English

• 1. INTRODUCTION

  Antifouling coatings have played crucial roles in the field of biosensors^{[1, 2]}, biomedical implants^{[3, 4]}, and especially marine coatings^{[5, 6]}. To prevent marine organisms growing and residing on the surfaces, three types of coatings are mainly employed, including fouling resisting coating, fouling releasing coating and biocides releasing coating^[7]. Among these, fouling resisting coating based on hydrophilic surface is particularly attractive as it prevents biofouling via forming a robust water-binding layer which is unfavorable for the marine organisms^[8-12], rather than releasing toxic agents. As a result, fouling resisting coating is much more environment-friendly and enables sustainable developments. Further, fouling resisting coating can also efficiently inhibit protein adhesion^[13] and various oil contaminants^[14], rendering the capability for long-term service in complicated environments.

  To achieve fouling resisting coating with hydrophilic surfaces on a variety of substrates, two approaches are frequently used: (1) surface-initiated radical polymerization of hydrophilic monomers. For example, Ishihara et. al. grafted hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine) from PDMS surface pre-embedded with photo-initiator by surface-initiated photo-induced radical polymerization^[15]; Zhou's group realized a hydrophilic three-dimensional network of PEG from bisphenol A epoxy acrylate primer by UV irradiation^[16]; Zhao and his coworkers prepared hydrogel skin through in-situ photo-polymerization of hydrogel monomer on the polymer substrate containing a hydrophobic initiator^[17]. Although this method has been widely used, it still suffers from several disadvantages. For instance, the hydrophobic substrates are hard to be wetted by the hydrophilic monomers, leading to non-uniform surficial modifications. Despite that in-situ hydrolysis via acid or base could help to alleviate the wetting issue^[18], this approach is only suitable for limited hydrophilic molecules, such as carboxylic derivatives or zwitterions. In addition, the radical polymerization generally requires oxygen-free atmosphere, severely compromising the handleability of such method. (2) self-assembled monolayers (SAMs). SAM possesses a larger number of chains per unit area than most other grafting techniques. Typical examples include PEG-based SAM anchor to the gold surface via thiol terminal group and silane-chemistry based SAM formation^{[19, 20]}. Although SAM has been proved effective, it is only suitable for limited substrates, most of which are noble metals^[21]. Moreover, the resulting hydrophilic layer only has very limited thicknesses, and therefore is susceptible to oxidation^{[22, 23]}, giving rise to poor long-term stability.

  Herein, we develop a facile yet efficient approach to hydrophilize targeted substrates based on the in-situ aminolysis reaction between poly(pentafluorophenyl acrylate) (pPFPA) and desired alkylamines (e.g., zwitterionic, anionic and neutral hydrophilic amines, Scheme 1a and 1b). As demonstrated by previous reports, pPFPA and its derivatives were often used as a precursor to prepare various functional materials via post-modification owing to their fast and quantitative reactions with alkylamines^[24-27]. Nevertheless, to the best of our knowledge, pPFPA used as a primer for hydrophilic coatings via post-modification with diverse hydrophilic molecules has been rarely explored. In this work, the substrates coated with pPFPA are immersed into given alkylamine solutions for a certain amount of time, dependent on the demanded thickness of the hydrophilic layer. The fast and quantitative aminolysis between pentafluorophenyl ester groups and alkylamines allows the replacement of pentafluorophenyl groups with hydrophilic groups, resulting in diverse hydrophilic surfaces with desired functions. To evaluate the generality of such method, three alkylamines including 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate (ADPS), β-alanine and amine-terminal poly(ethylene glycol) (NH₂-PEG) are employed, respectively. Detailed studies reveal that the resulting hydrophilic surfaces show good transparency, high thermal stability, good antifogging and self-cleaning capabilities. Notably, attributed to the high efficiency of this method, patterned surface hydrophilization could be realized by applying a patterned filter paper containing alkylamine solutions on the surface of substrate, which shows potential applications in anticounterfeiting and data encryption. In addition, by culturing these hydrophilic surfaces in P. tricornutum and N. closterium suspensions for 5 days, respectively, undetectable algae are observed for these hydrophilic surfaces, indicating their good antifouling feature. Further, we have demonstrated that these hydrophilic surfaces could be regenerated simply by immersing the physically-damaged surfaces into desired amines. This work opens a new door for surface hydrophilization and may find potential applications in numbers of fields including but not limited to sensing, patterning, coating, and data encryption.

