A plasticizer-free ion detective sensor for detecting a target ion in a sample is provided. The sensor comprises a copolymer of methacrylate monomers with pendant alkyl groups of different length, and an ionophore for detecting the target ion. The copolymer matrix of the present invention may be in a form of membrane or particles. The sensors of the present invention may be Carrier-based ion-selective electrodes (ISEs) or optodes such as thin film ion-specific optodes or particle-based optodes. The ionophore may be a target ionophore selective for a target ion H.sup.+, Li.sup.+, Na.sup.+, K.sup.+, Ca.sup.2+, or Mg.sup.2+. The ion detective sensor of the present invention may further include an ion exchanger such as halogenated carboranes. Also provided is an ion detective sensor comprising halogenated carboranes as ion exchangers. Particularly, trimethylammonium-2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 undecabromocarborane (TMAUBC) is used as ion exchangers.