No abstract

A kinetic model for polymerization rate and molecular weight development in the RAFT polymerization of styrene activated by microwave irradiation has been developed. The effect of microwave irradiation was modeled assuming that the monomer can decompose into free radicals, even at temperatures where thermal initiation is negligible. The typical reactions of RAFT polymerization were also included in the model. The model was validated using experimental data from the literature for the RAFT polymerization of styrene with and without AIBN as initiator, and using CPDN as RAFT agent. Overall, good agreement between model predictions and experimental data was obtained.

The polycondensations of 3,3′-diaminobenzidine with two acids, 4,4′-oxybis(benzoic acid) and hexafluoroisopropylidene bis(benzoic acid), were conducted in Eaton’s reagent at the unusually high temperature of 180°C and under microwave irradiation at 90°C. Both protocols resulted in soluble polybenzimidazoles, OPBI and CF3PBI, of high molecular weights in very short reaction times. The synthesized polybenzimidazoles exhibited high thermostability and excellent mechanical properties. The influence of the reaction conditions on the polymer structure and molecular weights was studied. The “microwave effect” was demonstrated by comparison of the polycondensations conducted under microwave irradiation and conventional heating.

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.

A critical review on the synthesis, characterization, and modeling of polymer grafting is presented. Although the motivation stemmed from grafting synthetic polymers onto lignocellulosic biopolymers, a comprehensive overview is also provided on the chemical grafting, characterization, and processing of grafted materials of different types, including synthetic backbones. Although polymer grafting has been studied for many decades—and so has the modeling of polymer branching and crosslinking for that matter, thereby reaching a good level of understanding in order to describe existing branching/crosslinking systems—polymer grafting has remained behind in modeling efforts. Areas of opportunity for further study are suggested within this review.