Polymers molar mass

Unfortunately, Kp often depends on polymer molar mass, makes the use of Eq. (2) and similar expressions (7) impractical. 

Huber, A. (1992). In Analysis of Polymers/Molar-Mass and Molar-Mass Distribution of Polymers, Polyelectrolytes and Latices (W.-M. Kulicke, ed.), Hiithig Wepf Verlag, 61, 248. 

Step polymerisation Monomer concentration drops rapidly to zero early in the reaction. Polymer molar mass rises steadily during reaction. Long reaction times increase molar mass and are essential to obtain very high molar masses. At all stages of the reaction every possible molecular species from dimers to polymers of large degrees of polymerisation are present in a calculable distribution. 

For the determination of polymer molar masses, very dilute solutions are used, typically of the order of 1% by mass. In using viscosity techniques, a number of functions are used. These are ... 

An increase in polymer molar mass and/or concentration and a decrease in the thermodynamic quality of the solvent will lead to a decrease in the critical... 

The symbol n in Fig. 5.4 refers to the number of repeat units which are joined together in the polymer. This is termed the degree of polymerisation (X ), and could easily be a number as high as 10000. Thus for a repeat unit of mass 28 (ethene), this would give a polymer molar mass (R.M.M., Mj ) of 280000. 

FIGURE 16.3 Dependences of the polymer retention volume on the logarithm of its molar mass M or hydrodynamic volume log M [T ] (Section 16.2.2). (a) Idealized dependence with a long linear part in absence of enthalpic interactions. Vq is the interstitial volume in the column packed with porous particles, is the total volume of liquid in the column and is the excluded molar mass, (b) log M vs. dependences for the polymer HPLC systems, in which the enthalpic interaction between macromolecules and column packing exceed entropic (exclusion) effects (1-3). Fully retained polymer molar masses are marked with an empty circle. For comparison, the ideal SEC dependence (Figure 16.3a) is shown (4). (c) log M vs. dependences for the polymer HPLC systems, in which the enthalpic interactions are present but the exclusion effects dominate (1), or in which the full (2) or partial (3,4) compensation of enthalpy and entropy appears. For comparison, the ideal SEC dependence (Figure 16.3a) is shown (5). (d) log M vs. dependences for the polymer HPLC systems, in which the enthalpic interactions affect the exclusion based courses. This leads to the enthalpy assisted SEC behavior especially in the vicinity of For comparison, the ideal SEC dependence (Eigure 16.3a) is shown (4). 

The concentration effects for the oligomers and also for the excluded (high) polymer species, are usually small or even negligible, k values depend also on the thermodynamic quality of eluent [108] and the correlation was found between product A2M and k, where A2 is the second virial coefficient of the particular polymer-solvent system (Section 16.2.2) and M is the polymer molar mass [109]. Concentration effects may slightly contribute to the reduction of the band broadening effects in SEC the retention volumes for species with the higher molar masses are more reduced than those for the lower molar masses. 

The excessive peak broadening. Under critical conditions, the effect of molar mass distribution of sample disappears. Therefore, the peak width reflects only the chromatographic processes and these seem to be rather slow in the case of LC CC. The peak broadening in LC CC raises with the increasing polymer molar mass and with the decreasing packing pore size [180]. 

Polyethylene glycol has been used as reducing and stabilizing agent for Au NPs. The stability of the resulting Au colloids and the reaction rates are dependent on polymer molar mass. The Au NPs are characterized using UV-Vis, analyzing the plasmon bands [108]. 

Here, p and m are the standard chemical potential and concentration (molal scale) of the /-component (z = 1 for solvent, z = 2 for biopolymer) A2 is the second virial coefficient (in molal scale units of cm /mol, i.e., taking the polymer molar mass into account) and m° is the standard-state molality for the polymer. 

One objective of the copolymerization of DADMAC is to obtain higher polymer molar mass since the molar mass of the homopolymer is limited by a slow chain propagation (Table 4). Therefore, DADMAC has been copolymerized with various ionogenic and nonionic monomers of which acrylamide is the most common. A variation of the general properties such as water solubility or charge density also becomes possible by copolymerization. 

Figure 5-1. Polymer molar mass as polymerization proceeds by step-growth mechanism.

Figure 5-4. Polymer molar mass versus polymer formation for living polymerization.

To overcome the problems associated with classical SEC of complex polymers, molar mass-sensitive detectors are coupled to the SEC instrument. Since the response of such detectors depends on both concentration and molar mass, they have to be combined with a concentration-sensitive detector. The following types of molar-mass-sensitive detectors are used frequently [25-28] ... 

However all the samples heated in the presence of US-Y catalyst (polymer-to-catalyst mass ratio 2 1) showed a deviation from the original polymer molar mass distribution in the region of lower molar masses. In the first experiment, the polymer/US-Y-zeolite sample was exposed at a temperature of 378 K, which is below its melting point, for 120 min and then for 30 min at 418 K. No volatile products were initially observed, but traces of isobutane and isopentane were detected when the temperature was raised to 418 K. Although these conditions were much milder than in the equivalent experiment with pure polymer (curve number 2), the molar mass distribution, curve number 5 in Figure 7.5, was different from that of the original polymer. 

It is more convenient and therefore, customary to report the mass of such a polymer as M = 28 000g mol" rather than 4.65 x 10" g molecule A related measure of the mass is the polymer molecular weight, with units of Daltons (Da) defined as 12 times the ratio of the polymer molar mass and the molar mass of C. Hence, in the above example, the molecular weight is 28 000 Da. 

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