High Performance Polymer Derived from a Biorenewable Plant Oil

Jan 25, 2017 - (Figure S1) GPC curve of polymer P1, prepared by radical polymerization; (Figure S2) SEM image of a P2 film on a silicon wafer; (Figure...
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Research Article pubs.acs.org/journal/ascecg

High Performance Polymer Derived from a Biorenewable Plant Oil (Anethole) Fengkai He, Kaikai Jin, Yuanqiang Wang, Jiajia Wang, Junfeng Zhou, Jing Sun, and Qiang Fang* Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, People’s Republic of China

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S Supporting Information *

ABSTRACT: A high performance polymer with both low water uptake and high thermostability derived from a biorenewable plant oil (anethole) is reported here. By using the plant oil as the feedstock, a new monomer containing benzocyclobutene and vinyl units was successfully synthesized. The monomer was then converted to a polymer via radical polymerization, and the polymer was further postpolymerized to form an insoluble and infusible cross-linked network at high temperature (>200 °C). The cross-linked network exhibited water uptake of below 0.40% (kept at boiling water for 4 days) and dielectric constant of less than 2.9 at a range of frequencies varying from 1.0 to at 30.0 MHz at room temperature. TGA and TMA data showed that the cross-linked network had 5 wt % loss temperature of 432 °C (in N2) and a Tg of 369 °C, respectively. The cross-linked network also showed low thermal expansion coefficient of 41.24 ppm/°C at the range of temperatures varying from 50 to 300 °C. Nanoindentation tests indicated that the cross-linked film had an average hardness of 0.87 GPa and a Young’s modulus of 11.40 GPa. These data suggest that the new polymer derived from anethole possess excellent thermal and mechanical properties, and it has potential application in the microelectronic industry. KEYWORDS: Biomass, Plant oil, Anethole, Thermosetting polymer, High performance polymer

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for petroleum-based materials.12−18 Among biomasses, the ones that contain aromatic units are particularly gathering interest because of their excellent properties including high glass transition temperature (Tg) and high storage modulus (E).19−21 For example, Lignin, a well-known biomass with a branched polyphenolic network, has been successfully converted into a lot of polymeric materials or useful precursors via the chemical or biological reactions.22−26 However, most of the biomasses containing aromatic units can not be easily transformed to the small molecules, which can be used for the synthesis of the polymers. Therefore, the investigation on the easily processable biomasses with aryl units is desirable. It is noted that a plant oil named anethole is a typical biomass with a phenyl ring. This oil is derived from star anise, and can be used as a precursor for the preparation of high performance materials.27,28 Previously, we studied the con-

INTRODUCTION With the rapid development of the aeronautics/astronautics and microelectronic industries, high performance polymers are urgently required. Thus, tremendous efforts have been made to develop the synthesis and applications of the polymers.1 Among various high performance polymers, those with thermosetting groups have attracted a lot of attention because of their ease of processability and can thermally form densely cross-linked networks having high performance, including high thermostability, good electrical properties and low water uptake. Of the thermosetting polymers, benzocyclobutenebased polymers have seen much interest from both academia and industry.2−11 These polymers show excellent thermal, mechanical and dielectric properties. In particular, their crosslinked films exhibit very low roughness and high hydrophobicity. Consequently, they have been recognized as an important candidate for the preparation of high performance materials, and are widely used in microelectronic industry.5−11 Recently, polymeric materials derived from the renewable biomasses have become one of the most promising alternative © 2017 American Chemical Society

Received: December 1, 2016 Revised: January 15, 2017 Published: January 25, 2017 2578

DOI: 10.1021/acssuschemeng.6b02919 ACS Sustainable Chem. Eng. 2017, 5, 2578−2584

Research Article

ACS Sustainable Chemistry & Engineering version of the oil to a fluoropolymer with good dielectric and hydrophobicity.29 As an extended investigation, by using anethole as a feedstock, we designed and synthesized a new functional monomer containing thermocrosslinkable ethylene and benzocyclobutene units. The chemical structure of the monomer is depicted in Scheme 1. In the presence of a radical initiator, the monomer was converted to a polymer with average number molecular weight (Mn) of near 780 000. Such a high Mn suggests that the polymer is suitable as a basic resin for the preparation of the plastic parts, as well as a matrix for the fiber reinforced composite. After postpolymerization at high temperature, the polymer formed a cross-linked network, which exhibited low water uptake and high thermostability. These results indicate that the polymer is very suitable as an encapsulation or a matrix resin utilized in the microelectronic industry. In this contribution, we report the detailed results.

