Adsorption of PNIPAmx-PEO20-PPO70-PEO20-PNIPAmx pentablock terpolymer on gold surfaces: effects of concentration, temperature, block length, and surface properties

Abstract

The effects of concentration, relative block length and environmental temperature as well as the surface chemical and wetting properties of solid substrates on the adsorption behaviors and mechanisms of a series of pentablock terpolymer poly(N-isopropylacrylamide)x-poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20-poly(N-isopropylacrylamide)x (PNIPAmx-PEO20-PPO70-PEO20-PNIPAmx or PNIPAmx-P123-PNIPAmx) with x of 10, 63 and 97 on gold were studied by using a quartz crystal microbalance (QCM) technique. It was found that increasing the solution concentration did not alter the adsorption mechanism of thickness growth mode but increase the adsorption amount of PNIPAm97-P123-PNIPAm97 on a bare gold substrate at 20 °C. Increasing the length x of PNIPAm block decreased the adsorption rate constant and shifted the adsorption mechanism from the densification adsorption process for PNIPAm10-P123-PNIPAm10 to the thickness growth mode for PNIPAm63-P123-PNIPAm63 and PNIPAm97-P123-PNIPAm97 on bare (unmodified) gold substrate at 20 °C. The adsorption mechanisms of PNIPAm97-P123-PNIPAm97 at 20 °C on the hydrophobic and hydrophilic gold surfaces were the thickness growth mode and densification adsorption process, respectively. A complex adsorption behavior with large adsorption amounts was observed at the lower critical solution temperature (LCST) of PNIPAm block, i.e. 34.7 °C, for the adsorption of PNIPAm97-P123-PNIPAm97 not only on hydrophobic gold substrates but also on hydrophilic gold substrates. The adsorption mechanism of PNIPAm97-P123-PNIPAm97 micelles at 45 °C was the densification adsorption process regardless of the surface wetting and chemical properties of gold substrate. Overall, the adsorption behavior and mechanism of PNIPAmx-P123-PNIPAmx pentablock terpolymers were mainly determined by the interactions of the pentablock terpolymers with different chain conformations in dilute aqueous solutions at various temperatures and the gold substrates with surface wetting and chemical properties.

Nanoscale monolayer adsorption of polyelectrolytes at the solid/liquid interface observed by quartz crystal microbalance

“…[18][19][20] In principle, this type of technique can detect the adsorption, conformation and interactions of macromolecules at an interface. [21][22][23] For instance, Du and colleagues 24,25 investigated the adsorption of block copolymers on a gold (Au) surface using a QCM technique. The results indicated that the adsorption mechanism of a PNIPAm x -P123-PNIPAm x pentablock terpolymer was mainly determined by the interactions between the pentablock terpolymers molecules with different chain conformations in dilute aqueous solutions at various temperatures and the Au substrates with surface wetting and chemical properties.…”

Observation of Double Gyroid and Hexagonally Perforated Lamellar Phases in ABCBA Pentablock Terpolymers

“…With addition of a third block C, more than 30 different phase structures have been identified for ABC-type linear triblock terpolymers, − including four traditional phases: lamellae, cylinders, spheres, and gyroid as well as some other special hierarchical structures, such as the ring on cylinder, cylinder on lamellae, and knitting pattern . In recent years, the chemical and physical properties as well as self-assembly behaviors of BCPs with more complicated block architectures, including ABAC-type and ABCA-type tetrablocks, ABCBA pentablocks, − and other multiblock terpolymers, − have increasingly attracted the experimental and theoretical attention of the research community. The multiblock copolymers have various structural parameters such as the number of blocks, block sequence, monomer types, functionality, and composition.…”

“…The symmetric linear ABCBA pentablock terpolymers have been considered as the simplest model system of multiblock copolymers and the excellent candidate for exploring the structures and properties of multiblock copolymers. However, most investigations of ABCBA pentablock terpolymers were focused on the synthesis methods, micellization in solutions, and stimuli-sensitive behaviors in solvent. − ,− Only a few studies have reported experimentally and theoretically on the phase behaviors of ABCBA pentablock terpolymers in bulk. Kopchick et al have reported that poly­(acrylic acid- b -styrene- b -isobutylene- b -styrene- b -acrylic acid) pentablock terpolymers formed three-phase morphologies with a considerable order.…”

Controlling Growth of Poly (Triethylene Glycol Acrylate-Co-Spiropyran Acrylate) Copolymer Liquid Films on a Hydrophilic Surface by Light and Temperature

“…These studies showed different behaviors of the adsorbed polymer depending on its state of adsorption, e.g., whether chemisorbed [50,51] or physisorbed [52,53]. The adsorption of thermosensitive block copolymers based on PNIPAAm on a gold surface was also investigated by QCM-D [54]. For example, the adsorption mechanism of a pentablock terpolymer poly (N-isopropylacrylamide)x-block-poly (ethylene oxide) 20 SP is one of the chromophores that is not only a photo-switch but also responds to other stimuli such as temperature, solvent, metal ions, and pH [41].…”

“…These studies showed different behaviors of the adsorbed polymer depending on its state of adsorption, e.g., whether chemisorbed [ 50 , 51 ] or physisorbed [ 52 , 53 ]. The adsorption of thermosensitive block copolymers based on PNIPAAm on a gold surface was also investigated by QCM-D [ 54 ]. For example, the adsorption mechanism of a pentablock terpolymer poly ( N -isopropylacrylamide) x - block -poly (ethylene oxide) 20 - block -poly (propylene oxide) 70 - block -poly (ethylene oxide) 20 - block -poly ( N -isopropylacrylamide) x (PNIPAAm x - b -PEO 20 - b -PPO 70 - b -PEO 20 - b -PNIPAAm x ) on gold was found to be affected by several parameters including concentration, relative block length, temperature, and the substrate’s physical properties.…”