PREPARATION OF NANOCOMPOSITE BASED ON FUNCTIONALIZED GRAPHENE - PDF document

18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS PREPARATION OF NANOCOMPOSITE BASED ON FUNCTIONALIZED GRAPHENE NANOPLATELET AND EPOXY-ACRYLATE BIFUNCTIONAL POLYSILOXANES Quang-Trung Truong, Gwang Seok Song, and Dai Soo Lee * Division of Semiconductor and Chemical Engineering Chonbuk National Univeristy Jeonju, 561-756, South Korea * Corresponding author : daisoolee@chonbuk.ac.kr Keywords : graphene nanoplatelets, epoxy-acrylate bifunctional polysiloxanes, nanocomposite thermo-mechanical properties of NCs are discussed 1. Introduction in this paper. Graphene nanoplatelets (GNPs) based 2. Experimental nanocomposites (NC) are attracting attentions of 2.1 Synthesis and functionalization of graphene researchers because of their potential use in devices nanoplatelets and other electronic applications [1,2]. Most of the processes for the preparation of GNPs based NC 2.1.1. Synthesis of GICs and GNPs used graphene produced from oxidation method [3], GICs of NG with lithium was prepared by stirring a in which oxidative intercalation/exfoliation normally 20 g of NG (98 %, 50 mesh, Hyundai Coma Ind. Co., destroys sp 2 hybrids of graphitic carbon. Therefore a Korea) in a solution of 2.31 g (0.277 mol) of lithium reduction step is needed in order to restore the metal (99.5 %, Aldrich) dissolved in 100 ml oxides to graphenes exhibiting inherent properties of tetrahydrofurane (THF, 99 %, Aldrich) containing pristine graphenes. However the reduction process 35.5 g (0.27 moles) of naphthalene (98 %, Aldrich) could not fully restore graphitic structures and many at room temperature for 24 hrs in a closed vial. Then, defects are still existed on graphene sheets resulting the GICs was filtered through the filtering funnel in an electrical conductivity several orders of (0.2 µm pore size) under inert nitrogen environment magnitude lower than pristine graphene.[4] In order and washed several times with fresh THF to remove to develop graphene based NC with high electrical naphthalene. Ion-exchange induced intercalations as well as thermal conductivity, an alternative were carried out in a closed vial with stoichiometric production of “pristine” graphene is desirable. amount TMAB (99 %, Aldrich) in the presence of Our approach begins with natural graphite (NG) as THF as solvent. The vials were stirred magnetically graphene source. First, pristine GNP (p-GNP) was at room temperature for 12 hrs. The resulting prepared by microwave exfoliation of reductive product, GIC, was dried at 40 o C in convection oven graphite intercalation compound (GICs) of NG for 3 hrs. intercalated with organic tetramethyl ammonium p-GNPs were prepared by microwave irradiation of bromides (TMAB). Next, p-GNP was functionalized GICs in an oven (LG Electronics, 700 watt) for 2 with 4-aminobenzoic acid (BA) through Friedel- min under inert N 2 gas. A volume expansion of 200 Crafts acylation, resulting in the introduction of 4- ml/g was observed. aminobenzoyl groups on the egdes of graphene sheets. This functionalization could improve the 2.1.2 Functionalization of GNPs via Friedel-Crafts dispersion as well as physico-chemical interaction acylation Functionalization of GNP was followed the process between GNPs with polymer matrix. A reactive reported by Choi [5] as follows: polymer matrix based on epoxy-acrylate bifunctional p-GNPs (5.0 g, 0.42 mol) and 4-aminobenzic acid polysiloxanes (EABFPS) was synthesized with (5.0 g, 0.0364 mol, Aldrich) were introduced into unsaturated double bonds as reactive sites for 500 ml three necked round bottom glass reactor. grafting with graphene surfaces during the curing of Next, 200 g of polyphosphoric acid (83 % P 2 O 5 basis, nanocomposites. Hybrid of this polysiloxanes with Aldrich) was added and the mixture was cycloaliphatic epoxy and pristine and/or mechanically stirred at 500 rpm until homogenous functionalized GNPs was studied and electrical and mixture was obtained. Then, 50 g (0.5 mol) of

