Effects on Molecular Weight Distribution

Table II. Effect of Lewis acid Nd compound molar ratio on molecular-weight distribution. Polymerization conditions butadiene concentration, 10 wt % in cyclohexane catalyst concentration, 7.5 X 10 5 mol/1 molar ratio Nd(vers)3, Et3AI2Cl3, AlEt3 is 1 X 30 polymerization time 2 h, and 60°C.

Figure 7. Effect of polymerization temperature on molecular weight distribution...

Figure 6. Effect of molecular weight distribution on sensitivity for P(HI-VBC) resists.

The molecular weight distribution obtained from SEC analysis was also shown in Fig. 8. In order to check the effect of the estimated exponent a(-0.55) on molecular weight distribution for Ei branched PVAc, we used another a(-0.58) value to compute a new calibration curve as shown in Fig. 9. The two calibration curves almost overlapped with each other. The results are listed in Table 2. In both cases, we obtained the same weight-average molecular weight and the polydispersity index (M /M ). Thus, we could confirm that in using a two-point (Bq and %l) estimate for a, we have not introduced an appreciable error in the determination of molecular weight distribution of branched PVAc. 

Graessley,W.W., Segal,L. Effect of molecular weight distribution on the shear rate dependence of viscosity in polymer systems. A-I.Ch.E. J. 16,261-267 (1970). 

The amount of thermal initiation which takes place at 138°C. and its effect on molecular weights and their distributions were also studied. Two batches were polymerized thermally using monomer mixture A. 

Time Effect of Gegenion on Molecular Weight Distribution. The... 

Figure 6 shows the GPC chromatograms of the phenolic resins. Other than the phenolic resin at 46%, resin solid content resulted in slightly higher molecular weight (Table V), the effect of resin solid content on molecular weight distribution was not significant. 

Table 9.2 Effect of the microflow system on molecular-weight distribution control...

Polymerization of benzyl methacrylate (BMA) is much slower than that of BA. Although the yield of the polymer increased with an increase in the residence time, the polymerization did not complete within 12 min. The value of M /Mn was much smaller than that for BA, both in the microflow system and the macrobatch system. The effect of the microflow system on molecular-weight distribution control is, however, smaller than for the BA case. Probably, temperature control for BMA polymerization is better than that for BA polymerization, even in the macrobatch system, because heat generation per unit time for BMA polymerization seems to be much less than that for BA polymerization. 

Studies on the relative rates of the polymerization are helpful in obtaining a deeper insight into the effect of the microflow system on molecular-weight distribution control. It can be seen from Figure 9.11, where the polymer yield obtained in the microflow system is plotted against the reaction time (residence time) for each monomer, that the rate of polymerization increases in the order St < VBz < MMA < BMA < BA. This trend is consistent with the propagation rate constants reported in the literature (Table 9.2). It is reasonable to consider that a similar order is... 

Effects of added BPA on molecular weight distribution for PC exposed to X > 314 nm. 

What has been said above about the effect of molecular-weight distribution on rjo and J° is similarly applicable to the low-molecular-weight region where the contributions of the p,A t) and px t) processes cannot be neglected. The analjTical expressions for 770 and J° cannot be obtained from the full expression of the relaxation modulus (Eq. (9.19)). Yet theoretical values of rjo and J°, including the contributions of PA t) and px(f)> can be numerically calculated with a computer program. 

Liberatore, M. W., Baik, S., McHugh, A. J., and Hanratty, T. J., Turbulent drag reduction of polyacrylamide solutions effect of degradation on molecular weight distribution, J. Non-Newtonian Fluid Meek, 123, 175-183 (2004). 

Ben-Ghedalia, B., Yosef, E. Effect of isolation procedure on molecular weight distribution of wheat straw lignins. J. Agric. Food Chem. 42, 649-652 (1994)... 

The effect of the flow rate on molecular weight distribution (Table 1, runs 4-6) indicates the importance of mixing, because it is known that mixing efficiency decreases with a decrease in the flow rate in the micromixer [65]. Reaction temperature is also important for controlling molecular weight distribution, as demonstrated by an increase in with an increase in temperature (runs 4... 

Kamide,K., Sugamiya,K., Ogawa,T., Nakayama.C., Baba,N. Experimental verification of effects of conditions ofpredpitational fractionation on molecular weight distribution of the first fraction by atactic polystyrene/methylcyclo-hexan system. MakromoL Chem. 1, 23 (1970). 

What is the effect of molecular weight distribution on negative Nft What is the origin and nature of the large periodic fluctuations in normal force observed in lyotropic but not isotropic solutions of PBG + m-cresol ... 

Spiegelberg S.H., S.M. Kurtz, and A.A. Edidin. 2001. Effects of molecular weight distribution on the network properties of radiation- and chemically crosslinked ultra-high molecular weight polyethylene. Trans. 25th Society for Biomaterials 215. 

---