Influence of the Molecular Weight

IV Behavior and Properties of Side Group Thermotropic Liquid Crystal Polymers 

Polymer Phase transitions Polymer Phase transitions 

The influence of the molecular weight on the mesomorphic properties of SmC polymers has been studied for a few examples [18, 34, 64, 65]. It turns out that the transition temperatures increase with the molecular weight, and in one case, a different phase succession occurs (Table 3). 

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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. 

The general correlations of structure and properties of homopolymers are summarized in Table 2.13. Some experiments which demonstrate the influence of the molecular weight or the structure on selected properties of polymers are described in Examples 3-6 (degree of polymerization of polystyrene and solution viscosity), 3-15, 3-21, 3-31 (stereoregularity of polyisoprene resp. polystyrene), 4-7 and 5-11 (influence of crosslinking) or Sects. 4.1.1 and 4.1.2 (stiffness of the main chain of aliphatic and aromatic polyesters and polyamides). 

The influence of the molecular weight of the dispersant on the quality of the slurry dispersion has been studied on both PCCs. The dispersants ranged in molecular weight from 2000 to 5800 (according to our internal standards) made by the process C. Results are summarised in Tables 4 and 5, below. 

Table II. Influence of the Molecular Weight of the Calibrating Compound ...

Obviously, this approach does not only take into consideration the influence of the molecular weight and concentration, but also the contribution of the solvent power on the state of solution. With these shear stability criteria, it is therefore possible to make ad hoc predictions on the basis of the data of the single chain, which can be taken from handbooks in many cases. In addition, it should be noted that theoretical forecasts fit the experimental data very satisfactorily (Kulicke, Kniewske 1986). 

Furthermore, we studied the influence of the molecular weight and degree of branching on transfection efficiency and cell toxicity, which is supposed to have influence, as initially analyzed in several adherent cell lines (NIH/3T3, CHO-K1, COS-7, and HeLa), with unfunctionalized poly(ethylene imine)s [91, 95, 96]... 

Fig. 26. Influence of the molecular weight Mg of the polyisoprene block on the thickness dg of the polyisoprene layer.

The relationship between 77/770 and qx0 appears to be dependent on the molecular-weight distribution. As a first approximation, this influence may be taken into account by using the distribution factor Q = Mw/Mn as a parameter. The available experimental data do not show an influence of the molecular-weight distribution on the relationship between t/t0 and qx0. Consequently, the factor Q should also be used as a parameter in correlating the data on G/G0 as a function of qx0. 

Fig. 11. Influence of the molecular weight of the polymer additive. Separation conditions PVA capillary L=50-57 cm, i.d.=75 pm buffer 60 mM AMPD/phosphoric acid, pH 8.8 + 10% w/w dextran =-300 V cm4 injection f=20 s,p=0.5 psi detection UV 254 nm...

The influence of the molecular weight of homopolystyrene POO on the formation of polystyrene occlusions is vividly seen in fig,7, where photographs of miorostructures of HIPS specimens are represented The specimens of HIPS are obtained by the polymerization of model emulsions, prepetred by mixing solutions of rubber - 8% and polystjprene - 30% in ratio 1 1, MW PS varied at 0,7-r-3 10, As seen in fig,7 the rubber particles, formed from multiphase model emulsion as a result of redistribution of monomer, differ greatly from each other, M of polystyrene... 

Superimposed on the temperature influence is an influence of the molecular weight of the amylose, as the rate of gelation (= retrogradation) increases with decreasing chain-length. ... 

Table 92. Influence of the molecular weight of the povidone type on solubilization ...

There are a large number of publications and papers in which the increase in absolute solubility of active substances by povidone has been tested and described. However, if the selection is restricted to the low-molecular types, this number becomes significantly smaller (Table 93). Naturally, a solubilization effect can also be expected of povidone K 12 and povidone K17, even if such an effect is reported in the literature only for the medium-molecular povidone (see Table 97), though the amounts of active substance complexed may differ according to the molecular weight of povidone (see Table 92). However, the influence of the molecular weight depends very much on the active substance with trimethoprim and chloramphenicol it is very large, while with phenobarbital it is small. 

Experimental and calculated data of the partial molar volume of polymers 36 (R=H), 37 (R=allyl), 37 (R=n-Bu, n-Oct) are in good agreement. In contrast to investigations with polyanions no influence of the molecular weight is detectable [75]. 

The influence of the molecular weight distribution of diblock copolymers on their segregating properties is considered in Sect. 4.2.4. It describes first experimental study [255] on a bimodal mixture of short symmetric and long asymmetric copolymers added to a polymeric matrix. Shorter copolymers were found to adsorb preferentially at the homopolymer interfaces in accord with brush formation observed from a solvent host matrix [274-276]. The mean field model is able [255] to predict the segregation isotherm of the bimodal mixture of copolymers, basing on single component adsorption data [254]. 

Schilinsky P, Asawapirom U, Scherf U, Biele M, Brabec CJ (2005) Influence of the molecular weight of poly(3-hexylthiophene) on the performance of bulk heterojunction solar ceUs. Chem Mater 17 2175... 

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