Diblock Polymer Brush (PHEAA-b-PFMA): Microphase Separation

Subscriber access provided by UNIV OF DURHAM

Interface Components: Nanoparticles, Colloids, Emulsions, Surfactants, Proteins, Polymers

Diblock Polymer Brush (PHEAA-b-PFMA): Microphase Separation Behavior and Anti-Protein Adsorption Performance Hai-Xia Wu, zhang xiaohong, Lin Huang, Lu Fang Ma, and Chuanjun Liu Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.8b02584 • Publication Date (Web): 27 Aug 2018 Downloaded from http://pubs.acs.org on August 28, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Diblock Polymer Brush (PHEAA-b-PFMA): Microphase Separation Behavior and Anti-Protein Adsorption Performance Hai-Xia Wu1,2,#, Xiao-Hong Zhang1#, Lin Huang1, Lu-Fang Ma2, Chuan-Jun Liu1*

1. Key Laboratory of Biomedical Polymers of Ministry of Education, College of Chemistry and Molecular Science, Wuhan University, Wuhan, 430072, P. R. China. 2. College of Chemistry and Chemical Engineering, and Henan Key Laboratory of Function-Oriented Porous Materials, Luoyang Normal University, Luoyang, 471022, P. R. China.

*Corresponding author, E-mail:[email protected] # H-X Wu and X-H Zhang contributed equally to this work.

Abstract:

In

this

paper,

a

series of amphiphilic

diblock

polymers

of

poly(hydroxyethylacrylamide)-b-poly(1H,1H-pentafluoropropylmethacrylate) (PHEAA-b-PFMA) were grafted from silicon wafer via surface-initiated atom transfer radical polymerization (SI-ATRP). Surface wettability and chemical compositions of the modified surfaces were characterized by contact angle and X-ray photoelectron spectroscopy (XPS). Molecular weight and polydispersity of each block were measured using gel permeation chromatography (GPC). The topography and the microphase separation behavior of PHEAA-b-PFMA surfaces were investigated by atomic force microscope (AFM). The results show that only when the grafting density (σ) and thickness of PHEAA brush were in the range of 0.9-1.3(chain/nm2) and 6.6-15.1nm, respectively, and the ratio of PFMA/PHEAA varied from 89/42 to 89/94, could the diblock copolymer phase separate into nanostructures. Further, the anti-protein adsorption performance of the modified surfaces against BSA, Fibrinogen, and Lysozyme was studied. The results indicated the modified surfaces could reduce 1

ACS Paragon Plus Environment

Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

the protein adsorption compared to the pristine silicon wafer. For Fibrinogen, the anti-adsorption effect of PHEAA-b-PFMA modified surfaces with microphase segregation was better than that of corresponding PHEAA modified surfaces. The results provide further evidence that surface composition and microphase segregation of fluorinated moieties of block copolymer brushes significantly impact protein adsorption behaviors.

Keywords: Anti-protein adsorption surface, Polymer brushes, PHEAA-b-PFMA, Surface-initiated atom transfer radical polymerization, Microphase separation

2


Page 2 of 26

Page 3 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Introduction Biofouling, the undesired adsorption of protein and microbes on surfaces, is a crucial challenge in many fields ranging from biosensors1 to biomedical devices,2,3 and from food packaging4 to marine equipment.5-7 Nonspecific protein adsorption on surfaces serves as the first step in the formation of biofilms8. To handle these puzzles of biofouling, the surfaces with ability of strongly resistance to protein adsorption and cell adhesion have been the focus of much research. However, with the increase of environmental awareness, more research efforts are now being focused on developing environmentally friendly anti-fouling polymer surfaces. At present, there are mainly following a few non-toxic and anti-biofouling surfaces modified with polymer. Firstly, hydrophilic surfaces modified with hydrophilic polymers like poly (ethylene glycol) (PEG) or its derivates, most widely investigated.9-12 They can inhibit nonspecific protein adsorption because of the hydration layer creating via hydrogen bonds, which constructs a steric barrier to resist protein adsorption and cell adhesion.13-17 Therefore, the hydrophilicity of surface is usually listed as a key criterion for surfaces that resist protein adsorption, along with the presence of hydrogen bond acceptors, lack of hydrogen bond donors, and being neutral in charge.18 It indicates in general, hydrophilic surfaces tend to foul less than hydrophobic ones. While, some hydrophobic surfaces such as perfluorinated polymer and poly(dimethylsiloxane) (PDMS) also showed good “fouling-release” or “self-clean” properties,19,20, which is the results of the reduction of the adhesion of proteins, and cells on surfaces. Nevertheless, it is proved that the anti-fouling efficiency of the surface modified by single hydrophilic or hydrophobic polymer is low due to the amphiphilic characteristic of proteins and organisms. To further improve the anti-fouling efficiency of surface, recently, research started to increasingly explore amphiphilic polymers to modify surface21-23. Currently, the amphiphilic polymers modified surface to resist protein and cell adhesion mainly include SEBS polymers24, PDMS-based polymers25, 26, polyelectrolyte multilayers27, and hyperbranched polymers that combine PEG or PHEAA and perfluorinated 3


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

hydrocarbons.8, 28-30 In most of the cases, the introduction of amphiphilicity polymer to surface enhanced the fouling-release performance, under certain conditions. That is, not all surfaces modified with amphiphilic polymer have better anti-fouling performance for all proteins and cells. The specific anti-fouling mechanism and conditions of the amphiphilic polymer surface are not clear, and further discussion and exploration are needed. However, according to current literatures reported, it is inferred that the microphase separation behavior of amphiphilic polymers surfaces is related to their anti-fouling properties. Microphase separation phenomenon is ubiquitous especially in amphiphilic block copolymers (BCPs)

