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RSC Advances This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. This Accepted Manuscript will be replaced by the edited, formatted and paginated article as soon as this is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/advances Page 1 of 7 RSC Advances Journal Name RSC Publishing ARTICLE A new polymer with low dielectric constant based on trifluoromethyl substituted arene: preparation and Cite this: DOI: 10.1039/x0xx00000x properties Jiajia Wang, Kaikai Jin, Fengkai He, Jing Sun and Qiang Fang * Received 00th January 2012, Accepted 00th January 2012 A new polymer with low dielectric constant is reported here. This polymer contains a DOI: 10.1039/x0xx00000x trifluoromethyl substituted phenyl unit and a binaphthyl unit, and shows high thermostability with a glass translation temperature of 244 °C and a 5 wt% loss temperature at 518 °C in www.rsc.org/ nitrogen. The polymer also exhibits good film-forming ability and the formed films exhibits high hydrophobicity with a contact angle to water of 103.6 o. In a range of frequencies from 1 to 25 MHz, the polymer reveals an average of dielectric constants of about 2.56. In regard to the mechanical properties, the polymer film shows an average hardness of 0.37 GPa and a Manuscript Young’s modulus of 15.07 GPa. Those results imply that the polymer could be used as the varnish for enameled wire, sizing agents for high performance carbon-fiber, and the matrix resin for production of laminated composites utilized in the print-circuit-boards (PCB) industry . 1. Introduction least polarizable bonds such as C-F bond in molecular backbone and/or side chains,29-37 the other is to generate pores Polymers with low dielectric constants (low k) have been paid in polymer networks. 38-46 However, favorable size and Accepted much attention for many years because they are a kind of distribution of the pores should be carefully controlled. necessary materials for fabrication of insulating varnish of Based on that polymeric materials have an advantage of easy enameled wire in electrical industry as well as for production of structure design, consequently, their k values and other 1-4 printed-circuit-boards (PCB) in electronic industry. In recent properties such as thermostability and mechanical properties years, the development of multilevel interconnection could be tunable via well defining molecular structures. It is technology in the production of ultra-large scale integration noted that poly(aryl ether)s show high bonding strength to (ULSI) circuits has raised (up) an urgent requirement to the low metals and low thermal expansion coefficient (CTE) and that k materials due to the fact that they play a very important role fluoro-containing polymers exhibit lower k values. 47,48 Thus, for decreasing the cross-talk noise, power dissipation and the studies on the synthesis and properties of the new poly(aryl interconnect signal delay (RC delay) generated with the ether)s with fluoro groups are significant. Advances minimization of electronic devices in microelectronic Previously, we have reported 3 a thermally cross-linkable 5-10 industry. Accordingly, various polymers have been well molecule composed of bis(trifluoromethyl)benzene and 11- investigated and many low k materials have been developed. benzocyclobutene units, which shows both low dielectric 28 Nevertheless, commercially available low k polymers utilized constant at high frequencies and high thermostability. In order at the high frequencies (> 10 MHz) are rare. It is known that the to further investigate the properties of the organic materials RSC materials having a k value of below 3.0 at the high frequencies containing bis(trifluoromethyl)benzene units, we design and can meet the requirement of 90 nm procedure in ultra-large synthesize a new polymer composed of a binaphthyl unit and a 6-8 scale integration (ULSI) circuits. Moreover, such low k bis(trifluoromethyl)benzene unit, whose chemical structure is materials are also desirable for the production of high shown in Scheme 1. The polymer exhibits good film-forming frequency printed circuit boards. Therefore, exploring and ability and the formed films possesses high hydrophobicity with developing