Poly molecular weight characterization

Y. Fu, J. Li, S. Yan, and Z. Bo, High molecular weight dendronized poly(fluorene)s with peripheral carbazole groups synthesis, characterization, and properties, Macromolecules, 37 6395-6400, 2004. 

The solution behavior of poly(amic acids) was until recently, probably the least understood aspect of the soluble polyimide precursor. However, the advent of sophisticated laser light scattering and size exclusion chromatography instrumentation has allowed elucidation of the solution behavior of poly(amic adds). In the early days of polyimide chemistry, when most molecular weight characterization was based on viscosity determinations, a decrease in viscosity was associated with molecular weight degradation [15, 28, 29]. Upon combination of the two monomers an increase in the viscosity to the stoichiometric equivalence point is observed, followed by a decrease in the solution viscosity as a... 

Polyelectrolytes are a substance class notoriously difficult to analyze. This problem also exists for Fl-FFF due to polymer-polymer or polymer-wall/mem-brane interactions. Benincasa and Giddings [59] completed a systematic study of ionic-strength effects in the application of Fl-FFF to both cationic and anionic polyelectrolytes over a broad molecular weight range. Poly(2-vinylpyridine) was effectively characterized in a 20 mM solution of nitric acid (pH 2), while the best results on poly(styrene sulfonate) were obtained in a dilute (6.5 mM) solution of... 

Table IV. Molecular Weight Characterization of Aminopropyl-Terminated Poly(dimethylsiloxane) and Its Fractions...

We have previously reported on the coupling of an SEC to a mass spectrometer operated in the electrospray mode of ionization and its application to the molecular weight characterization of octylphenoxy-poly(ethoxy)ethanol oligomers (20). The analysis of nonionic surfactants... 

Ganachaud E, Monteiro MJ, Gilbert RG, Dourges MA, Thang SH, Rizzaedo E. Molecular weight characterization of poly(N-isopropylacrylamide) prepared by living free-radical polymerization. Macromolecules 2000 33 6738-6745. 

Agus J, Kahar P, Abe H, Doi Y, Tsuge T (2006) Molecular weight characterization of poly[(/J)-3-hydroxybutyrate] synthesized by genetically engineered strains of Escherichia coli. Polym Degrad Stab 91 1138-1146... 

Li Y, Wang F, Yang J, Liu D, Roy A, Case S, et al. Synthesis and characterization of controlled molecular weight disulfonated poly(arylene ether sulfone) copolymers and their applications to proton exchange membranes. Polymer 2006 47(ll) 4210-7. 

Figure 4 Influence of several other resin variables on (a) the density, (b) the birefringence of as-spun iPP filaments with similar molecular weight and poly-dispersity (data from [6]). See Table 2 for characterization of the various resins.

Poly(L-lactide)- -poly(e-caprolactone) (PLLA-fe-PCL) diblock copolymers were synthesized by controlled/ living sequential block copolymerization as initiated by aluminum trialkoxides in toluene solution. These procedures were reported in detail previously [50,98]. Table 11.6 lists the molecular weight characterization data obtained by size exclusion chromatography (SEC) and by NMR. The diblock nomenclature we have used denotes the PLEA block as L and the PCL block as C, the subscripts indicate the approximate composition in wt% and the superscripts the approximate number average molecular weight of the entire block copolymer in kg/mol. 

Table 1. Molecular Weight Characterization and Film Forming Performance of PXPXDA-Based Poly(amic add)s and Soluble Polyimides...

When 2,6-dimethylphenol 1 was oxidized at room temperature with oxygen in pyridine solution in the presence of copper (I) chloride an exothermic reaction took place and the solution rapidly became very viscous. The polymer was isolated and characterized as the high molecular weight, linear poly (phenylene oxide) 2. 

Kruczek, Boguslaw, Development and Characterization of Dense Membranes for Gas Separation Made from High Molecular Weight Sulfonated Poly (Phenylene Oxide). Effect of Casting Connditions on the Morphology and Performance of the Membranes, Ph.D. Thesis, University of Ottawa, Ottawa ON 1999. 

The phenomena we discuss, phase separation and osmotic pressure, are developed with particular attention to their applications in polymer characterization. Phase separation can be used to fractionate poly disperse polymer specimens into samples in which the molecular weight distribution is more narrow. Osmostic pressure experiments can be used to provide absolute values for the number average molecular weight of a polymer. Alternative methods for both fractionation and molecular weight determination exist, but the methods discussed in this chapter occupy a place of prominence among the alternatives, both historically and in contemporary practice. 

A commercially available cationic standard that can be used for the calibration of CATSEC columns is poly(2-vinyl pyridine), or PVP. Cationic PVP can be characterized easily on CATSEC columns over a broad range of molecular weight. DRI chromatograms of two cationic PVP standards using a bank of CATSEC columns (100-, 300-, 1000-, and 4000-A pore size) and a mobile phase of 0.05 N NaNOi/0.1% TFA are shown in Fig. 20.10. 

Synthesis of hydrolytically stable siloxane-urethanes by the melt reaction of organo-hydroxy terminated siloxane oligomers with various diisocyanates have been reported i97,i98) -yhg polymers obtained by this route are reported to be soluble in cresol and displayed rubber-like properties. However the molecular weights obtained were not very high. A later report56) described the use of hydroxybutyl terminated disiloxanes in the synthesis of poly(urethane-siloxanes). No data on the characterization of the copolymers have been given. However, from our independent kinetic and synthetic studies on the same system 199), unfortunately, it is clear that these types of materials do not result in well defined multiphase copolymers. The use of low molecular weight hydroxypropyl-terminated siloxanes in the synthesis of siloxane-urethane type structures has also been reported 198). 

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