Robust Conductive Micropatterns on PTFE Achieved via Selective UV

Subscriber access provided by TULANE UNIVERSITY

Surfaces, Interfaces, and Applications

Robust conductive micropatterns on PTFE achieved via selective UVinduced graft copolymerization for flexible electronic applications Qi Qiang, Jiaxiang Qin, Yi Ma, Zenglin Wang, and Chuan Zhao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 10 Jan 2019 Downloaded from http://pubs.acs.org on January 10, 2019

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 29 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

ACS Applied Materials & Interfaces

Robust conductive micropatterns on PTFE achieved via selective UV- induced graft copolymerization for flexible electronic applications

Qi Qianga, Jiaxiang Qinb, Yi Maa, Zenglin Wang*a and Chuan Zhao*a, c a

Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, and School

of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’ an 710062, China b

State Key Laboratory of Environmental Adaptability for Industrial Products, China National

Electric Apparatus Research Institute Co., Ltd, Guangzhou 510663, China c

School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia

E-mail: [email protected]; [email protected] Fax Number: (0086)-29-81530727

ABSTRACT:

Fabrication

of

stable

and

functional

patterns

on

the

surface

of

polytetrafluoroethylene (PTFE) remains a great technical challenge owing to its inertness and high hydrophobicity. Here, we report for the first time the fabrication of functional micropatterns on the PTFE surface by selectively irradiating plasma-treated PTFE coated with the

1 Environment ACS Paragon Plus

ACS Applied Materials & Interfaces 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

monomer solution. A series of uniform, highly dense polydopamine methacrylamide (denoted as PDMA) line patterns with the line/pitch width 20μm/20μm and 50μm/50μm were fabricated on the surface of PTFE (denoted as PDMA-p/PTFE) using dopamine methacrylamide (DMA) as the monomer. The surface graft copolymerization occurs attributed to the universal adsorption of DMA and the low grafting energy barrier, comparing with the polymerization energy barrier, which is also demonstrated by the density functional theory (DFT) calculations. Further, robust, well-defined metal Ag or Cu patterns with the strong adhesion strength are fabricated on the surface the PTFE film by electroless deposition, and demonstrated for applications in flexible electronics. The approach is demonstrated to be versatile for fabrication of PDMA micropatterns onto a wide range of polymeric substrates including polypropylene (PP), and acrylonitrile butadiene styrene (ABS).

KEYWORDS: Surface grafting, PTFE, dopamine methacrylamide, UV irradiation, graft copolymerization, metal patterns


Page 2 of 29

Page 3 of 29 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


INTRODUCTION Flexible electronic devices with highly electrically conductive patterns have attracted wide attention for their wide range of applications in printed circuit boards, super-capacitors, biochips, and sensors.1-4 PTFE possesses excellent physical and mechanical characteristics including dimensional stability, radiation resistance and aging resistance, and is very suitable for the flexible electronic devices.5-7 However, due to its inert and hydrophobic properties, it is challenging to fabricate robust metal micro-patterns on PTFE substrate for the applications in ultra-large-scale integrated (ULSI) circuits and printed circuit boards (PCBs). Micro-fabrication techniques, such as photolithography,8,9 electron beam lithography,10 contact printing (CP),11 inject printing (IP),12 and magnetron sputtering,13-16 have been introduced to create topographic patterns on the surfaces of Si, glass, metal and paper substrates.17-22 Nevertheless, these techniques rely on the strong attachment of the patterned layers on the substrates, it is difficult to fabricate stable patterned layers on PTFE surface due to the chemical inertness and poor adhesion of PTFE.5 Polydopamine (PDA) exhibits universal adhesion on many types of materials,23,24 and has been used for fabricating various patterns on polymeric substrates.25-27 After surface adsorption and reduction of metal ions, metal patterns can be deposited on the PDA pattern via electroless deposition without Pd and Sn catalysts.28-30 However, the interaction between PDA and these substrates is non-covalent and PDA is unstable and easy to peel off in alkaline solution.31,32 By the functional phenylazide group,33 Ishihara et al. selectively grafted an initiator of transfer radical polymerization (ATRP) on the surfaces of polystyrene (PS) and polyethylene terephthalate (PET) by UV irradiation, and fabricated stable polymeric patterns on the substrates via ATRP,34 however, this method could be applied only the substrates with alkyl groups.



In this study, inspired by the graft copolymerization on the surface of plasma treated polymer via UV irradiation,35,36 we show for the first time the fabrication of functional micro-patterns on the PTFE surface by selectively irradiating plasma-treated PTFE coated with the monomer solution. We attempted to graft monomers on the desired areas of the PTFE substrate via selectively UV irradiation. However, due to the surface inertness, it is difficult for the monomer to adsorb on the surface of PTFE, which leads to inhomogeneous and incomplete patterns.37 High stability of the carbon radicals connected to F atoms on the PTFE surface also result in inhomogeneous growth of the patterns, making surface grafting more difficult than polymerization.38,39 We overcome this problem by introducing a new monomer, dopamine methacrylamide (DMA) for surface graft copolymerization. DMA contains dopamine group and H2C=C(CH3)-CO- group, and could adsorb on PTFE surface easily and quickly due to its universal adhesion23,24 and the conjugated H2C=C(CH3)-CO- group also enables the graft copolymerization to be more active under a UV irradiation. Interestingly, when the H2C=C(CH3)-COO- groups were translated into -H2C-Ċ(CH3)-COO- radical groups after the initial surface grafting,40 the high stability and steric hindrance of the radical groups cause the surface polymerization much more difficult than the surface grafting. As a result, the covalently bonded, dense and uniform PDMA patterns can be achieved on PTFE surface.

