Effect of Polymerization Conditions

It has been reported that polymerization temperature has a considerable effect on particle break-up and, therefore, on the final particle morphology [108, 109]. Maneshi et al. [69] observed that higher polymerization temperatures, up to a certain upper limit, enhanced clay exfoliation. Above this upper limit (which varies depending on the polymer and solvent type) active site and/or polymer chain start being extracted from the clay surface, resulting in poor exfoliation, inadequate powder morphology, and severe reactor fouling. 

In some investigations, it has been shown that the clay content in nanocomposites can be tuned by setting the polymerization time [30, 52]. However, it should be remembered that, depending on the in-situ polymerization system, the particle morphology may undergo noticeable changes during polymerization [52, 70]. 

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Figure 4. Effect of polymerization conditions on the release characteristics of the insulin/poly(acrylic acid) resin system.

Effect of Polymerization Conditions on Structure. The properties and structural classification of some polymers obtained from MPP and DPP under varying reaction conditions are summarized in Table VI. 

Block copolymers were also produced by oxidizing mixtures of the two homopolymers. A summary of the effect of polymerization conditions on the structures of polymers prepared using equimolar amounts of the two monomers is presented in Table III. The preformed blocks used in these examples were a DMP homopolymer prepared with a diethylamine-cuprous bromide catalyst and a DPP polymer prepared with tetramethyl-butanediamine-cuprous bromide at 60°C. Each had an average degree of polymerization of approximately 50 units. 

The effect of polymerization conditions on Cp has been studied mainly for two-component systems based on titanium chloride and vanadium chloride . The number of propagation centers changes with the polymerization time proportionally to the reaction rate and is independent of the monomer concentration (0.2-2 mol/1 at 70 °C). Most interesting is the effect of the polymerization temperature on Cp. It has been found that with rising temperature Cp ingreases (Table 3). In the... 

Hjerten and his research group [41] introduced monolithic columns based on acrylamides as chromatographic separation media in the late 1980s. Xie et al. [42] prepared rigid porous polyacrylamide-co-butylmethacrylate-co-A,A -methylene-bis-acrylamide monolithic column for hydrophobic interaction chromatography. They also prepared polyacrylamide-co-At, M-methylene-bis-acrylamide monolithic rods and smdied the effect of polymerization conditions on rods morphology. 

The effects of polymerization conditions on the molecular weight distribution of polyethylene synthesized with Cp2TiCl2/MAO catalysts have been studied in comparison with analogous zirconium and hafnium complexes.1206,1207... 

Effect of polymerization conditions Hagiwara et al. on elongation of films [115]... 

On the other hand, we reexamined in detail the ring size of the cyclic structural units of poly-AA s by means of IR, 1H-NMR, and C-NMR spectroscopy these analytical procedures were applied to the structural analysis of poly-AA, the poly(acrylic acid) derived from hydrolysis of the poly-AA, and the poly(methyl acrylate) obtained by subsequent esterification of the poly(acryl-ic acid) in comparison with the corresponding model polymers of five- or six-membered ring structure. Then, we investigated in detail the effects of polymerization conditions on the ring size of poly-AA s, i.e., on the intramolecular addition modes in the cyclopolymerization of AA since five- or six-membered ring anhydride structure can be formed via intramolecular hh or ht addition of the uncyclized radical to the internal double bond(22,23). 

In light of the results discussed above, it appears that literature reports on the effect of polymerization conditions (such as temperature. Al/Zr ratio, cocatalyst, and solvent type) on chiral metallocene performance (not only activity but also stereo- and regio-regularity, propagation/transfer rates), unless obtained in liquid propene. should be taken with some precautions. 

Stefani, M., Coudane, J. and Vert, M. (2006) Effects of polymerization conditions on the in vitro hydrolytic degradation of plaques of poly(dl-lactic add-block-ethylene glycol) diblock copolymers. Polymer Degradation and Stability, 91, 2853-2859. 

Pazzagli Federico, Paci Massimo, Magagnini Pierluigi, Pedretti Ugo., Como Carlo, Bertolini Guglielmo, Veracini Carlo, A. (2000). Effect of Polymerization Conditions on the Microstmcture of a Liquid Crystalline Copolyester. J. Appl. Polym. Sci., 77(1), 141-150. 

The results obtained by Bergstrom and Avela [7] by methyl content analysis of the TREF fractions from these four resins are illustrated in Fig. 21. It was noted that only the reference resin and to a lesser extent grade 1 gave the normal relatively linear relationship between methyl content and separation temperature whereas many fractions from grades 2 and 3 exhibit significantly higher separation temperatures than expected from methyl content data. It was concluded that this was due to the presence of composite molecules and reflected effects of polymerization conditions. 

The radiation-initiated polymerization of vinylidene fiuoride is used on a laboratory scale only. The effect of polymerization conditions on the chain defects, content, and changes in the crystalline phases have been studied [528,536,537,544]. Doll and Lando [544] used a °Co source with an average dose rate of 0.33 Mrad/h. The polymerization was carried out between 0 and 400 °C at a pressure equal to the vapor pressure of the solvent-vinylidene fluoride mixture. Esters and ketones (acetone, methyl ethyl ketone, ethyl acetate, acetophenone), DMF, DMSO, and y-butyrolactone were used as solvents. All these solvents are good chain-transfer agents for vinylidene fluoride. The molding characteristics of the resulting polymers were very poor and the intrinsic viscosity of the sample polymerized in acetone solution was low (0.183 dL/g) compared to that of a suspension-polymerized polymer (1.68 dL/g) [544]. 

Table I. Effect of Polymerization Conditions on the Co-Polymerization Parameters (r, T2) of Dilactide and Caprolactone...

Hild, G, Lamps, J.P., and Rempp, P. (1993) Synthesis and characterization of anionic 2,3-epoxypropyl methacrylate polymers and of related random and block copolymers with methyl methacrylate. Polymer, 34,2875-2882. Hirano, T., Miki, H., Seno, M., and Sato, T. (2005) Effect of polymerization conditions on the syndiotactic-specificity in radical polymerization of Wisopropylacrylamide and fractionation of the obtained polymer according to the stereoregularity. Polymer, 46,5501-5505. 

The above kinetic model allows the calculation of monomer conversion, polymer molecular weight, and branching frequency. The effects of polymerization conditions and the reactor types (e.g., batch, continuous segregated, and continuous micromixed reactors) have been investigated using the above kinetic model [71]. 

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