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H2SO4 (150 g) was added dropwise during a period of 0.5 h. The mixture was raised to 85 °C and kept at the temperature for 4 h with vigorous stirring. The solution was cooled to room temperature and extracted with ethyl acetate. The organic phases were combined, washed with water, and dried over anhydrous Na2SO4. After filtration and concentration, the crude product was prepared, which was further purified by distillation under reduced pressure. The pure 1 was thus obtained as a transparent liquid in a yield of 76.2%. 1H NMR (400 MHz, CDCl3, δ): 9.87 (s, 1H), 7.83 (d, 2H), 7.00 (dd, 2H), 3.88 (s, 3H). Synthesis of 2. To a stirring mixture of 1 (220.35 mmol, 30.00 g) and CH2Cl2 (40 mL) was added a solution of Br2 (264.42 mmol, 42.26 g) in CH2Cl2 (100 mL) dropwise at room temperature. After addition, the mixture was heated to reflux and maintained at the temperature for 12 h. After being cooled to room temperature, the mixture was treated with a saturated aqueous solution of NaHSO3 to consume the excess of bromine (note: in many cases, highly volatile Br2 with strong corrodibility was reduced to bromide using Na2S2O3 as a reducer. However, such a reducer reacted with Br2 to form sulfur, which is difficult to remove completely from organic solvent. Thus, NaHSO3 is appreciated for removal of Br2). The solution was then extracted with CH2Cl2, washed with water, dried over anhydrous Na2SO4, filtered and concentrated to afford the crude product. Compound 2 was purified using column chromatography with a mixture of petroleum ether and ethyl acetate as the eluent (20:1, v/v). White solid, 41.00 g, yield of 86.53%. 1H NMR (400 MHz, CDCl3, δ): 9.84 (s, 2H), 8.08 (d, 2H), 7.82 (dd, 2H), 7.01 (d, 2H), 3.99 (s, 6H). Synthesis of 3. Under an argon atmosphere, a mixture of methyltriphenylphosphonium bromide (93.00 mmol, 33.22 g), potassium tert-butylate (93.00 mmol, 10.44 g) and THF (40 mL) was stirred at 0 °C for 30 min, and then heated to 50 °C and kept at the temperature for 2 h. The mixture was cooled to room temperature, and a solution of 2 (46.50 mmol, 10.00 g) in THF (20 mL) was added dropwise. After stirring at 50 °C for 6 h, the mixture was treated with water to quench the reaction, and then extracted with CH2Cl2. The combined organic layers were dried over anhydrous Na2SO4, filtered and concentrated. The crude product was further purified by column chromatography with petroleum ether as a eluent; 3 was obtained as a transparent liquid in a yield of 96.9%. 1H NMR (400 MHz, CDCl3, δ): 7.61 (d, 1H), 7.29 (dd, 1H), 6.84 (d, 1H), 6.59 (dd, 1H), 5.61 (d, 1H), 5.16 (d, 1H), 3.89 (s, 3H). Synthesis of Benzocyclobutene-4-magnesium Bromide. Under an argon atmosphere, a solution of 4-bromobenzocyclobutene (70.40 mmol, 12.89 g) in THF (30 mL) was added dropwise to a mixture of magnesium turnings (93.87 mmol, 2.28 g) and THF (10 mL) at 40 °C during a period of 0.5 h. After addition, the resulting mixture was stirred for an additional 1 h at the temperature, and cooled to room temperature. A solution of benzocyclobutene-4magnesium bromide was thus prepared. Synthesis of Monomer 4. A solution of benzocyclobutene-4magnesium bromide (70.40 mmol, 14.49 g) in THF (40 mL) was added dropwise to a mixture of 3 (46.93 mmol, 10.00 g), Pd(PPh3)4 (234.66 μmol, 271.2 mg) and THF (40 mL) at room temperature under N2. The mixture was heated to 70 °C and maintained at the temperature for 12 h. After cooling to room temperature, the mixture was treated with water (100 mL), and extracted with ethyl acetate. The organic layers were combined, dried over anhydrous Na2SO4, filtered and concentrated. The residue was purified by using column chromatography with petroleum ether as an eluent. Pure monomer 4 was obtained as a sticky transparent liquid in a yield of 64.10%. 1H NMR (400 MHz, CDCl3, δ): 7.36−7.32 (m, 3H), 7.21 (s, 1H), 7.11 (d, 1H), 6.93 (d, 1H), 6.69 (dd, 1H), 5.65 (d, 1H), 5.15 (d, 1H), 3.82 (s, 3H), 3.23 (s, 4H). 13C NMR (126 MHz, CDCl3, δ): 156.33, 145.44, 144.83, 137.12, 136.28, 131.87, 130.48, 128.91, 128.28, 126.35, 123.87, 122.30, 111.92, 111.15, 55.80, 29.65, 29.58. HRMS-ESI (m/z): calcd for C17H17O [M + H]+ 237.1274; found, 237.1274. Anal. calcd for C17H16O: C, 86.40; H, 6.82. Found: C, 86.53; H, 6.96. Bulk Polymerization. A mixture of monomer 4 (2.12 mmol, 0.50 g) and azobis(isobutyronitrile) (AIBN, 9.135 μmol, 1.5 mg) was stirred for 10 min at the room temperature under argon atmosphere.

