Single-phase polymerization

In a fundamental sense, the miscibility, adhesion, interfacial energies, and morphology developed are all thermodynamically interrelated in a complex way to the interaction forces between the polymers. Miscibility of a polymer blend containing two polymers depends on the mutual solubility of the polymeric components. The blend is termed compatible when the solubility parameter of the two components are close to each other and show a single-phase transition temperature. However, most polymer pairs tend to be immiscible due to differences in their viscoelastic properties, surface-tensions, and intermolecular interactions. According to the terminology, the polymer pairs are incompatible and show separate glass transitions. For many purposes, miscibility in polymer blends is neither required nor de-... 

The most widely used method for preparing extended-chain crystals involves solid-phase polymerization when the monomer exists as a single crystal. The polymerization of single crystals of the monomer permits the preparation of a polymer material with a maximum orientation a polymeric single crystal composed of fully extended macromolecules. Such polymer crystals are needle-shaped22. ... 

The drug and other molecules are assumed to be in a single phase with the polymeric structure. 

A kinetic model for single-phase polymerizations— that is, reactions where because of the similarity of structure the polymer grows as a solid-state solution in the monomer crystal without phase separation—has been proposed by Baughman [294] to explain the experimental behavior observed in the temperature- or light-induced polymerization of substimted diacetylenes R—C=C—C=C—R. The basic feature of the model is that the rate constant for nucleation is assumed to depend on the fraction of converted monomer x(f) and is not constant like it is assumed in the Avrami model discussed above. The rate of the solid-state polymerization is given by... 

The catalyst life might be improved. Several studies on isomerization and polymerization processes indicate that supercritical solvents can dissolve coke-precursors on the catalyst surface, and remove them before they can form actual coke, and this improves the catalyst life [33,34]. Since coke formation also occurs in hydrogenation processes, it is reasonable to believe that catalyst life can be improved also for supercritical single-phase hydrogenation. 

The electronic properties are also modified by polymerization. Experimentally, the band gap decreases to less than 1.2 eV in the low-pressure orthorhombic phase [65], and experiments [66,88,108] and calculations [80,109-111] agree that the band gap should decrease with an increasing number of intermolecular bonds. (We note the possible exception of the high-pressure polymerized orthorhombic phase, as discussed above.) Calculations [85, 111] show that the rhombohedral phase should have a more three-dimensional band structure than the orthorhombic phase but still be a semiconductor. However, recent measurements by Makarova et al. [88] showed that oriented samples of the rhombohedral phase had an extremely large electrical anisotropy, larger than that of single-crys-... 

Single Phase Polymerization Mathematical Modelling Ziegler-Natta Polymerization Polymerization Processes (Monograph) Emulsion Polymerization Polymerization Reactions and Reactors Continuous Reactors (ed. volume)... 

In a later patent (1986) it is disclosed that phase separation of cz s-1,4-BR and BD occurs at 30 to 35 °C. Below 30 °C there is a single phase and above 35 °C there are two distinct phases of BR and BD. By the application of two polymerization steps the first of which is performed below and the second above the critical solution temperature molar mass is decreased and costs for aluminum alkyls which are used for molar mass control are reduced [511,512], Control of molar mass is further improved by the sequen-... 

Least atomic motion. Single-phase polymerizations will in general be more favorable for topochemical reactions than for nontopochemical reactions. That is, reactions which require only small degrees of atomic translation or reorientation are more likely to proceed without phase separation. 

Reaction uniqueness. The structure of the monomer lattice must uniquely determine which monomer molecules will react, and in what fashion. Further, symmetry elements of the monomer lattice must be preserved for molecular subunits of the polymer. If this is not the case, local disorder can result. This criterion severely limits the number of monomer crystal structures which can be expected to polymerize via single-phase mechanisms. External forces of some kind which reduce the symmetry of the monomer lattice can be used to help meet the uniqueness criterion. 

As the exothermal reaction occurs after 200 min of stirring, the cubic octamer and the species with molecular weights higher than the cubic octamer are recovered from the bottom phase. As indicated with the mixture containing sodium ions, it appears that the polymerization of silicate species following the hydrolysis of tetraethoxysilane proceeds abruptly when the exothermal reaction occurs. Actually, the amount of tetraethoxysilane in the top phase decreases pronouncedly as the temperature rises, and the mixture becomes a single phase within a few minutes of the exothermal reaction. 

Similar results have been reported recently by Parent and Thompson (16) for blends prepared by polymerizing MMA in the presence of PS. In their work, in which the M of PS was varied from 2100 to 49,000, a single phase was observed under electron microscopy up to 20 wt% PS-2100, a concentration somewhat higher than observed in this work but in general agreement with our results. Trends in miscibility with M were in agreement with this work as well. 

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