SynopsisIn the reactions of 1,3-cyclohexadiene(l,3-CHD) with polar vinyl monomers, CH*=C(X)Y (X is -CN and -CO&Hs; Y is -C1, -H, and -CHz), the two a-chlorosubstituted monomers underwent rapid spontaneous copolymerization, accompanied by the formation of a small amount of cycloadduct. Both polar monomers also gave predominantly copolymers in the reaction with 1,3-cycloheptadiene(l,B-CHpD) in lower yield. 1,3-Cyclooctadiene (1,3-COD) reacted only with a-chloroacrylonitrile (CAN) to give a copolymer, while only cycloaddition took place in systems involving cyclopentadiene(CPD1 as diene. The charge-transfer (CT) complex formation of 1,3-CHD with CAN and methyl a-chloroacrylate(MCA) was confirmed by ultraviolet spectroscopic studies and the equilibrium constants estimated were 0.18 and 0.07 liter/mole, respectively, a t 25OC in chloroform as solvent. The activation energies for the copolymerizations of 1,3-CHD with CAN and MCA in benzene were determined to be ca. 6.6 and 9.6 kcaI/mole, respectively. In the system composed of 1,3-CHD and CAN, only the copolymerization was affected by solvents used and oxygen. Although addition of ZnClz t o the system resulted in the acceleration of the both reactions, the variation in the product ratio of copolymer to cycloadduct with ZnClz concentration showed a maximum. Based on the results in the present and preceding studies for systems involving 1,3-cyclodienes and acceptor monomers, the relationship between the cycloaddition and the spontaneous copolymerization is discussed.

SynopsisThe reaction of 1,3-cycloheptadiene (1,3-CHpD) with acrylonitrile (AN) in the presence of ZnClz leads spontaneously to the simultaneous formation of an alternating copolymer and a small amount of cycloadduct. The copolymer has a predominantly cis-l,.i-structure. The formation of the charge-transfer complex between 1,3-CHpD and (AN)c (AN coordinated to ZnClz) in AN was detected by ultraviolet (UV) spectroscopy. The activation energies for the cycloaddition and for the copolymerization under the conditions used were determined to be 17.6 (in the presence of 1,ldiphenyl-2-picrylhydrazyl) and 16.3 kcal/mole, respectively. The rate of copolymerization in AN was found to depend on the 1.5th power of the concentrations of (AN)c and of 1,3-CHpD. Oxygen and UV irradiation causes an acceleration of the copolymerization only. On the basis of these results the mechanism of the spontaneous copolymerization is discussed and its relation to the cycloaddition in systems of 1,3-cyclodienes and AN in the presence of ZnClz is mentioned.(CPD)? 1,3-cyclohexadiene (1,3-CHD),8 and 1,3-cycloheptadiene ( ~,~-C H P D )~ undergo either spontaneous copolymerization or cycloaddition, or both, with SO2 and MAn, whereas 1,3-cyclooctadiene (1,3-COD) copolymerizes with these comonomers only in the presence of a radical initiator.lOJ1Recently it has been found that acrylonitrile (AN), when coordinated to ZnCl2, copolymerizes spontaneously with 1,3-CHD12 and even with 1,3-COD,I3 and that the former diene gives also a yield of cycloadduct which is higher than that of the copolymer.As to the relationship between cycloaddition and alternating copolymerization, it has been proposed so far, that these reactions proceed via a ground and an excited structure, respectively, in the charge-transfer (CT) complex between dienes and dienophile~.~,~ However, it was recognized that the product ratio of copolymer to cycloadduct in the reactions of 1,3-cyclodienes with MAn is not always related to the donor properties of the dienes but rather to the interplanar angle (6) subtended by the two double-bond planes.6In order to further confirm such a dependence of the reactivity of 1,3-cyclo-

Low-melting point polypropylene prepared with metallocene catalysts was modified with maleic anhydride and acrylate monomers. The degree of modification depends on the tacticity of the base polypropylene. Low-melting point polypropylene can be easily modified compared to high isotactic polypropylene. The reason came from the low crystallinity of the lowmelting point polypropylene and the random arrangement of methyl groups. The base polymer molecular weight was almost constant at the low temperature modification condition. Polypropylene is one of the most common materials used in various industrial fields. The material is mainly used in nonpolar systems, but is unsuitable for use with polar materials such as polar polymer, glass, or metal.To use polypropylene with polar materials, free-radical reactions with unsaturated monomers, such as maleic anhydride or acrylic acid derivatives are often used.1-20 Polypropylene is partly polarized by this method, and can be utilized in many products, such as adhesives, 19 coatings, improvement materials for polar polymers, 20 master batch 21 for inorganic materials, and colors. However, the characteristics are limited considering the use of polypropylene from the conventional catalyst system. Isotactic and atactic polypropylene are mainly used for industry, and some fields like adhesives utilize atactic polypropylene for its low melting point and high fluidity. An effective method to change the properties of base polymer over a wide range is to use metallocene catalyst.Some metallocene catalyst systems are formed using a combination of a co-catalyst and a transition metal compound having a cross-linked structure with two cross-linking groups and offer a characteristic structure. 22 Homo polypropylene obtained from the catalyst system has middle-range tacticity, and shows a low melting point under 100C. The conventional catalyst system can also offer low melting point polypropylene by lowering its tacticity and by copolymerization. However, in this case, low molecular weight polymer and atactic polymer are provided, and often have adverse effect on the mechanical properties of the polymer. These adverse-effect components do not appear in metallocene catalyst systems. This catalyst system gives polypropylene ranging from low-molecular weight to high-molecular weight. Therefore, various application ranges may be expected from metallocene type polypropylene.This polymer also has non-polar characteristics, and can be modified with unsaturated monomers for wide-range utilization. As this polymer has low melting-point and high solubility, different reaction systems can be used to obtain the modified polypropylene. Especially this polymer is useful for research of modification mechanism. Many papers deal with the modification of isotactic 6-14 and atactic polypropylene, 15-18 but tacticity effect is not considered because of the difference of molecular weight. And broad molecular weight distribution and un-uniform tacticty further make difficult to understand the effect of tacticity...

No abstract

No abstract