EXPERIMENTAL SECTION Materials. Dopamine hydrochloride, methacrylic anhydride, 2, 2’-bipyridine, silver nitrate and polyethylene glycol (1000) were purchased from Aladdin Industrial Corporation Shanghai, China. Other chemicals were obtained from Sinopharm Chemical Reagent Co., Ltd. China. Ultrapure water used was supplied by Milli-Q Advantage A10 (Millipore, USA). Before the experiment, PTFE (0.1 mm), polyethylene terephthalate (PET) (0.1 mm) and polypropylene (PP)


Page 4 of 29

Page 5 of 29 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


(0.01 mm) were ultrasonicated in ethanol and acetone for 20 minutes. For acrylonitrile butadiene styrene (ABS) substrate, it was ultrasonicated in ethanol for 20 minutes. All organic solvents were of analytical grade. All inorganic chemicals were purchased and used as received without further purification. Synthesis of DMA. DMA was synthesized and purified according to the literature method20 (the detailed process sees the Supporting Information). The spectra of 1H NMR and 13C NMR for DMA were presented in the Figure S1. The DMA solution (10 wt. %) was prepared by mixing the DMA with the mixture of ethyl acetate and methanol (1:1 v/v). The solution was stirred and stored in a refrigerator. Fabrication of polymeric DMA patterns on PTFE films. PTFE film was first treated by Ar plasma at a power of 200 W in a PMT100A plasma apparatus (Shenzhen OKSUN Co., LTD, Shenzhen, China) with a gas flow of 120 ppm and pressure of 45 Pa for 6 mins to form the radicals on the surface of PTFE film. The radical concentration on the surface of PTFE film was measured by UV-Vis spectrophotometer (Figure S2). About 100μL of DMA solution (10 wt.% ) was dropped and infiltrated to the surface of PTFE with an area of 1 cm2, very thin PP film was sheathed on the PTFE film. A photo-mask with several patterns was covered on the PP film and an UV illumination system equipped with a high-pressure mercury lamp (1000 W, UV365nm intensity = 6 mW·cm-2) was used to illuminate the PTFE film for 80 mins. The polydopamine methacrylamide patterns (denoted as PDMA-p) were fabricated on surface of PTFE film, which then was washed with methanol, and dried under a stream of nitrogen. As the same method, PDMA-ps were fabricated on the PP and ABS surfaces. The 10 wt. % DMA solution of ethyl acetate to methanol of 1:1(v:v) is used to fabricate PDMA-p on the PP substrate, and the solution of methanol is used to fabricate PDMA-p on the ABS substrate.



Adsorption of monomers on PTFE surface. In order to compare the surface absorbability of monomers on the surface of PTFE, the plasma pretreated PTFE films were first immersed into 10 wt.% DMA solution, 30 wt.% 2-hydroxyethylmethacrylate (HEMA) and 30 wt.% glycidyl methacrylate (GMA) solution, respectively, for surface adsorption. After absorption, the films were washed with methanol or ethanol solution three times and dried in vacuum. The effects of treatment time and monomer species on the surface hydrophilcity of PTFE film were investigated using surface contact angle measurements. Formation and characterization of Ag NPs/PDMA-p/PTFE. When PDMA-p/PTFE films were immersed into the 0.05 M AgNO3 solution for 2h, Ag+ ions were adsorbed on the surface of PDMA-p, some adsorbed Ag+ ions were reduced by the dopamine group in the PDMA and formed Ag nanoparticles (Ag-NPs) on the surface of PDMA patterns. Then the films were rinsed with ultrapure water to remove free Ag+ ions and were stored in vacuum oven at 40 °C. The adhesion strength and stability of Ag NPs on PDMA-p/PTFE substrate (denoted as AgNPs/PDMA-p/PTFE) was measured by 3M adhesive tape peel tests and alkaline solution treatment. When Ag-NPs/PDMA-p/PTFE was immersed in 0.1 M NaOH solution for 5 h at 70 °C, the surface morphology of the films were characterized using scanning electron microscope (SEM) and the NaOH solution used was analyzed using UV-Vis spectrophotometer to identify whether the Ag NPs dissolved from the PDMA pattern. Electroless plating silver and copper on the PDMA-p/PTFE. Before electroless plating, the PDMA-p/PTFE films were immersed in 0.05 M AgNO3 for 30 mins at room temperature, then the electroless plating process of silver and copper were carried out. The composition of the electroless silver plating solution was similar to the literature.41 The pH of the solution was adjusted to 12.0 using NaOH and the bath temperature was kept at 45 °C. After electroless


Page 6 of 29

Page 7 of 29 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


plating for 1 h, the film was washed with distilled water and dried in a vacuum oven at 40 °C. The composition of the electroless copper plating solution was similar to the literature.42 pH of the solution was adjusted to 12.5 using NaOH and the bath temperature was 70 °C. After electroless plating for 30 mins, the film was washed with distilled water and dried in a vacuum oven at 40 °C. Characterization.

1H

NMR and

13C

NMR measurements were conducted on a Bruker

AV600 NMR spectrometer. ATR-FTIR spectra were recorded on a Vetex 70 V (Brucker). X-ray photoelectron spectra (XPS) were obtained using AXIS ULTRA from Kratos Analytical Ltd., the energy resolution is 0.48 eV/(Ag 3d5/2), 0.61 eV (C1s). SEM was performed on FEI Quanta 200. Mapping spectroscopy was performed with a Genesis EDX system attached to the FEI Quanta 200 microscope. Field Emission Scanning Electron Microscope (FE-SEM) observations were conducted on SU 8020 (Hitachi). 3D morphology was observed on Confocal Microscope (ECLIPSE LV100, Nikon). Atomic Force Microscopy (AFM) was performed on Dimension Icon (Brucker

Nano,

Inc.

Germany).

Automatic

X-Ray

diffraction

was

determined

by

D/Max2550VB+/PC (Rigulcu Co., Japan) using Cu Ka radiation, with the diffraction angle (2θ) at a range of 20-90°. UV-vis spectrum was collected by UV-Vis spectrophotometer (U3900/3900H, Hitachi) with a wavelength range of 250 - 650 nm. Surface contact angle was measured on an OCA 20 (Dataphysics, Germany). Electron spin resonance (ESR) was conducted on E500-9.5/12 (Bruker), and the sheet resistances of electroess Cu and Ag films on the surface of PTFE were measured by four-point resistivity probe. Density functional theory calculations. The DFT calculations were performed using the Dmol3 module of Materials Studio. Optimizations and energy calculations were carried out through the widely used generalized gradient approximation (GGA) with the Perdew–Burke–



Ernzerhof (PBE) exchange-correlation function. The double numerical plus polarization (DNP) basis set as well as the DFT semi-core Pseudopots (DSPP) were used. The convergence criterions were set as: energy 1 × 10-5 Ha, gradient 2 × 10-3 Å, displacement 5 × 10-3 Å. Besides, a Fermi smearing of 0.003 Hartree and a global cutoff of 4.4 Å were also used to improve the computational performance.

