alpha-Methyleneindane (MI), possessing an exo-methylene group, was synthesized by the Wittig reaction of 1-indanone and methyltriphenylphosphonium bromide in the presence of potassium tert-butoxide in THF. Since the synthesized MI was contaminated with 0.2-1.5 mol % of the isomeric byproduct, 3-methylindene (3MI), showing a high acidity (pK(a) similar to 22), the basic anionic initiators, such as sec-BuLi, were immediately destroyed by the acidic 3MI prior to the polymerization of MI. After the partial deactivation of the initiator, the polymerization of MI quantitatively proceeded with the residual anionic initiator including sec-BuLi, lithium naphthalenide, and potassium naphthalenide in THF at -78 degrees C to form the polymers having predicted molecular weights based on the molar ratios between MI and the residual initiators and narrow molar mass dispersities (D-M = M-w/M-n < 1.1). Since the polymerization of MI, a cyclic analogue of alpha-methylstyrene (alpha MeSt), quantitatively occurred at 0 degrees C in THF, the polymerizability of MI significantly differed from that of alpha MeSt having the low ceiling temperature around 0 degrees C. A tailored block copolymer of MI and styrene, poly(MI)-b-polystyrene, was obtained with a quantitative efficiency in THF at -78 degrees C by the sequential anionic copolymerization of MI and styrene, indicating the living character of the propagating carbanion of poly(MI). The relative anionic polymerizability of MI was estimated by the density functional theory (DFT) calculations. MI also underwent the free-radical polymerization with alpha,alpha'-azobis(isobutyronitrile) (AIBN) and the cationic polymerization with boron trifluoride diethyl etherate (BF3OEt2). The resulting poly(MI) possessed indane ring structures vertical to the main chain via the addition polymerization of the exo-methylene group and showed the glass transition temperature at 137 degrees C.