Article pubs.acs.org/IECR
Preparation and Performance of Amphiphilic Polyurethane Copolymers with Capsaicin-Mimic and PEG Moieties for Protein Resistance and Antibacteria Xi Chen, Guangfa Zhang, Qinghua Zhang,* Xiaoli Zhan, and Fengqiu Chen College of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027, China ABSTRACT: Antifouling (AF) coatings have been a research focus on effectively resisting biocontamination of equipment applied in the aquatic environments. The amphiphilic ternary copolymers P(H−P−A) composed of N-(4-hydroxy-3methoxybenzyl)acrylamide (HMBA), poly(ethylene glycol) methyl ether methacrylate, and 2-hydroxyethyl acrylate were synthesized by free-radical polymerization. Then the polyurethane (PU) copolymer coatings with capsaicin and poly(ethylene glycol) (PEG) moieties were prepared by cross-linking with polymeric phenyl methanediisocyanate. Fourier transform infrared and 1H NMR were employed for chemical structural analysis of the products. The surface composition and concentration of nitrogen atoms on the copolymer films were quantitatively analyzed by X-ray photoelectron spectroscopy. The AF properties of the copolymers were assessed by static protein adsorption and antibacterial tests. The targeted copolymer film samples can achieve an average antibacterial efficiency of 93.3% and a protein-resistant rate of 97.3%, which demonstrated that P(H−P−A) is a potential environmentally friendly material for AF application.
1. INTRODUCTION Biofouling is of great concern in numerous applications including implanted materials and devices, food packaging, ship hulls, and so on.1−3 Biocide-containing antifouling (AF) coatings have been developed for many years to resist the settlement of fouling organisms, such as bacteria, protein, and microorganism.2−5 In the past, the most widely used AF compounds were mainly based on heavy metals such as copper, lead, tin, arsenic, and cadmium.2,3,6,7 However, many of the heavy-metal biocides are also a threat to the marine environment and have been banned by many countries in recent years. The restriction on the use of toxic compounds promoted the research on synthetic and natural biocides, which are environmentally friendly.1,8−10 Accordingly, a more effective approach is being pursued by designing specific surface features with nonfouling performance or nontoxic biocide activity. Majumdaret al. fabricated a series of excellent AF coatings containing environmentally friendly quaternary ammonium compounds with different alkyl chain lengths.11−14 Researchers are always looking for suitable nontoxic or less toxic alternatives. A large number of natural products and synthesized compounds15,16 with effective AF activities,17 such as butenolide,18−20 polybrominated diphenyl ethers,21 xanthones,22 and isocyanide23 have been reported. Indeed, the molecular mechanisms and their acute toxicity to marine organisms of these novel biocides remain unknown. In recent years, capsaicin of chili peppers was reported as a natural nontoxic biocide agent for AF application.24 The research work showed that capsaicin-mimic compounds possessed much more attractive properties than the current toxic antifoulants.25 As one of the capsaicin-mimic materials, the functional monomer N-(4-hydroxy-3-methoxybenzyl)acrylamide (HMBA) has been reported to prepare a copolymer AF coating material for oceanic and membrane modification applications.26−28 HMBA has been regarded as a significantly © 2015 American Chemical Society
natural antibacterial agent that can be allowed for polymerization with other monomers to produce hydrophobic AF coatings.5,29 It is well-known that hydrophobic surfaces have significant binding affinity toward organic contaminants and proteins. Also, the nonspecific adsorption of proteins will lead to biofouling, which was considered to be a cause for the failure of biomaterials in medical application.30−36 Hydrophilic modification of surfaces using poly(ethylene glycol) (PEG) and zwitterionic polymers with high wettability was found to be promising for microbe and protein resistance.37−44 Hydration of PEG plays an important role in the mechanism of protein