31

, which can generate various nanostructures. The

separated size of BCPs, inter domain space, along with domain shape usually can be modulated by some parameters, such as molecular weight, polydispersity, thickness, volume fraction, Flory-Huggins interaction parameter(χ)32. Recently, a few studies have been reported to investigate the microphase separation behavior and corresponding antifouling performance of amphiphilic block copolymers33,34. Among of them, the surfaces with microphase separated structures become popular to resist nonspecific proteins adsorption and bacteria adhesion35,36. Given the different hydrophilic/hydrophobic ratios, as well as the diversity of size and configuration from proteins and bacteria, it is not enough to prevent their fouling just by employing hydrophilic or low surface energy materials.37,38 The size of separated nanodomains by BCPs has micro/nanometer level, which is usually much less than the area of each adhesive pad of proteins and is too small to irreversible adsorption for proteins.39,40 For instance, Shen et al prepared series of microphase-separated diblock copolymers on surfaces using PS-b-PHEMA and explored the relationship between antifouling properties and the nanodomain size of the microphase separated surfaces. Results showed that the nanopattern with features down to 20 nm is highly resistant to protein adsorption and cell adhesion.41 Copper-White et al exploited PS-b-PEO coated surfaces to resist protein and cell adhesion, and found that the antifouling performance of the surfaces could be optimized via adjusting PEO molecule weight and surface coverage.42 4


Page 4 of 26

Page 5 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Most of the amphiphilic antifouling coatings with micro/nanostructures were prepared by the means of spinning or dipping and though annealing process.43 Except for the spin or dip coating methods to prepare phased separated surfaces, “grafting from” is becoming one of the versatile surface modification methods44, 45, by which polymer brushes were covalently linked to substrate. Poly(ethylene glycol) (PEG)46 poly

(N-isopropyl

acrylamide)

(PNIPAM)47,

and

poly(methyl

methacrylate

(PMMA)48 and fluorine-containing polymers are widely adopted to regulate the interaction of proteins or cells with surfaces.49,

50

In previous work, we prepared

random amphiphilic copolymer brushes of PAM-ran-PFMA8 and PHEAA-C3F724 grafting from Si surface, respectively. The anti-protein adsorption and bacteria adhesion performance of amphiphilic surface prepared were further investigated. However, there is little work focused on investigating the microphase separation behavior and resistance to protein adsorption of phase separated surfaces modified with fluorine-containing block copolymer brush. Given the conditions of microphase separation in thin polymer films, it is realizable choosing fluorine-containing diblock copolymer brushes to repel protein adsorption. Poly(hydroxylethylacrylamide) (PHEAA) is a hydrophilic polymer and possesses good adsorption-repellent and lubrication performance when the brush thickness is in a suitable range51. Poly (1H,1H-Pentafluoropropyl methacrylate) (PFMA), containing five fluorine atoms in each of monomer, is a hydrophobic polymer with low surface energy. More importantly, the two polymers are immiscible. With appropriate parameters in PHEAA-b-PFMA, the appearance of microphase separated structure in block copolymer of PHEAA-b-PFMA brush is possible. 52Herein, we synthesized a series of diblock copolymers (PHEAA-b-PFMA) from silicon wafers via SI-ATRP and investigated the microphase separation behavior of PHEAA-b-PFMA brush on substrate and without any annealing, the anti-adsorption protein performance of these morphologies spontaneously formed in the diblock copolymer brushes was investigated.

5


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Experimental Section Materials. Silicon wafers [0.56 mm thick, 100 mm diameter with one side polished] were purchased from Zhejiang Crystal Photoelectric Technology Co., Ltd. N-Hydroxyethylacrylamide (HEAA) and 3-Aminoprpoyltriethoxyesilane (APTES) were purchased from TCI. 1H, 1H-Pentafluoropropyl methacrylate (FMA) and Tris[2-(dimethylamino)ethyl]amine (Me6TREN) were purchased from Alfa Aesar and used

without

further

purification.

N,N,N',N',N''-Pentamethyldiethylenetriamine

(PMDETA), 2-Bromoisobutyryl bromide (BiBB), Ethyl-α-bromobutyrate (EBiB) were obtained from Aladdin and used as received. Copper bromide (CuBr) was obtained from Sinopharm Chemical Reagent. Prior to use, CuBr was stirred in acetic acid at 80°C overnight and washed with ethanol and acetone several times. All solvents used were analytical grade and the trace water in dimethylformamide (DMF), triethylamine (TEA), dichloromethane (DCM), toluene was removed according to the standard method. BSA, fibrinogen, and Lysozyme were purchased from Alfa Aesar. Corresponding FITC labeled proteins prepared according to the reported method. Deionized water (DIW) with 18.2 MΩ.cm resistivity used in experiments was prepared through a Millipore (Bedford, MA) Milli-Q filtration system. Preparation of the diblock copolymer brush Amination of silicon wafers. Silicon wafer was ultrasonically cleaned with acetone and DIW, sequentially. Then the cleaned silicon wafer was immersed into piranha solution and heated to 100°C for 2 h. Then, the surface was rinsed with DIW four times and dried with argon stream to obtain hydroxylated surface (Si-OH). Si-OH surface was immersed into anhydrous toluene concluding 2.5% (v/v) APTES, the system was sealed and placed at 30°C for 24 h. Then, the surface was rinsed with toluene, ethanol, and DIW sequentially. The substrate was dried with argon stream to obtain aminated surface (Si-NH2). The preparation of initiator-immobilized surface. Anhydrous DCM including 5%(v/v) TEA, as well as the fresh prepared Si-NH2 was sealed in a tube and immersed into the ice bath for 30 min. After the temperature decreased to 0-4°C, BiBB with a 6


Page 6 of 26

Page 7 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

total 5%(v/v) concentration was added dropwise into the solution, and then the reaction was performed at 0 °C for 2 h and kept at room temperature overnight. The substrate was washed with DCM, ethanol, DIW and dried with argon stream to obtain initiator-immobilized surface (Si-initiator). The polymerization of PHEAA brush grafting from Si-initiator PHEAA-b-PFMA was synthesized via consecutive Surface-Initiated ATRP. Firstly, HEAA (2.03 g), Me6TREN (46 µL) were dissolved in 10 mL mixed solvent with 1:1 methanol/H2O. The reaction tube was sealed and deoxygenated via two freeze-thaw cycles, then CuBr (25 mg), EBiB (25 µL) and Si-Br were added, the system was sealed and deoxygenated via another two freeze-pump-thaw cycles. The reaction was carried out at room temperature with slow stirring and stopped at desired time by exposing the system to air. The Si-PHEAA was washed ethanol, DIW sequentially and dried with argon stream. The PHEAA polymer synthesized in solution was precipitated in acetone and dialyzed in DIW. The

polymerization

of

PHEAA-b-PFMA

brushes.

