The monomolecular particle agglomerates of polystyrenes were obtained by freeze-drying of its very dilutesolutions of 1.3×10~(-5)-2.0×10~(-5) g/mL in benzene: cylcohexane (100:1) solvents, and they were annealed at roomtemperature for hundred days before use. According to ~(13)C-NMR measurement the polystyrenes should be practically atactic.The number average molecular weights of the samples are 2.80×10~3, 2.00×10~4, and 1.55×10~6, respectively. The freeze-dried aPS with a molecular weight higher than 10~4 show two new IR absorption bands at 1098 and 1261 cm~(-1), which areabsent in the normal aPS and freeze-dried styrene oligomer. It was also found that the low molecular weight samples canonly form powders, whereas the freeze-dried aPS with higher molecular weight form a mixture of powders and fibrils, ofwhich the longer fibrils show a much stronger 1261 cm~(-1) band than the shorter fibrils and the powder. It seems that the1261 cm~(-1) band corresponds to the stacking behavior of monomolecular particles. The monomolecular particle agglomerates of polystyrenes were obtained by freeze-drying of its very dilute solutions of 1.3 × 10 -5 to 2.0 × 10 -5 g / mL in benzene: cylcohexane (100: 1) solvents, and they were annealed at roomtemperature for hundred days before use. According to ~ (13) C-NMR measurement the polystyrenes should be practically atactic.The number average molecular weights of the samples are 2.80 × 10 ~ 3, 2.00 × 10 ~ 4, and 1.55 × 10 ~ 6, respectively. The freeze-dried aPS with a molecular weight higher than 10 ~ 4 show two new IR bands at 1098 and 1261 cm -1, which are absent in the normal aPS and freeze-dried styrene oligomer It was also found that the low molecular weight samples canonly form powders, whereas the freeze-dried aPS with higher molecular weight form a mixture of powders and fibrils, ofwhich the longer fibrils show a much stronger 1261 cm -1 band than the shorter fibrils and the powder. It seems that the 1261 cm -1 band corresponds to the stacking behavior o f monomolecular particles.