Homogeneous polymerization, monitoring

For concentrated dispersions where interparticle interactions are dominant, several theoretically based, semiempirical and empirical equations have been reported in the hterature [55-57]. As for homogeneous polymerization systems, the viscosity of disperse phase polymerization changes hence, indirect information of particle number and size can be obtained by monitoring the viscosity. Furthermore, since the viscosity of the polymerization media affects the heat transfer coefficient, onhne monitored viscosity will be very useful for understanding process changes and safety during the polymerization. 

POE 6000 was used as polymeric support, a soluble polyethylene glycol derivative functionalized at both termini with an amino group and with an average molecular mass of 6000 Da [62-63]. After completion of the homogeneous reactions it can be precipitated, filtered off, and washed with diethyl ether, thereby facilitating the separation of surplus reagents and the side products. Furthermore it allows for NMR spectroscopic monitoring of the reactions [64]. 

Mesoporous silicas with various pore sizes are hydrophobic by silylation with silanes. Changes in the pore structure as a result of the silylation reactions are monitored in order to assess the distribution of the hydrophobic groups. Extensive polymerization of dimethyldi-chlorosilane causes blocking of the micropore fraction. For silica with pore sizes in the supermicroporous range (2nm), this leads to hydrophobization of almost exclusively the outer surface. While for trimethylchlorosilane a smaller number of molecules react with the surface, modification is more homogeneous and an open structure is optimally preserved. Both silanes lead to lower surface polarity and increased hydrothermal stability, i.e., preservation of the porous structure during exposure to water.12231... 

IR calibration and polymerizations were carried out in an MBraun LabMaster 130 glove box under dry nitrogen at -80° C. The moisture (< 1 ppm) and oxygen (5 ppm) contents were monitored. The hexane bath was cooled with an FTS Flexi Cool Immersion Cooler. A 500 ml round bottom flask equipped with an overhead stirrer was charged with the diluent (Hx/MeCl 60/40 wt/wt or MeCl) and DrBP. For calibration, the appropriate monomer was added to the mixture and IR spectra were taken. For the homogeneous carbocationic polymerizations, the initiator (TMPCl, TMPO-1, MSE) was added to the diluent, followed by the addition of the... 

In summary, the results presented here demonstrate that the fiber optic ATR and TR FTIR methods developed in our laboratory can conveniently be used to monitor both homogeneous and heterogeneous polymerizations, and various ancillary reactions, yielding very useful information about these processes. Our research group has extensively been using the fiber optic mid-IR ATR-FTIR and TR-FTIR techniques for macromolecular engineering. ... 

The polymerization reactors are equipped with two sapphire windows [8], which allow for initiation of the polymerization by UV laser pulses, for in-line FT-NIR spectroscopic monitoring of the degree of monomer conversion, and for visual and NIR-spectroscopic inspection of homogeneity of the polymerizing system [10]. 

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