Polymerization mechanism, factors affecting

The formation mechanism of structure of the crosslinked copolymer in the presence of solvents described on the basis of the Flory-Huggins theory of polymer solutions has been considered by Dusek [1,2]. In accordance with the proposed thermodynamic model [3], the main factors affecting phase separation in the course of heterophase crosslinking polymerization are the thermodynamic quality of the solvent determined by Huggins constant x for the polymer-solvent system and the quantity of the crosslinking agent introduced (polyvinyl comonomers). The theory makes it possible to determine the critical degree of copolymerization at which phase separation takes place. The study of this phenomenon is complex also because the comonomers act as diluents. 

Chapter 3 describes basic mechanical testing procedures. This chapter describes various structural-related factors which affect polymeric mechanical properties. 

Price, C. C. Mechanism of vinyl polymerizations. IX. Some factors affecting copolymerization. J. Polymer Sci. 1, 83 (1946). 

Another factor affecting addition is the tendency of monomers to form complexes with other components of the polymerizing system. This was discussed in Chap. 2, Sects. 4.2 and 5.2. The effect of the medium is, of course, also reflected in the mechanisms of termination and transfer. A somewhat unusual but interesting and instructive effect of the environment of an active centre on the course of propagation was observed in polymerization on a liquid—gas phase boundary, and during polymerization of liquid crystals. 

Because the hydrodynamic thickening mechanism of conventional ASTs (ASE and ASNE) is also present in the associative ASTs (HASE and HASNE), common factors affecting the thickening behavior of both types of thickeners would be expected, and are indeed observed. In a previously unpublished study (DeSoto, Inc. internal report), Brizgys and Shay examined the effect of the nonassociative hydrophobic comonomer on the thickening behavior of urethane-functional HASE thickeners prepared under identical conditions of semicontinuous emulsion polymerization. The results (Table I) obtained with respect to Tg and water solubility of the hydrophobic comonomer were generally similar to those observed for conventional ASTs by others cited earlier in this chapter. 

Temperature and other environmental factors affect the mechanical behavior. Thus, polymers can show all features of a glassy brittle solid, an elastic rubber, or a viscous liquid depending on the temperature and time scale of measurements. At low temperatures or high frequencies, a polymeric... 

The morphology of IPNs can be determined by electron microscopy. The morphology has a great influence on the physical and mechanical behaviour. The phases differ, however, in amount, size and shape, sharpening of their interface and degree of continuity. The factors affecting morphology are chemical compatibility of the polymers, interfacial tension, crosslink density of the networks, polymerization methods and IPN composition. 

J. A., and Volpert, VA. (2005) Isothermal frontal polymerization confirmation of the mechanism and determination of factors affecting Ifont velocity, front shape, and propagation distance with comparison to mathematical modeling. 

Since the configurations of the polymeric chains are affected by mechanics-based factors, as well as by the magnitude of the free volume, they necessarily interact with the diffusion process. Unlike the aforementioned case of creep, the imposition of a constant strain would presumably maintain all fully relaxed polymeric chains at nearly fixed configurations during fluid ingress and thus yield data that may be largely uncoupled. Accordingly to this supposition such data - collected... 

As a main difference with main-chain LSCEs, in side-chain LSCEs, the photoactive azo chromophores, which are responsible for the observed photo-mechanical effect, are connected to the polymeric main chain via flexible spacers. Therefore, it should be expected that the length of such flexible spacer, in other words, the flexible alkyl chain that links the azobenzene core to the main polysiloxane backbone, is one of the main factors affecting the mechanical response produced by artificial musclelike actuators based on this type of elastomeric materials (Garcia-Amoros et al. 2011a). 

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