patterned orientationspblg brush organizationpblg chainsliquid crystalsbrush organizationpblg brushespatterned orientationsversatile classthermally denaturedsolvent pretreatmentresults expandpretreated brushespreparing solventorientational behaviormicrometer scalelike organizationlc orientationgrafted polymerseither gooddroplets formedcontinuous changeadditional experiments50 nm