Thin films of PS/PS‐b‐pnipam and ps/pnipam polymer blends with tunable wettability

Abstract

We developed thin films of blends of polystyrene (PS) with the thermoresponsive polymer poly(N‐isopropylacrylamide) (PNIPAM) (PS/PNIPAM) and its diblock copolymer polystyrene‐b‐poly(N‐isopropylacrylamide) (PS/PS‐b‐PNIPAM) in different blend ratios, and we study their surface morphology and thermoresponsive wetting behavior. The blends of PS/PNIPAM and PS/PS‐b‐PNIPAM are spin‐casted on flat silicon surfaces with various drying conditions. The surface morphology of the films depends on the blend ratio and the drying conditions. The PS/PS‐b‐PNIPAM films do not show an increase in their water contact angles with temperature, as it is expected by the presence of the PNIPAM block. All PS/PNIPAM films show an increase in the water contact angle above the lower critical solution temperature of PNIPAM, which depends on the ratio of PNIPAM in the blend and is insensitive to the drying conditions of the films. The difference between the wetting behavior of PS/PS‐b‐PNIPAM and PS/PNIPAM films is due to the arrangement of the PNIPAM chains in the film. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 670–679

Functional surfaces of laser-microstructured silicon coated with thermoresponsive PS/PNIPAM polymer blends: Switching reversibly between hydrophilicity and hydrophobicity

“…4a and b). The vibrational mode of C-H for PS chains appears at 2852 cm -1 , 2907 cm -1 , 2976 cm -1 , 2999 cm -1 , and 3054 cm -1 , and the vibrational mode of C-H for PNIPAM chains appears at 11 2874 cm -1 , 2921 cm -1 , 2935 cm -1 , and 2976 cm -1 , verified by Raman spectroscopy on solid PS and PNIPAM [32]. Previous studies have shown these PNIPAM Raman peaks down-shift to lower wavenumbers when heating above the PNIPAM LCST, as a result of the PNIPAM phase transition to a compact and collapsed conformational state, which also induces the hydrophobic behavior of the material [40][41][42].…”

“…4a, spectrum # 1 presents peaks that correspond only to PS, indicating the absence of PNIPAM in this area, in contrast with spectra #2 and #3 that present peaks that correspond to both polymers. The absence of PNIPAM peaks in spectrum #1 is due to macrophase separation, that occurs between the components of the homopolymer blend [32,43]. Additionally, the low ratio of PNIPAM in the blend of Fig.…”

“…In this work, we develop functional surfaces of laser-microstructured silicon coated with PS/PNIPAM polymer blends and we study their switching wetting behavior between hydrophilicity and hydrophobicity upon heating. Based on our previous work on the wettability of PS/PNIPAM blend systems casted on flat silicon substrates, which showed a tunable, thermoresponsive wetting behavior [32], we take advantage of the large specific area of microstructured silicon to enhance the PS/PNIPAM film thermoresponsiveness. Silicon surfaces are microstructured via laser processing, inducing roughness on the surface, and spin-coated with PS/PNIPAM thin films of two blend ratios.…”

Ternary Nanoswitches Realized with Multiresponsive PMMA‐b‐PNIPMAM Films in Mixed Water/Acetone Vapor Atmospheres

“…As of now, many stimuli−responsive polymers have been successfully synthesized and characterized, and often the polymer configuration has been tailored additionally to fit to the requirements of given applications. To name a few examples, doubly thermoresponsive block copolymers were used as micellar systems for biomedical applications, [ 17,18 ] grafted nanopatterned brushes were used for controlled biointerfacial interactions (e.g., for bacteria “attach and kill” mechanisms), [ 19 ] various architectures served as drug delivery systems, [ 20 ] grafted and spin‐coated films were used in surface engineering, [ 21–23 ] and hydrogels were applied in tissue engineering [ 24 ] and autonomous sensors. [ 25–27 ] Microgel films and other specialized systems served as functional cell substrates.…”

Molecular design of polymer coatings capable of photo‐triggered stress relaxation via dynamic covalent bond exchange

“…Surface properties, such as antifouling, 1,2,3,4,5 corrosion resistance, 6,7 adhesion, 8,9 electrochemistry, 10,11 wettability, 12,13,14 and light absorption, 15 are commonly modified by the application of polymer coatings to base material. Despite the benefits that polymer coatings offer, residual stresses build at the coating/substrate interface.…”