Degrafting of Poly(poly(ethylene glycol) methacrylate) Brushes from Planar and Spherical Silicon Substrates

Abstract

Densely grafted, hydrophilic polymer brushes produced via surface-initiated controlled radical polymerization have been shown to undergo degrafting upon exposure to aqueous media. This degrafting process has been proposed to involve swelling-induced, mechanochemically facilitated hydrolysis of bonds located at the brush−substrate interface. While a number of reports have described degrafting of hydrophilic polymer brushes, only little is known about the key structural parameters of these thin films that dictate this process. Using a series of PPEGMA and PPEGMEMA brushes produced by surface-initiated atom transfer radical polymerization (SI-ATRP), this report investigates the influence of three parameters: (i) the chemical structure of the ATRP initiator, (ii) the molecular weight of the surface-grafted polymer chains, and (iii) surface curvature. Studies performed with PPEGMA and PPEGMEMA brushes grown from substrates modified with different ATRP initiators indicated that hydrolysis of both siloxane as well as ester/amide bonds contributes to degrafting. Finally, experiments with PPEGMEMA-modified silica nanoparticles revealed the influence of surface curvature and suggested that degrafting is more pronounced as surface curvature decreases.

Functionalization of halloysite nanotube surfaces via controlled living radical polymerization: covalent immobilization of penicillin for a bioactive interface

“…The C1s core‐level spectrum of the HNTs‐ g ‐PPEGMA surface (Fig. (f)) could be curve‐fitted to three peaks, attributed to CH (BE of 283.6 eV), CO (BE of 285.7 eV), and OCO (BE of 288.8 eV) . The area ratio of these peaks was estimated to be 3.7:11.6:1, which is close to the theoretically expected 3:12:1 for PPEGMA, indicating that PPEGMA was successfully grafted onto the HNTs.…”

“…2(f )) could be curve-fitted to three peaks, attributed to C-H (BE of 283.6 eV), C-O (BE of 285.7 eV), and O C-O (BE of 288.8 eV). 45,46 The area ratio of these peaks was estimated to be 3.7:11.6:1, which is close to the theoretically expected 3:12:1 for PPEGMA, indicating that PPEGMA was successfully grafted onto the HNTs. Figure 3 displays the thermal decomposition behaviors of HNTs, HNTs-Br, and HNTs-g-PPEGMA.…”

Swelling‐Induced Chain Stretching Enhances Hydrolytic Degrafting of Hydrophobic Polymer Brushes in Organic Media

“…[9] Degrafting of the end tethered PtBMA chains via hydrolysis of the siloxane or amide bonds that anchor the polymer to the substrate will result in ag radual decrease in the grafting density of the polymer brush (Scheme 2). [5] Ellipsometry was used to characterize the swelling behavior of the PtBMA brushes and to monitor the degrafting process.T od escribe the swelling properties of the PtBMA brushes in the different media, the swelling ratios were determined, which are defined as the ratio of the swollen and dry film thickness of the initial polymer brush. Theb ond tension in chain end tethered, swollen brushes scales with the inverse of the grafting density and has been estimated to 1-10 pN in ad ense brush to 0.1-1.0 pN in the mushroom regime.…”

Swelling‐Induced Chain Stretching Enhances Hydrolytic Degrafting of Hydrophobic Polymer Brushes in Organic Media

“…[4] Thedegrafting of hydrophilic polymer brushes from silicon oxide surfaces in aqueous media has been attributed to as welling-induced stretching of the surface-anchored polymer chains and ac oncomitant amplification of the tension that acts on the siloxane and ester/amide bonds that anchor the chains to the surface. [5] Thei ncreased tension at the polymer brush-substrate interface has been postulated to facilitate hydrolysis of the anchoring siloxane and ester/amide bonds resulting in the observed degrafting of the surfaceattached polymer chains.…”

“…Degrafting proceeds to al imiting, non-zero film thickness where this tension is believed to be reduced to avalue that is no longer sufficient to facilitate hydrolytic cleavage. [5] Ellipsometry was used to characterize the swelling behavior of the PtBMA brushes and to monitor the degrafting process.T od escribe the swelling properties of the PtBMA brushes in the different media, the swelling ratios were determined, which are defined as the ratio of the swollen and dry film thickness of the initial polymer brush. Degrafting was monitored by determining the dry film thickness of the PtBMA brushes at regular time intervals.…”