CRYSTALLINE POLY(BETA-PINENE)

This paper reports results of an experimental investigation in which poly- beta -pinene was polymerized and characterized. In the course of our fundamental studies on the homo- and copolymerization of beta -pinene the authors observed that when neat beta -pinene was heated and maintained at 160 degree C under a blanket of dry nitrogen for about 1 week, a voluminous white precipitate formed. Significantly, the white precipitate obtained upon heating was found to be highly crystalline by x-ray diffraction and polarized light birefringence studies. The solubility characteristics and heat response on a hot-stage microscope of the crystalline poly( beta -pinene) were also significantly different from those of the amorphous modification. Figure 1a shows the powder x-ray diffraction pattern of a poly( beta -pinene) sample obtained after 1 week of heating beta -pinene to 160 degree C, and figure 1b shows that of a poly( beta -pinene) produced by the use of AlCl//3 in EtCl solution at minus 100 degree C. The heat-polymerized beta -pinene showed birefringence under polarized light. Birefringence persisted after heating the sample at 180 degree C and cooling to room temperature; however, degradation started upon prolonged heating to 210 degree C in air. The effect of heat is also different on the crystalline and amorphous modifications of poly( beta -pinene). Experimental data are tabulated and discussed.