RESULTS AND DISCUSSION Fig. 1 shows the schematic of the fabrication of functional PDMA patterns and subsequent metallic patterns on the PTFE substrate. DMA molecules first adsorb on the surface of the plasma treated PTFE, and then the graft copolymerization of DMA is initiated via selective UV irradiation. After surface adsorption, electroless deposition, metal line patterns were fabricated on the surface of the PTFE.

Figure 1. Schematic diagram to fabricate functional PDMA patterns and the metallization process on the PTFE substrate Fabrication and characterization of PDMA patterns on PTFE substrate. To form stable radicals on the PTFE surface, the PTFE films were pretreated with Ar plasma process.37 Fig. 2a shows the radical concentration on the PTFE surface with the discharge conditions. Using Ar


Page 8 of 29

Page 9 of 29 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


plasma treatment, numerous radicals were formed on the surface of PTFE film, with the maximum of radical concentration at 6 mins of discharge time. Further, the chemical compositions of the PTFE surface before and after plasma treatment were analyzed by XPS. Before plasma treatment, only F and C1s signals were observed in the XPS spectrum (Figure S3a). A single peak at 292.0 eV on the C1s spectrum is attributed to CF2-CF2 species (Fig. 2b), no peak for the O1s was found (Figure S3b). After Ar plasma treatment for 6 mins, the C1s spectra is deconvoluted into six peaks, which are attributed to -CF2-CF3 at 294.2 eV, -CF2-CF2 at 292.3 eV, -CF2-CF at 290.2 eV, -CO-O at 288.8 eV, -C(O)- at 288 eV, and C-C at 284.8 eV, respectively (Fig. 2c).43-45 These results indicates that the breakings of C-F and C-C bonds on the surface of PTFE had occurred during the plasma process. The CF2-CF peak reveals the existence of -CF2-ĊF-CF2- radical and the fraction of C-C suggests the existence of -CF2-ĊF2 radical. The small peaks of -CO-O and -C(O)- indicated that the carbon radicals without F bonding were oxidized in air after the plasma treatment, which is consistence with the previous reports.37 Meanwhile, the electron spin resonance (ESR) analysis demonstrated that the radicals of -CF2CF(OO•)-CF2- (g1=2.022, g2=2.005) and -CF2-CF2(OO•) (giso=2.017) were formed on the surface of the plasma treated PTFE film by the reaction of CF2-ĊF-CF2 and CF2-ĊF2 radicals with O2 in the air (Figure S4).46,47 However, the -CF2-CF(OO•)-CF2-, and -CF2-CF2(OO•) radicals cannot initiate the polymerization of the C=C bonds, but are able to capture H atom to form -CF2CF(OOH)-CF2- and -CF2-CF2(OOH).48 Further, the -CF2-CF(OOH)-CF2- and -CF2-CF2(OOH) can be converted to -CF2-CF(O•)-CF2- and -CF2-CF2(O•) radicals under UV irradiation, which are able to initiate the polymerization of the monomer.49 And so, -CF2-ĊF-CF2-, -CF2-ĊF2, -CF2CF(O•)-CF2- and -CF2-CF2(O•) radicals are used for the DFT calculations.



Figure 2. (a) The radical concentration on the PTFE surface with different plasma treatment conditions (black line: discharge at 200 W, red line: discharge for 6 min). (b) C1s spectra of the pristine PTFE surface, (c) C1s spectra of the PTFE surface with 6 min treatment. After the graft copolymerization via selectively illuminating the plasma pretreated PTFE coated with DMA solution, PDMA-p were formed on the surface of PTFE (denoted as PDMAp/PTFE). The surface morphology and composition of PDMA-p/PTFE were characterized by SEM, AFM, XPS, IR and surface contact angle measurement. Fig. 3a and 3b showed the SEM images of PDMA-p with line width of 50 and 20 µm, respectively on the surface of PTFE. The PDMA patterns with high feature precision are uniformly patterned on the PTFE surface, and no bare substrate was observed in the PDMA area. The high resolution SEM image of PDMAp/PTFE further revealed that PDMA layers are uniform and compact (Fig. 3c). Conversely, no PDMA layer was observed in the blank areas, and the surface morphology of the blank areas is same as the original PTFE (Fig. 3d, Figure S5). Focused ion beam (FIB) cross-sectional SEM of PDMA-p/PTFE showed that the PDMA layer is very dense, no gap was observed between the PTFE substrate and the PDMA layer. The thickness of the PDMA layer is approximately 330 nm (Fig. 3e). 3D confocal microscope image of PDMA patterns with a wide range was used to characterize the roughness of PDMA layer, it found that the surface of PDMA layer is relatively flat with no appearance of sags and crests (Fig. 3f). The AFM measurement results showed that


Page 10 of 29

Page 11 of 29 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 3. Characterizations of the PDMA-p/ PTFE film. SEM images of PDMA-p/PTFE, strip width 50 µm (a) and 20 µm (b), high resolution SEM images of PDMA layer (c) and black space (d), FIB cross-sectional SEM image of PDMA-p/PTFE (e), 3D confocal microscope image (f) and AFM image of PDMA-p/PTFE (g), and PDMA surface (h), IR spectra of PTFE (black line) and PDMA-p (red line) (i), XPS C1s spectra (j) and N1s spectra (k) of PDMA-p/PTFE, the surface contact angles of plasma treated PTFE and PDMA surface (l).