PHEAA-Br,

as

the

macromolecule initiator was utilized to polymerize FMA monomer. FMA (2 mL), PMDETA (100 µL) were dissolved in 3 mL anhydrous DMF, the reaction tube was sealed and deoxygenated via two freeze-thaw cycles, then CuBr (20 mg), EBiB (20 µL) and Si-PHEAA-Br were added into, the system was sealed and deoxygenated via another two freeze-thaw cycles. The reaction was carried out at 110°C in oil bath with slow stirring and stopped at desired time by exposing the system to air. The surface was washed with DMF, THF, DIW, successively and dried with argon stream to obtain Si-PHEAA-b-PFMA. The PFMA polymer polymerized in solution was precipitated in methanol and dissolved in THF two times, finally dried in oven at 40°C overnight. Gel Permeation Chromatography Measurements. Gel permeation chromatography (GPC) was performed using a Waters 2690D-2410 system (Waters, America). PHEAA and PFMA were individually dissolved in 0.1M NaNO3 and THF, then, samples were run with a ﬂow rate of 0.6 mL min−1 and 0.3 mL min−1 at 15°C. Polyethylene oxide and polystyrene were used as standards for PFMA and PHEAA, respectively. Contact Angle Measurements. Water static contact angles (WCA) were measured by 7


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

an OCA20 contact angle goniometer (Data Physics Instruments GmbH, Germany) using the sessile drop method at 25°C. The volume of water applied on sample surfaces was 2 µL and the value of WCA was obtained from three different positions of each sample. The measurement of X-ray Photoelectron Spectroscopy. The surface composition of the modified Si wafer was characterized by X-ray photoelectron spectroscopy (XPS) (ESCALAB 250Xi) and spectrometer (Thermo Fisher, USA) using a monochromatic Al Kа X-ray source (150W, 15Kv). The Photoelectron data was acquired at a taken off angle of 90º from the sample surface, and the binding energy (BE) scale is calibrated by C 1s of the hydrocarbon peak at 284.8 eV. Survey spectra were run in the binding energy range of 0-800 eV, and the spectra of Br 3d, C 1s, N 1s, O 1s, and F 1s were collected. In addition, a high-resolution C 1s spectrum was fitted using a Shirley background subtraction and a series of Gaussian peaks Ellipsometer. The thickness of the PHEAA brush was characterized using an alpha-SE Ellispsometer (J.A. Woollam, USA). The measurements were performed at an azimuthal angle of 70º from five different positions and the data was calculated via the Complete EASE Software. Atomic Force Microscope (AFM). The AFM images of samples were obtained in air from a Cypher Es (Asylum Research, USA) in tapping mode at 25°C. The silicon cantilever tips (Bruker, Germany) with the parameter of 150 kHz and 5 N/m were used. Protein adsorption test. BSA, Fg, and Ly were adopted as the model proteins to investigate the anti-protein adsorption performance of the modified surfaces. And the amount of adsorbed proteins was characterized via fluorescence microscope (FM) and BCA assay reagent. Typically, the bare and modified silicon wafers with 0.5 cm×0.5 cm area were immersed in PBS solution containing 1 mg/mL FITC labeled protein. Under dark conditions, the adsorption was incubated in shaker at 37°C for 4 h. After adsorption, the samples were taken out and rinsed with PBS three times to remove the non-adsorbed protein. And then, the substrates were dried with argon stream for FM observation. 8


Page 8 of 26

Page 9 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

For quantificational analysis, the bare and modified silicon wafer with 1cm×1cm area was immersed in PBS solution containing 1 mg/mL test protein. The adsorption was incubated in shaker at 37°C for 24 h. After adsorption, the samples were taken out and rinsed with PBS three times to remove the non-adsorbed protein. And then, the remaining protein adsorbed on the surfaces was detached in 1 mL Reporter Lysis 1×Buffer by ultrasonic washing for 30 min at room temperature. The micro BCA protein-analysis kit (no 23235, Pierce, Rockford, IL), based on the bicinchoninic acid (BCA) method was used to determine the concentration of the protein in Reporter Lysis 1×Buffer by measuring the absorbance at 562 nm by UV-Vis spectrophotometer (Shimadzu UV-200) measurement. The amount of adsorbed protein on each sample surface was calculated based on the concentration of protein and predetermined calibration curve obtained by measuring the absorbance of 0-2 mg/mL protein solution in Reporter Lysis 1×Buffer. The reported data is the average of three parallel groups.

Results and Discussion Characterization of fluoride grafted amphiphilic polymer brush As shown in Scheme 1, the diblock copolymer brush PHEAA-b-PFMA was grating from silicon wafer via sequential SI-ATRP. PHEAA brush as the hydrophilic segment was firstly prepared according to previously reported method.53 In the process of polymerization, the initiator of bromine atoms (Br) transferred from Si-Br to the end of polymer brush (PHEAA-Br). As a macromolecule initiator, PHEAA-Br was still active to initiate the second block polymerization of FMA. The changes of surface wettability in different samples were characterized with water static contact angle measurements. As shown in Figure 1, the WAC of Si-OH was close to 0º, indicating Si-OH was hydrophilic due to the generation of hydroxyl groups. After silanization, the WCA increased to 50º. After the introduction of the initiator (BiBB) from Si-NH2, the WCA increased to 79º, which was consistent with the reported reference54, suggesting the initiator-immobilized surface was successfully 9


