The cationic ring-opening polymerizations of an alicyclic epoxyalcohol, 3,4-epoxycyclohexanemethanol (1), were carried Out using boron trifluoride diethyletherate (BF3 center dot OEt2) as a catalyst. Polymerization of I heterogeneously proceeded to yield a gel-free polymer (poly-1). On the basis of the C-13 NMR measurement, poly-1 was a hyperbranched polymer with numerous terminal units, and the degrees of branching (DBs) of poly-1 were in the range from 0.36 to 0.42. The three-dimensional property of poly-1 was investigated by comparison to the physical property of a linear poly(3,4-epoxycyclohexanemethanol) (poly-3). The viscosity and Mark - Houwink exponent a of poly-1 were much lower than those of poly-3, suggesting that poly-1 had a compact conformation in solution. In addition, the glass-transition temperature (T-g) of poly-1 was ca. 105 degrees C, which was also lower than that of poly-3. A novel amphiphilic dendritic polymer (poly-1ASP) having a hydrophobic poly-1 core and hydrophilic L-aspartic acid shell was synthesized. On the basis of the results of an encapsulation experiment, poly-1ASP possessed an encapsulation property for hydrophobic molecule (Reichardt's dye) in water.