Molecular weight of poly

Figure C2.1.8. Reduced osmotic pressure V l(RTc as a function of the polymer weight concentration for solutions of poly(a-metliylstyrene) in toluene at 25 °C. The molecular weight of poly(a-metliylstyrene) varies...

Fig. 9. Melt flow index as a function of temperature for varying molecular weights of poly(ethylene oxide). WSR = Polyox water-soluble resins.

Molecular Weight. Measurement of intrinsic viscosity in water is the most commonly used method to determine the molecular weight of poly(ethylene oxide) resins. However, there are several problems associated with these measurements (86,87). The dissolved polymer is susceptible to oxidative and shear degradation, which is accelerated by filtration or dialysis. If the solution is purified by centrifiigation, precipitation of the highest molecular weight polymers can occur and the presence of residual catalyst by-products, which remain as dispersed, insoluble soHds, further compHcates purification. 

Molecular weights of poly(propylene oxide) polymers of greater than 100,000 are prepared from catalysts containing FeCl (40,41). The molecular weight of these polymers is gready increased by the addition of small amounts of organic isocyanates (42). Homopolymers of propylene oxide are also prepared by catalysis using diethylzinc—water (43), diphenylzinc—water (44), and trialkyl aluminum (45,46) systems. 

Liquid trichloroethylene has been polymerized by irradiation with Co y-rays or 20-keV x-rays (9). Trichloroethylene has a chain-transfer constant of <1 when copolymerized with vinyl chloride (10) and is used extensively to control the molecular weight of poly(vinyl chloride) polymer. 

HYDROPHOBIZATION AND THE MOLECULAR WEIGHT OF POLY(MA-CDA) ON CYTOKINE-INDUCING ACTIVITY... 

While our primary objective of developing conditions for the LC Pzn of P-PIN has not been reached, a simple route to relatively high molecular weight product (at least up to 40,000) was found. Experiments described in this communication also demonstrate that the molecular weight of poly(P-PIN) can be controlled by the polymerization temperature. 

Poly(malic acid) is a biodegradable and bioadsorbable water-soluble polyester having a carboxylic acid in the side chain. The chemoenzymatic synthesis of poly(malic acid) was achieved by the lipase-catalyzed polymerization of benzyl (3-malolactonate, followed by the debenzylation. The molecular weight of poly(benzyl (3-malolactonate) increased on copolymerizafion with a small amount of (3-PL using lipase CR catalyst. ... 

Table XXIX.—Molecular Weights of Poly-(Methyl Methacrylate) Fractions from Sedimentation and Diffusion Measurements ...

Weight average molecular weights of poly(HAMCL) with saturated or unsaturated pendent groups are relatively low, compared to Mw s of poly(HASCL), and in the range of 60,000 to 360,000 g mol as depicted in Table 2 [4,30,35,36]. Also for the poly(HAMCL) copolymers, the molecular weight distributions are unimodal. Their polydispersities are in the range of 1.6-2.4, which is narrower than the polydispersity of poly(3HB-co-3HV) copolymers, and close to the theoretical value of 2.0 for synthetic polycondensates such as chemically synthesized polyesters [54]. 

The molecular weights of poly(ketone)s obtained from diphenyl ketone and diphenyl sulfone are lower than those from diphenyl ether and diphenyl sulfide. The former monomers possess highly electron-withdrawing carbonyl or sulfone groups, which lower the electron density of the rings. 

Fig. 46. Determination of molecular weight of poly [ 1 (2-hydroxyethylpyridinium benzene sulphonate methacrylate by extrapolation of (Kc/R0)0=o to zero polymer concentration in aq. KC1 of different molarity141) (a) 0.01 M, (b) 0.02 M, (c) 0.1 M, (d) 3.0 M. The resultant molecular weight is 4.3 x 106...

Wolfert MA, Seymour LW. Atomic force microscopic analysis of the influence of the molecular weight of poly(L)lysine on the size of polyelectrolyte complexes formed with DNA. Gene Ther 1998 3(3) 269-273. 

Microspheres were monitored by scanning electron microscopy (SEM JEOL 35C), and their diameters were determined from the corresponding SEM microphotographs. Typically, ca. 500 particles in randomly sampled areas of microsphere specimens were analyzed. Molecular weight of poly(L-Lc) was determined by GPC. A system consisting of a LKB 2150 pump, Ultrastyragel 1,000, 500, 100, 100 columns, and Wyatt Optilab 903 interferometric refractometer was used for the measurements. GPC traces were analyzed by using calibration with narrow polydispersity < 1.15)... 

Molecular weight of poly(NAM-co-NAS) is determined by size exclusion chromatography (SEC) analysis. The eluent used is a DMF including 50 mM LiBr at a flow rate of 0.5 mL/min see Table 1). 

Table 6.4 Effect of the molecular weight of poly(vinyl pyrrolidone), PVP, on the polycondensation reaction of L-leucine. [Reprinted from N. Yamazaki and F. Higashi, Adv. Polym. Sci., 38,1 (1981)]...

The presence of poly(vinylpyrrolidone) in the system increases substantially molecular weight of poly(L-leucine) obtained. If the ratio of template to monomer is 1.35, the molecular weight is more then 10 times higher than for the blank reaction. The influence of molecular weight of PVP template on the molecular weight of the daughter polymer was very significant as seen from the Table 6.4. 

A method for controlling the molecular weight of poly(4-methyl-1-pentene) was devised by Hustad et al. (4) and entailed limiting the monomer concentration using a precatalyst and by adding a catalytic amount of a titanium(in)-containing salt as an ethylene interceptor. 

Table 12. Effect of counterion on the molecular weight of poly- N-vinylcarbazole) (/5)a...

A similar contribution from the counterion in the transition state for propagation would require formation of an energetically unfavoured four membered ring. Parallel data have been reported for the molecular weights of poly-(isobutenes) produced by y-ray irradiation (free ions) and chemical catalysis (ion pairs) (161), though in this case it was shown that entropy rather than enthalpy factors were more important. 

Effect of Conversion on the Weight-Average Molecular Weight of Poly(4-... 

The number-average molecular weights of poly(4-methyl-1 -pentene) s were measured in toluene at 37° C with a Hewlett-Packard membrane osmometer (model 503). 

Table 12. The effect of conversion on the molecular weight of poly(4-methyl-l-pentene)...

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