  Scheme 1

  

  Scheme 1.  Schematic illustration of (a) aminolysis reaction between alkylamine and pPFPA; (b) chemical structures of ADPS, β-alanine and NH₂-PEG, respectively; (c) surface hydrophilization procedure

  DownLoad: Full-Size Img PowerPoint

  2. EXPERIMENT

  2.1 Materials

  Acryloyl chloride (99%) was purchased from Beijing Ouhe technology Co., Ltd. Propane sultone (99%), azobis(isobutylronitrile) (AIBN, 99%) and di-tert-butyl decarbonate (99%) were purchased from Aladdin (China); β-alanine (99%), 3-dimethylaminopropylamine (99%) and citric acid (≥99.5%) were purchased from Macklin Inc.; Benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (Bop, 98%) and pentafluorophenol (98%) were purchased from Jiangsu Aikon Biopharmaceutical R & D Co., Ltd; Bis(benzylsulfanyl)methanethione (98%) was purchased from Shanghai Xushuo Biotech Co., Ltd. Methoxypolyethylene glycols (HO-PEG, M_w = 350 g/mol) and 4-dimethylami-nopyridine (DMAP, 98%) were purchased from Bide Pharmatech Ltd. Anion exchange resin, FLUORIDE ON AMBERLYST(R) A-26, was purchased from Alfa Aesar Co., Inc. All these materials were used as received unless where noted.

  2.2 Characterization

  Nuclear Magnetic Resonance (NMR) measurements were performed on a Bruker AVANCE III NMR 400M instruments; Fourier-transform infrared (FTIR) spectroscopy analyses were carried out with a NICOLET iS5 spectrometer (Thermo Fisher Scientific, USA) by attenuated total reflectance (ATR) method; Thermogravimetric Analysis (TGA) measurements were carried out with a Netzsch STA449F3 analyzer at a heating rate of 10 ℃/min in a nitrogen atmosphere. The water contact angle (WCA) was measured using a contact angle analyzer (Powereach, China), which uses the micro-lens and camera to obtain the shape of the droplets on the surface of the coating sample, and automatically calculates the contact angle of the droplets with respect to the coating surface. Fluorescence microscope (Nikon) was used for diatoms observation with a wavelength of 475 nm. We used ImageJ for color addition, as well as brightness and contrast adjustment.

  2.3 Preparation of hydrophilic surfaces

  Firstly, the crosslinked pPFPA coating with a thickness of 830 ± 250 nm was formed by spin-coating the mixture of pPFPA and 1, 3-diaminopropane toluene solution on the substrates that is pre-modified with 3-aminopropyltrimethoxysilane. Next, amine end-functionalized PEG (NH₂-PEG) and ADPS were synthesized and unambiguously characterized by NMR analysis (Scheme 1b and Fig. S1). Finally, the pPFPA coated substrates were immersed in ADPS, β-alanine and NH₂-PEG solutions, respectively, giving rise to three hydrophilic surfaces donated as pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively (Scheme 1b and 1c).

  3. RESULTS AND DISCUSSION

  To confirm the success of surface treatment, the resultant coatings are characterized by FTIR-ATR. As shown in Fig. 1a, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG give new peaks at 3380 and 1654 cm^-1, which are assigned to the stretching of amide N–H and C=O, respectively. Meanwhile, the peak at 1787 cm^-1 assigned to C=O of ester groups notably attenuates or disappears. Further, ¹⁹F NMR provides additional evidence for the fast reaction between pPFPA and three alkylamines (Fig. S2). The absence of "F1s" peak in X-ray Photoelectron Spectroscopy (XPS) surface analysis for the coatings also confirms the completion of surface modification (Fig. S3). All these results clearly indicate the successful reaction between pPFPA and alkylamines. TGA indicates that the aminolysis only causes slight impact to the thermal stability of the surfaces (Fig. 1b). It should be noted that all these hydrophilic coatings barely swell in DI water probably due to their highly-crosslinked feature (Fig. S4). The hydrophilization depth is estimated to be around 200 nm according to the capacitance measurements (see supporting information for detail).

