Supporting information

Supramolecular Gel Lubricants Based on Amino acid

Derivative Gelators

Qiangliang Yu,a,b Dongmei Li a Meirong Cai,a* Feng Zhou,a* Weimin liua

a State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou

730000, China

b University of Chinese Academy of Sciences, Beijing 100049, China

Gly: 1H NMR (400 MHz, CDCl3, TMS) δ :4.78 (s, 1H), 4.44 (s, 1H), 4.17 – 3.91 (m, 4H), 3.18 (t, J = 7.1, 5.9 Hz, 2H), 1.68 – 1.59 (m, 2H), 1.53 – 1.44 (m, 2H), 1.41 – 1.21 (m, 27H), 0.90 (t, J = 13.7, 7.2 Hz, 6H). 13C NMR (100 MHz, CDCl3, TMS) δ: 171.32, 157.63, 65.56, 42.27, 40.46, 32.21, 31.93, 29.69, 29.66, 29.65, 29.57, 29.50, 29.36, 29.23, 28.55, 25.83, 22.69, 19.99, 14.11, 13.74. HRMS (ESI+) m/z: calcd for C23H46N2NaO3 [M+Na]+ 421.3411, found 421.3401.FTIR (KBr, cm-1): 3316.13, 2954.76, 2916.37, 2850.22, 1737.59, 1625.98, 1471.17, 1214.26.

L-Ala: 1H NMR (400 MHz, CDCl3, TMS) δ: 4.87 (d, J = 7.5 Hz, 1H), 4.40 (d, J = 10.4 Hz, 1H), 4.18 – 4.05 (m, 2H), 3.16 (t, J = 13.1, 6.2 Hz, 2H), 1.69 – 1.61 (m, 2H), 1.53 – 1.41 (m, 2H), 1.36 – 1.21 (m, 27H), 0.99 – 0.80 (m, 6H). 13C NMR (100 MHz, CDCl3, TMS) δ: 174.38, 157.23, 65.51, 48.93, 40.37, 32.21, 31.93, 29.69, 29.67, 29.66, 29.64, 29.57, 29.51, 29.36, 29.22, , 28.55, 25.82, 22.69, 20.00, 19.31, 14.11, 13.75. HRMS (ESI+) m/z: calcd for C24H48N2NaO3 [M+Na]+ 435.3571, found 435.3557. FTIR (KBr, cm-1): 3352.14, 2959.11, 2921.01, 2849.42, 1736.89, 1630.36, 1566.86, 1469.38, 1189.18.

L-Val :1H NMR (400 MHz, CDCl3, TMS) δ: 4.81 (s, 1H), 4.41 (s, 2H), 4.12 (s, 2H), 3.18 (s, 2H), 2.19 – 2.05 (m, 1H), 1.70 – 1.54 (m, 3H), 1.52 – 1.42 (m, 2H), 1.41 – 1.16 (m, 28H), 0.91 (q, J = 16.3, 12.1, 6.8 Hz, 12H). 13C NMR (100 MHz, CDCl3, TMS) δ: 172.43, 156.70, 64.30, 56.98, 39.41, 31.22, 30.91, 30.50, 28.68, 28.66, 28.64, 28.63, 28.56, 28.48, 28.34, 28.18, 27.57, 24.88, 21.67, 19.00, 18.00, 16.70, 13.09, 12.74. HRMS (ESI+) m/z: calcd for C26H52N2NaO3 [M+Na]+ 463.3887, found 463.3880. FTIR (KBr, cm-1): 3340.37, 2961.24, 2921.54, 2851.28, 134.90, 1636.36, 1583.09, 1466.44, 1399.93,1189.32.

L-Ile: 1H NMR (400 MHz, CDCl3, TMS) δ: 4.83 (d, J = 8.5 Hz, 1H), 4.47 (d, J = 20.1 Hz, 2H), 4.08 (t, J = 16.0 Hz, 2H), 3.13 (t, J = 16.9, 10.2 Hz, 2H), 1.77 – 1.56 (m, 4H), 1.49 (d, J = 33.7 Hz, 3H), 1.43 – 1.19 (m, 28H), 1.05 – 0.77 (m, 12H). 13C NMR (100 MHz, CDCl3,

