Polymers measurement

The use of water as a co-catalyst in Ziegler-type polymerizations was first introduced in 1962 (47). The reaction kinetics and crystallinity of the resulting polymers measured by x-ray scattering has been studied (48—51). 

Measurement of tensile or shear stress is the most commonly used in vitro method to determine bioadhesion. All in vitro measurements provide a rank order of bioadhesive strength for a series of candidate polymers. Measurement of tensile strength involves quantitating the force required to break the adhesive bond between the test polymer... 

Laquai F, Wegner G, frn C, Bassler H, Heun 8 (2006) Comparative study of frole transport in polyspirobifluorene polymers measured by the charge-generation layer time-of-flight technique. J Appl Phys 99 023712... 

X-ray diffraction techniques can be used to establish the structure of crystalline polymers. Measurements are typically made on crystalline lamellar platelets grown from dilute solution, fibres or stretched films. Such methods have been applied to several different inorganic polymers. For example, based on measurements on stretched samples of silicone rubber, poly(dimethylsiloxane) (Me2SiO) has been shown to possess a helical conformation (Figure 8.4). ... 

Thermal properties of the polyesters obtained were studied by TG and DSC. The starting temperature of decomposition (Tfrom Table III, Tpolymer measured in air is lower than that measured in nitrogen. T[Pg.219]

Band gaps of the polymers measured from the UV absorption onsets. 

When a low viscous solvent must be used in combination with a rather low molecular weight of the polymer, measurements are restricted to low /3-values, due to the discussed onset of turbulent flow. As in such a case the extinction angle % does not deviate very much from 45 degrees within the regime of laminar flow, it must be measured with a high absolute accuracy to furnish a reliable value for cos 2% or cot 2% [cf. eq. (3.42) or (3.44a)]. Measurements on a polydisperse sample become more reliable under such conditions due to the fact that cot 2 is increased by the polydispersity factor [eqs. (3.75a) and (3.83a)]. Examples for such a behaviour will be discussed in Section 3.8.3. 

The most convenient of these methods is viscosity measurement of a liquid in which particles coated with a polymer are dispersed, or measurement of the flow rate of a liquid through a capillary coated with a polymer. Measurement of diffusion coefficients by photon correlation spectroscopy as well as measurement of sedimentation velocity have also been used. Hydrodynamically estimated thicknesses are usually considered to represent the correct thicknesses of the adsorbed polymer layers, but it is worth noting that recent theoretical calculations52, have shown that the hydrodynamic thickness is much greater than the average thickness of loops. 

Table III shows x values for other structurally regular substituted silane high polymers measured both at 1.064 and 1.907 /an. Examination of this data suggests relatively little difference between the polysilanes with nonplanar, yet regular structures and trans planar PDN6S which is included in the table for comparison. This result is a little surprising given that changes in backbone conformation can cause spectral absorption shifts of more than 60 nm.

Polymerization of phenolic compounds (measurement of optical density) IR spectra resembling natural humic substances yields of humic polymers measurement of 02 uptake... 

In the first case the resulting polymer has two dendrons for every three phe-nylene rings and in the second case there are two dendrons on every second phe-nylene ring. The higher apparent MW of the polymers, measured by SEC, suggest that the first polymer is easier to prepare than the denser substituted second polymer [114]. 

For the comparison with the materials discussed just now the nonlinear refractive indices of PTA and TEE can be estimated. These estimations lead to values comparable with PPV and other polymers measured outside resonance result (Table 8). 

Shamov (1966) has pointed out the importance of the time dependence of the Poisson ratio of polymers. Measurements on polymers at very low frequency will yield values near Z2, whereas data obtained at very high frequencies will yield values asymptotically approaching Ms. The value of v is thus a function of the rate of measurement. This fact is illustrated by data of Warfield and Barnet (1972) and Schuyer (1959) ... 

TABLE 13.14 A comparison of the statistical segment volume for flow for a polymer measured in solution with the flow volumes, Vact, derived from the Eyring theory... 

Table 6. Thermal stability of metal-poly-yne polymers (measured by thermogravimetric analysis at heating rate of 5 °Omin)...

Table 3.2 Excited electronic states of polymers measured by UV spectroscopy and...

Table 3.4 Macroscopic non-linear optical properties ofpoled polymers. Measurement wavelengths are shown in square brackets.

Let s start our discussion of the range of viscoelastic properties of amorphous polymers by considering the modulus of an amorphous polymer measured as a function of temperature. We know that any measurement of stress, hence modulus, we make is going to vary with time (see Equation 13-71), so to compare values at different temperatures we make all our measurement... 

Network polymers can also be made by chemically linking linear or branched polymers. The process whereby such a preformed polymer is converted to a network structure is called cross-linking. Vulcanization is an equivalent term that is used mainly for rubbers. The rubber in a tire is cross-linked to form a network. The molecular weight of the polymer is not really infinite even if all the rubber in the tire is part of a single molecule (this is possible, at least in theory), since the size of the tire is finite. Its molecular weight is infinite, however, on the scale applied in polymer measurements, which require the sample to be soluble in a solvent. 

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