Supplemental Materials
Stimuli-Degradable Cross-Linked Polymers Synthesized by
Radical Polymerization Using A Size-Complementary
[3]Rotaxane Cross-Linker
Keisuke Iijima, Yasuhiro Kohsaka, Yasuhito Koyama, Kazuko Nakazono, Satoshi Uchida, Shigeo Asai and
Toshikazu Takata*
Department of Organic and Polymeric Materials, Tokyo Institute of Technology
2-12-1 (H-126), Ookayama, Meguro, Tokyo 152-8552, Japan
*Corresponding author. Tel.: +81-3-5734-2898, Fax: +81-3-5734-2888
E-mail address: ttakata@polymer.titech.ac.jp (T. Takata).
Contents
I. Experimental Section
II. Original spectra (1H NMR, 13C NMR, and IR spectra) of all new monomers.
I. Experimental Section
Synthetic Procedure.
Synthesis of DB24C8 possessing a vinyl group 3.
Scheme S1.
DB24C8 with a vinyl group 3 was synthesized as shown in Scheme S1. To a solution of monohydroxy DB24C8 (1.92 g,
3.03 mmol) in dichloromethane (45.0 mL) was added 2-isocyanatoethyl methacrylate (1.35 mL, 9.54 mmol) and dibutyltin
dilaurate (183 L, 0.297 mmol) at 0 °C and the mixture was stirred for 48 h at ambient temperature. The mixture was
concentrated to 10 mL, then precipitated to 100 mL of hexane. The residual mixture was filtered and then subjected to
purification by a silica gel column chromatography (hexane:AcOEt = 2:3 → AcOEt) to give the titled compound as a white
solid (2.45 g, 2.91 mmol) in 96% yield; m.p. 99.7–101.7 °C; 1H NMR (400 MHz, CDCl3, 298 K)  6.91–6.82 (m, 7H, ),
6.10 (s, 1H, D), 5.58 (s, 1H, D), 5.00 (s, 2H, A) 4.23 (t, J = 5.1 Hz, 2H, C), 4.17–4.11 (m, 8H, ), 3.93–3.91 (m, 8H, ),
3.86–3.75 (m, 8H, ), 3.53–3.49 (m, 2H, B), 1.93 (s, 3H, E) ppm;
13C
NMR (100 MHz, 298 K, CDCl3):  167.1, 156.3,
148.9, 148.7, 135.8, 129.3, 126.0, 121.5, 121.3, 114.2, 113.9, 113.5, 71.2, 71.1, 69.8, 69.7, 69.3, 69.2, 66.7, 63.6, 40.0,
18.2 ppm; IR (KBr) 3315, 2923, 2871, 1715, 1691, 1546, 1505, 1449, 1256, 1173, 1132, 1107 cm –1; FAB HRMS: calc’d
for C32H43NO12 [M]+ 633.2785, Found 633.2807.
Synthesis of size-complementary [3]rotaxane 4
Scheme S2.
Size-complementary [3]rotaxane 4 was synthesized as shown in Scheme S2.
Axle 1 (0.21 g, 0.60 mmol) was mixed
with wheel 3 (0.38 g, 0.60 mmol) in dichloromethane (3.0 mL) and the mixture was stirred for 3 h to form a
pseudorotaxane. Then, to the mixture was added methylene diphenyl diisocyanate (75 mg, 0.45 mmol) and dibutyltin
dilaurate (23 L, 37 mol) at 0 °C. After stirring for 12 h at ambient temperature, the solvent was removed under reduced
pressure. The residual mixture was subjected to purification by a silica gel column chromatography (CHCl 3:MeOH = 30:1)
to give the titled compound as a white solid (0.47 g, 0.21 mmol) in 71% yield; m.p. 110.4–111.7 ºC; 1H NMR (400 MHz,
298 K, CDCl3)  7.59 (d, J = 7.6 Hz, 4H, d), 7.36 (br, 4H, NH2+), 7.31 (d, J = 7.6 Hz, 4H, e), 7.04 (d, J = 8.6 Hz, 4H, g),
6.93–6.78 (m, 18H, , H and N–H), 6.11 (s, 2H, D), 5.56 (s, 2H, D), 5.44 (br, 4H, N–H), 5.09 (s, 4H, f), 5.04–5.00 (m, 4H,
A), 4.65(br, 4H, c), 4.30–4.13 (m, 20H,  and C), 3.82–3.74 (m, 18H,  and i), 3.52–3.26 (m, 20H,  and B), 3.00 (br, 4H,
b), 1.91 (s, 6H, E), 0.76 (s, 18H, a) ppm;
13C
NMR (100 MHz, 298 K, CDCl3):  167.3, 156.5, 153.5, 147.5, 147.4, 147.2,
137.8, 136.2, 136.0, 135.8, 131.1, 130.8, 130.0, 129.1, 127.7, 126.0, 121.7, 121.2, 118.7, 112.7, 112.6, 112.4, 77.2, 70.9,
70.8, 70.4, 70.2, 70.1, 68.4, 68.3, 68.2, 66.1, 65.8, 63.6, 61.2, 53.4, 40.5, 40.4, 30.1, 28.3, 18.2 ppm; IR (KBr) 3401,
3485, 2952, 1718, 1595, 1517, 1253, 1223, 1127, 1101, 1056, 843, 558 cm–1; ESI–TOF MS: calc’d for C105H140N6O282+
[M–2PF6–]2+ 966.9869, Found 966.9885.