the polymers with a low k value at high frequencies a contact angle to water of 103.6°. In a range of frequencies are still necessary. from 1 to 25 MHz, the polymer reveals an average of dielectric So far, there are two manners to scale down the dielectric constants of about 2.56. Moreover, the polymer shows high constants of polymers. One is to use the polymers containing This journal is © The Royal Society of Chemistry 2013 J. Name ., 2013, 00 , 1-3 | 1 RSC Advances Page 2 of 7 ARTICLE Journal Name thermostability and good mechanical properties. Those data formed during the reaction was removed by a Dean-Stark trap. suggest that the polymer could be used as the insulating varnish After being kept at the temperature (about 150-160 °C) for 8 h, for enameled wire, sizing agents for high performance carbon- the reaction mixture was cooled to room temperature, and fiber, and the matrix resin for production of laminated poured into 200 mL of water, extracted with ethyl acetate. The composites utilized in the printed circuit boards (PCB) industry. organic layer was washed with saturated brine and dried over anhydrous Na 2SO 4. The crude product was purified by column chromatography using n-hexane as an eluent on silica gel. The obtained product was further purified by recrystallization from n-hexane, Pure monomer 2 was obtained as a white solid in a 1 yield of 67% with a purity of 99.6% (HPLC). H NMR (400 MHz, CDCl 3) δ (TMS, ppm): 7.02-7.03 (dd, 2H), 7.25 (s, 2H), Scheme 1. Chemical structure of the new polymer in this work. 7.45-7.49 (t, 2H), 7.54-7.57 (td, 4H), 7.73-7.75 (d, 2H), 7.92- 19 7.94 (m, 2H), 8.15-8.17 (dd, 2H). F NMR (376 MHz, CDCl 3) 13 δ (TMS, ppm): -62.57 (s, 6F). C NMR (100 MHz, CDCl 3) δ 2. Experimental (TMS, ppm): 113.98, 117.94, 121.64, 122.36, 125.01, 125.48, 125.81, 126.65, 127.79, 127.19, 128.11, 135.23, 150.62, Materials 151.86. All starting materials were purchased from Aldrich and Acros companies and used without further purification unless an Synthesis of the polymer additional statement elsewhere. 1,4-Bis(tri-fluoromethyl)-3,5- dibromobenzene ( 1) was prepared according to the previously Monomer 2 (0.498 g, 1 mmol) was dissolved in 1,1,2,2- 3,49,50 1 reported. Characterization: H NMR (400 MHz, CDCl 3) δ tetrachloroethane (3.5 mL) at room temperature under argon. 19 Manuscript (TMS, ppm): 8.02 (s, 2H); F NMR (376 MHz, CDCl 3) δ The obtained solution was cooled to -5 °C, and then added to a (TMS, ppm): 63.94 (s, 6F). All solvents were dehydrated and mixture of anhydrous iron(III) chloride (0.406 g, 2.5 mmol) in distilled under an inert atmosphere before use. 1,1,2,2-tetrachloroethane (1.5 mL) under argon atmosphere. After being stirred at -5 °C for 24 h, the reaction mixture was Measurement poured into methanol (200 mL) containing a small amount of concentrated HCl. The obtained precipitate was purified by 1H NMR, 13 C NMR and 19 F NMR spectra were obtained on a column chromatography on neutral Al O with CHCl as the Bruker AV400 instrument. Elemental analysis was carried out 2 3 3 eluent. After the solvents were evaporated, the polymer was re- on an Elementar vario EL III system. Molecular weights were dissolved in chloroform and reprecipitated with methanol. A measured at room temperature by gel permeation yellowish power was thus obtained, which was dried at 80 °C chromatography (GPC) with a Waters Breeze2a 200 GPC Accepted for 12 h under vacuum to get polymer sample. Yield: 80%. system, equipped with a UV detector using tetrahydrofuran Characterization: 1H NMR (400 MHz, acetone-d ) δ (TMS, (THF) as the eluent. All data were relative to polystyrene 6 ppm): 7.37-7.39 (d, 2H), 7.46-7.54 (m, 4H), 7.59-7.61 (d, 2H), standards. Differential scanning calorimetric (DSC) analysis 7.64-7.70 (m, 2H), 7.78 (s, 2H), 8.37-8.39 (d, 2H). 19 F NMR was determined with TA Instrument DSC Q200 at a heating (376 MHz, acetone-d ) δ (TMS, ppm): -62.87 (s, 6F). 13 C NMR rate of 10 °C min -1 in nitrogen. Thermogravimetric analysis 6 (100 MHz, CDCl ) δ (TMS, ppm): 113.01, 118.56, 121.11, (TGA) was measured on a Netzsch TG 209F1 apparatus with a 3 121.91, 123.83, 126.04, 126.59, 126.86, 127.52, 128.01, heating rate of 10 °C min -1 in nitrogen and air atmosphere, 134.60, 134.79, 150.61, 152.05.