Molecular mass Control

The weight average molecular mass controls light scaUering because the polarizabihty of the solvated polymer governs the scattering of light and polarizability, in turn, depends on molecular mass. 

Relative molecular mass controls the magnitude of A, but has no effect on the general pattern of behaviour (the stress dependence of A). 

Journal of Applied Polymer Science 61, No.l, 5th July 1996, p.9-19 MOLECULAR MASS CONTROL IN METHACRYLIC COPOLYMER LATEXES CONTAINING GLYCIDYL METHACRYLATE Guerts J M Jacobs PE Muijs J G Van Es J J G S German A L... 

The main role of the alkyl halide (RX) is to generate growing chains quantitatively. The structure of the alkyl group R preferably mimics the growing polymer chain. Therefore a-halopropionates are effective initiators for the ATRP of acrylates [288]. The main importance of the choice of the initiator for the polymerization of acrylates and methacrylates is based on the requirement of a fast initiation to obtain molecular mass control. A slow initiation results in higher moleeular masses than predicted and a higher polydispersity, which is specified in Table 9 for the polymerization of MMA [299]. Similar results were also observed for the phosphine-based Ni(II) eomplexes [301,302] and the Ni(0) complex. Here, well controlled radical polymerization was only possible with bromide initiators [303]. 

Formulation example monomer(s), hydrogen (molecular mass control), catalyst Maier, R-D Bidell, Encyclopedia of Materials Science Technology, 7694-97, Elsevier, 2008. 

In addition to favorably affecting rate, high pressure is advantageous with respect to molecular mass control. Dispersity, PDI, of polystyrene generated via CDB-mediated polymerization could be improved, for example, has been... 

For situations controlled by anodic dissolution of a film P = 1/density of metal, but if the corrosion is controlled by the cathodic reaction P = 1/density of metal x nc Ma/na Me where n and M are the number of electrons and the molecular masses of anodic and cathodic reactants. 

The first DNA preparations in this part of the study was PCR product - DNA of Chlamydia trachomatis 17 > bp), in the presence of a smaller by molecular mass internal control of human DNA. After migration the gel was exposured for 5, 30, 300 and 600 seconds by transilluminator Vilber Lourmat, equipped with 6 UV lamps with irradiance W = 0,24 W/m2 and 254 nm filter. The degree of structural integrity loss of amplificated DNA was evaluated by the decrease of brightness intensity of the of the bands processed by using the tools of "ImageJ" computer program. 

Polymerisations triggered by butyl lithium have often led to detonations, which destroyed the installations. The reaction can be best controlled by first incorporating polystyrene with a low molecular mass. 

The termination of Ziegler-Natta synthesis is obtained by neutralisation of the catalytic site using, for instance, alcohol. The reaction can also simply be stopped (with no clear termination) by embedding of the catalyst into the polymer. Industrially, the control of final molecular mass is often accomplished by a hydrogen transfer reaction (see Figure 28). 

First step radical polymerisation of butadiene in the presence of a chain transfer agent to control its molecular mass. 

The concentration of the synthase or the number of enzyme copies has been assumed to have an influence on the molecular mass and molecular mass distribution of the synthesized polymer [33],but this has not been confirmed. The only variables found so far to control the molecular mass of the polymer are the initial ratio of substrate to enzyme levels, and the concentration of inducing factors in the culture medium [34-36] cf. also Chap. 9 of this book. 

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