Tacticity coefficient

In statistical copolymers a total of 20 configurational sequences occur i.e., for the MMA-centred triads, the following 10 tacticity coefficients and sequences are possible (1 - < mm) Pmmm, and (1 - for the MMM sequence,... 

Results and Discussion. As a first step in the analysis of the absorption behaviour of SAN copolymers, the effects of tacticity and molecular weight on the extinction coefficients of well-characterized polystyrene samples were investigated. 

What if a friend is balancing chemical equations by changing the values of the subscripts instead of using the coefficients How would you explain to your friend that this tactic is the wrong approach ... 

In all of these systems, propagation involves radical species, and therefore chemoselectivities (reactivity ratios and transfer coefficients), regioselectivities (head-to-head units), and stereoselectivities (tacticity) determined for CRPs are similar to those in conventional RP. 

Based on this finding, they proposed a method for determining the tacticity of amorphous samples of PVC. Because some samples cannot be easily transformed into an amorphous state, Schneider and co-workers [68] devised an IR method of tacticity determination which is independent of sample crystallinity. From the temperature dependence of IR spectra of PVC samples prepared by different methods, the intensity of the band at 14.40 pm (proportional to the number of isotactic diads in the sample), as well as that of the tacticity-independent C-H stretching band, was found to be independent of sample crystallinity. These lines were applied to the tacticity determination in PVC, measnred in potassium bromide pellets. The numerical tacticity value was obtained from the known values of absorbance coefficients of S h and S h type C-Cl stretching bands in solution, and from the shape of the spectrum. 

Table 9. Characteristic ratios and temperature coefficients for PMMA chains of varying tacticity...

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