Probing carbonyl–water hydrogen-bond interactions in thin polyoxazoline brushes

Abstract

Temperature-responsive oxazoline-based polymer brushes have gained increased attention as biocompatible surfaces. In aqueous environment, they can be tuned between hydrophilic and hydrophobic behavior triggered by a temperature stimulus. This transition is connected with changes in molecule–solvent interactions and results in a switching of the brushes between swollen and collapsed states. This work studies the temperature-dependent interactions between poly(2-oxazoline) brushes and water. In detail, thermoresponsive poly(2-cyclopropyl-2-oxazoline), nonresponsive hydrophilic poly(2-methyl-2-oxazoline), as well as a copolymer of the two were investigated with in situ infrared ellipsometry. Focus was put on interactions of the brushes' carbonyl groups with water molecules. Different polymer–water interactions could be observed and assigned to hydrogen bonding between C=O groups and water molecules. The switching behavior of the brushes in the range of 20–45 °C was identified by frequency shifts and intensity changes of the amide I band.

Investigation of design parameters in generating antifouling and lubricating surfaces using hydrophilic polymer brushes

“…The higher persistent length for MOXA units, in comparison to EG, result from the helical rearrangement of poly(oxazoline) chains to stabilize hydrogen bonding in presence of local solvation structure. The carbonyl groups (CO) along the backbone of PMOXA chains form H 2 O bridges between the neighboring chains suggesting chain stiffening via inter‐chain solvation structures. A similar solvation‐structure‐dependent effective bond length was also observed for dextran and NIPAM brushes as a function of solvent quality, influencing the bulk modulus of the films .…”

In-situ Deposition of Graphene Oxide Catalyst for Efficient Photoelectrochemical Hydrogen Evolution Reaction Using Atmospheric Plasma

“…The mechanism that made the surface hydrophilic is the ion energy in plasma, which is usually higher than 10 eV exceeding the binding energy for carbon: 2.7 eV and 3.6 eV for π-bonding and σ-bonding, respectively, forming oxygen-containing functional groups [17]. Functional groups like C-OH, C-H, C-O-C, -COOH, C-O-C, C-OH, -C=O, C=O, and carboxylates (O-C=O) make hydrophilic GO surfaces due to dynamic interaction with water by generating intermolecular forces called hydrogen bonding [28][29][30][31]. Figure 4 shows TEM images of obtained rGO in order to investigate its morphology, and the images were examined through FE-TEM to confirm that rGO was formed well.…”

Intermolecular interaction of thermoresponsive poly‐2‐isopropyl‐2‐oxazoline in solutions and interpolymer complex with fiber‐forming polyethylene oxide

“…We suppose that a significant displacement (+22 cm −1 ) can be associated with the formation of intramolecular hydrogen‐bonded bridges СО ··· СН 3 ··· ОС, involving hydrogen atoms of the terminal methyl groups and СО ··· CH 2 ··· OC of the methylene groups of PiPrOx or PEO main chains. Similar concept was proposed to explain the interactions within the collapsing polyoxazoline brushes 28 . The participation of CH 2  and CH 3 groups in the binding is confirmed by a noticeable decrease in the absorption frequency of their stretching vibrations: PiPrOx CH 3 peak of 2969 cm −1 shifted by 2888 cm −1 (−81 cm −1 ), PiPrOx CH 2 peak of 2928 cm −1 by 2862 cm −1 (−66 cm −1 ), and PEO CH 2 peak of 2878 cm −1 by 2862 cm −1 (−16 cm −1 ), which was observed in the processes of PiPrOx hydration–dehydration 22 …”