repellency, and the hydration layer generates a repulsive force on protein adsorption and microbe adhesion. Although attachment of PEG to a surface is one of the most widely used approaches in the fabrication of protein-resistant surfaces, it is not effective in reducing bacterial colonization.27,29 In order to solve this problem, an alternative method is to introduce the antimicrobial activity groups to the hydrophilic copolymers, combining both protein-resistant and antibacterial properties.45 In this study, we designed a functional ternary copolymer composed of HMBA, poly(ethylene glycol) methyl ether methacrylate, and 2-hydroxyethyl acrylate. Then the reactive copolymer with hydroxyl was cross-linked with polymeric phenyl methanediisocyanate to form polyurethane (PU) coatings for endowing protein resistance and antibacterial performance. Moreover, the PU shows excellent AF performance, relying on the release of antifoulants in the marine environment.46 The microstructure and surface wettability of the copolymer films were studied. The antibacterial properties Received: Revised: Accepted: Published: 3813
December March 19, March 27, March 27,
30, 2014 2015 2015 2015 DOI: 10.1021/ie505062a Ind. Eng. Chem. Res. 2015, 54, 3813−3820
Article
Industrial & Engineering Chemistry Research Scheme 1. Synthesis Route for the Preparation of P(H−P−A) and PU Films
to Escherichia coli and protein resistance of the copolymer films influenced by the composition were investigated in detail.
Table 1. Different Molar Compositions of Monomers in the Copolymer P(H−P−A) copolymer composition
2. MATERIALS AND METHODS 2.1. Materials. Poly(ethylene glycol) methyl ether methacrylate (PEGMA; ∼300 g/mol, Aldrich) and 2-hydroxyethyl acrylate (HEA; 99.9%, Aldrich) were filtered through a basic alumina column to remove the radical inhibitor. 2,2′-Azobis(isobutyronitrile) (AIBN; Aldrich) was recrystallized from ethanol. Diethyl ether, tetrahydrofuran (THF), and ethanol were obtained from Sinopharm Chemical Reagent and used as received. Bovine serum albumin (BSA), dimethyl-d sulfoxide (DMSO-d; 99.8%), N-hydroxymethylacrylamide, and guaiacol (2-methoxyphenol) were purchased from Aladdin and used as received. The PBS buffer solution was prepared in distilled water with a pH of about 7.4 at 25 °C. 2.2. Synthesis of HMBA by Friedel−Craft. N-(4Hydroxy-3-methoxybenzyl)acrylamide (HMBA) was synthesized to act as an antibacterial agent. The synthesis method of HMBA was described in the literature.29 A total of 80 g (0.78 mol) of N-hydroxymethylacrylamide and 100 g (0.8 mol) of guaiacol were dissolved in 200 mL of absolute ethanol. Also, 20 mL of H2SO4 was added dropwise into the mixture under stirring at 25 °C. The reaction mixture was kept stirring for 7 days at 35 °C. Then the product was washed with water several times until the washing liquid was neutral. The yellow liquid was poured into diethyl ether, and a white precipitate of HMBA formed. The crude product was recrystallized from ethanol. 2.3. Synthesis of Copolymer P(H−P−A) with Capsaicin and PEG Moieties. A series of copolymers composed of HMBA and PEGMA (Mn = 300) were synthesis to act as AF agents. AIBN (0.08 g) and N,N-dimethylformamide (DMF; 2 mL) were added to a 25 mL three-necked flask fitted with a nitrogen inlet and outlet, and the flask was heated to 80 °C in an oil bath under nitrogen. Then HMBA (0.014 mol), PEGMA (0.004 mol), HEA (0.002 mol), and AIBN (0.12 g) were dissolved in DMF to form a homogeneous solution. The mixture was dropwise added into the flask in 4 h. The reaction mixture was stirred for 24 h at 80 °C under nitrogen to form a pale-yellow transparent solution. The reaction route is shown in Scheme 1. The product polymer was isolated by precipitation into ice ether and recovered by filtration. The polymer sample was dissolved in DMF again followed by precipitation and filtration. This purification process was repeated three times, and finally a viscous liquid of the random copolymer P(H−P− A) was obtained after being dried in a vacuum oven at 60 °C for 24 h. Different molar compositions of monomers in the copolymers were summarized in Table 1.