TMS) δ: 174.70, 157.59, 65.39, 51.75, 42.36, 40.36, 32.24, 31.93, 29.63, 29.65, 29.58, 29.51, 29.35, 29.22, 28.54, 25.86, 24.87, 22.76, 22.12, 20.01, 14.10, 13.76. HRMS (ESI+) m/z: calcd for C27H54N2NaO3 [M+Na]+ 477.4035 found 477.4027. FTIR(KBr, cm-1): 3354.26, 2932.19, 2853.09, 1748.86, 1642.02, 1575.71, 1468.35, 1272.79,1173.90.L-phe: 1H NMR (400 MHz, CDCl3, TMS) δ: 7.30 – 7.27 (m, 1H), 7.22 (s, 2H), 7.14 – 7.10 (m, 2H), 4.75 (t, J = 9.7, 4.5 Hz, 2H), 4.35 (s, 1H), 4.13 – 3.98 (m, 2H), 3.23 – 2.98 (m, 4H), 1.62 – 1.56 (m, 2H), 1.48 – 1.40 (m, 2H), 1.36 – 1.23 (m, 27H), 0.92- 0.86 (t, J = 12.2 Hz, 6H). 13C NMR (100 MHz, CDCl3, TMS) δ: 172.83, 157.11, 136.37, 129.41, 128.44, 126.92, 65.54, 53.98, 40.33, 38.68, 32.19, 31.93, 29.70, 29.66, 29.60, 29.51, 29.36, 29.24, 28.50, 25.87, 22.69, 19.97, 14.11, 13.74. HRMS (ESI+) m/z: calcd for C30H52N2NaO3 [M+Na]+

511.3874 found 511.3870. FTIR (KBr, cm-1): 3322.33, 3240.29, 3063.88, 2919.41, 2850.16, 1736.88, 1684.84, 1469.90, 1183.62, 1126.05, 1037.93, 1013.18.

Figure S1-1.1HNMR of Gly.

Figure S1-2.13CNMR of Gly.

Figure S1-3. HRMS of Gly.

Figure S1-4. FTIR of Gly.

Figure S2-1.1HNMR of L-Ala.

Figure S2-2. 13CNMR of L-Ala.

Figure S2-3. HRMS of L-Ala.

Figure S2-4. FTIR of L-Ala.

Figure S3-1.1HNMR of L-Val.

Figure S3-2. 13CNMR of L-Val.

Figure S3-3. HRMS of L-Val.

Figure S3-4. FTIR of L-Val.

Figure S4-1.1HNMR of L-Ile.

Figure S4-2. 13CNMR of L-Ile.

Figure S4-3. HRMS of L-Ile.

Figure S4-4. FTIR of L-Ile.

Figure S5-1.1HNMR of L-Phe.

Figure S5-2. 13CNMR of L-Phe.

Figure S5-3. HRMS of L-Phe.

Figure S5-4. FTIR of L-Phe.

Figure S6-1. COSY of L-Ile.

Figure S6-2. HMBC of L-Ile.

Figure S6-3. HMQC of L-Ile.

Figure S7. (a) gelation process of 3 wt % L-phe in PAO10, (b) Digital pictures of gels

with different L-phe concentrations in PAO10, (c) Optical micrograph of 3 wt % L-

phe in PAO10 gel, and (d) Polarized micrograph 3 wt % L-phe in PAO10 gel.

Table S1. Gelation of different solvents. a

SolventsLMWG

1 Gly 2 L-Ala 3 L-Val 4 L-Leu 5 L-pheethyl acetate P p S S Sbutyl acetate P p S S S

acetonitrile G（1.0） p SG（0.9） G（0.7）

cyclohexane G（0.9） G（0.8） S SG（0.9）

petroleum ether G（0.9） G（0.9） S SG（0.6）

n-butyl alcohol P p S S Sethyl alcohol P S S S Sisopropanol P S S P Sacetone P S S S Schloroform S S S S Sdichloromethane P S S S Sdiethyl ether S p S S PTHF S S S S S1, 4 - dioxane G (2.0) S S S Sa G: gel. S: soluble. PG: partially gel. TG: transparent gel. P: precipitate

Table S2. The gel–sol transition temperature and thermal properties of gel lubricants.

base oil gelTg-

s(oC)Td(oC)

TG temperature °C / per weight loss

10% 30% 50%PAO 10@3% L-phe 56.1 243.10 262.83 291.23 314.83PAO 10@4% L-phe 61.5 259.24 282.41 319.58 340.58PAO 10@5% L-phe 62.2 264.80 285.38 322.18 345.18PAO 10@10% L-phe 72.3 293.20 301.80 346.80 373.70

Figure S8. Shear rate dependencies of viscosity for PAO10 gel lubricants with

different concentration L-phe.