  Figure 1

  

  Figure 1.  (a) FTIR-ATR spectra, (b) TGA analysis of pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively. (c) Image of the glass substrates coated with pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG on a piece of paper written with Chinese characters. (d) UV-vis spectra at the transmittance mode of glass slide, pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively

  DownLoad: Full-Size Img PowerPoint

  Fig. 1c shows the images of the glass substrates coated with pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG on a piece of paper written with Chinese characters, respectively. The easy observation of the characters through the samples indicates high transparency of the coatings both before and after amine treatment. UV-vis spectra at the transmittance mode shown in Fig. 1d demonstrate the transmittance of all samples is above 86% from 400 to 700 nm, clearly verifying their high transparency.

  Next, the hydrophilicity of the coatings is measured using a contact angle analyzer. Fig. 2a shows the WCAs of these coatings after 10 hours of immersion in the solutions of ADPS, β-alanine and NH₂-PEG. Owing to high hydrophilicity of the alkylamines, the WCAs are 20 ± 3°, 20 ± 1° and 29 ± 1° for pPFPA-ADPS pPFPA-β-alanine, and pPFPA-PEG surface, respectively. As a control, the WCAs of glass and pPFPA are 60 ± 1° and 95 ± 2°. Besides, to monitor the progress of the surface modification, the WCAs of the pPFPA coatings after different immersion time are also measured, as shown in Fig. 2b. It is worth noting that the WCAs of pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG decrease sharply within the first 2 hours, and then slightly decrease from 2 to 10 hours, and are nearly constant from 10 to 20 hours. This demonstrates high efficiency of the surface reaction between pPFPA substrate with ADPS, β-alanine and NH₂-PEG. After 20 hours of soaking, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG show WCAs of 24 ± 2°, 6 ± 1° and 26 ± 1°, respectively, which are comparable to the values in the previous reports via other approaches^{[28, 29]}. Considering no obvious additional decreases in WCA after 10 hours, we thus choose the samples with 10 hours' aminolysis for the following tests.

  Figure 2

  

  Figure 2.  (a) WCAs of the glass, pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively. The insets are the water droplet images on the coating surfaces. (b) WCAs of the coatings at different aminolysis time. (c) Different adhesive behaviors of dichloroethane droplet on three coating surfaces under water. (d) Underwater oil contact angles of the coatings and the insets are the oil droplet on the coating surfaces

  DownLoad: Full-Size Img PowerPoint

  To further confirm the surface hydrophilicity, we conduct underwater oil contact angles (UWOCAs) measurement for the coatings using dichloroethane droplet. Owing to the robust water binding layer, the dichloroethane droplet cannot adhere to the surfaces of pPFPA-ADPS and pPFPA-PEG, even by the slight press (Fig. 2c, Movie S1 and S3); however, the dichloroethane droplet can easily adhere to the pPFPA-β-alanine surface (Fig. 2c and Movie S2), though their WCAs are comparable. This may be ascribed to the low strength of hydration layer on the pPFPA-β-alanine surface. Moreover, the adhesive force of the oil droplet to pPFPA-PEG is lower than that of pPFPA-ADPS (Fig. 2c), probably due to strong steric repulsion of the long chain of PEG. All pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG express underwater superoleophobicity, and corresponded oil contact angles are 156 ± 3°, 156 ± 3° and 152 ± 5°, respectively. In contrast, the dichloroethane droplet can easily wet the bare glass substrate and pPFPA surface underwater, and their UWOCAs are 85 ± 9° and 28 ± 2°, respectively. These results further verify the successful hydrophilization of surface by the in-situ aminolysis approach. It should be noted that this hydrophilization method is substrate-independent, and a variety of substrates including silicon wafer, plastics, and metals could be adapted to such method (Fig. S5).

