From Hofmeister to hydrotrope: Effect of anion hydrocarbon chain length on a polymer brush

Cosolvent effects on the structure and thermoresponse of a polymer brush: PNIPAM in DMSO–water mixtures

“…We have previously characterised the behaviour and structure of PNIPAM brushes with NR across a broad extent of conditions and wider Q-range. 3,46,50,51 A larger Q-range was not possible in this study due to access restraints. A comparison of optimised models, scattering length density (SLD) profiles and volume fraction (VF) profiles against identical reflectivity measurements of small and large Q-ranges is presented in the ESI, Fig.…”

“…Silicon wafers for spectroscopic ellipsometry and neutron reflectometry were functionalised according to our previously reported method. 3,45,46 PNIPAM brushes were synthesised adhering to an established protocol, which was upscaled for the 100 mm silicon blocks used for neutron reflectometry experiments. 3 To achieve appropriate polymerisation kinetics, a 4 : 1 v/v methanol/water solvent ratio was used in conjunction with a monomer/catalyst/ligand/reducing agent molar ratio of 900/1/10/10 with NIPAM/CuBr 2 /HMTETA/sodium ascorbate.…”

“…3,45,46 PNIPAM brushes were synthesised adhering to an established protocol, which was upscaled for the 100 mm silicon blocks used for neutron reflectometry experiments. 3 To achieve appropriate polymerisation kinetics, a 4 : 1 v/v methanol/water solvent ratio was used in conjunction with a monomer/catalyst/ligand/reducing agent molar ratio of 900/1/10/10 with NIPAM/CuBr 2 /HMTETA/sodium ascorbate. A summary of the dry thickness for each PNIPAM brush sample is presented in Table 1.…”

“…Spectroscopic ellipsometry measurements were conducted on an Accurion EP4 variable angle spectroscopic imaging ellipsometer. 2,3 Surface mapping of the dry brush was performed at a single wavelength (658 nm) across four equally spaced angles of incidence from 40 to 70°. In situ measurements were conducted on a single brush sample in a solidliquid cell at an angle of incidence of 65°across 12 equidistant wavelengths from 400 to 910 nm.…”

“…Stimulus-responsive polymers respond to changes in the surrounding environment by altering their conformation. [1][2][3][4] When densely grafted to a surface, these polymers form a 'brush' with switchable interfacial and physicochemical properties; establishing a basis for smart coatings, 1,[5][6][7] with myriad applications ranging from controlled drug delivery to rheology modification. 8,9 One subset of stimulus-responsive polymers is thermoresponsive polymers, such as poly(N-isopropylacrylamide) (PNIPAM) or polymers from the poly(oligo (ethylene glycol methyl ether methacrylate) (POEGMA) family, which undergo a thermotransition at a critical temperature.…”