Figure S9. Step strain measurement of the PAO10 gel lubricants with different

concentration L-phe, step strain was a continuous measurement (three cycles).

Figure S10. The 3D optical microscopic images of wear tracks corresponding to

500SN (a), 500SN@1%L-phe (b), 500SN@2%L-phe (c), 500SN@3%L-phe (d) and

500SN@4%L-phe (e). Note that the Z-scales are different.

Figure S11 SEM morphologies of worn surfaces lubricated by PAO10 and gel with

different L-phe concentration: (a, a’) PAO10, (b, b’) 1% L-phe, (c, c’) 2% L-phe, (d,

d’) 3% L-phe, and (e, e’) 4% L-phe (magnification on the above is 80×, and on the

below is 400×; load, 200 N; stroke, 1 mm; frequency, 25 Hz; duration, 30 min;

temperature, 25 oC).

Tribological test

The friction and wear test was performed on a Optimol SRV-IV oscillating

reciprocating friction and wear tester, using a 10 mm in diameter, AISI 52100 steel

ball sliding against the lower stationary steel disk (ø 24mm-7.9 mm, AISI 52100 steel,

hardness of approximately (66-68 HRC) ). The tribological properties of the 500SN

gels (3% Gly, 3% L-Ala, 3% L-Val and 3%L-Ile) and PAO10 gels (3% Gly, 3% L-

Ala, 3% L-Val and 3%L-Ile) at RT and 200 N were investigatedand shown in the

Figures S10. It was found that all gel lubricants have better lubricating properties than

the base oils.

Figure S12. Evolution of friction coefficient/time of the lower disks lubricated by

500SN and PAO10 gel lubricant with different gelator.(A, blank lubricant oil, B.

3%Gly as gelator, C.3% L-Ala as gelator, D. 3% L-Val as gelator, E.3% L-Ile as

gelator. load, 200 N; stroke, 1 mm; frequency, 25 Hz; duration, 30 min; temperature,

25 oC).

Scanning electron microscope analysis

After the friction and wear test (with amplitude of 1 mm, frequency of 25 Hz and

test duration of 30 min), scanning electron microscope (SEM) study was conducted to

examine the morphologies of the worn surfaces of the wear scars. The analysis was

performed on a JSM-5600LV scanning electron microscope. The magnification on the

above is 80× and the below is 400×. The SEM of wear spot lubricated of these gel

lubricants and as comparison with blank 500SN and PAO10 were shown in Figures

S11 and S12(supporting information), respectively. It is clearly seen that the wear

scars on the surfaces lubricated by all gel lubricants are slighter than that lubricated by

blank 500SN and PAO10.

Figure S13. SEM morphologies of worn surfaces lubricated by 500SN and 500SN gel

lubricant with different gelator: (a, a’)500SN, (b, b’) 3% Gly, (c, c’) 3% L-Ala, (d, d’)

3% L-Val, and (e, e’) 3% L-Ile (magnification on the above is 80×, and on the below

is 400×; load, 200 N; stroke, 1 mm; frequency, 25 Hz; duration, 30 min; temperature,

25 oC).

Figure S14. SEM morphologies of worn surfaces lubricated by PAO10 and PAO10

gel lubricant with different gelator: (a, a’)500SN, (b, b’) 3% Gly, (c, c’) 3% L-Ala, (d,

d’) 3% L-Val, and (e, e’) 3% L-Ile (magnification on the above is 80×, and on the

below is 400×; load, 200 N; stroke, 1 mm; frequency, 25 Hz; duration, 30 min;

temperature, 25 oC).

Figure S15 SEM morphologies of worn surfaces lubricated by PAO10 (a), gel with

3% L-phe (b), Li-base grease (c), Li-base grease with 2% MoS2 (d) and 400x

magnification images on wear track (a’~d’); load, 200 N; stroke, 1 mm; frequency, 25

Hz; duration, 30 min; temperature, 25 ºC).

Figure S16 (a)Fe2p, (b) C1s and (c) O1s of the worn surfaces lubricated by PAO10,

gel with 3 wt % L-phe and neat L-phe.