  Having demonstrated the successful hydrophilization of the substrates, we next assess their antifogging properties. The fog condensed on the eyeglass or windscreen in cold weather severely obstructs the view and imposes potential danger to our life. A highly hydrophilic surface is known to facilitate the microdroplet spreading out and eliminate the fog^{[30, 31]}. Considering the high transparency and hydrophilicity of these coatings, they are expected to show a good antifogging feature. To verify this, the antifogging tests are carried out for these coatings. We first immerse an 'A' shaped paper into ADPS, the β-alanine and NH₂-PEG solutions, respectively. Then, the wetted papers containing amine solution are attached to the pPFPA coating surfaces for 2, 5 and 10 hours, respectively (Fig. 3a). After removing these papers from the coating surfaces, the coatings well-maintain their original transparency, and the modified area cannot be discerned by the naked eyes (Fig. 3b). Moreover, the 'A' patterned area remains clear after the coatings being exposed to moisture (Fig. 3c), indicating good antifogging properties. Further, the antifogging performance improves with the treating time. In addition, among the three coatings, the pPFPA-ADPS shows the best antifogging performance, which can be attributed to its lowest WCA. Notably, the ranking of pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG antifogging performance is in line with their WCAs, in good agreement with the fact that the fogging resistance relies on the spread out of water droplet on the surface^{[30, 31]}. As a control, pPFPA and glass are easily fogged and become opaque immediately after being exposed to moisture (Fig. S6). Further, this hydrophilization method can be adapted to printing technology (Fig. S7 and Movie S4), beyond the reach of previously reported hydrophilization approaches.

  Figure 3

  

  Figure 3.  (a) Schematic illustration of the process of surface patterning. (b) The pPFPA coatings patterned with 'A' character with different time length and (c) the fogging tests of the surfaces. The scale bar is 1 cm

  DownLoad: Full-Size Img PowerPoint

  We next evaluate the self-cleaning ability of these coatings. Self-cleaning capability is essential to maintain the original physicochemical surface properties after being contaminated by oils or other organic matters. Here, silicone oil and salad oil-stained by fluorescent dye are used as prototype contaminants for assessing the self-cleaning performance of three coatings. These dyed oils show cyan and bluish fluorescence under 365 nm UV light, enabling to track the residual oil contaminant on the surfaces. Fig. 4 shows the procedures of the self-cleaning tests. Prior to the test, these surfaces are thoroughly clean and free from oil spots (Fig. 4a and 4b). Upon dropping silicone oil and salad oil on the surfaces, cyan and bluish fluorescence drops could be clearly observed under 365 nm UV light (Fig. 4c and 4d). After 24 hours, the surfaces are rinsed with DI water. As shown, surfaces with pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG coatings are well-cleaned, and only trace amount of oil could be observed on the surfaces of pPFPA-β-alanine and pPFPA-ADPS, whereas pPFPA-PEG surface is thoroughly clean, indicating the best self-cleaning capability (Fig. 4c and 4d). However, bare glass and pPFPA surfaces still show considerable amount of residual oil spots after being rinsed by DI water. These results clearly demonstrate that the highly hydrophilic surfaces rendered by amine modification possess good self-cleaning ability.

  Figure 4

  

  Figure 4.  Image of five different surfaces before and after oil contamination under natural light and UV light. From left to right: bare glass, glass coated with pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively. (a-b) Clean surfaces prior to tests; (c) The coatings are covered with silicone oil and rinsed with water after 24 hours; (d) The coatings are covered with salad oil and rinsed with water after 24 hours. The scale bar is 1 cm

  DownLoad: Full-Size Img PowerPoint

  We move forward to evaluate their antifouling behavior against algae. Here, P. tricornutum and N. closterium are used as the target algae to characterize the antifouling performance due to their high abundance in the ocean. After culturing in the algae suspension for 5 days, the coating surfaces are observed by fluorescence microscope. As shown in Fig. 5c, bare glass and pPFPA surfaces exhibit bright green fluorescence, indicating significant high density of algae. In sharp contrast, surfaces of pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG remarkably reduce the algae density by 98.6%, 98.3%, and 99.7% for P. tricornutum, and 98.0%, 99.1%, and 99.8% for N. closterium, respectively, which can be attributed to the hydration and the steric repulsion of the water-binding layer^[32-35]. This result demonstrates the excellent antifouling performance of the hydrophilic surfaces^{[11, 36, 37]}. It is also interesting to find out that the algae density on pPFPA coatings is lower than hydrophilic glass, probably due to the easy detachment of algae from the low surface energy pPFPA coatings^[38].

