This study deals with modeling the propagation and the chain transfer reactions in the free radical polymerization of ethylene, methyl methacrylate (MMA), and acrylamide (AM). The chain transfer agents modeled in the free radical polymerization of ethylene are the experimentally widely used species such as ethylene, methane, ethane, propane, trimethylamine, dimethylamine, chloroform, and carbon tetrachloride. The role of 4-X-thiophenols as chain transfer agents in the polymerization of MMA and AM has been investigated. Geometry optimizations have been carried out with the B3LYP/6-31+G(d) methodology. Reaction rate constants are calculated via the standard transition-state theory with the B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d), MPWB1K/6-311+G(3df,2p)//B3LYP/6-31+G(d), and M05-2X/6-311+G(3df,2p)//B3LYP/6-31+G(d) methodologies, which reproduce qualitatively the experimental trends for the chain transfer rate constants. The usage of simple continuum models with the MPWB1K/6-311+G(3df,2p)//B3LYP/6-31+G(d) methodology for the solvation energies has slightly improved the accurate prediction of the chain transfer constants. Polar interactions highly influence the barrier heights for chain transfer reactions in the FRP of ethylene, MMA, and AM. Calculated chain transfer rate constants in the FRP of MMA and AM correlate quite well with the Hammett constants.

The kinetics of the free-radical propagation of methyl acrylate (MA), methyl methacrylate (MMA), ethyl R-fluoroacrylate (EFA), ethyl R-chloroacrylate (ECA), ethyl R-cyanoacrylate (ECNA), and methyl R-hydroxymethacrylate (MHMA) have been calculated using quantum chemical tools. Various DFT functionals such as BMK, BB1K, MPW1B95, MPW1K, and MPWB1K were used to model the relative propagation kinetics of the monomers. Among the methodologies used, MPWB1K/6-311+G(3df,2p)//B3LYP/6-31+G(d) was found to yield the best qualitative agreement with experiment. We explored chain length effects by examining addition reactions of monomeric, dimeric, trimeric, and tetrameric radicals to the monomers. We have also modeled the tacticity of the widely used monomers MA and MMA by considering all of the alternatives of attack of the radical in the 3D space around the monomer. This study has qualitatively confirmed the experimental syndiotactic/ isotactic ratio of 66/3 for MMA. Finally, the kinetics of the initiation to polymerization for MA and MMA is also successfully reproduced.

Radical polymerization processes occur through a complex network of many different reactions. It is well-known that the polymerization rate is directly related to the monomer structure. The experimental polymerizability behavior is expressed as k p /k t 1/2 , where k p is the rate coefficient of propagation and k t is the rate coefficient of termination. In this study, the reactivity of a series of acrylates and methacrylates is modeled in order to understand the effect of the pendant group size, the polarity of a pendant group, and the nature of the pendant group (linear vs cyclic) on their polymerizability. The geometries and frequencies are calculated with the B3LYP/6-31+G(d) methodology whereas the energetics and kinetics of these monomers have been studied using the two-component BMK/6-311+G(3df,2p)//B3LYP/6-31+G(d) level of theory. For rotations about forming/ breaking bonds in the transition state, an uncoupled scheme for internal rotations has been applied with potentials determined at the B3LYP/6-31+G(d) level. Generally the rate constants for propagation k p mimic the qualitative polymerization trend of the monomers modeled and can be used with confidence in predicting the polymerizability behavior of acrylates. However in the case of 2-dimethylaminoethyl acrylate, chain transfer is found to play a major role in inhibiting the polymerization. On the other hand, the disproportionation reaction turns out to be too slow to be taken into consideration as a termination reaction.

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The synthesis of several difunctional monomers, derived from the introduction of two 4-styrenesubstituted moieties into a covalent skeleton, is described. The more rigid ones, built around malonate moieties and more preorganized to give 3,3′-cyclophane repeating units, failed completely to give soluble, ordered cyclopolymers. The introduction of a certain degree of flexibility in the tethering moiety afforded, by using freeradical initiation, structurally stable cyclopolymers with a high degree of cyclization and good degrees of polymerization. Theoretical calculations detail and strongly support the experimental results. Further chemical elaboration of the obtained cyclopolymeric backbones, by means of the removal of a ketal group, is possible in mild conditions to give systems which can be easily cross-linked thermally, with the loss of H 2 O, at temperatures higher than 100 °C.