Apolar polymers

The surface of silica is covered by a layer of acidic silanol and siloxane groups. This highly polar and hydrophilic character of the filler surface results in a low compatibihty with the rather apolar polymer. Besides, highly attractive forces between silica particles result in strong agglomeration forces. The formation of a hydrophobic shell around the silica particle by the sUica-sUane reaction prevents the formation of a filler-filler network by reduction of the specific surface energy [3]. 

SPE is a useful device for working up of polymer additive dissolutions the apolar polymer is retained on the Cj 8 sorbent, while analytes may be eluted. In the fractionation of dissolutions it is advantageous to make use of the differences in polarity and affinity of the components with the sorbent. SPE of applied samples may be done with cartridges or disks, either off- or on-line. A flow-chart for the use of SPE has been published [3], Applications of SPE have been described in several monographs [511,512]. 

Mohr G.J., Werner T., Oehme I., Preininger C., Klimant I., Kovacs B., Wolfbeis O.S., Novel optical sensor materials based on solubilization of polar dyes in apolar polymers. Advanced materials 1997 14 1108-1113. 

Polymers follow the same mles as other species, but more strongly so (Figure C3-9). This is because they can have multiple adsorption bonds on interfaces. An apolar polymer in a polar solvent will adsorb strongly on an apolar interface and vice versa. Such adsorption can get... 

The steric hindrance parameter a is a constant only in the case of apolar polymers in apolar solvents. A distinct dependence of the hindrance parameter on the type of solvent can be observed, however, for polar polymers and/or polar solvent combinations (see Table 4-7). Such effects are to be expected because of changes brought about in the trans I gauche ratios of conformers in the chain. 

Consequently, typical commercial plasticizers are molecules of not too low molar mass and are not too thermodynamically poor solvents. Apolar plasticizers are suitable for apolar polymers for example, heavy oils for polydienes. In contrast, polar plasticizers must be used for polar polymers, i.e.. 

Apolar substances have low solubility parameters, whereas those of polar substances are high, since the heat of vaporization is higher for the latter. Apolar, noncrystalline polymers will therefore dissolve well in solvents with low di values. Predictions about solubility on the basis of the solubility parameter are still quite permissible for polar, noncrystalline polymers in polar solvents (see Table 6-3). It is more difficult in the case of crystalline polymers or apolar polymers in polar solvents, and vice versa, since equation (6-13), which was derived for pure dispersion forces, no longer applies in these cases. 

SEC and high mass fractions were analyzed, the MS peaks due to distinct oligomers did not overlap. All-trans retinoic acid is used when the analyte is an apolar polymer. It gives good results for PS. It gives no signal if the cationization salt (silver salts work best) is not added. Small amounts of soaps and detergents such as sodium dodecyl sulfate have dramatic effects on spectral quality. 

Chlorosalycilic acid is used for apolar polymers too. Unfortunately, the ion yield falls quickly as the number of laser shots increases. 

To explore the use of PFD as a contrast-enhancing medium in force distance measurements on polymer surfaces, two series of polymers were chosen for the experiments a first series, consisting of apolar polymers with different refractive indexes, and a second series, in which polymers of different hydrophobicities/hydrophi-licities were selected. 

Mass spectrometry experiments in general, and MALDI-TOF in particular, require the sample to be in the gas phase and ionized. Ionization is commonly achieved by the complexation of a cation with the polymer molecule. Polymers containing heteroatoms such as polyethers, polyamides, polyesters, polymethyl-metacrylates, polysiloxanes, and polycarbonates are reasonably simple to be cationized by the addition of sodium or potassium salts. Apolar polymers containing double bonds such as polyst5Tene, polybutadiene, and polyisoprene can also... 

As mentioned in the section imder Normal Forces, van der Waals interactions in different media between SFM probes and apolar polymers have been successfully described using the Lifshitz theory (86). As shown in Figure 22 (left), various polymers can be differentiated clearly in force measurements. For polymers containing polar groups, a correlation of adhesive forces and the cosine of the water contact angle have been predicted and observed (66,85,204). An obvious requirement for reliable force data are flat substrates (205,217,218). 

In order to obtain materials stable with good properties, the blends have to be compatibilized. In this work, we have investigated the effects of the compatibilization on the structure, rheological, and mechanical properties of blends of PET and PP. The compatibilizer used in this study is a triblock copolymer consisting of polystyrene end-blocks and poly(ethylene-butylene) mid-blocks grafted with maleic anhydride, MA-g-SEBS. This copolymer was already used to compatibilize other blends of polar and apolar polymers with satisfactory results. 

This intricate scheme of interaction may be described in terms of sets of compatibility parameters easily calculated (or measured) for relevant binary systems (e.g., side chain/solvent, core/solvent, core/side chain) [49,50]. The knowledge of pairwise parameters is also necessary for a quantitative assessment of the temperature variation of solubility and demixing (two liquid phases or crystallization). According to an approximate treatment of binary solutions originally developed for mixtures of poorly interacting apolar polymers, a liquid-liquid phase separation is expected to occiu at a critical temperature T = 0 > 0 at which a balance of the enthalpy (k) and entropy i/r) components... 

This is satisfied for most polymers (e.g., Table XIII-5 in van Oss book ) except perfluorinated polymers and most of the polyolefins (polypropylene, polyisobutylene, etc). Miscibility is also promoted for all apolar polymers (y 0) with 26 mJ/m < y < 125 mJ/m, and for polar polymers with y J 26 mJ/m ... 

MALDI - Pyrolyzates with much higher molecular weight can be detected. - Observation of the thermally induced structural changes in the polymer samples. - Fast time of analysis. - MWD determination by SEC-MALDI. - Matrix interference - no low-molecular-weight detection (below miz 500). - Difficulties to analyse unsoluble or apolar polymers. - Indirect method - only the degradation products most thermally stable will survive. - Suppression of degradation products present in trace. - Only quahtative analysis. 

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