Retention of poly(N-isopropylacrylamide) on 3-aminopropyltriethoxysilane

Abstract

Silane coupling agents are commonly employed to link an organic polymer to an inorganic substrate. One of the widely utilized coupling agents is 3-aminopropyltriethoxy silane (APTES). In this study, the authors investigated the ability of APTES to retain thermo-responsive poly(N-isopropylacrylamide) (pNIPAAm) on hydroxylated surfaces such as glass. For comparison purposes, the authors also evaluated the retention behaviors of (1) polystyrene, which likely has weaker van der Waals interactions and acid-base interactions (contributed by hydrogen-bonding) with APTES, on APTES as well as (2) pNIPAAm on two other silane coupling agents, which have similar structures to APTES, but exhibit less interaction with pNIPAAm. Under our processing conditions, the stronger interactions, particularly hydrogen bonding, between pNIPAAm and APTES were found to contribute substantially to the retention of pNIPAAm on the APTES modified surface, especially on the cured APTES layer when the interpenetration was minimal or nonexistent. On the noncured APTES layer, the formation of an APTES-pNIPAAm interpenetrating network resulted in the retention of thicker pNIPAAm films. As demonstrated by water contact angles [i.e., 7 -15 higher at 40 C, the temperature above the lower critical solution temperature (LCST) of 32 C for pNIPAAm, as compared to those at 25 C] and cell attachment and detachment behaviors (i.e., attached/spread at 37 C, above LCST; detached at 20 C, below LCST), the retained pNIPAAm layer (6-15 nm), on both noncured and cured APTES, exhibited thermo-responsive behavior. The results in this study illustrate the simplicity of using the coupling/adhesion promoting ability of APTES to retain pNIPAAm films on hydroxylated substrates, which exhibit faster cell sheet detachment ( 30 min) as compared to pNIPAAm brushes (in hours) prepared using tedious and costly grafting approaches. The use of adhesion promoters to retain pNIPAAm provides an affordable alternative to current thermo-responsive supports for cell sheet engineering and stem cell therapy applications.

Thermoresponsive Poly(vinyl methyl ether) (PVME) Retained by 3-Aminopropyltriethoxysilane (APTES) Network

“…The PVME films fabricated via this simple entrapment method showed comparable switchable protein/cell adhesion behaviors as those of previous studies. 36,37 Additionally, PVME films (∼70 nm after rinsing) showed rapid cell detachment similar to that of pNIPAAm films reported previously. 35,36,38 This inexpensive, straightforward approach can be easily adopted by any laboratory, and the mild processing conditions (e.g., ethanol or water as the solvent; processing temperature ≤80 °C) also allow for the use of common polymers containing hydroxyl groups (e.g., cellulose, polyester, or oxidized polystyrene) as the substrates to expand its applications.…”

“…In addition, the noneasily accessible electron beam technique was applied for their immobilization of PVME. In the present study, we investigated the processing conditions in utilizing 3-aminopropyltriethoxysilane (APTES), which forms a cross-linked network on a surface upon thermal treatment and has been shown to successfully retain a stable layer of pNIPAAm, − for immobilizing PVME on a hydroxylated surface such as glass. We examined the annealing temperature, annealing time, and the PVME/APTES ratio.…”

Role of Near-Electrode Solution Chemistry on Bacteria Attachment and Poration at Low Applied Potentials

“…An APTES-functionalized BDD/OTE (APTES-BDD/OTE) electrode was prepared from a pretreated BDD/OTE after rinsing with methanol, ethanol, and water. The cleaned BDD/OTE was immersed in 5 mM APTES in anhydrous toluene and allowed to react in an Ar-filled glovebox for 3 h. The APTES-BDD/OTE was then rinsed three times with toluene and methanol and annealed at 120 °C for 30 min to promote cross-linking of the silanes. , …”

“…The cleaned BDD/OTE was immersed in 5 mM APTES in anhydrous toluene and allowed to react in an Arfilled glovebox for 3 h. The APTES-BDD/OTE was then rinsed three times with toluene and methanol and annealed at 120 °C for 30 min to promote cross-linking of the silanes. 27,28 The surface functional groups on the OTEs were characterized by X-ray photoelectron spectroscopy (XPS) (Kratos Axis-165). Cycle voltammetry (CV) scans (100 mV s −1 ) were performed with ionic redox couples (5 mM Fe(CN) 6…”

Retention of poly(N‐isopropylacrylamide) thin films on polycarbonate via polymer interdiffusion

“…A common approach for retaining pNIPAAm is grafting pNIPAAm as brushes to a surface, 2–422 ; such an approach could be expensive and laborious 2–5 . Recently, entrapping pNIPAAm in an organosilane network, 6,8,923–25 and simply coupling pNIPAAm chains to organosilanes 26 to retain pNIPAAm on a support have shown some success. One critical requirement of utilizing organosilanes to immobilize pNIPAAm is that the immobilizing supports need to contain hydroxyl groups that can chemically react with organosilanes.…”