Spatial Control over Cross-Linking Dictates the pH-Responsive Behavior of Poly(2-(tert-butylamino)ethyl methacrylate) Brushes

Abstract

Surface-initiated atom transfer radical polymerization (ATRP) of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) produced pH-responsive secondary amine-functionalized polymer brushes with dry thicknesses ranging from 4 to 28 nm, as determined by ellipsometry. At low pH, linear PTBAEMA brushes became protonated and highly swollen; brush collapse occurred when the solution pH was increased to ca. 7.7 due to deprotonation. PTBAEMA brushes were subsequently cross-linked using tolylene-2,4-diisocyanate-terminated poly(propylene glycol) (PPG-TGI) in either THF (a good solvent for PTBAEMA) or n-hexane (a poor solvent). The intensity of the C–C–O component (286.5 eV) in the C1s X-ray photoelectron spectrum increased after reaction with PPG-TDI, suggesting that cross-linking was successful in both solvents. Ellipsometry studies indicated that the pH-responsive behavior of these cross-linked brushes is dictated by the spatial location of the PPG-TDI cross-linker. Thus, uniformly cross-linked brushes prepared in THF became appreciably less swollen at a given (low) pH than surface-cross-linked brushes prepared in n-hexane. Micro- and nanopatterned PTBAEMA brushes were prepared via UV irradiation and interference lithography, respectively, and characterized by atomic force microscopy. The change in brush height was determined as a function of pH, and these AFM observations correlated closely with the ellipsometric studies.

Hybrid Mesoporous Silica Nanoparticles Grafted with 2-(tert-butylamino)ethyl Methacrylate-b-poly(ethylene Glycol) Methyl Ether Methacrylate Diblock Brushes as Drug Nanocarrier

“…When the particles were suspended in a solution with pH > 8, the diblock brushes exhibited a relatively larger particle size of approximately 350 nm (red datasets in Figure 5) due to the neutral hydrophilic PEGMEMA polymer. The changes in the average hydrodynamic diameters of PTBAEMA-MSNs and PTBAEMA-b-PEGMEMA-MSNs at different pH values showed a pKa around 7.7, which is in agreement with the literature [32]. which results in larger particle diameter measurements.…”

“…The DOX-drug release behavior was reported to be pH dependent with good control. Alswieleh et al reported the growth of a secondary amine, poly(2-(tert-butylamino)ethyl methacrylate) (PTBAEMA), using SI-ATRP and studied the pH-responsive behavior of these linear brushes [32].…”

Upper critical solution temperature thermo-responsive polymer brushes and a mechanism for controlled cell attachment

“…In the exposed area, the C-Cl bond was removed from the initiator, but remained in the masked regions where the brushes could be grown by SI-CRP. 30 As shown in Figure 3c, AFM topographical images of PNAGAm-PNPhAm brushes on silicon wafer were achieved after SI-CRP. Significant height differences were observed between irradiated and non-irradiated regions.…”

Surface modification of pH-responsive poly(2-(tert-butylamino)ethyl methacrylate) brushes grafted on mesoporous silica nanoparticles

“…Little work has been focused on the synthesis secondary amine-functionalized polymer grafted on surfaces [31,32]. Morse and coworkers reported the preparation of latex particles from 2-(tert-butylamino)ethyl methacrylate (TBAEMA) using aqueous emulsion polymerization [33].…”

“…Ding et al reported the synthesis of PTBAEMA brushes from a planar surface via living radical polymerization [35]. It has been reported the growth of uniform PTBAEMA brushes from planar surfaces using SI-ATRP and studied the pH-responsive behaviour of these linear brushes [32].…”