Synthesis of 3,5-dimethylphenyl group terminated [3]rotaxane 5
3,5-Dimethylphenyl group terminated [3]rotaxane 5 was synthesized as shown in Scheme S2.
Axle 2 (60 mg, 0.15
mmol) was mixed with wheel 3 (95 mg, 0.15 mmol) in dichloromethane (0.75 mL) and the mixture was stirred for 3 h to
form a pseudorotaxane. Then, to the mixture was added methylene diphenyl diisocyanate (19 mg, 75 mol) and dibutyltin
dilaurate (5.7 L, 9.2 mol) at 0 °C. After stirring for 12 h at ambient temperature, the solvent was removed under
reduced pressure. The residual mixture was subjected to purification by HPLC to give the titled compound as a white
solid (100 mg, 43 mol) in 29% yield; m.p. 170.7–172.0 ºC; 1H NMR (400 MHz, 298 K, CDCl3)  7.52 (br, 4H, d), 7.35 (br,
4H, e), 7.24–7.17 (m, 8H, f and g), 7.05–7.03 (m, 6H, ), 6.88–6.67 (m, 14H,  and NH2+), 6.10 (s, 2H, D), 5.55 (s, 2H, D),
5.50 (br, 2H, N–H), 5.02 (s, 4H, f), 5.00–4.93 (m, 4H, A), 4.57 (br, 4H, b), 4.47 (br, 4H, c), 4.22–4.20 (t, J = 5.2 Hz, 4H, C),
4.08–4.01 (m, 16H, ), 3.82–3.72 (m, 18H,  and i), 3.50–3.42 (m, 20H,  and B), 2.15 (s, 12H, a), 1.90 (s, 6H, E) ppm;
13C
NMR (100 MHz, 298 K, CDCl3):  167.2, 156.5, 153.5, 147.5, 147.4, 147.2, 138.4, 137.6, 136.3, 136.1, 136.0, 131.6,
131.3, 130.6, 130.0, 129.6, 129.3, 128.0, 126.6, 126.1, 121.6, 121.2, 118.9 (2C), 112.6, 112.3, 70.7, 70.3, 70.2, 68.3,
68.2, 68.1, 66.3, 65.9, 63.7, 52.6, 52.3, 40.6, 40.2, 21.2, 18.3 ppm; IR (KBr) 3399, 3158, 3068, 2926, 1719, 1596, 1517,
1458, 1315, 1253, 1170, 1125, 1104, 1059, 953, 843, 558cm –1; ESI-TOF MS: calc’d for C113H140N6O282+ [M–2PF6–]2+
1014.9869, Found 1014.9869.
Typical procedure for preparation of rotaxane cross-linked polymer RCP1–4.
Scheme S3.
Rotaxane cross-linked polymers were prepared by the copolymerization of vinyl monomer with cross-linker 4 or 5 as
shown in Scheme S3.
Methyl Methacrylate (0.51 mL, 4.8 mmol), azobisisobutyronitrile (AIBN, 7.9 mg, 48 mol), and
[3]rotaxane 4 (108 mg, 48 mol) were dissolved in N,N-dimethylformamide (0.48 mL), and then degassed via freeze thaw
technique three times. The mixture was replaced to a polypropylene sealed tube, and then the tube was warmed at 60 °C
for 12 h. The obtained gel was purified by swelling in chloroform and methanol repeatedly, and gently dried at room
temperature for 1 d and in vacuo for 1 d to give the corresponding polyrotaxane network RCP-1 (0.576 g, 97%).
According to the same procedure, RCP-2 was obtained quantitatively from methyl methacrylate (0.26 mL, 2.4 mmol) and
AIBN (3.9 mg, 24 mol) in N,N-dimethylformamide (0.24 mL), and RCP-3 (0.64 g, 80%) was obtained from n-butyl
acrylate (0.62 g, 4.8 mmol) and AIBN (7.9 mg, 48 mol) in N,N-dimethylformamide (0.48 mL). RCP-4 (90 mg, 73%) was
also obtained from methyl methacrylate (0.11 mL, 1.0 mmol), AIBN (1.6 mg, 10 mol), and [3]rotaxane 5 (23 mg, 10
mol) in N,N-dimethylformamide (0.1 mL).
Glass transition temperature (Tg) of the resulted network polymers was determined by DSC as shown in Figure S1.
RCP–1: a white solid; Td5 413 °C; Tg 58.6 °C; IR (KBr) 3431, 2996, 2951, 1730, 1654, 1517, 1479, 1449, 1433, 1389,
1270, 1243, 1194, 1150, 1062, 990, 965, 844, 752, 560 cm –1.
RCP–2: a white solid; Td5 339 °C; Tg 55.2 °C; IR (KBr) 3431, 3192, 2996, 2951, 1732, 1596, 1518, 1450, 1389, 1242,
1149, 1059, 989, 963, 844, 752, 667, 588, 484 cm –1.