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

prepared. And the WCA of Si-PHEAA decreased to 9º after the PHEAA was grafted from the initiator-immobilized silicon wafer, meaning the successful polymerization of hydrophilic PHEAA brush on the initiator-immobilized surface. The WCA of surface modified with Si-PHEAA-b-PFMA increased to 46º due to the introduction of low surface energy PFMA in diblock copolymer brush, which indicated that PHEAA-b-PFMA brush modified surface was successfully prepared. However, the surface was still hydrophilic and didn’t display hydrophobicity of fluorine-containing polymers. It probably because that the side chain in PFMA was short and there were only five fluorine atoms in the monomer. More importantly the block copolymer possible separated in the copolymer brushes of PHEAA-b-PFMA. The chemical compositions of the modified surfaces were analyzed by XPS. As shown in Figure 2, compared with the XPS spectrum of Si-NH2, there was a new peak at 69 eV in the spectrum of Si-Br, which was attributed to Br 3d (1.57%). This result indicated that the initiator was successfully immobilized on the surface of aminated silicon wafer. In the XPS spectrum of Si-PHEAA, the peak intensity of N 1s obviously enhanced compared to Si-Br. As shown in the Table S1, the relative content of N atom in Si-PHEAA increased to 9.15 (at %) compared to 5.02 (at %) in Si-NH2. In the high-resolution C1s spectrum of Si-PHEAA (shown in Figure 3), the C=O around 288 eV was mainly attributed to the amide carbon O=C−N from PHEAA. And the ratio of C-N/C=O is 29.0/15.2, which was almost consist with the value of 2 in HEAA molecular formula. These results approved that PHEAA brush was successfully grafted from silicon wafer. After the introduction of PFMA block into the PHEAA brush, a new signal appeared at 690 eV in the XPS spectrum of Si-PHEAA-b-PFMA appeared, which was assigned to F1s. Moreover, the new signal of CF2 (291.5 eV) and CF3 (293.5 eV) appeared from the area-normalized C (1s) XPS (Figure 3) as the result of successfully grafted PFMA block. Besides, a series of PHEAA and PFMA blocks with different molecule weights were synthesized by controlling the polymerization time and monomer concentration. As shown in Table S2, the molecule weights of PHEAA and PFMA could be regulated from 4800 to 18700 and 9700 to 23800, respectively. Most of the molecule weights 10


Page 10 of 26

Page 11 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

had a narrow distribution index below 1.3 due to the living/controlling polymerization property of ATRP. As shown in Figure S1, the changes of intensity of N 1s and F 1s from (a) to (c) reflected the difference in elemental content. The special elemental contents were displayed in Table S1. From (a) to (c), with the increase of PHEAA molecule weights, the content of N 1s in Si-PHEAA increased from 9.15 (at %) to 11.7 (at %) and the ratios of C/N/O were 5.31/1/3.15, 4.93/1/2.7 and 5.2/1/1.97, which more and more approached to the ratio of 5/1/2 in HEAA monomer, indicating the PHEAA polymer brush become uniform and smooth with the increase of polymerization time. For PFMA block, from (a) to (c) the content of F 1s increased from 1.31 (at %) to 4.44 (at %). And the ratio of C/F decreased from 7.07/1.31 to 3.9/4.44, which reflected the changes in polymerization degree ratio of PHEAA/PFMA. The microphase separation behaviors of PHEAA-b-PFMA brush grafting from surfaces were systematically investigated using AFM. The height images of PHEAA and PHEAA-b-PFMA brushes modified surfaces were displayed in Figure 4. As the thickness of PHEAA brush increased, the root mean square (RMS) of Si-PHEAA for a 2 µm×2 µm area from (a) to (d) was 0.95 nm, 0.68 nm, 0.50 nm and 0.49 nm, respectively. This indicated that the silicon wafers became more and more smooth with the thickness increase of the PHEAA brushes covered on silicon surface, yet there was no obvious difference in RMS between these surfaces modified with PHEAA brushes. Compared to Si-PHEAA, the RMS of Si-PHEAA-b-PFMA was 0.60 nm, 0.68 nm, 0.61 nm and 0.52 nm which suggested that the introduction of PFMA block had no remarkable effect on the surface roughness of silicon wafer. The results indicated that the modified surfaces via SI-ATRP were smooth, which was consistent with the references reported.8 The corresponding phase images of these surfaces were also obtained via AFM. As shown in (a) and (c) from Figure 5, microphase separation phenomenon appeared. The worm-like morphology spontaneously formed on the surfaces with the modification of PHEAA-b-PFMA block copolymer without any annealing. The size of separated domains could be regulated by changing the polymerization conditions. 11


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

As shown in Figure S2 (supporting information), three kinds of sizes could be formed. And from (a) to (c), they were 48 nm, 67 nm and 111 nm, respectively. The corresponding block ratios of PHEAA/PFMA were 46/90, 72/90, and 80/98. As the PHEAA-b-PFMA molecular weight and the PHEAA content increase, the size of separated worm-like nanostructure became more and more large. Compared to (a) and (c), there was no obvious microphase separation in (b) and (d), which suggests that not all of the PHEAA-b-PFMA brushes could phase separated into nanostructure. The parameters, including the thickness (h), grafting density (σ) of PHEAA brush and the polymerization degree ration of PHEAA/PFMA (N1/N2) worked together determining the occurrence of microphase separation in PHEAA-b-PFMA diblock copolymer brushes. As shown in Table 1, the symbols of “√” and “×” respectively represented that the strong microphase separation occurred and didn’t occur in PHEAA-b-PFMA. The results indicated that when the thickness of PHEAA brushes (h) was in the range from 6.61 nm to 19.18 nm, the microphase separation arose in the diblock copolymer brushes of PHEAA-b-PFMA. The grafting degree of PHEAA brush (σ) also had limitation to microphase separation. According to the formula σ(chain/nm2)=ρhNA/Mn, where NA is the Avogadro constant, ρ, h and Mn is density, thickness and number average molecular weight of polymer, respectively55. In the range of σ from 0.82 chain/nm2 to 1.5 chain/nm2, the appearance of microphase separation in PHEAA-b-PFMA brush is possible. Apart from the σ and h of PHEAA brush, the ratio of PHEAA/PFMA (N1/N2) in diblock copolymer brush played an important role in the appearance of strong microphase separation. When the ratio of N1/N2 was in the range from 42/91 to 94/89, the strong microphase separation phenomenon could occur in PHEAA-b-PFMA brush grafting from silicon wafer. Protein adsorption test. The qualitative analysis of the modified surfaces in protein adsorption was characterized by FM. As shown in Figure 6, there was a great deal of protein adsorbed on pristine, yet, there was a little protein adsorbed on most of the surfaces modified with PHEAA and PHEAA-b-PFMA brushes. The amount of adsorbed protein on Si-PHEAA decreased with the increase of PHEAA brush thickness. The amount of 12


