Solid polymeric systems

Jones DS, Woolfson AD, Djokic J, Coulter WA. Development and mechanical characterization of bioadhesive semi-solid, polymeric systems containing tetracycline for the treatment of periodontal diseases. Pharm Res 1996 13(11) 1734—1738. 

Equipment for heterogeneous reactions is particularly flexible, since each phase can be processed more or less independently. In the fluidized-bed reactor (Fig. 1-4) the reactants flow continuously through and out of the reactor, but the solid-catalyst phase is withdrawn, regenerated, and returned. In the lime kiln (an example of a gas-solid noncatalytic reactor) the two phases pass continuously and countercurrently through the reactor. In heterogeneous liquid-solid polymerization systems the slurry of catalyst and reaction mixture flow together through the reactors. Walas, Brotz, and particularly van Krevelen have summarized the various types of... 

Dynamic Analysis of Solid Polymeric Systems of Pharmaceutical and Biomedical Importance... 

Smets G, De Blauwe F. 1974. Chemical reaction in solid polymeric systems. Photomecha nical phenomena. Pure Appl Chem 39 225 238. 

Astarita, G., Heat and Mass Transfer in Solid Polymeric Systems, Adv. Transp. Processes, 5, 339-351, 1989. 

The invasion of particles can be eliminated either by using solids-free systems or by formation of a competent filter cake on the rock surface. If the components forming the filter cake are correctly chosen and blended, they will form a very effective downhole filter element. This ensures that colloidal sized clays or polymeric materials are retained within the filter cake and do not enter the formation. Further protection is provided by ensuring that a thin filter cake is formed due to low dynamic and static filtrate losses. Thus, the cake may be easily removed when the well is brought into production. Additionally, the filter cake can be soluble in acid or oil. 

Although the purpose here is not to give a full understanding of photoeleciron spectroscopy, it can be useful to discuss some of the specific features in a photoelectron spectrum which can be helpful for the understanding of the different examples discussed in this chapter. The main emphasis in the background to PES will be focused on the molecular solids aspect since this chapter deals with condensed conjugated systems. The interested reader can find a more in-depth discussion on the technique, relative to organic polymeric systems, in Refs. [4, 9, 10]. 

Contrary to the phase separation curve, the sol/gel transition is very sensitive to the temperature more cations are required to get a gel phase when the temperature increases and thus the extension of the gel phase decreases [8]. The sol/gel transition as determined above is well reproducible but overestimates the real amount of cation at the transition. Gelation is a transition from liquid to solid during which the polymeric systems suffers dramatic modifications on their macroscopic viscoelastic behavior. The whole phenomenon can be thus followed by the evolution of the mechanical properties through dynamic experiments. The behaviour of the complex shear modulus G (o)) reflects the distribution of the relaxation time of the growing clusters. At the gel point the broad distribution of... 

Beyond the notion of physical networks in which flexible strands are connected by junctions, we will use the term physical gelation in the widest possible sense for polymeric systems which undergo liquid-solid transition due to any... 

While these spectroscopic and redox properties alone would be sufficient for direct use of transition metal complexes in solution-phase ECDs, polymeric systems based on coordination complex monomer units, which have potential use in all-solid-state systems, have also been investigated. 

Solid [Fe(salacen)(l-methyl-imidazole)2]C104 displays a relatively complete, gradual spin crossover [180]. Measurements of both 57Fe Mossbauer spectra and magnetism indicate that the transition observed in the one-dimensional polymeric system [Fe(salacen)(l,l -tetramethylenediimidazole)] C104 is also gradual but incomplete at both 290 K (/ze/j=5.37 B.M.) and 4.2 K (Heff=337 B.M.) [180],... 

The biphasic system was transferred to a separatory funnel (250 mL) and extracted with ether (3 x 40 mL). The organic fractions were combined. The solvent was removed using a rotary evaporator, to produce a yellow oil and a white solid (polymerized trimethoxysilane). 

A frequent complication in the use of an insoluble polymeric support lies in the on-bead characterization of intermediates. Although techniques such as MAS NMR, gel-phase NMR, and single bead IR have had a tremendous effect on the rapid characterization of solid-phase intermediates [27-30], the inherent heterogeneity of solid-phase systems precludes the use of many traditional analytical methods. Liquid-phase synthesis does not suffer from this drawback and permits product characterization on soluble polymer supports by routine analytical methods including UV/visible, IR, and NMR spectroscopies as well as high resolution mass spectrometry. Even traditional synthetic methods such as TLC may be used to monitor reactions without requiring preliminary cleavage from the polymer support [10, 18, 19]. Moreover, aliquots taken for characterization may be returned to the reaction flask upon recovery from these nondestructive... 

Values of Mw/M of 2 or less are common for the soluble catalyst systems whereas values of 4-8 are usual for ZNC systems. The soluble catalyst systems also are able to polymerize a larger number and greater variety of vinyl monomers to form homogeneous polymers and copolymers in comparison with solid catalyst systems. 

Figure 1.13—occur because of simultaneous crystallization and polymerization at 150°C. This temperature is near the maximum crystallization rate temperature ( 145°C) of nylon 6 homopolymer [66]. The presence of solid crystallites increases the complex viscosity of the polymerizing system because of a filler effect. 

The dynamic mechanical behavior of most homogeneous and heterogeneous solid and molten polymeric systems or composite formulations can be determined by DMA. These polymeric systems may contain chemical additives, including fillers, reinforcements, stabilizers, plasticizers, flame retardants, impact modifiers, processing aids, and other chemical additives, which are added to the polymeric system to impart specific functional properties and which could affect the process-ability and performance. 

Different pol)uneric materials respond to irradiation by electron beam in different ways. A large number of them will be modified by the formation of a cross-linked network, by changing their surface properties or structure, and some will be degraded. Another field applicable to polymeric systems is polymerization and grafting. Electron beam can also be used for pol5unerization and cross-linking of oligomers and monomers, i.e., in conversion of liquids to solids. 

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