The polymerization of 3-methyl butene-1 has been studied using aluAtiRurn &ide solutions at low working temperatures. A crystalline. high polymer was obtained at -130°C. Physical characterization of this product is reported. The X-ray diffraction pattern of this new crystalline polymer is different from that of isotactic poly(3-methyl butene-1) obtained with metal alkyl coordination catalyst. A tentative structure is discussed. ZUSAMMENFASSUNG:Die Polymerisation von 3-Methylbuten-1 wurde in Gegenwart von Aluminiumtrichlorid-Losungen bei tiefen Temperaturen untersucht. Ein kristallines hochpolymeres Produkt wurde bei -130°C erhalten; seine physikalische Charakterisierung wird beschrieben. Das Rontgenbeugungsdiagramm dieses neuen kristallinen Polymeren unterscheidet sich von dem des isotaktischen Poly(3-Methylbuten-l), das in Gegenwart von Metallalkyl-Koordinationskatalysatoren erhalten wurde. Ein moglicher Molekiilbau wird besprochen.

The low temperature cationic polymerization of 3-methyl butene-1 was studied. Two crystalline polymer modifications (a und @) have been characterized by their X-ray diffraction patterns. The "d" spacings of the a and @ forms are (in 8 ) : 7.8, 5.4, 4.6, 2.8, 2.4, and 2.1; and 9.0, 5.4, 4.8, 3.6, 2.8, and 2.1, respectively. The (x modScation was oriented and the repeat distance in the "c" direction is 7.8 A, This indicates 2 structural units in the repeat unit. The a modification is more stable than the f 3 form e.g., when p specimens were reprecipitated from solutions the a form was obtained. ZUSAMMENFASSUNG:Die kationische Tieftemperaturpolymerisation von 3-Methylbuten-1 wurde untersucht. Zwei kristalline Modifikationen (a und @) wurden durch RoNTGENdiagramme charakterisiert. Die ,,d"-Abstande sind (i .8): 1,8, 5,4, 4,6, 2,8, 2,4, 2,l fiir die a-Form und 9,0, 5,4, 4.8, 3,6, 2,8, 2,l fur die @-Form. Die a-Form ist orientiert,und die Identitiitspenode in der c-Richtung ist 1,8 A; dies deutet auf 2 Grundeinheiten in der Einheitszelle. Die a-Modifikation ist stabiler als die @-Form, d.h. wenn P-Proben aus Losung umgefiillt wurden, erhielt man die a-Form.

SynopsisThe cationic polymerization of 3-methylbutene-1 was investigated with the use of aluminum chloride and aluminum bromide initiators in the temperature range of -62 to -102°C. Polymerizations are homogeneous in the presence of pentane, and above -50°C. in methyl chloride. However, the polymer tends to precipitate below -5OOC. in methyl chloride. The molecular weight of poly-3-methylbutene-1 increases with decreasing temperatures a t the same conversion level. Significantly, the molecular weights increase with conversion and seem to reach their maximum a t high conversions. Higher molecular weights were obtained in n-pentane-alkyl chloride mixtures than in methyl chloride solution alone. The molecular weights are independent of catalyst concentrations in the range investigated (31.8-7.97 X loF4 mole/l. AlBr3 and 57.6-28.8 X mole/l. AlC13). The rate of homogeneous polymerization with aluminum bromide in propane solvent was studied. The rate is first order in monomer concentration and catalyst concentration and the rate constant is 0.610 l./mole sec. The apparent activation energy calculated from the Arrhenius plot is 6.57 kcal./mole. In methyl bromide the rate of polymerization increases significantly (effect of the dielectric constant). In toluene the molecular weight as well as the rate is strongly depressed indicating the preponderance of a chain breaking mechanism involving this solvent. 367

The low temperature cationic polymerization of 3‐methylbutene‐1 proceeds by intramolecular hydride shift mechanism. The secondary carbonium ion rearranges to a tertiary one prior to propagation. Thus the repeat unit of cationically obtained poly‐3‐methylbutene‐1 is not the expected or 1,2 structure but an α,α′‐dimethylpropane‐type 1,3 unit, e.g.,

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