Page 12 of 26

Page 13 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

adsorbed protein on Si-PHEAA-b-PFMA decreased as separated size in nanostructure increase, among them, the anti-adsorption performance of PHEAA-b-PFMA against Fg was best. We also quantitatively evaluated the anti-protein adsorption performance of PHEAA and PHEAA-b-PFMA brush modified surfaces via BCA assay, as shown in Figure 7. The adsorption quantity of proteins on PHEAA brush modified surfaces all has been reduced. Among them, the anti-adsorption performance of PHEAA brush against BSA was best. And with the increase of PHEAA brush thickness, the antifouling ability of corresponding surface strengthened. The results mentioned above were consistent with the reported literature.56 For PHEAA-b-PFMA modified surfaces, with the increase of PHEAA block content, the size of separated structure increased. Compared to smaller size separated structure (48 nm), the separated structure with larger size (111 nm) possessed better anti-adsorption performance against all the test proteins. This indicated that the content of PHEAA block played an important role in phase separation behavior and anti-protein adsorption of PHEAA-b-PFMA, diblock copolymer. The results mentioned above may be from two aspects. One was that the structure caused by PHEAA-b-PFMA with higher molecular weight possessed larger film thickness and surface coverage, which enhanced the performance of anti-protein adsorption.57 And the other was that the separated size caused by PHEAA-b-PFMA with higher molecular weight matched well with the test protein. And there was literature reporting that when the phase separation size approached to the size of protein, it was difficult for protein to adsorb onto surface stably.57 It was relatively complex to compare the anti-adsorption performance of the surface modified with PHEAA-b-PFMA and with PHEAA brushes. For Fg, the surfaces modified with PHEAA-b-PFMA whether with larger (111 nm) or smaller (48 nm) separation size all possessed better anti-protein adsorption performance than that of corresponding surfaces modified with single PHEAA brushes. This might due to the large size of Fg and the hydrophobic units in Fg structure. However, surfaces modified with PHEAA-b-PFMA brushes possessed amphiphilic alternation structures, 13


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

which was detrimental to Fg adsorption. 58,59 For BSA and Ly, there was no obvious difference in anti-adsorption performance between the surfaces modified with PHEAA-b-PFMA appearing larger separation size and with corresponding PHEAA bushes. However, the surface modified by PHEAA possessed better anti-adsorption protein performance than that of the surface modified by PHEAA-b-PFMA with smaller separation size.

Conclusion In summary, we successfully prepared a series of amphiphilic diblock copolymer brushes (PHEAA-b-PFMA) on silicon wafers by SI-ATRP. The AFM results indicated only when the grafting degree (σ) and thickness (h) of PHEAA brush was in the range of 0.82-1.5 (chain/nm2) and 6.61-19.18 nm respectively, the ratio of PFMA/PHEAA varied from 89/42 to 89/94, could the microphase separation phenomenon take place in PHEAA-b-PFMA brush. The results of protein adsorption experiments indicated that most of the modified surfaces could obviously reduce the protein adsorption compared to the pristine silicon wafers. For Fibrinogen, the anti-protein performance of PHEAA surfaces was significantly improved after the introduction of PFMA block. The results provide further evidence that surface compositional heterogeneities and microphase segregation of fluorinated moieties of block copolymer brushes significantly impact protein adsorption behaviors.

Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Detailed characterizations of XPS, AFM.

ACKNOWLEDGMENTS The research was financially supported by National Natural Science Foundation of China (grant number 21674084) and the Fundamental Research Funds for the Central Universities (2042018kf0209). H-X Wu thanks the Natural Science Foundation of 14


Page 14 of 26

Page 15 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

He'nan Province (no. 172102210098) and the Foundation of He'nan Educational Committee (no. 16A150037) for financial support.

15


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Reference 1. Wisniewski, N.; Reichert, M. Methods for Reducing Biosensor Membrane Biofouling. Colloid Surf. B: Biointerfaces 2000, 18, 197-219. 2. Cole, N.; Hume, E. B. H.; Vijay, A. K. Sankaridurg, P.; Kumar, N.; Willcox, M. D.P. In Vivo Performance of Melimine as an Antimicrobial Coating for Contact Lenses in Models of CLARE and CLPU. Microbiol. Immunol. 2010, 51, 390-395. 3. Vasilev, K.; Cook, J.; Griesser H. J. Antibacterial Surfaces for Biomedical Devices. Expert Rev. Med. Devices 2009, 6, 553-567. 4. Li, X. H.; Xing, Y. G.; Jiang, Y. H.; Ding, Y. L.; Li, W. L. Antimicrobial Activities of ZnO Powder-Coated PVC Film to Inactive Food Pathogens. Int. J. Food Sci. Technol. 2009, 44, 2161-2168. 5. Asuri, P.; Karajanagi, S. S.; Kane, T. S.; Dordick, J. S. Polymer-Nanotube-Enzyme Composites as Active Antifouling Films. Small 2007, 3, 50-53. 6. Yebra, D. M.; Kiil, S.; Dam-Johansen, K. Antifouling Technology-Past, Present and Future Steps towards Efficient and Environmentally Friendly Antifouling Coatings. Prog. Org. Coat. 2004, 50, 75-104. 7. Chambers, L. D.; Stokes, K. R.; Walsh, F. C.; Wood, R. J. K. Modern Approaches to Marine Antifouling Coatings. Surf. Coat. Technol. 2006, 201, 3642-3652. 8. Wu, H. X.; Tan, L.; Yang, M. Y.; Liu, C.J.; Zhuo, R. X. Protein-resistance Performance of Amphiphilic Copolymer Brushes Consisting of Fluorinated Polymers and Polyacrylamide Grafted from Silicon Surfaces. RSC Adv., 2015, 5, 12329-12337. 9. Zhi, Z.; Su, Y.; Xi, Y.; Tian, L.; Xu, M.; Wang, Q.; Padidan, S.; Li, P.*; Huang, W., Dual-functional PEG-b-Polyhexanide Surface Coating with In Vitro and In Vivo Antimicrobial and Antifouling Activity. ACS Appl. Mater. Interface 2017, 9, 10383-10397. 10. Su, Y.; Zhi, Z.; Gao, Q.; Xie, M.; Yu, M.; Bo, L.; Li, P.*; Ma P. X., Autoclaving-derived Surface Coating with in vitro and in vivo Antimicrobial and Antibiofilm Efficacies. Adv. Heal. Mater. 2017, 6 (6), 1601173. 11. Gao, Q.; Yu, M.; Su, Y.; Xie, M.; Zhao, X.; Li, P.; Ma, P. X., Rationally designed dual functional block copolymers for bottlebrush-like coatings: In vitro and in vivo antimicrobial, antibiofilm, and antifouling properties. Acta Biomater. 2017, 51, 112-124. 12. Gu, J.; Su, Y.; Liu, P.; Li, P.; Yang, P.*, An Environmentally Benign Antimicrobial Coating Based on A Protein Supramolecular Assembly. Adv. Heal. Mater. 2017, 9, 198-210. 13. Ma, H. W.; Hyun, J.; Stiller, P.; Chilkoti, A. “Non-Fouling” Oligo(ethyleneglycol)Functionalized Polymer Brushes Synthesized by Surface-Initiated Atom Transfer Radical Polymerization. Adv. Mater. 2004, 16, 338-341. 14. Cho, Y. J.; Sundaram, H. S.; Weinman, C. J.; Paik, M. Y.; Dimitriou, M. D.; Finlay, J. A.; Callow, M. E.; Callow, J. A.; Kramer, E. J.; Ober, C. K. Triblock Copolymers with Grafted Fluorine-Free, Amphiphilic, Non-Ionic Side Chains for Antifouling and Fouling-Release 16


