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1 Electonic upplementay Mateial (EI) fo Geen Chemisty. This jounal is The Royal ociety of Chemisty Electonic upplementay Infomation Cack healing and eclaiming of vulcanized ubbe by tiggeing eaangement of inheent sulfu cosslinked netwoks Hong Ping Xiang, a Hu Jun Qian, b Zhong Yuan Lu, b Min Zhi Rong *a and Ming Qiu Zhang *a a Key Laboatoy fo Polymeic Composite and Functional Mateials of Ministy of Education, GD HPPC Lab, chool of Chemisty and Chemical Engineeing, un Yat-sen Univesity, Guangzhou 2, P. R. China. cesmz@mail.sysu.edu.cn and ceszmq@mail.sysu.edu.cn. b tate Key Laboatoy of Theoetical and Computational Chemisty, Institute of Theoetical Chemisty, Jilin Univesity, Changchun 23, China Detemination of equilibium constant and kinetic paamete of model disulfide metathesis Fo the following disulfide metathesis in equilibium, A---A + B---B A---B, the equilibium constant, K eq, was calculated fom: K eq 2 A Beq A A eq B B eq whee [A---A] eq and [B---B] eq denote equilibium concentations of eactants A---A and B---B, while [A---B] eq denotes equilibium concentation of poduct A---B. upposing disulfide metathesis follows the fist- o second-ode kinetics: 1 ln 1 x kt (fist ode kinetics) 1 1 x kt (second ode kinetics) whee x is convesion, k ate constant and t eaction time. Linea fit of the data offes ate constant at a given tempeatue. Finally, activation enegy, E a, can be calculated fom Ahenius equation based on the elationship between k and T: /RT k Ae E a Detemination of densities of sulfu cosslinks [1-4] To detemine the pecentage of sulfu cosslinks in the total numbe of cosslinks of vulcanized ubbe, selective scission of specific cosslinks in association with cosslinking density 1

2 measuement was applied. Fistly, the vulcanizate was teated with.4m popanethiol in pipeidine at ºC fo 6 h to cleave only the polysulfidic cosslinks. Then, the cosslinking density of the teated vulcanizate was measued by equilibium swelling method (see below). Compaison of the cosslinking densities of the vulcanizate befoe and afte the teatment allowed the calculation of the contibution of polysulfidic cosslinks to the total degee of cosslinks. imilaly, the concentation of both polysulfide and disulfide cosslinks was estimated by teating the vulcanizate with 1M 1-hexanethiol in pipeidine at ºC fo 48 h to cleave polysulfide and disulfide cosslinks. As a esult, the individual contibution of disulfide cosslinks was obtained by subtacting the concentation of polysulfidic cosslinks fom that of polysulfide and disulfide cosslinks. To measue cosslinking density, vulcanized samples (~. g) wee immesed in toluene to swell at ºC fo 72 h. The swollen samples wee weighed afte emoval of suface liquid with filte pape. Then the swollen samples wee died at ºC in vacuum to constant weight and weighed again. The cosslinking density pe unit volume,, was calculated fom Floy-Rehne equation: 2 ln(1 ) 1/ 3 (. ) s m m m s s whee v is the volume faction of ubbe in the swollen sample, v s is the mola volume of the solvent, m is the weight of the ubbe netwok afte dying, m s is the weight of solvent absobed at equilibium, is the density of ubbe, s is the density of solvent, is the Floy-Huggins inteaction paamete fo polybutadiene ubbe-toluene system taken as a constant (.36). On the basis of the cosslinking densities, concentation of polysulfide cosslinks, x % (x>2), and total concentation of polysulfide and disulfide cosslinks, x1 % (x2), can be known by: t x %( x 2) % t x %( x 2) 1 % 2

3 whee v is the cosslink density of the vigin sample, v t is the cosslink density of the sample teated by popanethiol, v t1 is the cosslink density of the sample teated by hexanethiol Toque [Nm] Contol 1 Contol 2 VR-H.2. Time [min] Fig. 1 Rheogaphs of the ubbes cued at 1 ºC. The chaacteistic t, the optimum vulcanization time equied fo eaching specific toque value which is the sum of minimum toque and % of the diffeentials between maximum and minimum toque. Fig. 2 canning electon micoscopic (EM) micogaph of typical factued suface of CuCl 2 /polybutadiene ubbe (CuCl 2 content = 1 ph), which was compounded unde the same conditions as VR-H. Enegy dispesive spectoscopy (ED) image of typical factued suface of VR-H using coppe as the indicato element. 3