the PDMA layer is relatively compact and smooth with average roughness of 8 nm, and the thickness of the PDMA patterns is approximately 301 nm (Fig. 3g, 3h), which is consistent with the result of FIB cross-sectional SEM. The surface chemical compositions of PDMA-p were characterized using IR and XPS. Compared to the IR spectra of the plasma treated PTFE, several new peaks at 3300, 1720, 1650-1612, 1510 and 1448 cm-1 appeared in PDMA layer (Fig. 3i), which is attributed to the vibrations of -OH, -CO- and benzene groups, respectively, indicating that the catechol and C=O groups was formed on the patterns. In addition, the peak at 1347 also indicates the existence of -CH3. The XPS spectra of the PDMA-p/PTFE showed that the signals of O1s and N1s appeared, and the atomic ration of C/F increased significantly (Figure S6). The C1s peak is deconvoluted into a series peaks, which are attributed to C-C or C=C at 284.8 eV, CO or C-N at 286 eV, C-CF or C-CF2 at 287 eV, CO-N at 288 eV, C-CF at 289.2 eV and CF2-CF2 at 292 eV (Fig. 3j), respectively.43-45 The N1s peak shows one strong peak at 399.8 eV, assigning to CO-NH- (Fig. 3k).50 Comparing with the IR and XPS spectra of DMA and PDMA (Figure S7), we consider that the patterned layer is composed of PDMA entirely. The appearance of C-CF or C-CF2 in C1s spectra indicated that the PDMA is covalently grafted on PTFE surface. All the above results demonstrated that a uniform, smooth and dense PDMA patterns were fabricated on the PTFE substrate by selective surface graft copolymerization of the DMA. Because of the excellent hydrophilicity of the dopamine groups in PDMA layer, the surface contact angle of PDMAp/PTFE also decreased to 45.4°, which is much lower than that of the PTFE surface (97.4°) as observed in Fig. 3l. Understanding graft copolymerization mechanism of DMA on PTFE. In order to explore the formation mechanism of uniform and highly dense PDMA-p/PTFE via UV


Page 12 of 29

Page 13 of 29 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


irradiation, two monomers, 2-hydroxyethylmethacrylate (HEMA) and glycidyl methacrylate (GMA), were used to replace DMA for the surface adsorption and graft copolymerization. Both HEMA and GMA contain H2C=C(CH3)-CO- group, similar to DMA, but no dopamine group. When the PTFE substrates were immersed into 30 wt.% HEMA and 30 wt.% GMA solution, respectively for 20 mins, the surface contact angles of the PTFE only decreased to 86.7 ° and 85.7 °, respectively, and no significant change was observed at prolonged immersion time (Fig. 4a). However, when the PTFE film was immersed into 10 wt.% DMA solution for 20 mins, the surface contact angle of the PTFE film decreased to 47.2 °, which is consistent with that of the PDMA film (Fig. 4a). The large difference in surface contact angle is of the lack dopamine group. When the HEMA and GMA were used to replace DMA for the pattern fabrication on PTFE surfce, uneven and discontinuoud patterns were formed on the PTFE, even when the concentration of HEMA or GMA was increased to 30 wt. % (Fig. 4b and 4c, Figure S8). These results indicate that the surface adsorption of monomer is a key for the fabrication of patterned layers on PTFE surface.

Figure 4. Surface contact angles of the PTFE films treated with different monomer solutions (a). SEM images of PTFE surfaces after surface graft copolymerization using HEMA monomer (b) and GMA monomer (c).



In order to estimate the relative reaction rates of the grafting and polymerization and to verify the contribution of UV irradiation to the graft copolymerization, the DFT calculations were carried out to analyze the energy barrier of DMA in the grafting process and the polymerization process. The four immobilized radicals (-CF2-ĊF2, -CF2-ĊF-CF2-, -CF2-CF2(O•) and -CF2-CF(O•)-CF2-) on PTFE surface were employed to calculate the energy barriers of surface grafting and surface polymerization. Fig.5a and Figure S9 showed the mechanisms of CF2-ĊF2, -CF2-ĊF-CF2-, -CF2-CF2(O•) and -CF2-CF(O•)-CF2- radicals with DMA in surface grafting and surface polymerization processes. The corresponding energy barriers were calculated and showed in Fig.5b-5f. The energy barrier for -CF2-ĊF2 to attack the anomeric carbon of C=C in DMA is 3.57 kcal·mol-1 in surface grafting process, which is much lower than that for -CF2-ĊF2 to attack the quaternary carbon of C=C in DMA (12.84 kcal·mol-1). This result indicates that it is easier for the radical to attack the anomeric carbon of C=C in surface grafting process, which is in agreement with the previous literature.40 The energy barriers for -CF2-ĊF-CF2-, -CF2-CF2(O•) and -CF2-CF(O•)-CF2- radicals to react with DMA were also calculated, they are 3.89 kcal·mol-1, 3.48 kcal·mol-1 and 6.07 kcal·mol-1, respectively, for -CF2-ĊF-CF2-, -CF2-CF2(O•) and -CF2-CF(O•)-CF2- radicals to attack the anomeric carbon of C=C in DMA. Similarly, the energy barriers for the resultant tertiary carbon radical to attack the anomeric carbon of C=C in polymerization stage is 6.9 kcal·mol-1.


Page 14 of 29

Page 15 of 29 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 5. (a) The reaction states of -CF2-ĊF2, -CF2-ĊF-CF2-, -CF2-CF2(O•) and -CF2-ĊF(O•)CF2- to attack anomeric carbon of C=C in the grafting process and the resultant tertiary carbon radical to attack anomeric carbon of C=C in the polymerization process. The relative energies of the reaction states for (b) -CF2-ĊF2, (c) -CF2-ĊF-CF2-, (d) -CF2-CF2(O•) and (e) -CF2-ĊF(O•)-



CF2- to react with DMA in the grafting process. (f) The relative energies of the reaction states for the resultant tertiary carbon radical to react with DMA in the polymerization process. The energy of the irradiating light (Eλ365 nm = h(c/λ) is about 78.4 kcal·mol-1, which not only is higher than the energy barriers for -CF2-ĊF2, -CF2-ĊF-CF2-, -CF2-CF2(O•) and -CF2-CF(O•)CF2- radicals to attack the anomerio carbon in surface grafting process (3.57, 3.89, 3.48 and 6.07 kcal·mol-1), but also is higher than that of resultant tertiary carbon radical to attack the anomeric carbon of C=C in surface polymerization process (6.9 kcal·mol-1). The results indicate that the surface grafting and polymerization of DMA on the surface of PTFE could be initiated by UV irradiation. On the other hand, it is found that the energy barrier of grafting is much lower than that of polymerization. Therefore, the grafting rate should be much higher than the polymerization rate, which leads to a dense and uniform PDMA layer on the surface of PTFE. Though the temperature of the photomask in surface co-polymerization reached 50 °C after 80 mins UV irradiation, when the plasma treated PTFE was immersed into 10 wt. % DMA solution at 50 °C for 80 mins, followed by the treatment of 0.05 M AgNO3 for 2 h, no PDMA or Ag NPs can be observed on the surface of the PTFE (Figure S10), suggesting the surface graft copolymerization is not induced by the heat. Deposition of Ag NPs on the PDMA-p. The dopamine groups in PDMA-p have excellent hydrophilicity and reducibility. During immersion of the PDMA-p/PTFE films into 0.05 M AgNO3 solution for 2 h, Ag+ ions were adsorbed and reduced on the surface of PDMA-p, the formed Ag nanoparticles (Ag-NPs) were deposited on PDMA-p/ PTFE. Fig. 6a showed the SEM images of Ag NPs deposited PDMA patterns on PTFE surface (denoted as Ag-NPs/PDMAp/PTFE). It was found that Ag-NPs were deposited only on the PDMA-p surface, not in the bare space, as also confirmed by EDX mapping (Fig. 6b). The peaks at 368.0 and 374.0 eV in Ag 3d


