Polymer absorbed

The polymers absorb some moisture and at the high moulding temperatures employed this can be very troublesome, leading to streaks and splash marks. 

Infrared spectra and the degree of specific rotation show typical features of the malic acid polyester (Table 3). Ultraviolet absorbance spectra of )3-poly(L-malate) from both P. polycephalum and Aureobasidium sp, A-91 are similar and are reminiscent of malate itself [4,5]. For a solution of 1.0 mg/ml polymer, absorbance increases from 0.40 units at 230 nm to 10 units at 190 nm wavelength. After saponification and pH-neutralization, the absorbance increased from 8.7 units at 230 nm to 100 units at 190 nm. 

Fig. T A shows the GPC traces obtained at wavelength 2 k and 3U0 nm for a 312 nm Dow latex sample. Note the response at 3 0 nm is at twenty-five times the sensitivity of the response at 25 nm and hence considerably exaggerated in comparison. At 25 nm two peaks are clearly noted, a polymer peak and a secondary peak whose retention volume corresponds to that of styrene monomer. At 3 0 nm, since neither monomer nor polymer absorb, the observed peak is attributable to the presence of additives such as emulsifier.

A film of the branched chain 5-methylhexyl polymer absorbed at 315 nm and the position of this maximum was relatively insensitive to temperature. Likewise, no thermal transition was observed in the region where the side chain melting transition was seen for PDHS and its higher homologs. 

Other thiophene-thiophene-5,5-dioxide copolymers were reported by Berlin et al. [544], who synthesized copolymers 443 and 444 with an alternating electron acceptor thiophene-5,5-dioxide unit and donor ethylenedioxythiophene (EDOT) units (Chart 2.107). The polymers absorbed at 535 nm (Eg = 2.3 eV) in chloroform solution and in films (which is consistent with their electrochemistry Eox 0.40-0.50 V, Emd -1.75-1.8 V AE 2.2-2.25 V) and emitted at 650 nm (<1> M (film) 1%). Such a high band gap (which exceeds that in PEDOT... 

The absorption and emission of radiation in the near ultraviolet (UV) and visible regions of the electromagnetic spectrum are associated with electronic (and associated vibronic) transitions involving n- and/or n-electron systems of molecules. Synthetic and natural polymers absorb in the UV region and particularly strong absorption spectra are recorded for polymers containing aromatic and heteroaromatic groups (e.g., poly(styrenes), poly(vinyl naphthalenes), poly(vinyl carbazoles)). 

When a polymer absorbs very strongly in the visible region, near IR incident radiation is used. In a very coloured solution the scattered intensity is reduced by a factor exp(—e)2) where e is the absorption coefficient of the solvent. Hence i0 must be multiplied by exp(+e ) in order to obtain the true scattered intensity undiminished by absorption effects. For small values of efi, the quantity exp(efi) approximates well to (1 + e2) so that Eq. (42) becomes38. ... 

In this investigation, you will examine three different polymers. First, you will examine the addition polymer sodium polyacrylate. This polymer contains sodium ions trapped inside the three-dimensional structure of the polymer. When placed in distilled water, the concentration of sodium ions inside the polymer is much greater than the concentration of sodium ions outside the polymer. The concentration imbalance causes water molecules to move hy diffusion into the polymer. As a result, the polymer absorbs many times its own mass in distilled water. 

A fiber-optic device has been described that can monitor chlorinated hydrocarbons in water (Gobel et al. 1994). The sensor is based on the diffusion of chlorinated hydrocarbons into a polymeric layer surrounding a silver halide optical fiber through which is passed broad-band mid-infrared radiation. The chlorinated compounds concentrated in the polymer absorb some of the radiation that escapes the liber (evanescent wave) this technique is a variant of attenuated total reflection (ATR) spectroscopy. A LOD for chloroform was stated to be 5 mg/L (5 ppm). This sensor does not have a high degree of selectivity for chloroform over other chlorinated aliphatic hydrocarbons, but appears to be useful for continuous monitoring purposes. 

One of the most common techniques for determining x parameters for polymer-solvent systems is the vapor pressure method.(10) In this approach, the uncrosslinked polymer is exposed to solvent vapor of known pressure, p. The polymer absorbs solvent until equilibrium is established, x is related to p and V2, the volume fraction of polymer at equilibrium, by the Flory-Huggins equation (ll)... 

Note 1 A polymer sorbent may be a polymer adsorbent or a polymer absorbent. The... 

Enhanced reaction rates have also been observed in some instances of decreased polymer solubility with conversion when the precipitating polymer absorbs the small-molecule reactant. Adsorption results in an increased concentration of the reactant at the actual polymerization site (the polymer coils). Similar effects are observed if a catalyst is adsorbed onto the precipitating polymer [Beresniewicz, 1959]. 

G(s) and G(x) are defined as the number of scissons and the number of crosslinks produced when the polymer absorbs 100 eV. of ene and R is the radiation dose expressed in Mrads. JTable I lists values of M , and M measured for irradiated MP20 samples. A plot of M, and M vs. radiation dose is shown in Figure 1. The solid lines in Figure 1 are linear least-squares fits to the data in Table I. Values for G(s) and G(x) were determined from the slopes of these lines to be 6.8 0.9 and 0.3 0.3, respectively. 

Unless they are formed directly in solution, polymers dissolve in two general steps. First, the polymer absorbs solvent to form a swollen gel. The second step involves the dissolution of the gel into the solution, sometimes called a sol. Networked or thermoset... 

Little is known about the mass transport properties of reinforced-composite materials. Certainly, there are no new relations or concepts that govern estimations of diffusiv-ities that have not already been discussed. In most polymer-matrix composites, the transport properties of the polymer play an important role in diffusion through the composite. For example, hydrophilic polymers such as epoxy readily absorb water from the atmosphere. Thermoplastic polymers absorb relatively little moisture since they are more hydrophobic, but are more susceptible to uptake of organic solvents. 

Most polymers absorb electromagnetic radiation at characteristic wavelengths in the infrared region. Hence infrared spectroscopy is used for the... 

As noted earlier, many polymers absorb well in the UV and VUV region of the energy spectrum with successful surface modification occurring when these materials are exposed to sufficient photon intensity of appropriate wavelength. In the early 1980s, Kawarmura et and Srinivasan and Mayne-Banton... 

When the polymer absorbs small molecules, it swells and the conductivity decreases. 

If the polymer absorbs at a wavelength where both solvent and precipitant are transparent, HPPLC can be performed with the help of a UV detector. Styrene-containing copolymers can be analyzed with alkane hydrocarbon/THF eluents at around 254 nm. In order to gain high sensitivity in gradient elution, we removed the stabilizer from the THF by distillation under N2 123). Caution is required with respect to peroxides. 

Polysilanes with several oxygen atoms in the side chains have been studied by Cleij and coworkers.83 84 These polysilanes may become water soluble, as is the case for [MeSi(CH2)3(OCH2CH2)3OCFl3] . In THF solution at 20 °C this polymer absorbs at 305 nm, but in water the UV band is shifted to 281 nm. The water may cause tighter coiling of the polymer chains, perhaps due to micelle formation. Between 46 and 70 °C, the water solution undergoes phase separation. The UV band shifts to 320 nm, consistent with partial straightening of the polymer chain after phase transition. These polymers also display ionochromism. 

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