4 Mola faction Reaction time [min] HEED HED DED HED-DED-RT #9 RT:.33 AV: 1 B: , NL: 4.23E OH Fig. 3 Time dependences of mola factions of the disulfides in equimola mixtue of HED and DED detemined fom HLPC chomatogams in Fig. 1 ( ºC, acetonitile,. mol% CuCl 2 ). Mass spectum of the metathesis poduct HEED. The signal at 138 is a molecula ion peak, just half of the sum of 4 (HED) and half of 122 (DED). The ion peaks at 94, 79 and 66 belong to the fagments of ---C 2 H, ---CH 2, and ---, espectively. 4

5 .6 DED EPD DPD. o C o C o C o C Mola faction Reaction time [min] EPD DED DPD DED-DPD #792 RT: 8.23 AV: 1 B: , NL:.73E (c) Fig. 4 HLPC analysis of equimola mixtue of DPD and DED collected at diffeent tempeatues (3 h, n-heptane,. mol% CuCl 2 ). Hee, DPD eplaces HED used in (Fig. 1) because the latte does not dissolve in n-heptane. Time dependences of mola factions of the disulfides in equimola mixtue of DPD and DED detemined fom HLPC chomatogams at ºC. (c) Mass spectum of the metathesis poduct ethyl popyl disulfide (EPD). DED DPD C C Fig. HPLC analysis of equimola mixtue of DED and DPD in acetonitile at ºC fo h and in n-heptane ºC fo 1 h.

6 Mola faction mol%. mol%. mol% Mola faction :1, 2:1 1:2, 3:1 1: Reaction time [min].34 1 Reaction time [min] Fig. 6 Time dependences of mola factions of HEED poduced fom disulfide metathesis between HED and DED at ºC in acetonitile. Effect of CuCl 2 dosage on convesion of equimola HED and DED. Effect of initial mola atio of HED to DED on convesion (CuCl 2 :. mol%). Table 1. Effect of initial mola atio of eactants on K eq in acetonitile at ºC * [HED] o :[DED] o [HED] o [DED] o [HED] eq [DED] eq [HEED] eq K eq 1: : : : : *[HED] o and [DED] o ae initial concentations of HED and DED. [HED] eq, [DED] eq and [HEED] eq ae equilibium concentations of HED, DED and HEED. Unit of the concentations: mmol L -1. Content of CuCl 2 :. mol%. Table 2. Effect of tempeatue on K eq in acetonitile* T (ºC) [HED] o [DED] o [HED] eq [DED] eq [HEED] eq K eq *Content of CuCl 2 :. mol%. 6

7 Table 3. Effect of dosage of CuCl 2 on K eq in acetonitile at ºC Dosage (mol %) [HED] o [DED] o [HED] eq [DED] eq [HEED] eq K eq Table 4. Effect of tempeatue on K eq in n-heptane* T (ºC) [DPD] o [DED] o [DPD] eq [DED] eq [EPD] eq K eq *Content of CuCl 2 :. mol%. ln(1/(1-x)) o C - o C - o C - o C o C k=8.18x -3 dm 3 mol -1 s -1 (R 2 =.982) k=.81x -3 dm 3 mol -1 s -1 (R 2 =.994) k=4.7x -3 dm 3 mol -1 s -1 (R 2 =.994) k=4.3x -3 dm 3 mol -1 s -1 (R 2 =.977) k=2.97x -3 dm 3 mol -1 s -1 (R 2 =.3). Time [min] 1/(1-x) C -C -C -C C k=1.x -2 dm 3 mol -1 s -1 (R 2 =.991) k=7.2x -3 dm 3 mol -1 s -1 (R 2 =.997) k=.66x -3 dm 3 mol -1 s -1 (R 2 =.994) k=4.97x -3 dm 3 mol -1 s -1 (R 2 =.983) k=3.16x -3 dm 3 mol -1 s -1 (R 2 =.1) 1. Time [min] E a = 22.3 kj/mol (R 2 =.991) lnk /T [ 3 K -1 ] Fig. 7 Linea egession of convesion, x, vesus time, t, of disulfide metathesis between HED and DED with. mol% CuCl 2 in acetonitile accoding to fist-ode and second-ode kinetics. The highe egession coefficients of the plots in suggest that the second-ode kinetics eaction should be moe easonable. Theefoe, the activation enegy is estimated using k values povided by the second-ode kinetics. 7 (c)

