Modeling of Free Radical Styrene/Divinylbenzene Copolymerization with the Numerical Fractionation Technique

The modeling approach called “numerical fractionation” has been incorporated into a PREDICI model to simulate crosslinking copolymerization. To take into account inhomogeneities of the considered copolymerization, the kinetic parameters of the model are proposed to be different for each generation of the numerical fractionation. Using this approach the chain-length dependence of termination has been incorporated into the model so that even the method of moments could be applied to study crosslinking copolymerization. The styrene/m-divinylbenzene crosslinking copolymerization at low content of crosslinker has been simulated. The chain-length dependence of termination has been found to accelerate the gel point in monovinyl/divinyl copolymerization and must be taken into account for correct description of the gel points

Monitoring of chicken meat freshness by means of a colorimetric sensor array

A new optoelectronic nose to monitor chicken meat ageing has been developed. It is based on 16 pigments prepared by the incorporation of different dyes (pH indicators, Lewis acids, hydrogenbonding derivatives, selective probes and natural dyes) into inorganic materials (UVM-7, silica and alumina). The colour changes of the sensor array were characteristic of chicken ageing in a modi¿ed packaging atmosphere (30% CO2¿70% N2). The chromogenic array data were processed with qualitative (PCA) and quantitative (PLS) tools. The PCA statistical analysis showed a high degree of dispersion, with nine dimensions required to explain 95% of variance. Despite this high dimensionality, a tridimensional representation of the three principal components was able to differentiate ageing with 2-day intervals. Moreover, the PLS statistical analysis allows the creation of a model to correlate the chromogenic data with chicken meat ageing. The model offers a PLS prediction model for ageing with values of 0.9937, 0.0389 and 0.994 for the slope, the intercept and the regression coef¿cient, respectively, and is in agreement with the perfect ¿t between the predicted and measured values observed. The results suggest the feasibility of this system to help develop optoelectronic noses that monitor food freshness.Salinas Soler, Y.; Ros-Lis, JV.; Vivancos, J.; Martínez Mañez, R.; Marcos Martínez, MD.; Aucejo Romero, S.; Herranz, N.... (2012). Monitoring of chicken meat freshness by means of a colorimetric sensor array. Analyst. 137(16):3635-3643. doi:10.1039/C2AN35211GS3635364313716Anang, D. M., Rusul, G., Ling, F. H., & Bhat, R. (2010). Inhibitory effects of lactic acid and lauricidin on spoilage organisms of chicken breast during storage at chilled temperature. International Journal of Food Microbiology, 144(1), 152-159. doi:10.1016/j.ijfoodmicro.2010.09.014HINTON, A., & INGRAM, K. D. (2005). 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Scope for accessing the chain length dependence of the termination rate coefficient for disparate length radicals in acrylate free radical polymerization

A method that utilizes reversible addition fragmentation chain transfer (RAFT) chemistry is evaluated on a theoretical basis to deduce the termination rate coefficient for disparate length radicals kts,l in acrylate free radical polymerization, where sand / represent the arbitrary yet disparate chain lengths from either a "short" or "long" RAFT distribution. The method is based on a previously developed method for elucidation of kts,l for the model monomer system styrene. The method was expanded to account for intramolecular chain transfer (i.e., the formation of mid-chain radicals via backbiting) and the free radical polymerization kinetic parameters of methyl acrylate. Simulations show that the method's predictive capability is sensitive to the polymerization rate's dependence on monomer concentration, i.e., the virtual monomer reaction order, which varies with the termination rate coefficient's value and chain length dependence. However, attaining the virtual monomer reaction order is a facile process and once known the method developed here that accounts for mid-chain radicals and virtual monomer reaction orders other than one seems robust enough to elucidate the chain length dependence of kts,l' for the more complex acrylate free radical polymerization. Copyright © 2007 WILEY-VCH Verlag GmbH & Co. KGaA