copolymer sample
HMBA (mol %)
PEGMA (mol %)
HEA (mol %)
P1 P2 P3
24.4 30.3 45.4
74.6 68.7 53.6
1.0 1.0 1.0
2.4. Preparation of PU Films. Copolymer films were prepared for contact-angle measurement, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) imaging, and BSA protein adsorption testing on silicon wafers. The hydroxyl (−OH) content in P(H−P−A) for various samples was measured with the phthalic anhydride−pyridine method. Then P(H−P−A) was dissolved in THF (1% w/v) and reacted with a certain amount of PAPI (OH:NCO = 1:1.1). The mixed solution was coated by spin coating at 2500 rpm using a Cee model 100CB spin coater. These samples (PU-1,2,3) were allowed to evaporate at room temperature for 4 h in order to remove the solvent and then dried in a vacuum oven at 60 °C for 24 h. The thicknesses of the resulting films were 260−300 μm. 2.5. Analysis and Characterization. 2.5.1. FT-IR, 1H NMR, and Gel Permeation Chromatography (GPC) Analysis. 1 H NMR spectra of the copolymers were recorded using a Bruker 500 MHz NMR spectrometer (Advance DMX500) and carried out with a 5 wt % solution in DMSO-d at room temperature to determine monomer conversion. The chemical compositions of HMBA and P(H−P−A) were characterized using a Fourier transform infrared (FT-IR) spectroscope, which were cast as films from THF solutions on KBr disks (KBr crystal plates) using a Nicolet 5700 FT-IR instrument. The number-average molecular weights (Mn) and polydispersity indexes (PDI) of the copolymers were measured by a Waters 1525/2414 GPC system consisting of a Waters 1525 binary liquid chromatography pump, a Waters 717 plus autosampler, three Waters columns, and a Waters 2414 refractive index detector. THF was used as the eluent at a flow rate of 1.0 mL/ min at 35 °C. 2.5.2. Wettability Test. The water static contact angle was used to characterize the wettability of the copolymer film with glass slides of 2 mm × 8 mm as support. The measurement was done by the sessile-drop method using a CAM200 optical contact-angle meter (KSV Co., Ltd.) at room temperature with a relative humidity of (30 ± 2)%. The contact angle was recorded by the software automatically after 5 μL of deionized (DI) water was dropped onto glass slides with polymer films. 3814
DOI: 10.1021/ie505062a Ind. Eng. Chem. Res. 2015, 54, 3813−3820
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Industrial & Engineering Chemistry Research
3. RESULTS AND DISCUSSION 3.1. Structure Analysis of the Synthesized HMBA and Copolymer P(H−P−A). The chemical structures of the synthesized monomer HMBA and copolymer P(H−P−A) with different compositions were characterized by FT-IR and 1 H NMR spectra. The representative FT-IR spectra of the monomer HMBA and copolymer P(H−P−A) are shown in Figure 1. The strong absorption band at around 3324 cm−1 was
The values are shown as the average of 10 measurements of each film surface. 2.5.3. Surface Composition and Morphology Characterization. XPS for the top surfaces of the polymer films was recorded with a VG ESCALAB MARK II spectrometer with a standard Mg Kα X-ray source (1253.6 eV) operating at 300 W. The X-ray source worked at a power of 250 W (12.5 kV). Survey spectra were run in the binding energy (BE) range of 0−1000 eV, and detailed spectra of C 1s, O 1s, and N 1s were collected. The standard deviation in the BE values of the XPS line was 0.10 eV. AFM images of the films were obtained with a Nanoscope III scanning probe microscope from Digital Instruments. The copolymer surfaces were imaged in a scan size of 5 μm × 5 μm. The root-mean-square (rms) roughness values of the samples were evaluated from AFM images in the tapping mode with a Digital Instruments Bioscope instrument (dimension head and G scanner) under ambient conditions, with a silicon tip (160 μm, 325 kHz) with a nominal spring constant of 40 N/m. The surface mean roughness parameters of the films were expressed in terms of the mean roughness (Ra). 