  Figure 5

  

  Figure 5.  Density of (a) P. tricornutum and (b) N. closterium settling on different coating surfaces, and (c) corresponding representative fluorescence images. The scale bar is 50 μm (Excitation wavelength: 475 nm)

  DownLoad: Full-Size Img PowerPoint

  Remarkably, these coatings exhibit excellent regeneration capability. Regeneration is a significant and distinct process in the biological world. With such capability, creatures could efficiently renew, restore or heal the damaged parts and greatly extend their life. Introducing regeneration capability into materials would be a fascinating approach to design smart bionic system with long service period. The fast and quantitative aminolysis reaction renders the possibility of regeneration for these coatings. To verify this, we abrase the coating surfaces by 30 gram falling sand from a height of 40 cm (Fig. 6a), and then measure the WCA change. As shown in Fig. 6b, after being abrased, the WCAs of these coatings increase from ~20^o to ~50^o, indicating that the coating surfaces are partially damaged and the inner hydrophobic pPFPA surfaces are exposed to the air. Interestingly, immersing the damaged surfaces into corresponding amine solutions at room temperature brings the WCAs back to ~20^o, implying that the exposed hydrophobic pPFPA surfaces convert to hydrophilic surfaces again via aminolysis reaction. Moreover, several damage-regeneration tests demonstrate the good reproducibility and robustness of this hydrophilization method.

  Figure 6

  

  Figure 6.  (a) Schematic illustration of the abrasion tests of the coatings with a self-made device. (b) Change of WCAs during abrasion and regeneration cycles for pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively

  DownLoad: Full-Size Img PowerPoint

  4. CONCLUSION

  In this study, we have developed a simple yet robust approach to fabricate hydrophilic surfaces through in-situ site-specific aminolysis between pPFPA and alkylamines (i.e., ADPS, β-alanine and NH₂-PEG). The fast and quantitative feature of such method is evidenced by ATR, time-resolved WCA and UWOCA measurements. Moreover, this hydrophilization method shows negligible impact to the transparency and thermal stability of the surfaces. In addition, the hydrophilized surfaces exhibit excellent antifogging properties, with potential applications for anticounterfeiting and data encryption via patterned surface hydrophilization. Adhesion tests between fluorescent oil and hydrophilic surfaces reveal that all three surfaces possess good self-cleaning property. Culturing P. tricornutum and N. closterium for 5 days on the surfaces results in undetectable density of algae, implying their excellent antifouling property against algae. Finally, we have demonstrated that these hydrophilic surfaces could be regenerated simply by immersing the damaged surfaces into desired amine solutions. All above results clearly indicate the unique advantages of such method for surface hydrophilization. This work provides a new approach not only for surface hydrophilization but also for a variety of surface modifications, and may find a number of applications in the fields of smart coating, sensing, precise patterning, data encryption and many others.

  
  
• 1. [1]

     Banerjee, I.; Pangule, R. C.; Kane, R. S. Antifouling coatings: recent developments in the design of surfaces that prevent fouling by proteins, bacteria, and marine organisms. Adv. Mater. 2011, 23, 690–718. doi: 10.1002/adma.201001215

  2. [2]

     Sabaté del Río, J.; Henry, O. Y. F.; Jolly, P.; Ingber, D. E. An antifouling coating that enables affinity-based electrochemical biosensing in complex biological fluids. Nat. Nanotechnol. 2019, 14, 1143–1149. doi: 10.1038/s41565-019-0566-z

  3. [3]

     Zhang, Y.; Gao, H.; Wang, H.; Xu, Z.; Chen, X.; Liu, B.; Shi, Y.; Lu, Y.; Wen, L.; Li, Y. Radiopaque highly stiff and tough shape memory hydrogel microcoils for permanent embolization of arteries. Adv. Funct. Mater. 2018, 28, 1705962. doi: 10.1002/adfm.201705962

  4. [4]

     Wang, W.; Tan, B.; Chen, J.; Bao, R.; Zhang, X.; Liang, S.; Shang, Y.; Liang, W.; Cui, Y.; Fan, G. An injectable conductive hydrogel encapsulating plasmid DNA-eNOs and ADSCs for treating myocardial infarction. Biomaterials 2018, 160, 69–81. doi: 10.1016/j.biomaterials.2018.01.021

  5. [5]

     Dai, G.; Xie, Q.; Ai, X.; Ma, C.; Zhang, G. Self-generating and self-renewing zwitterionic polymer surfaces for marine anti-biofouling. ACS Appl. Mater. Interfaces 2019, 11, 41750–41757. doi: 10.1021/acsami.9b16775

