Smart Hydrogel Reactor of Poly(N-isopropylacrylamide)/Polyethylene Glycol Interpenetrating Polymer Networks for Oxidative Coupling of 2-Naphthol

Dedicated to Professor Hisashi Yamamoto on the occasion of his 80^th birthday

Abstract

Hydrogels with an interpenetrating polymer network (IPN) structure composed of poly(N-isopropylacrylamide) (poly-NIPAM) gel and a gel containing polyethylene glycol (PEG) chains were synthesized. They showed a typical temperature-responsive volume change in water owing to the constructed poly-NIPAM gel component. Oxidative coupling of 2-naphthol with IPN cryogels and a conventional catalyst, the CuCl₂ complex of N,N,N′,N′-tetramethylenediamine, was conducted in water under an O₂ atmosphere; the IPN gel prepared from PEG with a larger molecular weight of 11000 afforded a product with a good yield of 73% (91% conv.) during the reaction in basic media. The hydrogel effectively promoted the reaction but hardly produced any product without the catalyst, acting as a reactor vessel in the water. Owing to the low durability of the PEG gel component for hydrolysis, a limitation was also suggested during experiments on the recyclability of the hydrogel.

Key words

interpenetrating polymer networks - hydrogel reactor - smart gel - catalysis - oxidative coupling

• References and Notes

• 1a Ikegami S, Hamamoto H. Chem. Rev. 2009; 109: 583
• 1b Díaz DD, Kühbeck D, Koopmans RJ. Chem. Soc. Rev. 2011; 40: 427
• 1c Döring A, Birnbaum W, Kuckling D. Chem. Soc. Rev. 2013; 42: 7391
• 2a Hamamoto H, Kudoh M, Takahashi H, Natsugari H, Ikegami S. Chem. Lett. 2007; 36: 632
• 2b Sahiner N, Ozay H, Ozay O, Aktas N. Appl. Cat. B 2010; 101: 137
• 2c Sahiner N, Butun S, Sahiner N. Polymer 2011; 52: 4834
• 2d Sahiner N, Butun S, Ozay H, Dibek B. J. Colloid Interface Sci. 2012; 373: 122
• 3a Zhan K, You H, Liu W, Lu J, Dong J. React. Funct. Polym. 2011; 71: 756
• 3b Murthyl PS. K, Mohan YM, Varaprasad K, Sreedhar B, Raju KM. J. Colloid Interface Sci. 2008; 318: 217
• 3c Patwadkar MV, Gopinath CS, Badiger MV. RCS Adv. 2015; 5: 7567
• 3d Ding JD, Zhao L, Li X, Yue Q, Gao B. RCS Adv. 2017; 7: 17599
• 4a Peak CW, Wilker JJ, Schmidt G. Colloid Polym. Sci. 2013; 291: 2031
• 4b Dragan ES. Chem. Eng. J. 2014; 243: 572
• 4c Dhand AP, Galarraga JH, Burdrick JA. Trends Biotechnol. 2021; 39: 519
• 5a Singh S, Frisch HL, Ghiradella H. Macromolecules 1990; 23: 375
• 5b Chen P, Wu R, Wang J, Liu Y, Ding C, Xu S. J. Polym. Res. 2012; 19: 9825
• 5c Wang JJ, Liu F. Polym. Bull. 2013; 70: 1415
• 5d Sano J, Habaue S. React. Funct. Polym. 2019; 137: 21
• 6 Sano J, Habaue S. Polymers 2021; 13: 1750
• 7a Jo S, Park K. J. Bioact. Compat. Polym. 1999; 14: 457
• 7b Subramani S, Lee JM, Cheong IW, Kim JH. J. Appl. Polym. Sci. 2005; 98: 620
• 8a Buwalda SJ, Boere KW, Dijkstra PJ, Feijen J, Vermonden T, Hennink WE. J. Controlled Release 2014; 190: 254
• 8b Ullah F, Othman MB. H, Javed F, Ahmad F, Akil HM. Mater. Sci. Eng. C 2015; 57: 414
• 9a Otake K, Inomata H, Konno M, Saito S. Macromolecules 1990; 23: 283
• 9b Tokuhiro T, Amiya T, Mamada A, Tanaka T. Macromolecules 1991; 24: 2936
• 9c Zhang X.-Z, Yang Y.-Y, Chung T.-S, Ma K.-X. Langmuir 2001; 17: 6094
• 10a Wang H. Chirality 2010; 22: 827
• 10b Klussmann M, Sureshkumar D. Synthesis 2011; 353
• 11a Ding K, Wang Y, Zhang L, Wu Y. Tetrahedron 1996; 52: 1005
• 11b Matsushita M, Kamata K, Yamaguchi K, Mizuno N. J. Am. Chem. Soc. 2005; 127: 6632
• 11c Reddy KR, Rajgopal K, Kantam L. Catal. Lett. 2007; 114: 36
• 11d Eshghi H, Bakavoli M, Moradi H. Chin. Chem. Lett. 2009; 20: 663
• 11e Sako M, Takizawa S, Yoshida Y, Sasai H. Tetrahedron: Asymmetry 2015; 26: 613
• 12a Noji M, Nakajima M, Koga K. Tetrahedron Lett. 1994; 35: 7983
• 12b Nakajima M, Hashimoto S, Noji M, Koga K. Chem. Pharm. Bull. 1998; 46: 1814
• 12c Nakajima M, Miyoshi I, Kanayama K, Hashimoto S, Noji M, Koga K. J. Org. Chem. 1999; 64: 2264
• 12d Yan P, Sugiyama Y, Takahashi Y, Kinemuchi H, Temma T, Habaue S. Tetrahedron 2008; 64: 4325
• 13 The gels were immersed in water for 24 h at a predetermined temperature and weighed after careful removal of excess surface water. Q was calculated from the following equation by using the mass values of the swollen (m _s) and dry-state (m _d) samples: Q = (m _s − m _d)/m _d. All experiments were performed in triplicate for each sample.
• 14 Adão P, Barroso S, Carvalho MF. N. N, Teixeira CM, Kuznetsov ML, Pessoa JC. Dalton Trans. 2015; 44: 1612
• 15 Procedure for oxidative coupling of 2-naphthol in water: 2-Naphthol (182 mg, 1.25 mmol), a gel, and TMEDA were added to an aqueous solution of CuCl₂ (0.35 M). After gentle stirring of the mixture under an O₂ atmosphere (1 atm), the gel was separated and washed three times with CHCl₃. The organic layer of the filtrates was further washed with 1 M HCl and brine. The residual gel was immersed in excess THF for two days, and the eluent was combined with the organic layer, which was then dried over MgSO₄. Subsequent filtration and concentration afforded the crude products. Purification was accomplished by using silica gel column chromatography, which produced BINOL as the product. After the washed gel was dried, it was again swelled in water and freeze-dried for further reaction cycles.