2.5.4. Antibacterial Activity. The antibacterial property of the copolymer films was investigated using E. coli as the model microorganism. Glass slides (4 cm × 4 cm) were used as support for adhesion tests. Basically, E. coli was incubated in a Luria−Bertani (LB) liquid culture medium, shaken at 37 °C for 24 h, and then diluted with the LB liquid culture medium to a predetermined concentration using the standard serial dilution method. Polymer films coated on the glass slide were sterilized by ultraviolet radiation with all of the glassware for 30 min. These films were put into separate cuvettes containing 7 mL of a E. coli suspension, and they were then subjected to incubation in a shaking incubator at 37 °C for 24 h. Subsequently, the film was removed from the cuvettes, and the E. coli cells were detached from the film using 15 mL of the LB liquid culture medium, which was collected and diluted with the LB liquid culture medium until its concentration became 0.1% of the original value. Then 200 μL of the dilute solution was spread onto a LB solid culture medium and incubated at 37 °C for another 24 h. Each sample was tested three times. The antibacterial efficiency (Eb) was calculated from
Figure 1. FT-IR spectra of HMBA (a) and copolymer samples P1, P2, and P3 (b).
⎛ N − Nm ⎞ Eb = ⎜ b ⎟ × 100% ⎝ Nb ⎠
attributed to −NH and −OH stretching from the amino and phenolic hydroxyl groups in HMBA, while the absorption band at 1653 cm−1 corresponded to stretching of the carbonyl group (CO) in the acid amide of the HMBA monomer. The absorption bands at 1595 and 1523 cm−1 were assigned to stretching of the aromatic groups (CC). It is indicated that the HMBA monomer has been successfully synthesized. Figure 1b shows the FT-IR spectra of the ternary copolymers with different monomer compositions representatively. The absorption band at 3098 cm−1 for CC−H stretching and at 1595 cm−1 for CC stretching disappeared after copolymerization. The appearance of the comonomers PEGMA and HEA was characterized by stronger absorption bands at around 1653 and 1275 cm−1 assigned to CO and C−O stretching vibrations. The FT-IR spectrum basically confirmed formation of the ternary copolymers P(H−P−A) of HMBA, PEGMA, and HEA. In addition, with an increase in the concentration of the HMBA unit in the copolymers, the absorption band at about 3324 cm−1 for the −NH stretching vibration that overlaps with the −OH stretching vibration becomes stronger.
where Nb and Nm are the numbers of colonies corresponding to the blank glass slide and P(H−P−A) film, respectively. 2.5.5. Protein Adsorption Measurement. The test of the protein adsorption on the copolymer films was performed by the method as described in the literature.47 The adsorption of BSA onto the film was evaluated using a spectrophotometer [752(S,N), APL Instrument Shanghai Co., Ltd.]. The virgin and copolymer samples with 2 cm × 2 cm of surface area were rinsed with 1 mL of ethanol in 50% (v/v) water for 1 min and transferred into a glass bottle with 1 mL of DI water for 10 min repeatedly three times to fully remove the residual ethanol, followed by the addition of 1 mL of a PBS solution and soaked for 3 h. Then, these films respectively were soaked in 2 mL of 1 mg/mL BSA in a 0.1 M PBS solution (pH 7.4) for 3 h at room temperature. Finally, the protein solution concentration containing BSA in the glass bottle was determined by a UV− vis spectrophotometer with the absorbance at 280 nm. 3815
DOI: 10.1021/ie505062a Ind. Eng. Chem. Res. 2015, 54, 3813−3820
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Industrial & Engineering Chemistry Research The chemical structure and composition of the ternary copolymers were further demonstrated by 1H NMR. As shown in Figure 2, the peak at 2.5 ppm was characteristic for the
Figure 3. Water contact angles of the cross-linked copolymer films.
