Number-Average Molecular Weight Mn

The poly(styrene-b-isoprene) (P(S-b-IP)) and poly(-styrene-b-2-vinyl pyridine) (P(S-b-2VP)) block copolymers with narrow molecular weight distributions for blending with the microspheres were also synthesized using the additional anionic polymerization technique. The number-average molecular weights (Mns) and PS contents are also shown in Table 1. 

Attempts were made to determine number average molecular weights (Mn) by osmometry (Mechrolab Model 502, high speed membrane osmometer, 1 to 10 g/1 toluene solution at 37 °C), however, in many instances irreproducible data were obtained, probably due to the diffusion of low molecular weight polymer through the membrane. This technique was abandoned in favor of gel permeation chromatography (GPC). 

Functionalization yields have to be checked carefully by comparing the effective number average molecular weight Mn with its value calculated from the functional content of the sample, under the assumption that each macromolecule carries one function (two if a bifunctional initiator is used). Low molecular weight samples are preferred, as the functional analysis would otherwise lack accuracy. In all examples quoted high functionalization yields have been attained. 

Various studies have been made on the effects of radiation on lactide/glycolide polymers (24,38,58). Gilding and Reed (24) reported the effect of y rays on Dexon sutures. Those results confirmed that deterioration of the sutures occurs but that random chain scission is not the primary mechanism. Number average-molecular weight Mn showed a dramatic decrease at doses above 1.0 Mrad. Thus, unzipping of the polymer chain appeared to be the more dominant process, at least in the case of polyglycolide. 

The number average molecular weight (Mn) is calculated from Eq. 1.1. 

Living" carbocationic polymerizations are most difficult to achieve mainly because of chain transfer to monomer and termination processes both of which frequently occur in carbocationic polymerizations. It has recently been demonstrated (JL) that "quasiliving" polymerization of a-methylstyrene (aMeSt) can be achieved by slow and continuous monomer addition and that the number-average molecular weight (Mn) of PaMeSt increases linearly with the weight of added monomer. A theory for quasiliving polymerizations has been developed (2). 

Lipase-catalyzed polymerization of divinyl adipate or divinyl sebacate with a, co-glycols with different chain length has been reported [40]. Lipases CA, MM, PC, and PF showed high catalytic activity toward the polymerization. A combination of divinyl adipate, 1,4-butanediol, and lipase PC afforded the polymer with number-average molecular weight (Mn) of 2.1 x 104. The yield of the polymer from divinyl sebacate was higher than that from divinyl adipate, whereas the opposite tendency was observed in the polymer molecular weight. 

Overall number average molecular weight Mn = 7100 gmol 1 bOverall number average molecular weight Mn = 8100 gmol 1... 

InthisequationTm is the melting point in Kelvin of polymers with a number average molecular weight Mn. Polymer of infinite molecular weight melts at Tm,. The molecular weight of the monomeric unit is Ma, R the gas... 

Number-average molecular weight, Mn Weight-average molecular weight, /Ww Molecular weight distribution, /Ww//Wn... 

The determination of the molecular weight of nanoparticles is performed by gel permeation chromatography (GPC). The experimental setup consists of a high performance liquid chromatography system with a size exclusion column and a refractive index detector. The nanoparticles are usually freeze-dried and dissolved in tetrahydrofuran for analysis on the system. Poly(styrene) or poly(methylmethacrylate) standards are used to calibrate the column, to enable the determination of number average molecular weight (Mn), as in... 

A given polymer is characterized by its number-average molecular weight (Mn), together with its weight-average molecular weight (Mw), which can both be obtained by analytical techniques. 

Figure 4.6 Number-average molecular weight (Mn) as a function of the square root of time at various SSP temperatures [15]. From Jabarin, S. A. and Lofgren, E. A., J. Appl. Polym. Sci., 32, 5315-5355 (1986), Copyright John Wiley Sons, Inc., 1986. Reprinted by permission of John Wiley Sons, Inc...

Figure 18.5 Effect on number-average molecular weight (Mn) of Weather-Ometer testing with ( wet ) and without ( dry ) water spray for Spectar copolymer sheeting [7], From Fagerburg, D. R. and Donelson, M. E., Effect of water spray and irradiance level on changes in copolyester sheeting with xenon arc exposure, ANTEC 98 Conference Proceedings, Paper 808, Atlanta, GA, April 30, 1998, and reproduced with permission of the Society of Plastics Engineers...

Nadimide-terminated polysulfones (norbornene-terminated), as shown in Eq. 7 where the linear sulfone segment had a number average molecular weight (Mn) of 20,000g/mole were first reported in 1980 (18). This work was performed in an attempt to develop a tough solvent resistant resin for use in composites. The thermally induced reaction of the nadimide terminal groups involves a... 

Functionality. For reactive liquid polymers, the most important property is the functionality. Functionality is determined from number average molecular weight (Mn) and hydroxyl number by the following equation ... 

All the materials in this study are commercially available and were used as received. The compositions of the mixtures are given in Table I. The components can be described as follows Resin is a proprietary blend of acrylated epoxy resins with an number average molecular weight (Mn) of "4800, based on acrylated diglycidyl bisphenol A, DGEBAcr is the diacrylate derivative of diglycidyl bisphenol A, IBOA is isobomyl acrylate, TMPTA is trimethyloltriacrylate and DMPA is 2,2-dimethoxy-2-phenyl acetophenone. 

Polymerization reactions were carried out via a prepolymer formation followed by chain extension. One equivalent of poly(tetramethylene oxide) [number-average molecular weight (Mn) = 1400g/mol] was injected slowly by a syringe pump into a... 

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