Table 2. R ² and coefficient values for pH-sensitive hydrogels in the first-order, Higuchi, Hixson–Crowell, Korsmeyer–Peppas, and zero-order models.

	First order	Higuchi	Hixson–Crowell	Korsmeyer–Peppas		Zero order	Best fit model
	R 2	R 2	R 2	n	R 2	R 2
F1	0.9769	0.9163	0.9709	0.187	0.9268	0.8262	First order
F2	0.963	0.965	0.963	0.251	0.941	0.925	Higuchi
F3	0.9781	0.9779	0.9790	0.268	0.9613	0.9384	Hixson–Crowell
F4	0.7572	0.7867	0.8954	0.107	0.7339	0.6731	Hixson–Crowell
F5	0.8748	0.8704	0.9027	0.125	0.7728	0.8148	Hixson–Crowell
F6	0.8699	0.8788	0.8810	0.247	0.7601	0.8496	Hixson–Crowell
F7	0.1607	0.7417	0.8785	0.073	0.7627	0.5933	Hixson–Crowell
F8	0.1993	0.1132	0.9719	0.260	0.9659	0.9251	Hixson–Crowell
F9	0.8639	0.6086	0.8570	0.363	0.7143	0.6953	First order
F10	0.4572	0.8943	0.2633	0.250	0.8619	0.8030	Higuchi
F11	0.9530	0.9020	0.9745	0.182	0.8823	0.8151	Hixson–Crowell
F12	0.7515	0.1460	0.5624	0.264	0.8297	0.7623	Korsmeyer–Peppas
F13	0.3654	0.9195	0.0168	0.231	0.8935	0.8423	Higuchi
F14	0.5560	0.8029	0.9456	0.175	0.7944	0.6667	Hixson–Crowell
F15	0.9719	0.9039	0.9805	0.202	0.8862	0.8148	Hixson–Crowell