Polymers average molecular mass

SEC-GC-FID, according to Figure 7.40, has been used to carry out the simultaneous determination of the polymer average molecular masses and molar mass distribution and the concentration of additives [984]. The effluent was split and adsorbed on PTV packing material before GC analysis. The choice of PTV... 

Tgoa glass transition temperature of the uncrosslinked polymer Mc average molecular mass between crosslinks tj> empirical factor... 

Activation volumes of the polymers according to Eq. (6.5) were calculated with t, = 0.5ay and plotted in Fig. 6.6 versus the average molecular mass Mc of network strands. The volume of a molecular strand is plotted also... 

In POLYM the output data of KINREL are used with compositional information to calculate the number and mass average molecular masses (Rn and Rm, respectively) and number and end-group average functionalities (fp and fg> respectively) in the pre-gel region in all stages. In addition, the network characteristics such as sol fraction, mj, and the number of elastically active network chains per monomer (5), Ng, are calculated in the post-gel regime of stage 3. 

For correlation with most physical properties (mechanical strength, optical scattering), mass average molecular mass of a polymer Mw" appears more satisfactory. Higher-power averages like z-average molecular mass "Mz" seem to better correlate with rheological properties. Expressions of M , Mw and Mz are... 

The reactive nature of compound 22 is illustrated by the series of transformations shown in Scheme 7.12, in which its Zr—C bond reacts selectively with electrophilic reagents to produce a-haloboronates 36—38. Compound 22 also catalyzes the polymerization of styrene. The polymers thus obtained had weight-average molecular masses in the range 75000—100000 with polydispersities of 1.8—2.1. An X-ray analysis of 22 confirmed it to be a four-coordinate Zr complex with two cyclopentadienyl rings, chlorine, and the aliphatic C-l carbon atom as the ligands (Fig. 7.4). 

The average molecular mass of synthesized polymers can be measured by SEC. This system has been called gel-permeation liquid chromatography, using porous polystyrene gel as the stationary phase material. Polymers are usually dissolved in THF or chloroform for separation by SEC. The molecular density... 

Oligomerization and polymerization of terminal alkynes may provide materials with interesting conductivity and (nonlinear) optical properties. Phenylacetylene and 4-ethynyltoluene were polymerized in water/methanol homogeneous solutions and in water/chloroform biphasic systems using [RhCl(CO)(TPPTS)2] and [IrCl(CO)(TPPTS)2] as catalysts [37], The complexes themselves were rather inefficient, however, the catalytic activity could be substantially increased by addition of MesNO in order to remove the carbonyl ligand from the coordination sphere of the metals. The polymers obtained had an average molecular mass of = 3150-16300. The rhodium catalyst worked at room temperature providing polymers with cis-transoid structure, while [IrCl(CO)(TPPTS)2] required 80 °C and led to the formation of frani -polymers. 

Rgure 2.10. (a) Influence of the polymer molecular weight on the force-distance profiles between air-water (filled symbols) and oU-water interfaces (empty symbols). Polymer concentration = 0.5 wt%. Average molecular masses of the polymers oil-water interface (0) Mw = 10000 g/mol ( ) = 55000 g/mol (Q) = 155000 g/mol. air-water... 

Fig. 21 Representative microfluidic device and resulting data from ATRP on a chip a image of a microfluidic device (dimensions 25 mm x 75 mm) fabricated from UV curable thiolene resin between two glass slides b reaction data for ATRP of HPMA synthesized on a chip showing the correlation of flow rate (or residence time) to reaction time and resulting conversion of monomer (M) to polymer (ln([M]o/[M]) c comparison of number average molecular mass (M ) and poly-dispersity for -butyl acrylate prepared in a traditional round bottom flask ( Flask ) and on a chip ( CRP Chip ). (Reproduced with permission from [102])...

Molecular weight distribution of isolated samples. Mn is number-average molecular mass. c Polymer film. 

Size exclusion chromatography (SEC) is normally used for determining molar mass distribution in polymer and oligomer homologeous mixtures. Values for average molecular masses can be obtained. But it is difficult to get these results of specimen with different chemical heterogeneity SEC cannot provide... 

An average molecular mass (weight) of the polymer also needs to be defined, since components of various molecular masses (weights) M, are present in the polymer. The number of moles of species i in the polymer can be obtained from the typical formula ni = W] / Mi where W is the weight fraction of the component i", and M, is the molecular mass of species i . The masses of molecules or groups can be calculated using two different conventions. One convention considers the natural isotopic abundance of elements and takes their sum based on the compound chemical formula. For the masses of polymers, the first convention is typically used. The other convention considers only the masses of the most abundant isotope, which is useful for MS... 

A weight-average molecular mass M also is used for polymer characterization. This parameter is given multiplying the weight fraction Wi/W by the molecular mass M and is defined by the formula ... 

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