Polymers chain length

If, beside nonuniformity in chain length, polymer P is also characterized by nonuniformity in composition, then to solve the molecular recognition task it is necessary to know the dependence of AG on the structure of the macromolecule. 

Kestose synthesis by 1-SST is limited by the availability of sucrose in the 0 to 100 mol m 3 range (Cairns and Ashton, 1991 Van den Ende and Van Laere, 1993). Therefore, high sucrose concentrations favor the rate of the first polymerization step and indirectly the synthesis of longer-chain-length polymers due to an elevation in 1-kestose concentration, which acts as a fructosyl donor. Glucose is converted to sucrose by sucrose synthase in the cytosol (Pollock, 1986 Wiemken et al., 1986) (Figure 10.18). 

The fact that composite inulin extracts can be fractionated on a commercial scale into reasonably discrete chain length classes allows tailoring of the product to intended market uses. Hence, the chain length condition of the raw product is important in that it is relatively easy to depolymerize inulin to give shorter-chain-length fractions however, current in vivo attempts to create longer-chain-length polymers on an economically viable scale have not been optimistic. 

Reaction of a molecule that is activated with an initiator to form a free radical. This free radical, when reacting with a normal molecule creates a new free radical, causing a full fledged chain reaction. This process creates, from a monomer, a long chain polymer instantaneously. No intermediate chain length polymers are present. This process is also called vinyl polymerization. 

The lower theta temperature corresponds to the minimum solution temperature extrapolated to infinite chain length. Polymer precipitation at low temperatures comes about because of a poor heat of mixing between polymer and solvent. In a sealed tube at high temperatures, solvent volume expands much more than that of the polymer. Entropic factors make mixing more difficult when there is a large free volume mismatch between solute and solvent. One believes that the polymer dimensions contract as the LCST is approached. Phase separation occurs when it is exceeded. 

Three reasonably well-defined modifications of solid SO3 exist. y-SOs, which is often described as ice-like , is orthorhombic and consists of cyclic trimers with traces of monomeric SO3 included. With even traces of water, y-SO3 or liquid SO3 polymerize to give glistening needles of monoclinic jS-SOs. This modification is believed to consist of a mixture of different chain length polymers if warmed, it melts with depolymerization between 32-45 °C. o -S03 has a higher melting point than the other solid forms and consists of higher polymers, almost certainly in a layer structure. 

Termination is generally considered to involve the combination of two radicals, as shown in Scheme 3. The rate of termination in an ideal termination reaction, which is independent of chain length, polymer heterogeneity or impurities, and radical trapping, is as follows ... 

Madkour, T. Mark, J. E., Some Evidence on Pore Sizes in Poly(dimethylsiloxane) Elastomers Having Unimodal, Bimodal, or Trimodal Distributions of Network Chain Lengths. Polym. Bull. 1993, 31, 615-621. 

In addition to linear polymers, polymers of different shapes have also been of interest. For example, star polymers have been developed in which multiple chains are polymerized from a mnltivalent initiator—usually using living polymerization to control the chain length. Polymers with this kind of shape have quite different physical properties to linear polymers—for example, they have lower viscosity, as less chain entanglement takes place, and fewer polymer-polymer noncovalent interactions can occur. 

The molar mass (chain length) polymers with high molecular masses are more reluctant to crystallize than those of low molecular masses,... 

Chain length, polymer profile, and grating profiles... 

Unlike the case for metals, secondary bonds are of great importance in polymers. These bonds are much weaker than covalent bonds, but for even moderate chain length polymers these bonds have a significant impact on the molecular and bulk properties of these materials. These intermolecular bonds are based on electrostatic interactions and are due to either attractions between permanent dipoles, quadmpoles, and other multipoles, or between a permanent multipole and an induced charge on a second molecule (or moiety, in the case of a polymer), or between transient multipoles. All such secondary bonds can be considered van der Waals forces, but many texts use van der Waals to denote induced and/or transient multipole interactions only. The induced interaction is sometimes referred to as polarization, or sometimes induction bonding. The transient interaction is very weak and is known as dispersion or London dispersion forces, and arises from electrostatic interactions between two molecules due to temporary inhomogeneous electron density distributions in the outermost electron shells of these molecules. 

Dzunuzovic, E. S., J. V. Dzunuzovic, T. S. Radoman et al. 2013. Characterization of in situ prepared nanocomposites of PS and Ti02 nanoparticles surface modified with alkyl gallates Effect of alkyl chain length. Polym. Compos. 34 399-407. 

Figure 2 shows a plot of W f) versus r for polymers at different molecular weights. It can be seen that the probabihty that the chain ends are within the capture radius (i.e., the distance of a covalent bond) is highly sensitive to molecular weight. The smaller chain length polymer has a greater chance of being in a conformation... 

Koch H, Bachus R, Kimmich R. Molecular fluctuations in polyethylene melts. Dependence of the longitudinal and transverse proton relaxation on the chain length. Polymer 1980 21 1009. 

The temperature and molecular weight dependence of the surface tension for the n-alkanes is correctly predicted and is shown to be related to the dependence of liquid density on chain length. Polymer liquid surface tensions satisfy a corresponding states principle and can be estimated for many polymers with an error of less than 10%. This method of estimating pol3mier surface tensions appears to be the most accurate that is available. 

The concentrations of each chain length polymer at conversion p thns are predicted to follow... 

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