hydrophilic PEGMA segment in the copolymer plays a significant role in enhancing the surface hydrophilicity of films. Also, these hydrophilic surfaces containing more PEG segments should be favorable to resisting protein adsorption. AFM observations of the testing film surfaces revealed the roughness of standard deviation of the height values (rms) as 0.339, 0.589, and 1.107 nm for PU-1, PU-2, and PU-3. The surface roughness is relatively low, and it was considered that the roughness of standard deviation of the height values (rms) of 0.5−2 nm has no effect on the contact-angle measurement.50 Therefore, the water contact angles of the copolymer films were mainly dependent on the chemical compositions of the surfaces. Besides wettability, the performance of a coating is strongly dependent on its surface characteristics, such as the contribution of different reaction monomers on the film surface, morphology, and so on.48 Therefore, prior to antibacterial tests and protein adsorption studies, detailed surface properties were performed on the coatings. Quantitative analyses of the copolymer film surface compositions were determined by XPS measurement. Figure 4 shows the XPS
Figure 2. 1H NMR spectra of copolymer P(H−P−A) in DMSO-d (P3 in Table 1).
deuterated solvent DMSO. The chemical shift at 3.50 ppm was assigned to −OCH2− of PEGMA and HEA, and the integral area was 4.45. The chemical shifts from 3.23 to 3.45 ppm were attributed to the protons of −OCH2CH2− in PEGMA, where the integral area was 11.91. A small peak observed at around 6.13 ppm was assigned to the protons in −CHCH2 of HEA, and the chemical shift at 8.78 ppm was assigned to the proton of −OH in the HMBA. The proton peak at 3.73 ppm was assigned to −OCH3 from the HMBA and PEGMA units, where the integral area was 4.35. The results further demonstrated that the ternary copolymer has indeed been synthesized, and we can calculate the actual content monomers in the polymers according to the integral areas of the characteristic peaks in the 1 H NMR above. The results of GPC analysis of P1, P2, and P3 were 13039, 8738, and 6993 g/mol, respectively. Also, the PDI remained relatively low (PDI < 1.45), which further indicated that the copolymers have been successfully synthesized. 3.2. Hydrophilicity and Composition of the Copolymer Film Surface. A previous study showed that wettability is a critical parameter for the amphiphilic system to resist protein adsorption.48 The synthesized ternary copolymer P(H−P−A) containing hydrophobic segments HMBA and hydrophilic segments PEGMA should exhibit amphiphilic property. The wettability performance of the cross-linked copolymer films with different HMBA unit contents was studied by water contact-angle tests. As we know, the monomer HMBA and its homopolymer exhibited obvious hydrophobic properties. However, in this work, all of the copolymer film samples show hydrophilicity on different levels because of the introduction of hydrophilic PEG. Figure 3 presents the static water contact angles and corresponding schematic illustrations on the cross-linked copolymer films. With the content of HMBA decreasing from 45.4% to 24.4% in the copolymers, the water contact angles correspondingly decreased from 83.5° to 58.6°, which indicated that the film surfaces became more hydrophilic. Especially for PU-1, the water contact angle was 58.6°, which was very close to contact-angle value of PEG-based hydrogel materials reported in the literature.49 The results indicated that the
Figure 4. XPS survey spectra for the copolymer film surface of PU-1.
