Theoretical Molecular Weight

According to this equation, the polymer molecular weight in an ideal RAFT process will increase linearly with increasing monomer conversion, satisfying an important criterion of Uving polymerization. 

Problem 11.21 Bulk polymerization of methyl acrylate (MA) is carried out by the RAFT process at 60°C. The process is mediated by cyanoisopropyl dithiobenzoate (Fig. 11.35, Ib) used as the chain transfer agent (CTA) and initiated by AIBN with the ratio (molar) MA/CTA/AIBN = 1230 1 0.1, attaining 75% conversion of MA in 7 h. 

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Soum and Fontanillet prepared a living polymer of 2-vin yl pyridine using benzyl picolyl magnesium as the initiator. The values of were measured experimentally for polymers prepared with different concentrations of initiator and different initial concentrations of monomer. The results are given below calculate the theoretical molecular weights expected if polymerization proceeds completely from 100% predissociated initiator and compare the theoretical and experimental values ... 

Fig. 44a. Theoretical molecular weight distribution of a polymer sample degraded along the central streamline at different strain rates, calculated with a pre-exponential factor A = 1014s-1 (I) strain rate e = 75000s-1 (II) strain rate e = 88000s-1 (III) strain rate e = 190000 s- b Theoretical molecular weight distribution of a polymer sample degraded along the central streamline at different strain rates, calculated with A = 104 s-1 (I) strain rate e = 100000 s -1 (II) strain rate e = 120000 s 1 (III) strain rate e = 300000 s -1 (Solid line polymer before degradation, dotted line, degraded polymer)...

The GPC traces in Fig. 24 reveal a broad molecular weight distribution, MJMn = 4.42, for the dual reactor blend sample. On the other hand, the diblock OBC displays an overall MJMn of 1.67. The narrowing of the distribution indicates that the polymerization has CCTP characteristics. The theoretical molecular weight distribution from an ideal living polymerization in a series of two CSTR reactors is given by the following equation, where/j and/2 are the mass fractions of polymer comprising the two blocks [11] ... 

Figure 2.1 Evolution of experimental molecular weight, Mn, and polydispersity with theoretical molecular weight for the polymerization of styrene and 14 at 123°Cfor 18 h with no degassing or purification...

Theoretical molecular weight based on the PS and PCEVE block lengths. 

Table 12.1 Comparison of the mean molecular weight calculated by AFM and theoretical molecular weight of PAMAM dendrimers...

The presence of these end-groups leads to a broadening of the molecular weight distributions the theoretical molecular weight disper-sity ratios 1 /Mjj were shown to be 1.5 for linear telechelics (6) and 1.33 for three-arm star telechelics (see later) prepared at low monomer conversions. ... 

The purpose of this paper is to outline semicontinuous reaction conditions under which perfectly symmetrical end-reactive materials can be obtained with close to theoretical molecular weight dispers-ities, i.e., M M l.5 for linear and 1.33 for three-arm star products, even at complete monomer conversions. 

According to Equation 9 polymers with close to theoretical molecular weight distributions could be prepared even at very high conversions provided [M] and [I] remain constant throughout the polymerization. This condition can be fulfilled by continuously adding a mixed monomer/inifer feed at a sufficiently low constant rate to a coinitiator charge, making certain that the rate of monomer/inifer addition and that of monomer/inifer consumption are equal over the course of the polymerization. 

Fig. 16. Theoretical molecular weight distributions a kinetic reaction product b thermodynamic product leftside represents the monomer signal )...

The theoretical molecular weight distributions for cationic chain polymerizations are the same as those described in Sec. 3-11 for radical chain polymerizations terminating by reactions in which each propagating chain is converted to one dead polymer molecule, that is, not including the formation of a dead polymer molecule by bimolecular coupling of two propagating chains. Equations 2-86 through 2-89, 2-27, 2-96, and 2-97 withp defined by Eq. 3-185... 

Run №. [I] Initiator concentration xl04-mol.l-1 [M01 Initial monomer concentration XlO. mol.l-1 Experimental molecular weights Mn exp. Theoretical molecular weight calculated from [M0]/ti] Mn th. 

From the order 1 with respect to the concentration of active centers and taking Into account the agreement between measured and theoretical molecular weights, we can deduce that true active species are In a predominant concentration. 

Arylene ether/imide block copolymers were prepared as depicted in Eq. (15) from the reaction of amine terminated arylene ether oligomers with theoretical molecular weights of 3110 and 6545g/mol with anhydride terminated amide... 

The summative-fractioruition method was extended to apply to narrow-distribution polymers with polydispersity (Mw/ Mn) less than 1.12. A fractionation parameter H, previously defined and calculated for theoretical molecular weight distributions for normal polymers, was computed for narrow-distribution polymers. The calculations were made both with and without correction for fractionation errors, using the Flory-Huggins treatment. The method was applied to a well-characterized anionic polystyrene with Mw = 97,000, for which the polydispersity was estimated by this technique to be 1.02 (in the range 1.014-1.027, 95% confidence limits). 

Figure 2. Theoretical molecular weight error curves as a function of K from Equation 3...

These drawbacks explain the development of a new concept introduced by a NASA team. According to this concept polymerization of monomeric reactants (PMR), a bisortho ester acid replaces the dianhydride and the monomethyl ester of the nadic acid is used instead of the nadic anhydride as shown in Fig. 5. These esters and the diamine are dissolved in methanol (or in a metha-nol/isopropanol mixture) in a molar ratio calculated to get the desired theoretical molecular weight [14]. These mixtures of reactants are currently used for the preparation of composites and adhesives [15a,b]. 

Total cost = 0.63 for 2.25 lb material = 0.63/2.26 lb = 0.28/lb The above calculations are based on a theoretical molecular weight of 1000 with prices of bulk monomer quantities taken from CMR, February 27, 1978, resulting in a total material cost for the final product of 0.28/lb. (RMC phthalic anhydride, 0.26/lb RMC ethylene glycol, 0.25/lb). Manufacture is by simple fusion cook or solvent azeotropic water removal. 

Regarding the mass range, DNA ions of 108 Da were weighed by mass spectrometry [77], In the same way, non-covalent complexes with molecular weights up to 2.2 MDa were measured by mass spectrometry [78], Intact viral particles of tobacco mosaic virus with a theoretical molecular weight of 40.5 MDa were analysed with an electrospray ionization charge detection time-of-flight mass spectrometer [6]. 

M j,g =31000g.mol ) was higher than the theoretical molecular weight at the conversion (28000 g.mol at 99%), since molecular weights were calculated on a polystyrene standard calibration. 

The molecular weight is therefore 58.8, according to the determination, and the formula of the compound must be C2H6ON with the theoretical molecular weight of 59. 

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