Page 16 of 26

Page 17 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Applications. Macromolecules 2011, 44, 4783-4792. 15. Krishnan, S.; Weinman, C. J.; Ober, C. J. Advances in Polymers for Anti-Biofouling Surfaces. J. Mater. Chem. 2008, 18, 3405-3413. 16 Shen, D. F.; Xu, B. B.; Huang, X. Y.; Zhuang, Q. X.; Lin, S. L. (PtBA-co-PPEGMEMAco-PDOMA)-g-PPFA Polymer Brushes Synthesized by Sequential RAFT Polymerization and ATRP. Polymer Chemistry 2018, 2821-2829. 17. Li, X.; Cai, T.; Chung, T. S. Anti-Fouling Behavior of Hyperbranched Polyglycerol-Grafted Poly(ether sulfone) Hollow Fiber Membranes for Osmotic Power Generation, Environmental Science and Technology. 2014, 48, 9898-9907. 18. Bauer, S.; Alles, M.; Arpa-Sancet, M. P.; Ralston, E.; Swain, G. W.; Aldred, N.; Clare, A. S.; Finlay, J. A.; Callow, M. E.; Callow, J. A.; Rosenhahn, A. Resistance of Amphiphilic Polysaccharides against Marine Fouling Organisms. Biomacromolecules 2016, 17, 897-904. 19. Grozea, C. M.; Walker, G. C. Approaches in Designing Non-Toxic Polymer Surfaces to Deter Marine Biofouling. Soft Matter 2009, 5, 4088-4100. 20. 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. 21. Krishnan, S.; Weinman, C. J.; Ober, C. K. Advances in polymers for anti-biofouling surfaces. J. Mater. Chem. 2008, 18, 3405-3413. 22. Hawkins, M. L.; Faÿ, F.; Réhel, K.; Linossier, I.; Grunlan, M. A. Bacteria and diatom resistance of silicones modified with PEO-silane amphiphiles. Biofouling 2014, 30, 247–258. 23. Galli, G.; Martinelli, E. Amphiphilic Polymer Platforms: Surface Engineering of Films for Marine Antibiofouling. Macromol. Rapid comm. 2017, 38, 1600704. 24. Zhang, X. H.; Wu, H. X.; Huang, L.; Liu, C. J. From Homogeneous to Heterogeneous: A Simple Approach to Prepare Polymer Brush Modiﬁed Surfaces for Anti-Adhesion of Bacteria. Colloid and Interface Science Communications 2018, 23, 21-28. 25. Martinelli, E.; Suffredini, M.; Galli, G.; Glisenti, A.; Pettitt, M. E.; Callow, M. E.; Callow, J. A.; Williams, D.; Lyall, G. Amphiphilic Block Copolymer/Poly (Dimethylsiloxane) (PDMS) Blends and Nanocomposites for Improved Fouling-release. Biofouling 2011, 27, 529-541. 26. Martinelli, E.; Sarvothaman, M. K.; Galli, G.; Pettitt, M. E.; Callow, M. E.; Callow, J.A.; Conlan, S. L.; Clare, A. S.; Sugiharto, A. B.; Davies, C.; Williams, D. Poly(dimethylsiloxane) (PDMS)

Network

Blends

of

Amphiphilic

Acrylic

Copolymers

with

Poly(ethyleneglycol)-Fluoroalkyl Side Chains for Fouling-Release Coatings. II. Laboratory Assays and Field Immersion Trials. Biofouling 2012, 28, 571-582. 27. Zhu, X.; Guo, S.; Jańczewski, D.; Velandia, F. J. P.; Teo, S. L.-M.; Vancso, G. J. Multilayers of Fluorinated Amphiphilic Polyions for Marine Fouling Prevention. Langmuir 2014, 30, 288–296. 28. Gudipati, C. S.; Greenlief, C. M.; Johnson, J. A.; Prayongpan, P.; Wooley, K. L. Hyperbranched Fluoropolymer and Linear Poly(ethylene glycol) Based Amphiphilic Crosslinked 17