survey spectra of the copolymer film. As seen in Figure 4, three major emission peaks were observed at 290 eV for C 1s, 532 eV for O 1s, and 397 eV for N 1s, respectively. The theoretical bulk and surface atomic compositions calculated by XPS are summarized in Table 2. For all of the PU films, nitrogen was assigned to the carbamate group and HMBA. However, the XPS measurement 3816
DOI: 10.1021/ie505062a Ind. Eng. Chem. Res. 2015, 54, 3813−3820
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Industrial & Engineering Chemistry Research Table 2. Bulk and Surface Atomic Compositions for the Copolymer Film Surfaces C (%)
Nt (%)a
O (%)
sample
bulk
c
surface
PU-1 PU-2 PU-3
71.69 72.62 73.68
77.71 76.09 77.80
d
c
surface
24.91 23.66 20.97
18.73 19.56 15.75
bulk
d
bulk
c
Nh (%)b surface
3.40 3.72 5.35
d
bulk
3.56 4.35 6.45
e
surfacef
1.28 1.52 2.02
1.34 1.78 2.44
a
The total nitrogen atoms contained in the carbamate groups and HMBA. bThe nitrogen atoms contained in HMBA. cCalculated on the basis of the known composition of the copolymer film. dObtained from the XPS spectra. eCalculated on the basis of the HMBA content in the copolymer film. f Calculated on the value of Nt on the surface and the theoretical ratio of the nitrogen atoms contained in the carbamate groups and HMBA.
could not distinguish these two nitrogen atoms in different chemical environments. It is a reasonable assumption that the ratio of these two different nitrogen atoms on the surface was consistent with them in bulk. As seen in Table 2, the atomic nitrogen contents on the copolymer surface determined by XPS were very close to the values of the bulk for all of the samples, while the atomic carbon contents on the surface were a little higher than the bulk and the atomic oxygen content was a little lower. The reason should be that the atomic oxygen content is mainly contained in polar PEG chains with high surface energy. The process of thermal annealing for copolymer films promotes migration of the low surface energy group to the outermost surface. Anyway, the XPS results indicate that the amphiphilic PU network films containing rich HMBA units on the surface would exhibit antibacterial properties. 3.3. Antibacterial Activity of the Copolymer Films. The antimicrobial activities of the copolymer films are very significant for evaluating environmentally the AF coating performance. In this study, antibacterial assays toward E. coli were carried out to determine whether copolymer films possess any bactericidal effects. The antibacterial activities against the test E. coli microorganisms after 24 h of contact time of the sample films are shown in Figure 5. Compared with the control
Table 3. Antibacterial Efficiency for the Prepared Copolymer Films
a
film sample
no. of bacteria colonies
average Eb (%)a
control PU-1 PU-2 PU-3
75 14 10 5
0 81.3 86.7 93.3
Eb = antibacterial efficiency.
bactericidal rate against bacteria E. coli was above 80% when the content of HMBA in the copolymer film was 24.4%. With increasing HMBA content, the antibacterial activity corresponded to the increase. Especially, the copolymer film PU-3 containing 45.4% HMBA exhibited an average antibacterial efficiency of 93.3%. The test result shows that the introduction of HMBA in the amphiphilic copolymers endows the coatings obvious antimicrobial activity. Also, it is worth noting that the antibacterial activity of the copolymer film is related to the amount of HMBA on the film surfaces determined by XPS analysis. 3.4. Static Protein Adsorption. PEG-modified surfaces are well-known for their resistance to protein adsorption and cell adhesion.10 Also, the ability of resisting proteins to a film usually demonstrates a good relationship with the AF property of a hydrophilic film. However, the protein resistance performance of PEG-containing materials may be influenced by incorporation with hydrophobic segments. In this study, the model protein BSA was selected for the adsorption test. The amount of adsorbed BSA was evaluated by measuring two different concentrations of the BSA solution (0.1 and 1 g/L) before and after immersion of the copolymer films. The static adsorption amounts and specific BSA resistance (RBSA) values are presented in Table 4. Figure 6 shows the comparative amount of adsorbed protein on the copolymer films in 0.1 and 1 g/L BSA solutions. Here Table 4. Static Adsorption Amounts on the Copolymer Films in 0.1 and 1 g/L BSA Solutions
Figure 5. Results of bactericidal tests against E. coli: (a) control sample; (b) PU-1; (c) PU-2; (d) PU-3.
