Synthesis and properties of alternating copolymers of acrylics and olefins

The free radical copolymerization and terpolymerization of acrylic monomers with olefins in the presence of Lewis acid complexing agent for the acrylic monomer has been investigated. The course of the polyreaction is in agreement with the features of a radical chain growth reaction, and the polymer properties can be varied by changing the composition of the reaction mixture and the reaction conditions. The alternating copolymers are usually amorphous materials, and only the alternating ethylene/acrylonitrile copolymer can be obtained as a material of relatively high crystallinity. The degree of crystallinity can be varied through terpolymerization of complexed acrylonitrile with ethylene/propylene comonomers. The basic features of the polyreaction and the polymer structures as well as some of the physical and material properties of the copolymers have been studied.     

Angular correlations within coiled polymer molecules

Monte Carlo techniques were used to investigate angular correlations between the principal axes of inertia and the end-to-end vector as well as the first two normal coordinates. On the average, the first normal coordinate is nearly parallel to the longest principal axis. The parallelism is less distinct in the case of the end-to-end vector and the longest principal axis. The assumption made by some authors that the second normal coordinate is coplanar with the two longest principal axes could not be confirmed.     

The Meaning and Use of the Arrhenius Activation Energy

The nature of the Arrhenius activation energy and frequency factor is reexamined in terms of information now becoming available on the microscopic aspects of collisional reactions. It is pointed out that the activation energy is not generally equal to the threshold for reaction, and its correct conceptual meaning is discussed. The temperature dependence of this quantity and its relation to the threshold energy is developed for a number of representative forms of the energy dependence of the reaction cross-section (excitation function). The uses and limitations of the activation energy as a means of evaluating thresholds, excitation functions, and the presence of tunneling processes are discussed.