p phosphorous pentaoxide e was cau utiously add ded ev aporated usin ng rotary eva aporator at 6 60 ℃ , finally y m maintaining mechanical stirring. Th he reactor w was 0.0 04 wt % (bas sed on total c composite) c ationic at 130 o C f th hen heated in oil bath for 72 hrs, the cat talyst (Alum minium acetyl l acetonate, A Aldrich) and a re eaction mixt ture was cool led to the roo om temperat ture rad dical catalyst t (tert-butyl p perbenzoate) ) of 0.1 wt % % a and diluted with de-ion ized water. Functionaliz zed we ere added and d mixed by m mechanical s stirring. G GNPs (NH 2 -G GNPs) were collected by y filtering un nder Sa amples for th e tests were casted on Te eflon mold v vacuum suct tion, and r repeatedly w washed seve eral an d cured at 11 10 ℃ for 2 h hrs and additi ional 2 hrs at t ti imes with water until l neutral P PH, then w with 12 0 ℃ and fina ally post cur red at 150 ℃ for 3 hrs. water/ethanol w l mixture (1 1/1 v/v) seve eral times. T The o C OH re esulting pro oduct was d dried in vac cuum at 80 H 3 C Si CH 3 overnight. o CH 3 OC 2 H 5 n 1st step CH 3 C O CH H 3 2 2.2. Synthesis s of novel EA ABFPS + C 2 H 5 O Si OC 2 H 5 HO Si OH 5 n HO S i O Si O Si OH n n OC 2 H 5 CH 3 E EAFPS was s synthesized by two step non hydroly ytic CH 3 C O CH H 3 1 mol 4 mol 1 mol c condensation n (Scheme 1) ) as follows. TEOS H 3 C Si CH 3 OH-PDMS-561.96 g/e e mol) of hydro oxy terminat ated F First step: 50 0 g (0.044 m n OH O polydimethy p ylsiloxanes (OH valu ue of 112 23.9 O CH 3 OCH 3 2nd s step from Dow Corning) , 2 mgKOH/g, f m 2.364 g (0.0 011 Si OCH 3 H 3 CO Si O OCH 3 OCH 3 mol) of tetra aethoxyorth hosilicate (R Reagent gra ade, O m O 2 m mol O H 3 C Si CH 3 C 9 98 %, Aldr rich), and d 1000 ppm m of dibuty yltin OCH 3 CH 3 n O CH 3 OCH 3 O CH 3 C Si O Si O Si O O Si O Si n n dilaurate (98 d %, Aldrich) ) as catalyst were added d to O OCH 3 CH 3 O CH 3 OCH 3 O C H 3 C Si CH 3 C OCH H 3 th he round bo ottom three n necked flask k equipped w with CH 3 H 3 CO Si O n OCH H 3 O H 3 CO Si OCH 3 O nitrogen gas n inlet and d distillation c condenser,. T The 2 m mol 0 0 C re eaction flask k was immer rged in an oi il bath at 80 Mw = 5377.79 g/mo ol Epoxy EW = 2688.9 90 fo for 3 hrs. A After 3 hrs of reaction n, vacuum w was O a applied to th he flask for several hou urs in order r to Sc cheme1. Two o step synthes sis of EABF PS. re emove comp pletely ethan nol until no w weight loss w was 3. Results and discussion observed. o S Second step p: 5.48 g (0.022 mo l) of [2-(3 3,4- 3.1 1. Synthesis and function nalization of graphene e epoxycyclohe exyl)ethyl] trimethoxys silane (97 %, na noplatelets A Aldrich) an nd 5.524 g (0.022 mol) of 3- GN NPs were synthesize ed from N NG throug gh (t trimethoxysi ilyl) propyl m methacrylate e (ETCS, 98 %, int tercalation-m microwave exfoliation of GIC C. Aldrich) wer A re added to t the above re eaction mixtu ure. Ex xfoliation cou uld be obser rved employ ying Scannin ng out at 80 o C T The reaction was carried C for 8 hrs w with Ele ectron Mic croscope ( (SEM, SM M-5900) an nd continuous st c tirring under r reduced pr ressure until no Tr ansmission Electron M Microscope (TEM, JEM M- w weight loss w was observed d. 20 010). 2 2.3. Preparati ion of functio onalized g grapheme/EA ABFPS nanoc composites p-GNP NG N Matrix resin w M was a mixtur re of 60 wt % % of EABFP S, 26.67 wt % o 2 of cycloalipha atic epoxy re esin (Celloxi ide 2021p- Dicel 2 l Industry) a nd 13.33 wt % of ETCS. . The mixture i T is transparen nt even after c cure, the g 1.04 g/cm 3 . d density being Pristine and d functionaliz zed graphene disp g persion (0.1 w wt %) in eth anol was p prepared by u ultrasonicatio on at 200 wa atts for 5 hrs. C Calculated am mount of gra aphene disper rsion (by vol l %, 26 g/cm 3 ), an d density of GN NP was assum med to be 2.2 nd Fig g.1. SEM im mages of NG (scale bar 50 00 µm) and th he matrix res sin were mix xed in separa ted beakers mi icrowave exf foliated GNP P (scale bar 2 2 mm) and sonicated a d for 30 min. Then, solve ent were