EXPERIMENTAL SECTION

Materials. Anethole was purchased from Nanjing Chemlin Chemical Industry Co., China. 4-Bromobenzocyclobutene was purchased from Chemtarget Technologies Co., China. MnO2, resorcinol, potassium t-butoxide, dichloromethane and methyltriphenylphosphonium bromide were purchased from Sigma-Aldrich. Bromine, tetrakis(triphenylphosphine)palladium and 2,2′-azoisobutyronitrile were purchased from TCI Co. Tetrahydrofuran (THF) was purchased from Sinopharm Chemical Reagent Co., China, and dried over CaH2 and distilled under reduced pressure before use. Other solvents and reagents were used as received. Measurements. 1H NMR and 13C NMR spectra were recorded on a Bruker 400 spectrometer using TMS as internal standard with CDCl3 as a solvent at room temperature. High resolution mass spectra (HRMS) were recorded on a DARTSVP (IonSense Inc.) mass spectrometer. FT-IR spectra were run on a Nicolet spectrometer with KBr pellets. Differential scanning calorimetry (DSC) was measured on a TA Instrument DSC Q200 with sealed pans at a heating rate of 10 °C/min under nitrogen flow. Thermogravitric analysis (TGA) was performed on a TG 209F1 (NETZSCH) apparatus with a heating rate of 10 °C/min in N2 atmosphere. Elemental analysis was carried out on an Elementar vario EL III system. The dielectric constant (Dk) and dissipation factor (Df) of the cured polymer films were measured by the capacitance method at the range of frequencies from 1.0 to 30.0 MHz at room temperature by using a 4294A Precision Impedance Analyzer (Agilent). An aluminum-backed silicon wafer (heavily doped single crystal silicon with a resistivity of 3.5 × 10−3 Ω·cm) was used as the substrate for fabrication of the parallel plate capacitors. The top electrodes with an average diameter of about 3.0 mm were prepared by evaporation of aluminum on to the surface of the cured polymer film. The thickness of the cured polymer film was measured by field emission scanning electron microscopy (FE-SEM) on a FE-SEM S4800 (Hitachi). The thinness of the cured polymer film controlled at a range of more than 120 nm but less than 180 nm. The detailed measurement procedure was described in our previous report.30 The contact angle of the cured film was measured at 20 ± 1 °C using a sessile drop method on a dynamic contact angle measurement instrument (JC2000C). Deionized water was selected as the testing liquid. Surface toughness of the polymer film was measured by atom force microscopy (AFM) on a Shimadz SPM-9500J3. Molecular weights were measured by using a Waters Breeze2a 200 GPC instrument with polystyrene as standards and tetrahydrofuran (THF) as the eluent at 35 °C. Thermo-mechanical analysis (TMA) was recorded on the Mettler Toledo DMA/SDTA861e with a heating rate of 3 °C min−1 in air. The mechanical properties of the polymer films were measured on a nanoindentation/scrach system called UNHT/ NST (CSM Company). Synthesis of 1. To a stirring mixture of resorcinol (0.45 mmol, 0.50 g), MnO2 (460.10 mmol, 40.00 g) and H2O (100 mL) was added anethole (101.21 mmol, 15.00 g) dropwise at 60 °C during a period of 0.5 h. After addition, the mixture was heated to 80 °C, and then 35% 2579

