Polymer melt intrinsic viscosity

The present authors12,13) also studied the polymerization of 2 with boron tri-fluoride etherate as the initiator. High molecular weight polymers with intrinsic viscosities up to 1.87 dl/g were obtained in methylene chloride at —78 °C. The polymers melted at 160—180 °C, and showed some crystallinity as observed by X-ray diffraction. 

Because of their novel topologies, polyrotaxanes have properties different from those of conventional polymers. Solubility, intrinsic viscosity, melt viscosity, glass transition, melting temperature and phase behavior can be altered by the formation of polyrotaxanes. The detailed changes are related both to the properties of the threaded cyclics and to the backbone and the threading efficiency. 

Polyanhydrides can be synthesized by melt condensation of trimethylsilyl dicarboxylates and diacid chlorides to yield polymers with intrinsic viscosities up to 0.43 dl/g [31, 32] ... 

This polymer may be prepared by stirring the molten w-aminoundecanoic acid at about 220°C. The reaction may be followed by measurements of the electrical conductivity of the melt and the intrinsic viscosity of solutions in w-cresol. During condensation 0.4-0.6% of a 12-membered ring lactam may be formed by intramolecular condensation but this is not normally removed since its presence has little effect on the properties of the polymer. 

Due to dieir compact, branched structure and to die resulting lack of chain entanglement, dendritic polymers exhibit much lower melt and solution viscosity dian their lineal" counterparts. Low a-values in die Mark-Houwink-Sakurada intrinsic viscosity-molar mass equation have been reported for hyperbranched polyesters.198 199 Dendrimers do not obey diis equation, a maximum being observed in die corresponding log-log viscosity-molar mass curves.200 The lack of chain entanglements, which are responsible for most of the polymer mechanical properties, also explains why hyperbranched polymers cannot be used as diermoplastics for structural applications. Aldiough some crystalline or liquid... 

Poly(N-phenyl-3,4-dimethylenepyrroline) had a higher melting point than poly(N-phenyl-3,4-dimethylenepyrrole) (171° vs 130°C). However, the oxidized polymer showed a better heat stability in the thermogravimetric analysis. This may be attributed to the aromatic pyrrole ring structures present in the oxidized polymer, because the oxidized polymer was thermodynamically more stable than the original polymer. Poly(N-phenyl-3,4-dimethylenepyrroline) behaved as a polyelectrolyte in formic acid and had an intrinsic viscosity of 0.157 (dL/g) whereas, poly(N-pheny1-3,4-dimethylenepyrrole) behaved as a polyelectrolyte in DMF and had an intrinsic viscosity of 0.099 (dL/g). No common solvent for these two polymers could be found, therefore, a comparison of the viscosities before and after the oxidation was not possible. 

Figure 2.19 Intrinsic viscosity of the polymer melt as a function of extruder residence time and temperature for an initial water content of 3 ppm...

After reaching the desired DP, 40-50 % of the oligomeric melt is transferred to the polymerization vessel. Titanium butoxide (50-150 ppm) or dibutyl tin oxide catalyst (100-250 ppm), or some combinations of the two catalysts, is added to catalyze polymerization at 260-275 °C. A vacuum of <0.15 kPa is applied to remove the condensed water so as to drive the reaction until the polymer reaches an intrinsic viscosity (IV) of 0.7-0.9 dL/g. 

Solid-state polycondensation (SSP) is thus a technique applied to thermoplastic polyesters to raise their molecular weight or IV. During solid-state polycondensation, the polymer is heated above the glass transition temperature and below the melt temperature of the polymer either under an inert gas or under vacuum. Increasing the intrinsic viscosity requires a residence time of up to 12 h under vacuum or under inert gas, at temperatures from 180 to 240 °C. 

Subsequently, an improved method based on TPX materials is described (26). A starting polymer of TPX having an intrinsic viscosity of 9.38 dl g 1 and a melting point of 237°C as measured with a differential scanning calorimeter was degraded in the presence of dicumyl peroxide. The degraded polymer had an intrinsic viscosity of 1.17 dl g 1 and a melting point of 212-220°C. 

Tn the previous papers of this series (1, 2, 3, 4) calibration and repro- ducibility of gel permeation chromatography (GPC) have been extensively examined. This paper describes the application of GPC to two selected samples of linear polyethylenes, one having a narrow molecular weight distribution (NMWD) and another a broad molecular weight distribution (BMWD). These samples were distributed by the Macro-molecular Division of IUPAC (5) for the molecular characterization of commercial polymers. The average molecular weights by GPC are compared with the data obtained from infrared spectroscopy, osmotic pressure, melt viscosity, and intrinsic viscosity. Problems associated with data interpretation are discussed. 

In the manufacture of polyesters by melt polycondensation, the apparent polycondensation rate decreases with an increasing degree of polymerization, and the terminal carboxyls increase because of longer holdup time (3). Consequently, it is very difficult to obtain PET with an intrinsic viscosity above 0.9 and with carboxyls less than 15 eq/106 g polymer. 

Kehr M, Fatkullin N, Kimmich R (2007) Molecular diffusion on a time scale between nano-and milliseconds probed by field-cycling NMR relaxometry of intermolecular dipolar interactions Application to polymer melts. J Chem Phys 126 094903 Kirkwood JG, Riseman J (1948) The intrinsic viscosity and diffusion constant of flexible macromolecules in solution. J Chem Phys 16 565-573 Klein J (1986) Dynamics of entangled linear, branched, and cyclic polymers. Macromolecules 19(1) 105—118... 

The [Cr(H20)(0H) 0P(C H8)20 2]a polymer is a green solid which is readily soluble in chloroform, benzene, and tetrahydro-furan but is insoluble in water and diethyl ether. It does not melt before decomposing thermogravimetric analysis indicates decomposition starting at 365°C. A freshly prepared solution in chloroform has an intrinsic viscosity ranging from 0.03 to 0.04 dl./g. The intrinsic viscosity increases slowly when solutions in organic solvents (for example, 1 g./lOO ml. in chloroform) are allowed to stand at temperatures of approximately 55°C., and values of 0.6-0.8 dl./g. are common after a number of days. A sample with an intrinsic viscosity of 0.04 dl./g. 

Table 10 also contains values of the unperturbed dimensions of many aliphatic polyesters. Most of these have been evaluated from the extensive results of Batzer and his collaborators (32a, 32b, 32c, 32d, 32c, 33a, 168") which combine intrinsic viscosities with osmotic molecular weights of fractions. Since almost all of these polymers have rather high crystalline melting points, and since the fractionations were generally performed at temperatures well below these melting points, we have somewhat arbitrarily chosen a value of 1.5 for the molecular weight ratio which corresponds to a figure of 1.22 for the correc-... 

A derivation of Moore s equation relatii melt and intrinsic viscosities. J. Polymer Sci. 41, 551 (1959). 

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