The living cationic sequential block copolymerization of isobutylene (IB) with tert-butyl vinyl ether (tBVE) was studied using a one-pot procedure in hexanes/CH2Cl2 and hexanes/CH3Cl solvent systems at -80 degreesC. It was carried out by the so-called capping-tuning technique, involving the capping of living PIB chain ends with 1,1-ditolylethylene (DTE) followed by addition of titanium(IV) isopropoxide (Ti(OIp)(4)) to lower the Lewis acidity before the introduction of tBVE. Homopolymerizations/model block copolymerizations of tBVE were carried out using 2-chloro-2,4,4-trimethylpentane (TMPCl) instead of living PIB. The living nature was exhibited by the linear plots of ln([M](0)/[M]) vs time and number average molecular weight (M-n) vs conversion. C-13 NMR spectroscopy indicated that the PtBVE is highly isotactic with close to 80% meso dyads. Well-defined PIB-b-PtBVE diblock copolymers were synthesized by the living cationic polymerization of IB followed by capping the living PIB ends with DTE and fine-tuning the Lewis acidity to obtain 100% crossover efficiency and a desired tBVE polymerization rate. While both hexanes/CH2Cl2 and hexanes/CH3Cl solvent systems could be used, the polymerization was better controlled and the product exhibited narrower molecular weight distribution (MWD) in hexanes/CH3Cl solvent mixtures. Well-defined triblock copolymers with close to designed molecular weights and narrow MWDs (<1.1) were prepared using 5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene (tBuDiCumCl) as a difunctional initiator. Differential scanning calorimetry (DSC) of the block copolymers showed two glass transitions demonstrating microphase separation. The triblock copolymers with 23-39 wt % PtBVE content exhibited typical characteristics of a thermoplastic elastomer (TPE) with tensile strengths of 9-15 MPa and elongations at break of 760-1300%. Morphological studies by transmission electron microscopy (TEM), small-angle X-ray-scattering (SAXS), and atomic force microscopy (AFM) revealed lamellar or cylindrical morphologies of the triblock copolymers, depending on their molecular compositions.