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.

A mathematical model for pretreatment and hydrolysis of lignocellulosic biomasses in twin-screw extruders is presented. The model allows for calculation of the concentrations of extracted hemicellulose and sugars (xylose and glucose) at different operating conditions (pressure, temperature, and NaOH and H2SO4 concentrations, as well as screw rotational speed). Parameter sensitivity analyses on the effects of process variables on product concentrations are reported. Regarding the pretreatment case, the effects of NaOH concentration, liquid/solid ratio, and screw rotational speed on the extracted hemicellulose are studied. In the case of hydrolysis, the effects of NaOH concentration, screw rotational speed, and barrel temperature on the final concentrations of glucose and xylose are addressed. Reasonably good agreement between experimental data from different pretreatment/hydrolysis systems and laboratories and the calculations obtained with our model is observed.

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 copolymerization kinetics of hydroxyethyl methacrylate (HEMA) with either ethylene glycol dimethacrylate (EGDMA) or diethylene glycol dimethacrylate (DEGDMA) in the presence of RAFT controllers is studied using a mathematical model recently developed in our group. The model is based on the concept of multifunctional polymer molecules. The cases of conventional and controlled homopolymerizations of HEMA as well as the RAFT copolymerization of HEMA/EGDMA and HEMA/DEGDMA are addressed and are in good agreement with available experimental data. The bulk/solution version of the model is used as first approximation of the behavior of a RAFT dispersion copolymerization of HEMA/ EGDMA carried out in supercritical carbon dioxide.