Calculations of the polymerization rate and molecular weight development in the nitroxide‐mediated radical polymerization (NMRP) of styrene (STY), using hydroxyl‐TEMPO and dibenzoyl peroxide (BPO), and activated by microwave irradiation (MI), are presented. The calculations are based on a kinetic model developed in our group. Microwave activation is modeled by three approaches: microwave‐activated production of free radicals from monomer molecules, microwave‐enhanced thermal initiation, and microwave‐enhanced dormant polymer activation. The results obtained are compared against experimental data from the literature. The first approach is the most adequate. The NMRP of STY using TEMPO, BPO, and conductive heating, and the NMRP of STY activated by MI, without initiator, are also analyzed as reference cases.

The RAFT radical polymerization of vinyl monomers in supercritical carbon dioxide was modeled using the Predici® simulation package. The sensitivity of polymerization responses on formulation and process variables was analyzed. The simulations were carried out using kinetic and physical parameters corresponding to the polymerization of methyl methacrylate in supercritical carbon dioxide, using AIBN as initiator, at 65 °C and 200 bar, and using values of the addition and fragmentation kinetic rate constants of a “typical” RAFT agent, as reference conditions. This is the first report in the literature addressing the modeling or simulation of RAFT polymerization in supercritical carbon dioxide.magnified image

The synthesis, thermal, dielectric and conductivity properties of functionalized chitosan polymer derivatives are evaluated to determine their potential uses as a non-toxic electrolyte/separator for lithium batteries. Deacetylated chitosan (DAC) at 97% is used as a precursor to prepare two derivatives: N-propylsulfonic acid chitosan (SC), chitosan with zwitterionic pendant groups (ZWC). These derivatives increase the polar character of pure chitosan, and significantly improve its solubility. Likewise, they are thermally stable up to 220 °C, and their glass transition temperatures (Tg) are located in the region where they decompose, except for SC (Tg=158 ºC). The incorporation of the sulfobetaine and zwitterionic pendant groups improves the ionic conductivity at least two orders of magnitude with respect to pure chitosan at 25 °C, without the use of plasticizers or further modifications. The salt addition (LiPF 6 or LiClO 4 ) to ZWC does not modify the conductivity, whence it is suggested that its increase is due to an electronic modification, such that the energy barriers for conducting the Li + across the ZWC become decreased (i.e. charge dislocation), rather than a salt dissociation. This experimental finding is confirmed with Density Functional Theory (DFT) calculations conducted with the SC and ZWC structures.

A comparison of kinetic models for dispersion polymerization of MMA and styrene in supercritical CO2 is presented. The limiting case of solution polymerization, as a simplified case, was also addressed. Calculation of the partition of components between the continuous and dispersed phases was emphasized. Experimental data for the solution and dispersion polymerizations of styrene and MMA, using different types of stabilizers, were used to guide the study. Although all the models analyzed can be considered as “adequate” in representing the behavior of the system, some of their strengths and drawbacks have been highlighted.

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