Page 16 of 29

Page 17 of 29 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


XPS spectra and the peak at 358 eV in Ag Auger spectra (Figure S11) reconfirm the Ag-NPs exist in metallic state.51 Ag-NPs/PDMA-p/PTFE present excellent mechanical stability. The tape test shows no evidence of delamination or structural change (Figure S12). In order to investigate the stability of Ag-NPs/PDMA-p/PTFE in alkaline solution, the Ag-NPs/PDMA-p/PTFE film was immersed in 0.1 M NaOH solution at 70 ºC for 5 h, no obvious change on the surface of AgNPs/PDMA-p/PEFT film was observed (Fig. 6c), and no UV-vis characteristic peaks of DMA (282 nm) and Ag-NPs (410 nm) in the tested solution was observed (Fig. 6d), which further proves the stability of the patterns in alkaline solution.

Figure 6. SEM image (a) and Ag mapping image (b) of Ag-NPs/PDMA-p/PTFE, (insets a, enlarged Ag-NPs/PDMA and blank space), SEM image of the Ag-NPs/PDMA-p/PTFE after alkaline treatment (c), the UV-vis spectra of 0.1 M NaOH solution (d) (blue: DMA dissolved



NaOH solution, black: pure NaOH solution, red: the NaOH solution after an immersion of AgNPs/PDMA-P/PTFE film at 70 °C for 5 h). Electroless plating of Cu and Ag patterns on PDMA functionalized PTFE. When the Ag-NPs/PDMA-p/PTFE films were immersed into electroless copper solution at 70 °C for 30 mins or silver solution at 45 °C for 60 mins, a series of metal Ag and metal Cu patterns were formed on the PTFE surface, respectively. As shown in the SEM images in Fig. 7, the copper and silver layers only deposited on the surface of PDMA patterns, and formed uniform, continuous and regularly arranged metal line patterns with a width of both 50 μm and 20 μm, while no metal film was formed on the bare substrate (Fig. 7a-b and Figure S13a-b). The edges of the copper and silver line patterns are straight, well-defined boundaries between the metal layers and the bare substrate were observed (Fig. 7c-d and Figure S13c-d). Furthermore, the metal films are very compact and no interspace exists on the surface of metal layers (inset images of Fig. 7c-d and Figure S13c-d). The EDX mapping images of Cu and Ag elements distinguish the region of the deposited metals from the bare substrate meticulously, and further unveil the spatially defined distribution of copper on the substrate (Fig.7e-f and Figure S13e-f). XRD results of metal patterns further confirm the nature of metallic copper and silver films on the surface of Ag-NPs/PDMA-p/PTFE (Figure S14). Fig. 7g and Figure S13g showed the 3D confocal microscope images of the copper and silver metallization patterns with a line width of 20 μm. The boundary between the metal layer and bare substrate are very distinct and the surfaces of silver and copper patterns are smooth. The thicknesses of the electroless copper and silver layers are about 2.7μm and 0.7μm, respectively (Figure S15), and the resistivities of the electroless copper and silver films are 7.6 Ω sq-1 and 4.7 Ω sq-1.


Page 18 of 29

Page 19 of 29 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 7. SEM images of Cu/PDMA-p/PTFE with the line width: 50 µm (a) and 20 µm (b), high resolution SEM images of Cu/PDMA-p/PTFE with line width: 50 µm (c) and 20 µm (d), Cu element mapping images of Cu/PDMA-p/PTFE with the line width: 50 µm (e) and 20 µm (f), 3D confocal microscope image of Cu/PDMA-p/PTFE with the line width of 20 µm (g), photographic image of a circuit containing a repeated folding metal film (h). The adhesion strength of metal patterns is of great significance for application in electronics industry. The tape peel test is used to determine the adhesion strength of copper film on the 19 Environment ACS Paragon Plus


surface of PDMA-p patterns. After five times tests, no metal film was peeled off from the PTFE substrate (Figure S16a). Even when Cu/PDMA-p/PTFE was exposed in air for a month, and the surface copper was partially oxidized, no copper film was peeled off from the substrate, and partial sticky layer striped from the tape was bonded on the copper film in the repeated tape test (Figure S16b). These result confirmed that the adhesion strength between metal film and PDMA layer is very strong. Moreover, the conductivity of the metallization pattern under mechanical deformation was demonstrated for application in flexible electronics. As shown in Fig. 7h, a circuit containing a repeated folding metal film, an LED and a battery was used to measure the conductivity of metallization strip. When the circuit is connected, the LED brightens up for a long time, indicating a high stability of the metal patterns under the heavy folded status. PDMA micropatterning on other substrates. In order to verify the versatility of this method, PP and ABS substrates were also used for the fabrication of PDMA-p. After 6 min Ar plasma treatment, a lot of radicals appeared on the surface of PP and ABS substrates (Figure S17). Using the same method, a series of dense and uniform PDMA lines are clearly observed on the surface of PP and ABS substrates (Fig. 8a-b). The PDMA lines are straight and uniform, no breakpoint was observed in the PDMA strips, as well as, the boundary between PDMA layer and bare substrate is also clear and uniform, which is very important in PCB industry. When PDMAp/PP and PDMA-p/ABS substrates were immersed in 0.05 M AgNO3 for 2 h, Ag NPs were only deposited on the surface of PDMA patterns, while, no Ag NPs were observed in bare areas of the substrates (Figure S18 and Figure S19a-f). Further, the Ag EDX mapping also unveils the spatially defined distribution of Ag element on the different substrates (Figure S19g-h). After electroless deposition of copper and silver, uniform copper and silver layers were deposited on the patterns (Figure S20). The SEM images and EDX Cu (Ag) elemental mapping images further


Page 20 of 29

Page 21 of 29 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


proof that the contour profiles of the metal patterns are all consistent with that of the PDMA patterns (Fig. 8c-f, and Figure S21). Collectively, the above results demonstrate that the method is versatile and can be extended to a wide range of polymeric substrates for fabrication of PDMA pattern and Ag-NPs/PDMA-p and metallic micropatterns.