8 ln(1/(1-x)) o C o C 3 o C o C k=1.12x -3 dm 3 mol -1 s -1 (R 2 =.8) k=4.79x -4 dm 3 mol -1 s -1 (R 2 =.974) k=3.23x -4 dm 3 mol -1 s -1 (R 2 =.9) k=1.76x -4 dm 3 mol -1 s -1 (R 2 =.7) Time [min] 1/(1-x) o C o C 3 o C o C k=1.24x -3 dm 3 mol -1 s -1 (R 2 =.961) k=.7x -4 dm 3 mol -1 s -1 (R 2 =.9) k=3.4x -4 dm - mol -1 s -1 (R 2 =.9) k=1.6x -4 dm 3 mol -1 s -1 (R 2 =.7) Time [min] E a = kj/mol (R 2 =.996) lnk /T [ 3 K -1 ] (c) Fig. 8 Linea egession of convesion, x, vesus time, t, of disulfide metathesis between DED and DPD with. mol% CuCl 2 in n-heptane accoding to fist-ode and second-ode kinetics. The highe egession coefficients of the plots in suggest that the second-ode kinetics eaction should be moe easonable. Theefoe, the activation enegy is estimated using k values povided by the second-ode kinetics. 8

9 RT: Time (min) NL: 2.E7 TIC F: M DAD- DPD DAD-DPD # RT: 9.1 AV: 1 B: , NL: 6.41E Fig. 9 GC-M analyses of the metathesis between DAD and DPD with. mol% CuCl 2 in n-heptane at ºC fo 3 h. Gas chomatogaph of the eaction system, and mass spectum of the metathesis poduct. The peak at 9.1 min is assigned to be allyl popyl disulfide, because the molecula ion peak ( 148) is just half of the sum of DPD ( 1) and DAD ( 146). DBD-DMT #844 RT: 8.1 AV: 1 B: , NL: 1.E DBD-DMT #1494 RT: AV: 1 B: , NL: 8.41E Fig. Mass specta of the metathesis poducts between DBD and DMT with. mol% CuCl 2 in n-heptane at ºC fo 3 h. Because scission of DMT would offe two species (CH 3 -and CH 3 ---) to eact with DBD at the same time, two metathesis poducts appea, i.e. methyl butyl disulfide ( 136) and methyl butyl tisulfide ( 168). 9

10 DMT-CuCl2 #97 RT: 3.23 AV: 1 B: , NL: 2.89E DMT-CuCl2 #1384 RT: 7.44 AV: 1 B: , NL: 3.64E Fig. 11 Mass specta of the metathesis poducts of DMT with. mol% CuCl 2 in acetonitile at ºC fo 1 h. Dimethyl disulfide ( 94) and dimethyl tetasulfide ( 8). RT: RT: NL: 2.89E7 TIC F: M DED- DPD- DBD NL: 2.E7 TIC F: M DED- DPD- DBD Time (min) Time (min) DED-DPD-DBD-1 #393 RT: 8. AV: 1 B: , NL: 1.9E (c) DED-DPD-DBD-1 #13 RT: 9.67 AV: 1 B: 8.-9., NL:.71E (d)

11 DED-DPD-DBD-1 #623 RT: 11. AV: 1 B: , NL: 2.34E (e) Fig. 12 Dynamic evesibility of disulfide metathesis in acetonitile catalyzed by. mol% CuCl 2 at ºC. Gas chomatogaph of metathesis between DED and DPD in equilibium. Gas chomatogaph of metathesis among DED, DPD and DBD in equilibium. Equimola DBD was added when the metathesis between DED and DPD had eached the equilibium. (c) Mass spectum of the metathesis poduct (ethyl popyl disulfide (EPD)) between DED and DPD. (d) Mass spectum of the metathesis poduct (ethyl butyl disulfide (EBD)) between DED and DBD. (e) Mass spectum of the metathesis poduct (popyl butyl disulfide (PBD)) between DPD and DBD. The atios of DED:EPD:DPD:EBD:PBD:DBD attained fom the nomalized peak aeas ae 11:21:12:23:22:12, nea the statistical values. DED DPD PPh 3 EPD 12h 2h Fig. 13 HLPC analysis of disulfide metathesis between equimola HED and DED at ºC catalyzed by 1 mol% PPh 3. Because of the high evapoation ate of acetonitile and n-heptane at ºC, the eaction poceeded in the absence of any solvent. 11

