Fig 1

(a) Energy level diagram for an SFG process; (b) SFG experimental designs of two optical geometries. Top: prism geometry; bottom: window geometry. Reproduced with permission from Ref. 16. Acta Biomaterialia 2016, 40, 6. Copyright 2016 Elsevier. "

Scheme 1

Molecular formulae of the zwitterionic polymer brushes (A) and mixed charged polymers (B) reviewed in this article. Adapted with permission from Ref. 15. J. Phys. Chem. C 2014, 118, 15840. Copyright 2014 American Chemical Society and from Ref. 20. Langmuir 2018, 34, 6538. Copyright 2018 American Chemical Society."

Fig 2

SFG spectra of pCBAA1, pCBAA2, and pSBMA in air (A) and water (B). Adapted with permission from Ref. 15. J. Phys. Chem. C 2014, 118, 15840. Copyright 2014 American Chemical Society. "

Fig 3

SFG spectra collected from the interfaces between mixed charged polymers with different charge ratios and solutions with pH at 5, 7, and 9. Reproduced with permission from Ref. 20. Langmuir 2018, 34, 6538. Copyright 2018 American Chemical Society. "

Fig 4

(A) SFG spectra collected from two zwitterionic polymers, pCBMA and pSBMA, in water (pH ∼7). (B) Replotted SFG spectra in the C―H stretching frequency range from (A). (C) Schematic plots showing that water molecules have different absolute orientations on the pCBMA and pSBMA surfaces. Reproduced with permission from Ref. 21. Langmuir 2019, 35, 1327. Copyright 2019 American Chemical Society. "

Fig 5

(A) SFG spectra collected from the interfaces between pCBMA and water with different pH values. (B) Replotted SFG spectra in the C―H stretching frequency range from (A). (C) Time-dependent SFG signal intensity (detected at 3200 cm−1) from the interface between pCBMA and water before and after the contacting aqueous phase (pH = 12) was changed to water (pH = 7). Reproduced with permission from Ref. 21. Langmuir 2019, 35, 1327. Copyright 2019 American Chemical Society. "

Fig 6

(A) SFG spectra collected from the interface between pSBMA and water at different pH values. (B) Time-dependent SFG signal intensity (detected at 3200 cm−1) from the interface between pSBMA and water before and after the contacting aqueous phase (pH = 12) was changed to water (pH = 7). Reproduced with permission from Ref. 21. Langmuir 2019, 35, 1327. Copyright 2019 American Chemical Society. "

Fig 7

SFG spectra of (A, D) pCBAA1, (B, E) pCBAA2, and (C, F) pSBMA in contact with (A–C) NaCl or KCl solutions and (D–F) MgCl2 or CaCl2 solutions. The NaCl solutions were prepared with various concentrations. Inset in panel C: enlarged portion of the water spectra in panel C for a clear comparison. (G) Corresponding normalized H2O signal intensities. Reproduced with permission from Ref. 15. J. Phys. Chem. C 2014, 118, 15840. Copyright 2014 American Chemical Society. "

Fig 8

SFG spectra collected from the interfaces between the 1 : 1 mixed charged polymer or pSBMA and water or NaCl solutions. Reproduced with permission from Ref. 20. Langmuir 2018, 34, 6538. Copyright 2018 American Chemical Society. "

Fig 9

(A) After the contacting water was replaced by a 0.2 mol∙L−1 NaCl solution, SFG spectra were collected from the interface between pCBMA and 0.2 mol∙L−1 NaCl solution at different time points. (B) Time-dependent SFG signal intensity (detected at 3200 cm−1) from the interface between pCBMA and solution before and after the contacting water was changed to 0.2 mol∙L−1 NaCl solution. (C) Similar SFG spectra were observed from the interface between pSBMA and 0.2 mol∙L−1 NaCl solution at 5 and 75 min after the contacting water was changed to the 0.2 mol∙L−1 NaCl solution. (The spectra collected between 5 and 75 min are not shown because they have the same O―H stretching signal.) (D) Time-dependent SFG signal intensity (detected at 3200 cm−1) before and after water in contact with pSBMA was replaced by the 0.2 mol∙L−1 NaCl solution. Reproduced with permission from Ref. 21. Langmuir 2019, 35, 1327. Copyright 2019 American Chemical Society. "

Fig 10

(A) SFG signals of pSBMA collected in air before and after contacting proteins. (B) Time-dependent water SFG signals as the contacting aqueous phase was switched from water to protein solutions at 200 s. (C) SFG signals of pSBMA/water and pSBMA/water and pSBMA/protein solution interfaces. Adapted with permission from Ref. 14. ACS Appl. Mater. Interf. 2015, 7, 16881. Copyright 2015 American Chemical Society. "

Fig 11

SFG spectra collected from the mixed charged polymer/water and polymer/protein solution interfaces. (a1), (b1) and (c1) are the beginning mixed charged polymer/water interface SFG spectra. (a2), (b2) and (c2) are polymer/protein solution interface spectra for BSA, fibrinogen and lysozyme respectively. (a3), (b3) and (c3) are polymer/water interface spectra collected again after protein contact and washing. Reproduced with permission from Ref. 20. Langmuir 2018, 34, 6538. Copyright 2018 American Chemical Society. "

Fig 12

(A) Molecular structures of the polypeptoid samples studied here. (B) Time-dependent water contact angles at polypeptoid sample surfaces. (C) SFG signal intensity of strongly hydrogen-bonded water at 3200 cm−1 collected from polypeptoids/water interfaces. Adapted with permission from Ref. 57. Langmuir 2015, 31, 9306. Copyright 2015 American Chemical Society. "

Fig 13

Correlation between SFG signals and antifouling/fouling release properties of the polypeptoid samples. Reproduced with permission from Ref. 57. Langmuir 2015, 31, 9306. Copyright 2015 American Chemical Society. "

Fig 14

(A) Molecular structures of the PDMS-based block copolymers, incorporating either hydrogen-bonding peptoids or non-hydrogen-bonding peptoids. (B) Biofouling assay settlement data for U. linza on different polypeptoid sample surfaces. (C) SFG spectra collected from hydrogen-bonding peptoid/water interface and non-hydrogen bonding peptoid/water interface. Adapted with permission from Ref. 42. Macromolecules 2019, 52, 1287. Copyright 2019 American Chemical Society. "