  6. [6]

     Azemar, F.; Faÿ, F.; Réhel, K.; Linossier, I. Development of hybrid antifouling paints. Prog. Org. Coat. 2015, 87, 10–19. doi: 10.1016/j.porgcoat.2015.04.007

  7. [7]

     Xie, Q.; Pan, J.; Ma, C.; Zhang, G. Dynamic surface antifouling: mechanism and systems. Soft Matter. 2019, 15, 1087–1107. doi: 10.1039/C8SM01853G

  8. [8]

     Yang, W. J.; Neoh, K. G.; Kang, E. T.; Teo, S. L. M.; Rittschof, D. Polymer brush coatings for combating marine biofouling. Prog. Polym. Sci. 2014, 39, 1017–1042. doi: 10.1016/j.progpolymsci.2014.02.002

  9. [9]

     Yeon, D. K.; Ko, S.; Jeong, S.; Hong, S. P.; Kang, S. M.; Cho, W. K. Oxidation-mediated, zwitterionic polydopamine coatings for marine antifouling applications. Langmuir 2018, 35, 1227–1234.

  10. [10]

      Wang, D.; Liu, H.; Yang, J.; Zhou, S. Seawater-induced healable underwater superoleophobic antifouling coatings. ACS Appl. Mater. Interfaces 2019, 11, 1353–1362. doi: 10.1021/acsami.8b16464

  11. [11]

      Pranantyo, D.; Xu, L. Q.; Neoh, K. G.; Kang, E. T.; Ng, Y. X.; Teo, S. L. M. Tea stains-inspired initiator primer for surface grafting of antifouling and antimicrobial polymer brush coatings. Biomacromolecules 2015, 16, 723–732. doi: 10.1021/bm501623c

  12. [12]

      Koc, J.; Schönemann, E.; Amuthalingam, A.; Clarke, J.; Finlay, J. A.; Clare, A. S.; Laschewsky, A.; Rosenhahn, A. Low-fouling thin hydrogel coatings made of photo-cross-linked polyzwitterions. Langmuir 2018, 35, 1552–1562.

  13. [13]

      Shao, Q.; Jiang, S. Molecular understanding and design of zwitterionic materials. Adv. Mater. 2015, 27, 15–26. doi: 10.1002/adma.201404059

  14. [14]

      Gu, Y.; Yang, J.; Zhou, S. A facile immersion-curing approach to surface-tailored poly(vinyl alcohol)/silica underwater superoleophobic coatings with improved transparency and robustness. J. Mater. Chem. A 2017, 5, 10866–10875. doi: 10.1039/C7TA01499F

  15. [15]

      Goda, T.; Konno, T.; Takai, M.; Moro, T.; Ishihara, K. Biomimetic phosphorylcholine polymer grafting from polydimethylsiloxane surface using photo-induced polymerization. Biomaterials 2006, 27, 5151–5160. doi: 10.1016/j.biomaterials.2006.05.046

  16. [16]

      Yang, Y.; Luo, H.; Yang, J.; Huang, D.; Zhou, S. Facile UV-curing technique to establish a 3D-grafted poly(ethylene glycol) layer on an epoxy resin base for underwater applications. J. Appl. Polym. Sci. 2016, 133, 43972.

  17. [17]

      Yu, Y.; Yuk, H.; Parada, G. A.; Wu, Y.; Liu, X.; Nabzdyk, C. S.; Youcef-Toumi, K.; Zang, J.; Zhao, X. Multifunctional "hydrogel skins" on diverse polymers with arbitrary shapes. Adv. Mater. 2019, 31, 1807101. doi: 10.1002/adma.201807101

  18. [18]

      Leng, C.; Sun, S.; Zhang, K.; Jiang, S.; Chen, Z. Molecular level studies on interfacial hydration of zwitterionic and other antifouling polymers in situ. Acta Biomater. 2016, 40, 6–15. doi: 10.1016/j.actbio.2016.02.030

  19. [19]

      Zhao, Y.; Zhou, Q.; Li, Q.; Yao, X.; Wang, J. Passivation of black phosphorus via self-assembled organic monolayers by van der Waals epitaxy. Adv. Mater. 2017, 29, 1603990. doi: 10.1002/adma.201603990