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Networks as Efficient Antifouling Coatings: An Insight Into the Surface Compositions, Topographies, and Morphologies. J. Polym. Sci. A Polym. Chem. 2004, 42, 6193-6208. 29. Amadei, C. A.; Yang, R.; Chiesa, M.; Gleason, K. K.; Santos, S. Revealing Amphiphilic Nanodomains of Anti-Biofouling Polymer Coatings. ACS Appl. Mater. Interface 2014, 6, 4705-4712. 30. Nolte, K. A.; Schwarze, J.; Rosenhahn, A. Microfluidic Accumulation Assay Probes Attachment of Biofilm Forming Diatom Cells. Biofouling 2017, 33, 531-543. 31. Park, S.; Kim, Y.; Lee, W.; Hur, S.-M.; Ryu, D. Y., Gyroid Structures in Solvent Annealed PS-b-PMMA Films: Controlled Orientation by Substrate Interactions. Macromolecules 2017, 50, 5033-5041. 32. Nakatani, R.; Takano, H.; Chandra, A.; Yoshimura, Y.; Wang, L.; Suzuki, Y.; Tanaka, Y.; Maeda, R.; Kihara, N.; Minegishi, S.; Miyagi, K.; Kasahara, Y.; Sato, H.; Seino, Y.; Azuma, T.; Yokoyama, H.; Ober, C. K.; Hayakawa, T., Perpendicular Orientation Control without Interfacial Treatment of RAFT-Synthesized High-chi Block Copolymer Thin Films with Sub-10 nm Features Prepared via Thermal Annealing. ACS Appl Mater Interfaces 2017, 9, 31266-31278 33. Bates, C. M.; Bates, F. S., 50th Anniversary Perspective: Block Polymers-Pure Potential. Macromolecules 2016, 50, 3-22. 34. Epps, II I. T. H.; O'Reilly, R. K., Block Copolymers: Controlling Nanostructure to Generate Functional Materials – Synthesis, Characterization, and Engineering. Chemical Science 2016, 7, 1674-1689. 35. Li, S.; Yang, D.; Tu, H.; Deng, H.; Du, D.; Zhang, A., Protein Adsorption and Cell Adhesion Controlled by the Surface Chemistry of Binary Perfluoroalkyl/Oligo(ethylene glycol) Self-assembled Monolayers. J Colloid Interface Sci 2013, 402, 284-290. 36. Shen, L.; Zhu, J.; Liang, H., Heterogeneous Patterns on Block Copolymer Thin Film via Solvent Annealing: Effect on Protein Adsorption. J. Chem. Phys. 2015, 142, 101908. 37. Firkowska-Boden, I.; Zhang, X.; Jandt, K. D., Controlling Protein Adsorption through Nanostructured Polymeric Surfaces. Adv. Healthc. Mater. 2018, 7, 1700995. 38. Teruo, O.; Shoji, N.; Isao, S.; Toshihiro, A.; Yasuhisa, S.; Kazunori, K.; Teiji, T., Effect of Hydrophilic and Hydrophobic Microdomains on Mode of Interaction Between Block Polymer and Blood Platelets. J. Biomed. Mater. Res. 1981, 15, 393-402. 39. Shen, L.; Zhu, X. Y., Evidence of a Mobile Precursor State in Nonspecific Protein Adsorption. Langmuir 2011, 27, 7059-7064. 40. Amadei, C. A.; Yang, R.; Chiesa, M.; Gleason, K. K.; Santos, S., Revealing Amphiphilic Nanodomains of Anti-biofouling Polymer Coatings. ACS Appl Mater Interfaces 2014, 6, 4705-4712. 41. Shen, L.; Xie, J.; Tao, J.; Zhu, J., Anti-biofouling Surface with Sub-20 nm Heterogeneous Nanopatterns. J. Mater. Chem. B 2015, 3, 1157-1162.

18


Page 18 of 26

Page 19 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

42. George,

P.

A.;

Donose,

B.

C.;

Cooper-White,

J.

J.,

Self-assembling

Polystyrene-block-poly(ethylene oxide) Copolymer Surface Coatings: Resistance to Protein and Cell Adhesion. Biomaterials 2009, 30, 2449-2456. 43. Chen, W.; Wei, M.; Wang, Y., Advanced Ultrafiltration Membranes by Leveraging Microphase Separation in Macrophase Separation of Amphiphilic Polysulfone Block Copolymers. J. Memb. Sci. 2017, 525, 342-348. 44. Matyjaszewski, K., Advanced Materials by Atom Transfer Radical Polymerization. Adv Mater. 2018, 30, e1706441. 45. Zoppe, J. O.; Ataman, N. C.; Mocny, P.; Wang, J.; Moraes, J.; Klok, H. A., Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes. Chem. Rev. 2017, 117, 1105-1318. 46. Wang, H.; Jasensky, J.; Ulrich, N. W.; Cheng, J.; Huang, H.; Chen, Z.; He, C., Capsaicin-Inspired Thiol-Ene Terpolymer Networks Designed for Antibiofouling Coatings. Langmuir 2017, 33, 13689-13698. 47. Jia, P.; He, M.; Gong, Y.; Chu, X.; Yang, J.; Zhao, J., Probing the Adjustments of Macromolecules during Their Surface Adsorption. ACS Appl Mater Interfaces 2015, 7, 6422-6429. 48. Liu, D.; Guo, J.; Zhang, J.-H., Chain Mobility and Film Softness Mediated Protein Antifouling at the Solid–Liquid Interface. J. Mater. Chem. B 2016, 4, 6134-6142. 49. Wang, Z.; Zuilhof, H., Self-Healing Superhydrophobic Fluoropolymer Brushes as Highly Protein-Repellent Coatings. Langmuir 2016, 32, 6310-6318. 50. Wang, L.; Chen, X.; Cao, X.; Xu, J.; Zuo, B.; Zhang, L.; Wang, X.; Yang, J.; Yao, Y., Fabrication of Polymer Brush Surfaces with Highly-Ordered Perfluoroalkyl Side Groups at the Brush End and Their Antibiofouling Properties. J. Mater. Chem. B 2015, 3, 4388-4400. 51. Chen, H.; Zhao, C.; Zhang, M.; Chen, Q.; Ma, J.; Zheng, J., Molecular Understanding and Structural-Based Design of Polyacrylamides and Polyacrylates as Antifouling Materials. Langmuir 2016, 32, 3315-3330. 52. Lombeck, F.; Komber, H.; Sepe, A.; Friend, R. H.; Sommer, M., Enhancing Phase Separation and Photovoltaic Performance of All-Conjugated Donor–Acceptor Block Copolymers with Semifluorinated Alkyl Side Chains. Macromolecules 2015, 48, 7851-7860. 53. Wu, H. X.; Tan, L.; Tang, Z. W.; Yang, M. Y.; Xiao, J. Y.; Liu, C. J.; Zhuo, R. X., Highly Efficient

