Evaluation of the accessible inclusion sites in copolymer materials containing β-cyclodextrin

► The inclusion accessibility (θ) of copolymers containing β-CD was evaluated. ► θ was determined using phenolphthalein (phth) as an optical probe. ► θ was affected by steric effects, crosslinking density, and micropore structure. ► The method is versatile and reliable for the evaluation of θ in β-CD copolymers.