  20. [20]

      Hasan, A.; Pattanayek, S. K.; Pandey, L. M. Effect of functional groups of self-assembled monolayers on protein adsorption and initial cell adhesion. ACS Biomater. Sci. Eng. 2018, 4, 3224-3233. doi: 10.1021/acsbiomaterials.8b00795

  21. [21]

      Huang, C. J.; Chu, S. H.; Wang, L. C.; Li, C. H.; Lee, T. R. Bioinspired zwitterionic surface coatings with robust photostability and fouling resistance. ACS Appl. Mater. Interfaces 2015, 7, 23776–23786. doi: 10.1021/acsami.5b08418

  22. [22]

      Qiu, X.; Ivasyshyn, V.; Qiu, L.; Enache, M.; Dong, J.; Rousseva, S.; Portale, G.; Stöhr, M.; Hummelen, J. C.; Chiechi, R. C. Thiol-free self-assembled oligoethylene glycols enable robust air-stable molecular electronics. Nat. Mater. 2020, 19, 330–337. doi: 10.1038/s41563-019-0587-x

  23. [23]

      Devillers, S.; Hennart, A.; Delhalle, J.; Mekhalif, Z. 1-Dodecanethiol self-assembled monolayers on cobalt. Langmuir 2011, 27, 14849–14860. doi: 10.1021/la2026957

  24. [24]

      Lin, S.; Shang, J.; Theato, P. Facile fabrication of CO₂-responsive nanofibers from photo-cross-linked poly(pentafluorophenyl acrylate) nanofibers. ACS Macro. Lett. 2018, 7, 431–436. doi: 10.1021/acsmacrolett.8b00115

  25. [25]

      Son, H.; Ku, J.; Kim, Y.; Li, S.; Char, K. Amine-reactive poly(pentafluorophenyl acrylate) brush platforms for cleaner protein purification. Biomacromolecules 2018, 19, 951–961. doi: 10.1021/acs.biomac.7b01736

  26. [26]

      Zhao, H.; Gu, W.; Thielke, M. W.; Sterner, E.; Tsai, T.; Russell, T. P.; Coughlin, E. B.; Theato, P. Functionalized nanoporous thin films and fibers from photocleavable block copolymers featuring activated esters. Macromolecules 2013, 46, 5195–5201. doi: 10.1021/ma400659h

  27. [27]

      Li, C.; Feng, S.; Li, C.; Sui, Y.; Shen, J.; Huang, C.; Wu, Y.; Huang, W. Synthesizing organo/hydrogel hybrids with diverse programmable patterns and ultrafast self-actuating ability via a site-specific"in situ"transformation strategy. Adv. Funct. Mater. 2020, 30, 2002163. doi: 10.1002/adfm.202002163

  28. [28]

      Yeh, S. B.; Chen, C. S.; Chen, W. Y.; Huang, C. J. Modification of silicone elastomer with zwitterionic silane for durable antifouling properties. Langmuir 2014, 30, 11386–11393. doi: 10.1021/la502486e

  29. [29]

      Kim, S.; Gim, T.; Jeong, Y.; Ryu, J. H.; Kang, S. M. Facile construction of robust multilayered PEG films on polydopamine-coated solid substrates for marine antifouling applications. ACS Appl. Mater. Interfaces 2018, 10, 7626–7631. doi: 10.1021/acsami.7b07199

  30. [30]

      Chen, Y.; Zhang, Y.; Shi, L.; Li, J.; Xin, Y.; Yang, T.; Guo, Z. Transparent superhydrophobic/superhydrophilic coatings for self-cleaning and anti-fogging. Appl. Phys. Lett. 2012, 101, 033701. doi: 10.1063/1.4737167

  31. [31]

      Gu, Y.; Liu, H.; Yang, J.; Zhou, S. Surface-engraved nanocomposite coatings featuring interlocked reflection-reducing, anti-fogging, and contamination-reducing performances. Prog. Org. Coat. 2019, 127, 366–374. doi: 10.1016/j.porgcoat.2018.11.030

  32. [32]

      Kingshott, P.; Wei, J.; Bagge-Ravn, D.; Gadegaard, N.; Gram, L. Covalent attachment of poly(ethylene glycol) to surfaces, critical for reducing bacterial adhesion. Langmuir 2003, 19, 6912–6921. doi: 10.1021/la034032m

