Properties of alternating copolymers. A study was made of alternating copolymerization of diolefins with acrylic or olefinic monomers to produce synthetic rubber of very high tensile strength, which is dependent on the high degree of orientation of macromolecules during elongation. For example, alternating copolymers of propylene and butadiene have properties which are similar to those of natural polyisoprene rubber, while alternating copolymers of acrylonitrile and butadiene retain excellent properties even when immersed in oil. Alternating copolymers of cyclopentene and acrylonitrile were prepared recently. It was found that T g is not determined by the average relative composition of the copolymer, but depends on the proportion of diads, i.e. T g= F AA T A+ F BB T B+2 F AB T AB, is the proportion of diads AB and T AB, their glass temperature. The difference in T g of an alternating copolymer of 1: 1 composition and a homopolymer mixture of the same composition is determined by the proportion of F AB and the characteristic value of δ. The value of δ is positive or negative, according to the effect of steric factors, the same way as the bond energy of monomer units. Alternating copolymers are of interest as polymers with functional groups. Different poly-β-, γ- or β, γ-aminoacids were obtained during hydrolysis of alternating copolymers of aldimine with acrylonitrile, vinylisocyanide with acrylonitrile or vinylsuccinimide with maleic anhydride, respectively. A study was made of complex formation between polyamino acids and heavy metal ions. Mechanism of alternating copolymerization of donor-acceptor monomers. Kirooka et al. showed that during copolymerization of acrylic monomer with α-olefin an alternating copolymer is formed if Lewis acid is used as complex forming agent for the acrylic monomer. This method was used for the copolymerization of an acrylic monomer with butadiene, however, crosslinked polymers were obtained, apparently, as a consequence of the interaction of Lewis acid with unsaturated bonds of copolymers. This can be avoided on using small amounts of transition metal compounds. Traces of these compounds reduce the requisite amount of Lewis acid to a catalytic amount while a fully soluble copolymer is formed. The problem arises whether polymerization takes place with the formation of a monomer-donor-monomer-acceptor complex, or the monomers are added sequentially. In the latter case a maximum is observed in velocity with a monomer ratio of [M A]/[M B] = (k AB /k AB K [Al]) 1 2 , while in the former case ( [M A]/([M A]+[M B])=K 1[ M] n+1) 1 2 /K 1[ M] n≤ 1 2 , where [M A], [M B], [M] and [Al] are the concentrations of monomers, A,B, the overall concentration of monomers and Lewis acid, respectively. It was shown experimentally that copolymerization takes place with the formation of a donor-acceptor complex since the monomer ratio, for which product yield is maximum, is dependent of the concentration of the Lewis acid, and is only determined by the concentration of the monomer. NMR spectroscopic results and cryoscopic investigations confirm the formation of various complexes (such as M A-Al,(M A) 2-Al and M A-Al-M B. However, the structure of the latter complex has not finally been established. Stereoregulation in alternating copolymerization is very difficult, however, asymmetrical alternating copolymerization of acrylic monomer with olefin or diolefin could be carried out using an asymmetric Lewis acid. It is interesting to examine two processes: alternating copolymerization and addition according to Diels-Alders. Both reaction are accelerated by similar means using a Lewis acid of average strength. The difference in these two types of reaction is probably due to a different method of reactivation of the complex; alternating copolymerization is initiated by radical initiators or photochemically, whereas addition according to Diels-Alders is initiated by heat. The stereochemistry of these processes also shows a variation. Alternating copolymerization of mono- and diolefins. Alternating copolymers were obtained of ethylene, propylene and other olefins with butadiene, isoprene or trans-pentadiene using modified Ziegler-Natta catalysts based on vanadium or titanium and alkyl-aluminium compounds. Mixing catalyst components at as low a temperature as possible is very important for obtaining slightly associated and nonaggregated catalyst particles with a controllable coordination number. Catalyst structure was examined by potentiometric titration and EPR. The alternating structure of the copolymer was established by NMR (220 Mc/s) and ozonolysis.