Degree of molecular weight

Some other recent examples of the polymerization, and of its versatility, are summarized in Table 7.1. Thus, functional groups comprising full and partial perfluoroalkyl, ketal, aryl, alkoxy, alkynyl, and vinylene can each be successfully polymerized to varying degrees of molecular weight and polydispersity. 

A microflow system consisting of a T-shaped micromixer and a microtube reader is effedive for the polymerization (Figure 14.6). The polymerization is complete within a residence time of 0.37-1.5 s at — 25 °C (almost quantitative yield). The degree of molecular weight distribution control depends strongly on the inner diameter of the mixer and the flow rate, as depided in Table 14.3. M / M decreased with decrease in the mixer inner diameter, presumably because faster mixing is achieved by a mixer... 

Physical properties of 2 in the chemically oxidized (doped) form have been reported by several groups. Intervalence-transfer (IT) band of 2 oxidized with p-benzoquinone/HBr under argon appears at 1800-1850 nm irrespective of the degree of molecular weight... 

Other initiators that have been used for AN polymerization include trivalent phosphorous compounds dialkylaminotita-nium, allyl molybdenum, and tungsten compounds and metal-free ammonium salts of malonates and carbazo-lides. ° °° ° All of these initiators produce PAN less efficiently with varying degrees of molecular weight and MWD control. The side reactions can be classified as given in... 

This reaction pathway is not very favourable with the polyisoprene of NR as the formation of the complex is expected to be incomplete and thus restricts the transfer of energy. However if a triplet excited isoprene is formed a small degree of molecular weight reduction will be observed according to tlie following pathway ... 

Table 4.1 lists values of as well as AH and ASf per mole of repeat units for several polymers. A variety of experiments and methods of analysis have been used to evaluate these data, and because of an assortment of experimental and theoretical approximations, the values should be regarded as approximate. We assume s T . In general, both AH and ASf may be broken into contributions Ho and So which are independent of molecular weight and increments AHf and ASf for each repeat unit in the chain. Therefore AHf = Hq + n AHf j, where n is the degree of polymerization. In the limit of n AHf = n AHf j and ASf = n ASf j, so T = AHf j/ASf j. The values of AHf j and ASf j in Table 4.1 are expressed per mole of repeat units on this basis. Since no simple trends exist within these data, the entries in Table 4.1 appear in numbered sets, and some observations concerning these sets are listed here ... 

Crystallinity and Density. Crystallinity and density of HDPE resins are derivative parameters both depend primarily on the extent of short-chain branching in polymer chains and, to a lesser degree, on molecular weight. The density range for HDPE resins is between 0.960 and 0.941 g/cm. In spite of the fact that UHMWPE is a completely nonbranched ethylene homopolymer, due to its very high molecular weight, it crystallines poorly and has a density of 0.93 g/cm. ... 

Fig. 3. Graph based on an hplc chromatogram of a commercial PTMEG of molecular weight = 1000. The bars represent the weight percentage of the individual oligomer fractions. The degree of polymerization is the number of repeating monomer units per polymer chain.

Polyacrjiates (3), where R = H, CH n < 100, 000 and Y = OH, OCH, O, etc, or copolymers with compatible monomers, are probably the most flexible dispersant products, because they are produced in a variety of molecular weights and degrees of anionic charge. Moreover, reaction of acryflc acid with other monomers confers additional properties that make them more adaptable for niche appHcations. 

Individual pore size columns have variable pore volume, and because the column dimensions are fixed, the combination of different columns must result in variable slope of the overall calibration curve and hence variable degrees of resolution as a function of molecular weight. 

Steady State Population Density Distributions. Representative experimental population density distri-butions are presented by Figure 1 for two different levels of media viscosity. An excellent degree of theoretical (Equation 8) / experimental correlation is observed. Inasmuch as the slope of population density distribution at a specific degree of polymerization is proportional to the rate of propagation for that size macroanion, propagation rates are also observed to be independent of molecular weight. 

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