  33. [33]

      Park, J. H.; Bae, Y. H. Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethyl siloxane): synthesis, characterization, in vitro protein adsorption and platelet adhesion. Biomaterials 2002, 23, 1797–1808. doi: 10.1016/S0142-9612(01)00306-4

  34. [34]

      Wyszogrodzka, M.; Haag, R. Synthesis and characterization of glycerol dendrons, self-assembled monolayers on gold: a detailed study of their protein resistance. Biomacromolecules 2009, 10, 1043–1054. doi: 10.1021/bm801093t

  35. [35]

      Del Grosso, C. A.; Leng, C.; Zhang, K.; Hung, H. C.; Jiang, S.; Chen, Z.; Wilker, J. J. Surface hydration for antifouling and bio-adhesion. Chemical Science 2020, 11, 10367–10377. doi: 10.1039/D0SC03690K

  36. [36]

      Yandi, W.; Mieszkin, S.; di Fino, A.; Martin-Tanchereau, P.; Callow, M. E.; Callow, J. A.; Tyson, L.; Clare, A. S.; Ederth, T. Charged hydrophilic polymer brushes and their relevance for understanding marine biofouling. Biofouling 2016, 32, 609–625. doi: 10.1080/08927014.2016.1170816

  37. [37]

      Xu, G.; Liu, P.; Pranantyo, D.; Xu, L.; Neoh, K. G.; Kang, E. T. Antifouling and antimicrobial coatings from zwitterionic and cationic binary polymer brushes assembled via "click" reactions. Ind. Eng. Chem. Res. 2017, 56, 14479–14488. doi: 10.1021/acs.iecr.7b03132

  38. [38]

      Bauer, S.; Arpa-Sancet, M. P.; Finlay, J. A.; Callow, M. E.; Callow, J. A.; Rosenhahn, A. Adhesion of marine fouling organisms on hydrophilic and amphiphilic polysaccharides. Langmuir 2013, 29, 4039–4047. doi: 10.1021/la3038022

• 

  Scheme 1  Schematic illustration of (a) aminolysis reaction between alkylamine and pPFPA; (b) chemical structures of ADPS, β-alanine and NH₂-PEG, respectively; (c) surface hydrophilization procedure

  下载: 全尺寸图片 幻灯片
  

  Figure 1  (a) FTIR-ATR spectra, (b) TGA analysis of pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively. (c) Image of the glass substrates coated with pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG on a piece of paper written with Chinese characters. (d) UV-vis spectra at the transmittance mode of glass slide, pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively

  下载: 全尺寸图片 幻灯片
  

  Figure 2  (a) WCAs of the glass, pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively. The insets are the water droplet images on the coating surfaces. (b) WCAs of the coatings at different aminolysis time. (c) Different adhesive behaviors of dichloroethane droplet on three coating surfaces under water. (d) Underwater oil contact angles of the coatings and the insets are the oil droplet on the coating surfaces

  下载: 全尺寸图片 幻灯片
  

  Figure 3  (a) Schematic illustration of the process of surface patterning. (b) The pPFPA coatings patterned with 'A' character with different time length and (c) the fogging tests of the surfaces. The scale bar is 1 cm

  下载: 全尺寸图片 幻灯片
  

  Figure 4  Image of five different surfaces before and after oil contamination under natural light and UV light. From left to right: bare glass, glass coated with pPFPA, pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively. (a-b) Clean surfaces prior to tests; (c) The coatings are covered with silicone oil and rinsed with water after 24 hours; (d) The coatings are covered with salad oil and rinsed with water after 24 hours. The scale bar is 1 cm

  下载: 全尺寸图片 幻灯片
  

  Figure 5  Density of (a) P. tricornutum and (b) N. closterium settling on different coating surfaces, and (c) corresponding representative fluorescence images. The scale bar is 50 μm (Excitation wavelength: 475 nm)

  下载: 全尺寸图片 幻灯片
  

  Figure 6  (a) Schematic illustration of the abrasion tests of the coatings with a self-made device. (b) Change of WCAs during abrasion and regeneration cycles for pPFPA-ADPS, pPFPA-β-alanine and pPFPA-PEG, respectively

  下载: 全尺寸图片 幻灯片
•