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ACS Sustainable Chemistry & Engineering Scheme 1. Procedure for the Synthesis of the New Monomer and Polymer

Then the mixture was heated to 70 °C and kept at the temperature for 1 h. After cooling to room temperature, the transparent solid was treated with THF to obtain a solution. The solution was concentrated and poured into methanol (100 mL) to afford a white precipitate, which was redissolved in THF (5 mL). The obtained solution was reprecipitated in methanol. Polymer P1 was thus prepared as a white solid in a yield of 80%. GPC (polystyrene) results: Mn = 775 700, PDI = 1.21. 1H NMR (400 MHz, CDCl3, δ): 7.14−6.78 (m, 3H), 6.64− 6.17 (m, 3H), 3.52 (s, 3H), 3.09 (s, 4H), 2.18−1.75 (m, 1H), 1.60− 1.24 (m, 2H). Fabrication of the Samples for the Measurement of the Dielectric and Mechanical Properties. A solution of P1 in xylene was spin-coated on an aluminum-backed silicon wafer to form a smooth film. The silicon wafer was placed into a quartz tube furnace and heated to 200 °C. After maintaining the temperature at 200 °C for 2 h, the furnace was allowed to be heated to 250 °C and kept at the temperature for 5 h under N2 atm. The film was completely converted to a cross-linked network, which was used for the measurement of Dk, Df, surface toughness and contact angle, and used for nanoindentation/scratch tests. Preparation of the Sample for the Measurement of TMA. Monomer 4 was placed in a flat-bottomed glass tube (diameter = 10 mm and height = 85 mm) filled with argon. The tube was kept at 130 °C for 3 h until the liquid became a transparent solid. The tube was then heated to 200 °C and kept at the temperature for 4 h. Finally, the tube was maintained at 220 and 250 °C for 5 h, respectively. Thus, a fully cured sample was obtained. Measurement of Moisture Absorption of the Cured Monomer 4. A fully cured monomer 4 sample sheet (2 mm thick × 10 mm in diameter) was dried in a vacuum oven until a constant weight (0.0001 g) was achieved. The sample sheet was then immersed into boiling water of 50 mL (about 97 °C) and kept at the temperature for 4 days. After removal of water and drying by using filter paper, the sample sheet was weighed. The moisture uptake was estimated as the

increase of the weight of the sample sheet after immersion in the boiling water.

