Polymerizable phenolphthalein derivatives with pH-sensitive properties were synthesized in the course of electrophilic aromatic substitution reactions. N-(2-hydroxy-5-(1-(4-hydroxyphenyl)-3-oxo-1,3-dihydroisobenzofuran-1-yl)benzyl)acrylamide (3) and N,N'-(((3-oxo-1,3-dihydroisobenzofuran-1,1-diyl)bis(2-hydroxy-5,1-phenylene))bis(methylene))diacrylamide (4) were obtained and characterized. Copolymerization of 3 and 4 with acrylic acid (5a), N-(isopropyl)acrylamide (5b), and N,N-dimethylacrylamide (5c) enabled the synthesis of color switchable materials. Thereby, water-soluble pH sensitive linear polymers 6 and 7 were prepared using monomer 3. Additionally, cross-linked polymers 8 were prepared successfully by copolymerization of 4 and 5c. These pH-sensitive polymers form hydrogels in aqueous solution. Linear viscoelastic behavior depending on the concentration of the cross-linker was observed.