RCP–3: a white solid; Td5 358 °C; Tg –46.2 °C; IR (KBr) 3444, 2960, 2937, 2872, 1736, 1456, 1397, 1373, 1253, 1166,
1121, 1063, 945, 846, 742 cm –1.
RCP–4: a white solid; Td5 340 °C; Tg 118.3 °C; IR (KBr) 3442, 2998, 2952, 1732, 1521, 1489, 1450, 1389, 1271, 1244,
1195, 1149, 1059, 988, 845, 752 cm -1.
Figure S1. DSC profiles of RCP 1–4.
Preparation of covalently cross-linked network polymer
Butyl acrylate (1.20 g, 9.30 mmol), Irgacure 500 (3.0 mg), and diethyleneglycol dimethacrylate (6.0 L, 23 mol) were
dissolved in N,N-dimethylformamide (0.2 mL), and then degassed via freeze thaw technique three times. The mixture was
replaced to a glass template, and then the template was UV-irradiated for 10 min at room temperature. The obtained gel
was purified by swelling in chloroform and methanol repeatedly, and gently dried at room temperature for 1 d and in
vacuo for 1 d to give the chemical gel (0.852 g, 70%).
Dynamic mechanical analyses of RCP–3 and the chemical gel.
Dynamic mechanical properties of RCP–3 and the chemical gel were evaluated in a temperature range of –100 to 150 °C
by the use of an IT-DVA200s apparatus (ITK, Japan). The measurement was conducted in the oscillatory tensile mode at
a frequency of 10 Hz and a heating rate of 5 °C/min. The dimensions of a rectangular specimen were 5.0 mm in width
and 0.12 mm in thickness, and the distance between clamps was 10 mm. The glass transition temperature (Tg) of RCP–3
were evaluated from the peak of loss elastic modulus (E”) as –44.1 ºC. The dynamic mechanical analysis (DMA) profile of
RCP–3 was shown in Figure S2. It was found that the plateau region of tensile storage modulus
(E’) between 0–150 ºC
clearly indicated the network structure of RCP–3. The DMA profile of the chemical gel was also shown in Figure S3.
Figure S2. DMA profiles of RCP-3.
Figure S3. DMA profiles of the chemical gel.
Evaluation of the swelling ratio of RCP 1–4.
A typical procedure is as follows: Weight of gel RCP 1–4 was exactly measured before the evaluation of the swelling
ratio. The gel was swollen in solvent at room temparature for 24 h. The solution part of the mixture was removed by
decantation to determine the weight of the swollen gel. The results were summarized in Table S1.
Table S1.
Solvent
CHCl3
Toluene
MeOH
H2O
N,N-dimethylformamide
Swelling ratio of PRNs RCP 1–4.
7300
480a RCP–2 (%)
140
260
470
260
190
780
640a RCP–41060
170
120
250
150
260
RCP–14700
(%)
(%)
(%)
870a RCP–31210
1760
860a
a) Degree of swelling of gel was determined from the following equation:
[degree of swelling (%)] = [the weight of swollen gel] – [weight of dried gel] / [weight of dried gel]× 100.
Typical procedure for decross-linking of RCP-1 by Bu4NCl.
RCP–1 (10.6 mg) was added to the solution of Bu4NCl(195 mg, 0.70 mmol) in N,N-dimethylformamide (7.0 mL), and
warmed at 60 °C. After the solubilization of the gel for 12 h, the mixture was concentrated and then precipitated to 25 mL
of methanol. The obtained white solid was filtered and dried in vacuo to give PMMA–DB24C8 7 quantitatively. The 1H
NMR spectrum of the polymer 7 indicates that the polymer is composed of PMMA and DB24C8.
Recross-linking of polymer 7.
To a solution of polymer 7 (300 mg) in CH2Cl2 (500 L) was added axle 1 (9.1 mg, 17.7 mol) and the mixture was stirred
for 3 h to form a pseudorotaxane. Then, to the mixture was added methylene diphenyl diisocyanate (3.3 mg, 8.9 mol)
and dibutyltin dilaurate (5 L, 8 mol) at 0 °C and stirred for 12 h to obtain recross-linked polymer (RCP–1) as a white
solid.
III.Original Spectra
1H
NMR spectrum of 3 (400 MHz, CHCl3, 298 K).
13C
NMR spectrum of 3 (100 MHz, CHCl3, 298 K).
IR spectrum of 3 (KBr).
1H
NMR spectrum of 4 (400 MHz, CHCl3, 298 K).
13C
NMR spectrum of 4 (100 MHz, CHCl3, 298 K)
IR spectrum of 4 (KBr).
1H
NMR spectrum of 5 (400 MHz, CHCl3, 298 K).
13C
NMR spectrum of 5 (100 MHz, CHCl3, 298 K)
IR spectrum of 5 (KBr).
「
IR spectra of RCP 7-10 (KBr).
Reference
[1] S. J. Loeb and D. A. Tramontozzi, Org. Biomol. Chem., 2005, 3, 1393–1401.