Figure 8. SEM images of PDMA patterns fabricated on PP (a) and ABS (b) substrates. SEM images of copper patterns deposited on PDMA-p/PP (c) and PDMA-p/ABS (d) surfaces. The Cu mapping images of Cu/PDMA-p/PP (e) and Cu/PDMA-p/ABS (f) substrates.

CONCLUSION In summary, a series of PDMA patterns on PTFE surface have been fabricated by selective UV-motivated graft copolymerization. PDMA layers with width of 20 and 50 μm and thickness of 300 nm were dense, compact and uniformly deposited on the PTFE surface. Moreover, no 21 Environment ACS Paragon Plus


bare substrate was observed in the PDMA-p area. After surface reduction and electroless process, metal Ag and Cu patterns were formed on the surface of PDMA-p/PTFE. Highmagnification SEM and AFM results demonstrated that 2D copper and silver patterns with clear edges were observed. Both 50 μm and 20 μm line patterns are uniform, continuous and regularly arranged with no interspace exists on the surface of metal patterns. The EDX mapping results indicate the boundary between PDMA layer and bare substrate is also clear and uniform. The results are attributed to the universal adsorption of DMA and the low grafting energy barrier compared with the polymerization energy barrier, which was also demonstrated by the density functional theory (DFT) calculations. Using the same method, a series of dense and uniform PDMA patterns were obtained on the surface of PP and ABS substrates, which further verify the versatility and practicability of this method. As demonstrated in the study, these conductive micropatterns on PTFE, as well as other polymeric substrates, will find a range of applications in flexible electronics. ASSOCIATED CONTENT Supporting Information Some supplementary experimental details, supplementary XPS data, ESR data, SEM and EDX mapping images, IR spectra, tape tests and the radical concentrations on the substrate were provided in the Supporting Information. . ACKNOWLEDGMENT The project was financially supported by National Natural Science Foundation of China (grant No. 21273144, No. 21603134), Natural Science Basic Research Plan in Shaanxi Province of China (No.2016JQ2023) and an Australian Research Council Discovery (grant No.FT170100224


Page 22 of 29

Page 23 of 29 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


and DP160103107). The authors are grateful to Shaanxi Normal University for the permission to use Materials Studio. REFERENCES (1) Aldakov, D.; Bonnassieux, Y.; Geffroy, B.; Palacin, S. Selective Electroless Copper Deposition on Self-Assembled Dithiol Monolayers. ACS Appl. Mater. Interfaces 2009, 1, 584-589. (2) Kurra, N.; Hota, M. K.; Alshareef, H. N. Conducting Polymermicro-Supercapacitors for Flexible Energy Storage and Acline-Filtering. Nano Energy 2015, 13, 500-508. (3) M, Z.; Tang, L. Surface-Plasmon-Coupled Fluorescence Enhancement Based on Ordered Gold Nanorod Array Biochip for Ultrasensitive DNA Analysis. Anal. Chem 2017, 89, 633639. (4) Arya, S. K.; Wong, C. C.; Jeon, Y. J.; Bansal, T.; Park, M. K. Advances in ComplementaryMetal-Oxide-Semiconductor-Based Integrated Biosensor Arrays. Chem. Rev. 2015, 115, 5116-5158. (5) Shuko, S.; Michael R, W.; Edeline, W.; Michael J, M.; Lisbeth, G. Adsorption of WellDefined Fluorine-Containing Polymers onto Poly(tetrafluoroethylene). Langmuir 2008, 24, 13075-13083. (6) Sparnacci, K.; Antonioli, D.; Deregibus, S.; Laus, M.; Poggio, T.; Kapeliouchko, V.; Palamone, G.; Zuccheri, G.; Passeri, R. PTFE-Based Core-Soft Shell Nanospheres and Soft Matrix Nanocomposites. Macromolecules 2009, 42, 3518-3524. (7) Zhao, P. F.; Soin, N.; Prashanthi, K.; Chen, J. K.; Dong, S. R.; Zhou, E. P.; Zhu, Z.G.; Narasimulu, A. A.; Montemagno, C. D.; Yu, L. y.; Luo, J. K. Emulsion Electrospinning of Polytetrafluoroethylene

(PTFE)

Nanofibrous

Membranes

for

High-Performance

Triboelectric Nanogenerators. ACS Appl. Mater. Interfaces 2018, 10, 5880−5891. (8) Rodriguez Emmenegger, C.; Preuss , C. M.; Yameen , B.; Pop Georgievski , O.; Bachmann, M.; Mueller, J. O.; Bruns, M.; Goldmann, A. S.; Bastmeyer, M.; Barner Kowollik, C. Controlled Cell Adhesion on Poly(dopamine) Interfaces Photopatterned with Non-Fouling Brushes. Adv. Mater. 2013, 25, 6123-6127.



