Self-Healing Polymers Designed for Underwater Applications

Table 1

Metal–ligand coordination characterization methods.

Polymer	Metal	Ligand	Characterization methods			Ref
			FTIR	Raman	UV–Vis
Poly(ethylene glycol) diglycidyl ether (PEG-DE)	Fe^3+	Catechol	—	512–627 cm^−1 (catechol–Fe^3+ bond vibrations)	—	[58]
Polyethylene glycol (PEG)	Fe^3+	Dopa	—	500–650 cm^−1 (chelation of the Fe^3+ by catechol)	—	[56]
Methyl vinyl silicone rubber	Fe^3+	Dopa	—	500–600 cm^−1 (coordination between DOPA and Fe^3+)	500–600 nm (coordination between Fe^3+ and catechol groups)	[5]
Nitrile butadiene rubber (NBR)	Zn^2+	Acrylonitrile	2,280 cm^−1 (restricted −CN in Zn^2+−CN coordination) -	—	—	[57]
–	Zn^2+	Terpyridine	—	—	392 nm (Zn^2+-terpyridine complex)	[59]
Hexamethylene diisocyanate (HDI) and polydimethylsiloxane (PDMS)	Ln^3+	Terpyridine	1,587, 1,571, and 1,562 cm^−1 (terpyridine C = N, linked to terpyridine and Ln^3+ complexation)	—	292 nm (π–pyridine ring transition) and red-shifted to 324 nm	[60]
Polyethylene glycol (PEG)	Ni^2+	Histidine	—	1,596 cm^−1 (coordination between Histidine and Ni^2+)	—	[61]