Anionic polymerizations of new styrene derivatives, 4-(1-adamantyl) styrene ( 1) and 3-(4-vinylphenyl)- 1,1'-biadamantane ( 2), were carried out with sec-butyllithium, cumylpotassium, and lithium-or potassium naphthalenide in THF at -78 degrees C for 3-4 h. The polymerizations of 1 and 2 quantitatively proceeded to afford the polymers possessing the predicted molecular weights based on the molar ratios between monomers and initiators and the narrow molecular weight distributions (M-w/M-n = 1.03-1.13). The stability of propagating chain ends of poly(1) and poly( 2) was confirmed by the quantitative initiation efficiency in the sequential copolymerization of 1 and 2 with styrene or isoprene. Novel well-defined block copolymers, poly(1)-b-polystyrene, poly(1)-b-polyisoprene, poly(1)-b-polyisoprene-b-poly(1), poly(2)-b-polystyrene, and poly(2)-b-polyisoprene-b-poly(2), were anionically synthesized. The resulting poly(1) and poly( 2) started to decompose over 340 C and showed remarkably high glass transition temperatures (T-g) at 234 and 232 C, respectively. The Tg values of anionically synthesized random copolymers of 1 and styrene could be changed between 100 and 230 C by the feed molar ratio of comonomers. The incorporation of bulky and stiff adamantyl or 1,1'-biadamantyl moiety unequivocally induced the high thermal stability of novel 4-substituted polystyrenes, poly( 1) and poly( 2).