(9) Ye, X. L.; Jiang, X. S.; Yu, B.; Yin, J.; Vana, P. Functional Binary Micropattern of Hyperbranched Poly(ether amine) (hPEA-AN) Network and Poly(ether amine) (PEA) Brush for Recognition of Guest Molecules. Biomacromolecules 2012, 13, 535-541. (10) Joo, J.; Chow, B. Y.; Jacobson, J. M. Nanoscale Patterning on Insulating Substrates by Critical Energy Electron Beam Lithography. Nano Lett. 2006, 6, 2021-2025. (11) Camposeo, A.; Persano, L.; Manco, R.; Wang,Y.; Carro, P. D.; Zhang, C.; Li, Z.; Pisignano, D.; Xia, Y. N. Metal-Enhanced Near-Infrared Fluorescence by Micropatterned Gold Nanocages. ACS NANO 2015, 10, 10047-10054. (12) Sun, J. Z.; Bao, B.; He, M.; Zhou, H. H.; Song, Y. L. Recent Advances in Controlling the Depositing Morphologies of Inkjet Droplets. ACS Appl. Mater. Interfaces 2015, 7, 2808628099. (13) Roth, S. V.; Santoro, G.; Risch, J. F. H.; Yu, S.; Schwartzkopf, M.; Boese, T.; Döhrmann, R.; Zhang, P.; Besner, B.; Bremer, P.; Rukser, D.; Rübhausen, M. A.; Terrill, N. J.; Staniec, P. A.; Yao, Y.; Metwalli, E.; Müller-Buschbaum, P. Patterned Diblock Co-Polymer Thin Films as Templates for Advanced Anisotropic Metal Nanostructures. ACS Appl. Mater. Interfaces 2015, 7, 12470-12477. (14) Schwartzkopf, M.; Buffet, A.; Körstgens,V.; Metwalli, E.; Schlage, K.; Benecke, G.; Perlich, J. Rawolle, M.; Rothkirch, A.; Heidmann, B.; Herzog, G. Müller-Buschbaum, P. Röhlsberger, R.; Gehrke, R.; Stribeck, N.; Roth, S. V. From Atoms to Layers: in Situ Gold Cluster Growth Kinetics During Sputter Deposition. Nanoscale 2013, 5, 5053-5062. (15) Schwartzkopf, M.; Hinz, A.; Polonskyi, O.; Strunskus, T.; Löhrer, F. C.; Körstgens, V.; Müller-Buschbaum, P.; Faupel, F.; Roth, S. V. Role of Sputter Deposition Rate in Tailoring Nanogranular Gold Structures on Polymer Surfaces. ACS Appl. Mater. Interfaces 2017, 9, 5629-5637. (16) Schwartzkopf, M.; Santoro, G.; Brett, C. J.; Rothkirch, A.; Polonskyi, O.; Hinz, A.; Metwalli, E.; Yao, Y.; Strunskus, T.; Faupel, F.; Müller-Buschbaum, P.; Roth, S. V. RealTime Monitoring of Morphology and Optical Properties during Sputter Deposition for Tailoring Metal-Polymer Interfaces. ACS Appl. Mater. Interfaces 2015, 7, 13547-13556. (17) Chang, Y. H.; Wang, C. H. Electroless Deposition of Cu Nanostructures on Molecular


Page 24 of 29

Page 25 of 29 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


Patterns Prepared by Dip-Pen Nanolithography. J. Mater. Chem. 2012, 22, 3377-3382. (18) Nakanishi, T.; Hirai, Y.; Kojima, M.; Yabu, H.; Shimomura, M. Patterned Metallic Honeycomb Films Prepared by Photo-Patterning and Electroless Plating. J. Mater. Chem. 2010, 20, 6741-6745. (19) Basarir, F. Fabrication of Gold Patterns via Multilayer Transfer Printing and Electroless Plating. ACS Appl. Mater. Interfaces 2012, 4, 1324-1329. (20) Du, X.; Li, L. X,; Li , J. S.; Yang, C. W.; Frenkel, N.; Welle, A.; Heissler, S.; Nefedov, A.; Grunze, M.; Levkin, P. A. UV-Triggered Dopamine Polymerization: Control of Polymerization, Surface Coating, and Photopatterning. Adv. Mater. 2014, 26, 8029-8033. (21) Wang, Y.; Guo, Hong.; Chen, J. J.; Sowade, E.; Wang, Y.; Liang, K.; Marcus, K.; Baumann, R. R.; Feng Z. Paper-Based Inkjet-Printed Flexible Electronic Circuits. ACS Appl. Mater. Interfaces 2016, 8, 26112-26118. (22) Min, S. Y.; Lee, Y.; Kim, S. Y.; Park, C.; and Lee, T. W. Room-Temperature-Processable Wire-Templated Nanoelectrodes for Flexible and Transparent All-Wire Electronics. ACS Nano 2017, 11, 3681-3689. (23) Lee, H.; Dellatore, S.; Miller, W.; Messersmith, P. Musselinspired Surface Chemistry for Multifunctional Coatings. Science 2007, 318, 426-430. (24) Lee, H.; Lee, B.; Messersmith, P. A Reversible Wet/Dry Adhesive Inspired by Mussels and Geckos. Nature 2007, 448, 338-341. (25) Zhao, L.; Wang, W.; Hu, W. H. Simultaneous Transfer and Imaging of Latent Fingerprints Enabled by Interfacial Separation of Polydopamine Thin Film. Anal. Chem. 2016, 88, 10357-10361. (26) Huang, Y.; Chen, S.; Su, C.; Liao, Y. Fabrication of Copper Thin Film Patterns with Highly Adhesive Silver-Decorated Polydopamine Ink. Science of Adv. Mater. 2015, 6, 227-232. (27) Zhao, L.; Chen, D.; Hu, W. H. Patterning of Metal Films on Arbitrary Substrates by Using Polydopamine as a UV-Sensitive Catalytic Layer for Electroless Deposition. Langmuir 2016, 32, 5285-5290. (28) Ma, S. Y.; Liu, L.; Bromberg, V.; Singler, T. J. Electroless Copper Plating of Inkjet-Printed Polydopamine Nanoparticles: a Facile Method to Fabricate Highly Conductive Patterns at