Antibacterial

Surface

Grafted

with

a

Triclosan-decorated

Poly(N-hydroxy

ethylacrylamide) Brush. ACS Appl Mater Interfaces 2015, 7, 7008-7015. 54. Tang, Z.-W.; Ma, C.-Y.; Wu, H.-X.; Tan, L.; Xiao, J.-Y.; Zhuo, R.-X.; Liu, C.-J., Antiadhesive Zwitterionic Poly-(Sulphobetaine Methacrylate) Brush Coating Functionalized with Triclosan for High-Efficiency Antibacterial Performance. Progress in Organic Coatings 2016, 97, 277-287. 55. Patil, R.; Turgman-Cohen, S.; Srogl, J.; Kiserow, D.; Genzer, J., On-Demand Degrafting and the Study of Molecular Weight and Grafting Density of Poly(methyl methacrylate) Brushes on Flat Silica Substrates. Langmuir 2015, 31, 2372-2381. 19


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

56. Zhao, C.; Zheng, J., Synthesis and Characterization of Poly(N-hydroxyethylacrylamide) for Long-Term Antifouling Ability. Biomacromolecules 2011, 12, 4071-4079. 57. Liang, P.; Canoura, J.; Yu, H.; Alkhamis, O.; Xiao, Y., Dithiothreitol-Regulated Coverage of Oligonucleotide-Modified Gold Nanoparticles to Achieve Optimized Biosensor Performance. ACS Appl. Mater. Interfaces 2018, 10, 4233-4242. 58. Weinman, C. J.; Gunari, N.; Krishnan, S.; Dong, R.; Paik, M. Y.; Sohn, K. E.; Walker, G. C.; Kramer, E. J.; Fischer, D. A.; Ober, C. K., Protein Adsorption Resistance of Anti-Biofouling Block Copolymers Containing Amphiphilic Side Chains. Soft Matter 2010, 6, 3237-3243. 59. Gao, J.; Yan, D.; Ni, H.; Wang, L.; Yang, Y.; Wang, X., Protein-Resistance Performance Enhanced by Formation of Highly-Ordered Perfluorinated Alkyls on Fluorinated Polymer Surfaces. J Colloid Interface Sci. 2013, 393, 361-368.

20


Page 20 of 26

Page 21 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figures and Captions Table 1 Effect of parameters of the synthesized PHEAA-b-PFMA on microphase separation.

Samples

h (nm)-thickness of PHEAA brush

σ (chain/nm2)-grafting density of PHEAA brush

N1 (polymerization degree of PHEAA )

N2 ( polymerization degree of PFMA)

1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 17 18 19 20 21 22

6.61 8.28 8.47 10.64 12.34 12.99 14.5 15.01 15.1 19.18 12.95 11.29 15.06 15.29 16.02 16.48 17.79 21.76 27.13 30.4 42.35

0.90 1.18 1.18 0.93 0.82 0.96 1.05 1.38 1.19 1.5 0.85 0.76 0.74 0.83 0.83 1.0 0.93 0.85 1.05 1.7 2.32

46 44 42 72 94 85 86 68 80 81 96 93 127 116 120 103 120 161 163 112 115

90 90 91 90 89 90 92 100 98 115 92 100 90 91 45 93 90 89 105 85 63

21


microphase separation (√or×) √ √ √

√ √ √ √ √

√ √ × × × × × × × × × × ×

Langmuir

OH OH OH

O O O

Si

O

O O Si O

NH2

Si-OH

NH2

O

O O Si O

Br

Br

Si-NH2

NH

Si-Br

O HN

O

O

O O Si O

F

F

O

NH

n

m

O

Br O

O

Si-PHEAA-b-PFMA

F

O O Si O

F F

Br

CuBr/Me6TREN Methol/H2O(v:v=1:1),rt

OH

CuBr/PMDETA DMF,110

O NH O

Si-PHEAA

NH F

F F F

HO

HO

Scheme 1 Schematic representation of silicon wafer grafted with PHEAA-b-PFMA copolymer brush by SI-ATRP.

80 70 60 50 40 30 20 10 0 OH Si-

2 NH Si-

Br Si-

A MA EA -PF PH b i S AA HE P Si

Figure 1 Water static contact angles of the serial modified silicon wafers.

22


mBr NH

F

Water Contact Angle(degree)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 26

Page 23 of 26

Si-NH2 Si-Br Si-PHEAA Si-PHEAA-b-PFMA

Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

0

200

400

600

800

Binding Energy(eV)

Figure 2 XPS spectra of the modified silicon wafers.

Figure 3 Area-normalized C (1s) XPS signal for the surfaces after modification. a: Si-NH2; b: Si-Br; c: Si-PHEAA; d: Si-PHEAA-b-PFM.

23


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4 AFM height images of Si-PHEAA and the corresponding Si-PHEAA-b-PFMA. The thickness (h), grafting density (σ) of PEAA brush and the ratio of PHEAA/PFMA (N1/N2) vary from a to b. (a): h=6.61nm, σ=0.90 chain/nm2, N1/N2=46/90; (b): h=12.95 nm, σ=0.85 chain/nm2, N1/N2=96/92; (c): h=15.1 nm, σ=1.38 chain/nm2, N1/N2=68/100; (d): h=42.35 nm, σ=2.32 chain/nm2, N1/N2=115/63.

24


Page 24 of 26

Page 25 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 5 AFM phase images of Si-PHEAA and Si-PHEAA-b-PFMA corresponding to Figure 3.

Figure 6 Fluorescence microscopy images of pristine Si, Si-PHEAA and the corresponding Si-PHEAA-PFMA after 4 h incubation with FITC labeled proteins, (a) BSA, (b) Fg, (c) Ly and the fluorescence intensity statistics. (The thicknesses of PHEAA and PHEAA’ were 8.28 nm and 19.18 nm, respectively).

Figure 7 The adsorption amounts of proteins on pristine Si, Si-PHEAA and the corresponding Si-PHEAA-PFMA after 24 h incubation via BCA assay. (The thicknesses of PHEAA and PHEAA’ were 8.28 nm and 19.18 nm, respectively). 25


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TOC graph

26


Page 26 of 26

Diblock Polymer Brush (PHEAA-b-PFMA): Microphase Separation

Recommend Documents