12 with antioxidant, 2 h DED EPD DPD with antioxidant, min HED HEED DED a with antiage, 2 h b with antiage, min Fig. 14 HLPC analysis of disulfide metathesis between equimola DED and DPD in the pesence of mol% antioxidant tis(2,4-di-tet-butylphenyl)phosphate, and equimola HED and DED in the pesence of mol% antiage poly(1,2-dihydo-2,2,4-timethyl-quinoline). The eactions ae caied out in acetonitile at ºC with. mol% CuCl h 12 h HED HEED TEMPO DED Equimola mixtue of HED and DED in acetonitile with. mol% CuCl 2 and 1 mol% TEMPO Acetonitile solution of. mol% CuCl 2 and 1 mol% TEMPO 1. h 1 h min min min G HED DED h TEMPO G 3 h 1 h (c) (d) Fig. HLPC analysis of disulfide metathesis between equimola of HED and DED in acetonitile with. mol% CuCl 2 and 1 mol% TEMPO at ºC. All the chemicals ae mixed at 12

13 the same time. ER spectum of the eaction system in collected at 24 h in compaison with that of a efeence system, which has the same compositions as but the disulfide mixtues ae eplaced by isopycnic acetonitile. (c) Integation of. (d) HLPC analysis of the eaction system having the same components as, but CuCl 2 and TEMPO ae fistly mixed in acetonitile unde stiing fo min pio to the addition of acetonitile solution of HED and DED. Benzoquinone mol% CuCl, o C, 1 h HEED HED DED Benzoquinone Ethyl acetate HCl H 2 O Contol HED HEE DED 2 mol% CuCl, o C, 24 h 1 mol% CuCl, o C, 24 h Fig. 16 Effect of diffeent inhibitos ( mol %) on disulfide metathesis between equimola HED and DED in acetonitile fo min with. mol% CuCl 2 at ºC. HLPC analysis of disulfide metathesis between equimola HED and DED in acetonitile catalyzed by CuCl unde diffeent conditions. Weight [%] Contol 1 Contol 2 VR-H Tempeatue [ o C] Fig. 17 Themal decomposition behavios of the cued ubbes. 13

14 HED Cu 2 DED Cu Cu 2 O CuO Fig. 18 HLPC analysis of disulfide metathesis between equimola HED and DED in acetonitile at ºC fo 24 h catalyzed by mol% Cu 2, Cu, Cu 2 O and CuO, espectively. Fig. 19 Identification of non-contact egions on the combined factued sufaces. Fistly, paied tensile factued specimens wee cooled down by liquid nitogen. Then, one pat of the pai was unifomly dyed with ed oil paint. Finally, the dyed fagment was bought into contact with its undyed countepat. When the two halves of the boken specimen wee sepaated again, the unstained potions on the oiginally undyed fagment (efe to the photos shown above) epesent the non-contact egions on the combined factued sufaces. Fig. ED images of the factue suface of contol vulcanized ubbe without i-69 using a) coppe and b) sulfu as the indicato elements. Hee the vulcanized ubbe has the same composition as VR-H but excludes i-69. The attached scale bas epesent 1 mm in length. 14

15 Fig.21 Model expeiment showing impoved mobility of CuCl2 with the help of i-69. EM and (b-f) ED images of side faces of two pieces of contacted ubbes (left: VR-H; ight: polybutadiene). The VR-H in (a1-f1) contains i-69, while that in (a2-f2) does not. The indicato elements of ED images include coppe, (c) chloine, (d) silicon, (e) oxygen, and (f) sulfu. Afte teatment at 1 ºC fo 48 h, CuCl2 successfully migates fom VR-H to polybutadiene with the aid of i-69, and is dispesed in the latte (efe to b1-f1). Compaatively, only a few CuCl2 can migate fom VR-H to polybutadiene because of lack of i-69 (efe to b2-f2). The attached scale bas epesent 1 mm in length.

16 tess [MPa] VR-H (vigin, with i-69) VR-H (healed, with i-69) VR-H (vigin, without i-69) VR-H (healed, without i-69) tain [%] Fig. 22 Typical tensile stess-stain cuves of vigin and healed VR-H specimens in compaison with those of vigin and healed contol vulcanized ubbe without i-69. Healing tempeatue: 1 ºC; healing time: 12 h. Notes and efeences 1 P. Posadas, A. Fenández, J. Baseo, J. L. Valentín, A. Macos, A. Rodíguez and L. González, J. Appl. Polym. ci., 7, 6, L. González, A. Rodíguez, A. Del Campo and A. Macos-Fenández, J. Appl. Polym. ci., 2,, J. L. Valentín, A. Rodíguez, A. Macos-Fenández and L. González, J. Appl. Polym. ci., 4, 93, R. L. Fan, Y. Zhang, F. Li, Y. X. Zhang, K. un and Y. Z. Fan, Polym. Test., 1,,