Near Room Temperature. ACS Appl. Mater. Interfaces 2014, 6, 19494-19498. (29) Jin, Y. X.; Cheng, Y. R.; Deng, D. Y.; Jiang, C. J.; Qi, T. K,; Yang, D. L.; Xiao, F. SiteSelective Growth of Patterned Silver Grid Networks as Flexible Transparent Conductive Film by Using Poly(dopamine) at Room Temperature. ACS Appl. Mater. Interfaces 2014, 6, 1447-1453. (30) Ma, S. Y.; Liu, L.; Bromberg, V.; Singler, T. J. Fabrication of Highly Electrically Conducting Fine Patterns via Substrate-Independent Inkjet Printing of Mussel-Inspired Organic Nano-Material. J. Mater. Chem. C 2014, 2, 3885-3889. (31) Kang, S. M.; Park, S.; Kim, D.; Park, S. Y.; Ruoff, R. S.; Lee, H. Simultaneous Reduction and Surface Functionalization of Graphene Oxide by Mussel-Inspired Chemistry. Adv. Funct. Mater. 2011, 21, 108-112. (32) Kand, S. M.; Rho, J.; Choi, I. S.; Messersmith, P. B.; Lee, H. Norepinephrine: MaterialIndependent, Multifunctional Surface Modification Reagent. J. Am. Chem. Soc. 2009, 131, 13224-13225. (33) Ohno, K.; Kayama, Y.; Ladmiral, V.; Fukuda, T.; Tsujii, Y. Versatile Method of Initiator Fixation for Surface-Initiated Living Radical Polymerization on Polymeric Substrates. Macromolecules 2010, 43, 5569-5574. (34) Fukazawa, K.; Nakao, A.; Maeda, M.; Ishihara, K. Photoreactive Initiator for SurfaceInitiated ATRP on Versatile Polymeric Substrates. ACS Appl. Mater. Interfaces 2016, 8, 24994-24998. (35) Jhong, J. F.; Venault, A.; Hou, C. C.; Chen, S. H.; Wei, T. C.; Zheng, J.; Huang, J.; Chang, Y. Surface Zwitterionization of Expanded Poly(tetrafluoroethylene) Membranes via Atmospheric Plasma-Induced Polymerization for Enhanced Skin Wound Healing. ACS Appl. Mater. Interfaces 2013, 5, 6732-6742. (36) Wu, S. Y.; Kang, E. T.; Neoh, K. G.; Tan, K. L. Electroless Deposition of Copper on Surface Modified Poly(tetrafluoroethylene) Films from Graft Copolymerization and Silanization. Langmuir 2000, 16, 5192-5198. (37) Chang, Y,; Chang, W. J.; Shih, Y. J.; Wei, T. C.; Hsiue, G. H. Zwitterionic SulfobetaineGrafted Poly(vinylidene fluoride) Membrane with Highly Effective Blood Compatibility via


Page 26 of 29

Page 27 of 29 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


Atmospheric Plasma-Induced Surface Copolymerization. ACS Appl. Mater. Interfaces 2011, 3, 1228-1237. (38) Sreeruttun, R. K.; Ramasami, P.; Wannere, C. S.; Paul, A.; Schleyer, P. V.; Schaefer III, H. F. Effects of Fluorine on the Structures and Energetics of the Propynyl and Propargyl Radicals and Their Anions. J. Org. Chem. 2005, 70, 8676-8686. (39) Coote, M. L.; Davis, T. P.; Radom, L. Effect of the Penultimate Unit on Radical Stability and Reactivity in Free-Radical Polymerization. Macromolecules 1999, 32, 2935-2940. (40) Değirmenci, İ.; Aviyente, V. DFT Study on the Propagation Kinetics of Free-Radical Polymerization of R-Substituted Acrylates. Macromolecules 2009, 42, 3033-3041. (41) Chang, C; Lei, Z. W; Li, Y. H; Wang, Z. L. Electrochemical Research of a Stable Electroless Silver Bath. J. Electrochem. Soc. 2016, 163: D121-D125. (42) Zhao, W. X.; Ding, J.; Wang, Z. L. Improvement in the Etching Performance of the Acrylonitrile-Butadiene-Styrene Resin by MnO2-H3PO4-H2SO4 Colloid. Langmuir 2013, 29, 5968-5973. (43) Kim, B. H.; Lee, D. H.; Kim, J. Y.; Shin, D. O.; Jeong, H. Y.; Hong, S.; Yun, J. M.; Koo, C. M.; Lee, H.; Kim, S. O. Mussel-inspired Block Copolymer Lithography for Low Surface Energy Materials of Teflon, Graphene, and Gold. Adv. Mater. 2011, 23, 5618-5622. (44) Beamson, G.; Briggs, D. High Resolution XPS of Organic Polymers: the Scienta ESCA300 Database. Wiley: Chichester (England) and New York (USA), 1992. (45) Clark, D. T.; Feast, W. J.; Tweedale, P. J.; Thomas, H. R. ESCA Applied to Polymers. XXVI. Investigation of a Series of Aliphatic, Aromatic, and Fluorine-Containing Polycarbonates. J. Polym. Sci. Polym. Chem. Ed. 1980, 18, 1651-1664. (46) Olivier, D.; Marachi, C.; Che, M. An EPR Study of the Reactivity of Peroxy Radicals Trapped in Polytetrafluoroethylene. J. Chem. Phys. 1980, 72, 3348-3353. (47) Siegel, S.; Hedgpeth, H. Chemistry of Irradiation Induced Polytetrafluoroethylene Radicals: I. Re-examination of the EPR Spectra. J. Chem. Phys. 1967, 46, 3904-3912. (48) Jokinen, T.; Sipilä, M.; Richters, S.; Kerminen,V. M.; Paasonen, P.; Stratmann, F.; Worsnop, D.; Kulmala, M.; Ehn, M.; Herrmann, H.; Berndt, T. Rapid Autoxidation Forms Highly Oxidized RO2 Radicals in the Atmosphere. Angew. Chem. Int. Ed. 2014, 53, 14596-14600.



(49) Yoshikawa, C.; Goto, A.; Tsujii, Y.; Fukuda, T.; Yamamoto, K.; Kishida, A. Fabrication of High-Density Polymer Brush on Polymer Substrate by Surface-Initiated Living Radical Polymerization. Macromolecules 2005, 38, 4604-4610. (50) Yang, Z. L.; Yang, Y.; Yan, W.; Tu, Q. F.; Wang, J.; Huang, N. Construction of Polyfunctional Coatings Assisted by Gallic Acid to Facilitate Co-Immobilization of Diverse Biomolecules. ACS Appl. Mater. Interfaces 2013, 5, 10495-10501. (51) Wang, W. C.; Li, R. Y.; Tian, M.; Liu, L.; Zou, H.; Zhao, X. Y.; Zhang, L. Q. Surface Silverized Meta-Aramid Fibers Prepared by Bio-inspired Poly(dopamine) Functionalization. ACS Appl. Mater. Interfaces 2013, 5, 2062-2069.


Page 28 of 29

Page 29 of 29 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


Table of Contents graphic (TOC):


Robust Conductive Micropatterns on PTFE Achieved via Selective UV

Recommend Documents