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RESULTS AND DISCUSSION

As shown in Scheme 1, the functional monomer 4 was prepared with an overall yield of more than 40% via a four-step procedure by using anethole as the feedstock. The chemical structure of the monomer was confirmed by 1H NMR, 13C NMR, high-resolution mass spectra (HRMS), FT-IR and elemental analysis. In its 1H NMR spectrum, the characteristic peak at 3.23 ppm attributed to benzocyclobutene’s fourmembered ring was observed. In its FT-IR spectrum, the characteristic peak for benzocyclobutene group at 1470 cm−1 was also observed. In addition, the signals for vinyl group were found in the 1H NMR and FT-IR spectra. These results indicated that the target monomer 4 was synthesized successfully. It is noted that styrene-like monomers can form polymers via radical polymerization.31,32 In our case, monomer 4 converted to a polymer (P1) in the presence of AIBN with an average number molecular weight of near 775 000. To know well the progress of the radical polymerization, A DSC trace of monomer 4 with AIBN was carried out, and the results are shown in Figure 1. As depicted in Figure 1, the radical polymerization started at about 79 °C and gave a peak exothermic temperature of about 116 °C. When the temperature was raised to near 200 °C, a mountain-like peak was observed, which was attributed to the ring-opening reaction of benzocyclobutene units.6,7 2580

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Figure 1. DSC curves of monomer 4 at a heating rate of 10 °C min−1 in N2.

Figure 3. FT-IR spectra of monomer 4, polymer P1 and P2.

P1 showed good solubility in the common solvents such as CHCl3, THF and toluene. Casting a solution of P1 gave a tough and transparent film, which was free-standing. The chemical structure of P1 was characterized by its 1H NMR spectrum. As shown in Figure 2, characteristic peak for

suggests that P1 has been fully thermo-cross-linked to form P2 (see Scheme 1). Surface roughness is an important parameter for the evaluation of film quality. Low surface roughness reflects that there is no significant shrinkage or expansion during film forming. This parameter is more crucial for the materials utilized in the microelectronic industry, because low surface roughness implies that the array with high quality can be easily produced on the film surface. Benzocyclobutene-based resins usually exhibit good surface roughness. In our case, surface morphology of P1 and P2 films on silicon wafers were characterized by using atomic force microscopy (AFM). As can be seen from Figure 4, the surface average roughness of P1 film before and after curing is 0.33 and 0.46 nm over a 2 μm square area. No significant difference of surface roughness between P1 and P2 films implies that no obvious shrinkage occurs during the conversion of P1 to P2. Such a low surface roughness indicates that P1 is suitable for application in the electronic/ electrical fields. Water uptake is a very important parameter for the application of high performance material. In our case, a P2 disk with a thickness of 2.0 mm and a diameter of 10.0 mm was kept in boiling water for 4 days, exhibiting a water uptake of 0.40%. Such a low value indicates that the polymer has good hydrophobicity. The hydrophobicity of a P2 film also was investigated by the water contact angle test, and the results are shown in Supporting Information. As depicted in Supporting Information (Figure S3), on the surface of a P2 film, the water contact angle was measured as 96°, also indicating that the P2 film has good hydrophobicity. The dielectric properties of a P2 film were measured by the capacitance method, and the results are depicted in Figure 5. The average dielectric constant (Dk) of the film is less than 2.9 with a dissipation factor (Df) of below 7 × 10−3 at the range of frequencies varying from 1.0 to 30.0 MHz. This result is comparable to the values of the commercially available organic low-k materials, such as polyimides (3.1−3.4)33 and polycyanate esters (2.61−3.12).34 Thermostability of P2 was investigated by using thermal gravimetric analysis (TGA). As depicted in Figure 6, P2 exhibits a 5 wt % loss temperature of 432 °C. This high heat resistance of P2 implies that it could be used as the matrix for

Figure 2. 1H NMR spectra of monomer 4 and polymer P1.

vinyl group in monomer 4 completely disappears in P1, suggesting that monomer 4 has transformed to P1. It is noted that the characteristic peak at 3.2 ppm for the four-member ring of a benzocyclobutene unit in P1 still remains, indicating that the radical initiator (AIBN) is not able to make benzocyclobutene unit ring-opening. We further investigated the postpolymerization of polymer P1. As exhibited in Figure 1, P1 shows a Tg of 117 °C and a maximum exothermic peak temperature of 262 °C. This implies that P1 can be converted to the infusible and insoluble crosslinked networks via the postpolymerization reaction. In order to monitor the degree of postpolymerization, FT-IR spectra of P1 and P2 were carried out. As depicted in Figure 3, the characteristic signal attributed to benzocyclobutene at 1470 cm−1 disappears after treating P1 at 250 °C for 5 h. This result 2581

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Figure 4. AFM images of P1 film before (a) and after (b) curing.