0.1 g/L film sample c
control PU-1 PU-2 PU-3
sample of the virgin ordinary glass, the copolymer films caused considerable reduction in the E. coli counts after 24 h of incubation. This result indicated that the presence of functional copolymer films significantly decreased the number of cells attached to the coating surface. With increasing HMBA contents in the film surfaces, the antibacterial effect became more significant. The results of the antibacterial efficiency for different copolymer films are presented in Table 3. Compared with the blank control, the
PBSA (μg/cm2)a 97.1 12.2 24.2 34.2
± ± ± ±
2.7 2.5 0.7 1.4
1.0 g/L R
b BSA
(%)
87.4 75.1 64.8
PBSA(μg/cm2)a 752.4 20.0 48.5 145.6
± ± ± ±
3.2 1.2 0.8 2.5
R
b BSA
(%)
97.3 93.6 80.6
The adsorption amounts of specific BSA protein on the films. Specific BSA resistance (RBSA) of films is defined as the minimum adsorption amount of BSA protein on the film samples divided by the maximum adsorption amount of BSA protein on the control film. c Control−virgin glass. a b
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Article
AUTHOR INFORMATION
Corresponding Author
*Fax: +86 571 87991227. E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors gratefully acknowledge the National Natural Science Foundation of China for Awards 21176212, 21276224, and 21476195 and the Zhejiang Provincial National Science Foundation of China (Grant Y14B060038) for supporting this research.
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Figure 6. Comparative amount of adsorbed protein on the copolymer films in 0.1 and 1 g/L BSA solutions.
REFERENCES
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we used virgin glass made of Si/SiO2 as the blank control, which is water-wettable and fairly inert to protein adsorption.51 As described in Table 4 and Figure 6, BSA adsorption on the copolymer films with different compositions is much lower compared with that of the virgin glass surface. The amount of adsorbed BSA decreased significantly with increasing content of the PEGMA chain in the copolymer films. Furthermore, BSA adsorption for the films in a higher concentration BSA solution was more than that in lower ones on the whole. When the PEG chain increased to 74.6% in the copolymer films (PU-1), BSA adsorption decreased to 12.2 ± 2.5 μg/cm2 in a 0.1 g/L BSA solution compared to 97.1 ± 2.7 μg/cm2 for the blank control. As the BSA concentration increased to 1 g/L, the adsorption correspondingly increased to 20 ± 1.2 μg/cm2. Compared with adsorption of the control film, the protein resistance of this copolymer film is 97.3%. The significant decreasing of the BSA adsorption could be attributed to the distribution of hydrophilic PEG chains on the copolymer film surfaces with a repellent property for protein adsorption. Also, the ability of PEG layers to resist protein is mainly caused by repulsive elastic forces generated by unfavorable elastic and osmotic stresses.37 The research result shows that the copolymer film surface with a designed structure and composition could provide a good balance of hydrophilic protein resistance and antibacterial activity.
4. CONCLUSIONS Functional ternary copolymers composed of HMBA, PEGMA, and HEA were synthesized via a facile radical polymerization method, which was cross-linked with PAPI to form PU coatings. The prepared copolymer films exhibited composition heterogeneity and amphiphilic character. With increasing PEG content in the copolymers, the hydrophilicity of the copolymer film was enhanced. The obtained copolymer film exhibited excellent fouling resistance to the protein BSA because of the strong hydration of PEG. The incorporation of different amounts of HMBA into the copolymers demonstrated excellent antibacterial activity against E. coli. The copolymer films with appropriate composition achieved both an average antibacterial efficiency of 93.3% and a protein-resistant rate of 97.3% compared with the blank control. The designed copolymers show good prospects because of their excellent protein resistance and antibacterial properties and their potential applications in marine coating and membrane AF modification. 3818
DOI: 10.1021/ie505062a Ind. Eng. Chem. Res. 2015, 54, 3813−3820
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DOI: 10.1021/ie505062a Ind. Eng. Chem. Res. 2015, 54, 3813−3820