α (T ) =

1 d L (T ) L dT

(1)

Where α(T) represents CTE, L is the length of sample before test and L(T) is the length of sample at a temperature T. In our case, TMA results (Figure 7) indicate that P2 has a Tg of 369 °C, and shows a CTE of 41.24 ppm/°C varying from 50 to 320 °C. These data exhibit P2 processes excellent dimensionstability.

Figure 5. Dielectric constant and dielectric loss of a P2 film.

Figure 7. TMA curve of P2.

Nanoindentation/scratch technology was also used to evaluate the mechanical properties of P2. As depicted in the Figure 8, a P2 film shows that it has an average hardness of 0.87 GPa and a Young’s modulus of 11.36 GPa. The bonding strength between the film and a silicon wafer is measured as 1.10 GPa. These results are better than that of most epoxy resins,21 indicating that P2 has good mechanical properties.

Figure 6. TGA curves of P2 in N2 with a heating rate of 10 °C min−1.

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CONCLUSIONS In summary, we have successfully developed a new thermosetting polymer derived from anethole. After postpolymerization at high temperature, the polymer formed an insoluble and infusible cross-linked network, showing a water uptake of 0.40%. TGA and TMA data indicated that the crosslinked network had 5 wt % loss temperature of 432 °C (in N2) and a Tg of 369 °C, respectively. Furthermore, TMA data suggested that the coefficient of thermal expansion (CTE) was 41.24 ppm/°C at the range of temperatures varying from 50 to 300 °C. The cross-linked network also exhibited dielectric

the preparation of insulating enameled wire and the lamination of print circuit boards. High glass-transition temperature (Tg) and low coefficient of thermal expansion (CTE) are also important characteristics of high-performance engineering materials. The sample’s dimension change and glass-transition temperature (Tg) are usually evaluated by the static thermal mechanical analysis (TMA). According to the measurement results of TMA, the sample’s coefficient of thermal expansion (CTE) can be calculated according to eq 1: 2582

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ACS Sustainable Chemistry & Engineering Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Financial supports from Ministry of Science and Technology of China (2015CB931900) and the Natural Science Foundation of China (NSFC No. 21574146 and No. 21504103) and the Science and Technology Commission of Shanghai Municipality (15ZR1449200 and 16JC1403800) are gratefully acknowledged. The authors are also grateful to the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant XDB 20020000).

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(1) Meador, M. A. Recent advances in the development of processable high-temperature polymers. Annu. Rev. Mater. Sci. 1998, 28, 599−630. (2) Kirchhoff, R. A.; Bruza, K. J. Benzocyclobutenes in polymer synthesis. Prog. Polym. Sci. 1993, 18, 85−185. (3) Farona, M. F. Benzocyclobutenes in polymer chemistry. Prog. Polym. Sci. 1996, 21, 505−555. (4) Wang, J.; Piskun, I.; Craig, S. L. Mechanochemical strengthening of a multi-mechanophore benzocyclobutene polymer. ACS Macro Lett. 2015, 4, 834−837. (5) Hayes, C. O.; Chen, P.-H.; Thedford, R. P.; Ellison, C. J.; Dong, G.; Willson, C. G. Effect of ring functionalization on the reaction temperature of benzocyclobutene Thermoset Polymers. Macromolecules 2016, 49, 3706−3715. (6) Tian, S.; Sun, J.; Jin, K.; Wang, J.; He, F.; Zheng, S.; Fang, Q. Postpolymerization of a fluorinated and reactive poly(aryl ether): an efficient way to balance the solubility and solvent resistance of the polymer. ACS Appl. Mater. Interfaces 2014, 6, 20437−20443. (7) Tong, J.; Diao, S.; Jin, K.; Yuan, C.; Wang, J.; Sun, J.; Fang, Q. Benzocyclobutene-functionalized poly(m-phenylene): A novel polymer with low dielectric constant and high thermostability. Polymer 2014, 55, 3628−3633. (8) Cheng, Y.; Yang, J.; Jin, Y.; Deng, D.; Xiao, F. Synthesis and properties of highly cross-Linked thermosetting Resins of benzocyclobutene-functionalized benzoxazine. Macromolecules 2012, 45, 4085−4091. (9) Wang, Y.; Sun, J.; Jin, K.; Wang, J.; Yuan, C.; Tong, J.; Diao, S.; He, F.; Fang, Q. Benzocyclobutene resin with fluorene backbone: a novel thermosetting material with high thermostability and low dielectric constant. RSC Adv. 2014, 4, 39884−39888. (10) Cao, K.; Yang, L.; Huang, Y.; Chang, G.; Yang, J. High temperature thermosets derived from benzocyclobutene-containing main-chain oligomeric carbosilanes. Polymer 2014, 55, 5680−5688. (11) He, F.; Yuan, C.; Li, K.; Diao, S.; Jin, K.; Wang, J.; Tong, J.; Ma, J.; Fang, Q. A new low dielectric material with high thermostability based on a thermosetting trifluoromethyl substituted aromatic molecule. RSC Adv. 2013, 3, 23128−23132. (12) Meier, M. A. R.; Metzger, J. O.; Schubert, U. S. Plant oil renewable resources as green alternatives in polymer science. Chem. Soc. Rev. 2007, 36, 1788−1802. (13) Karumuri, S.; Hiziroglu, S.; Kalkan, A. K. Thermoset-crosslinked lignocellulose: a moldable plant biomass. ACS Appl. Mater. Interfaces 2015, 7, 6596−6604. (14) Mauck, S. C.; Wang, S.; Ding, W. Y.; Rohde, B. J.; Fortune, C. K.; Yang, G. Z.; Ahn, S.-K.; Robertson, M. L. Biorenewable tough blends of polylactide and acrylated epoxidized soybean oil compatibilized by a polylactide Star polymer. Macromolecules 2016, 49, 1605−1615. (15) Yang, Y.; Deng, Y.; Tong, Z.; Wang, C. Renewable lignin-based xerogels with self-cleaning properties and superhydrophobicity. ACS Sustainable Chem. Eng. 2014, 2, 1729−1733. (16) Nguyen, H. T. H.; Reis, M. H.; Qi, P. X.; Miller, S. A. Polyethylene ferulate (PEF) and congeners: polystyrene mimics

Figure 8. Results from (a) nanoindentation and (b) nanoscratch tests for a P2 film.

constant (Dk) of near 2.90 and dissipation factor (Df) of below 7 × 10−3, respectively, ranging from 1.0 to 30.0 MHz at room temperature. These results indicate that the thermosetting polymer derived from anethole show high thermostability and good dielectric properties, implying that the polymer has potential application in microelectronic industry.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.6b02919. (Figure S1) GPC curve of polymer P1, prepared by radical polymerization; (Figure S2) SEM image of a P2 film on a silicon wafer; (Figure S3) picture of contact angle of water on a P2 film; (Figure S4) 1H NMR spectrum of monomer 4 (400 MHz, CDCl3); (Figure S5) 13C NMR spectrum of monomer 4 (126 MHz, CDCl3); (Figure S6) 1H NMR spectrum of P1 (400 MHz, CDCl3) (PDF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*Q. Fang. E-mail: [email protected]. ORCID

Jing Sun: 0000-0002-1714-0283 Qiang Fang: 0000-0002-3549-5600 2583

DOI: 10.1021/acssuschemeng.6b02919 ACS Sustainable Chem. Eng. 2017, 5, 2578−2584

Research Article

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DOI: 10.1021/acssuschemeng.6b02919 ACS Sustainable Chem. Eng. 2017, 5, 2578−2584