Comparison with conventional polymerization

In summary, microflow systems are quite effective for molecular-weight distribution control of very fast, highly exothermic free-radical polymerizations. The superior heat transfer ability of the microflow system in comparison with conventional macrobatch systems seems to be responsible for the high molecular-weight distribution controllability. It should be noted that the controllability is much lower than is achieved by conventional living free-radical polymerization, because residence time control does not work for controlling radical intermediates. The lifetime of a radical intermediate is usually much shorter than the residence time in a microflow system. It is also noteworthy that the more rapid and exothermic the polymerization is, the more effective the microflow system is. These facts speak well for the potentiality of microflow systems in the control of highly exothermic free-radical polymerization without deceleration by reversible termination. 

Table 9-8. Dielectric Properties of Plasma-Polymerized Films in Comparison with Conventional Polymers at Temperature 20°C and Frequency 1 kHz...

The development of photoinitiators for cationic polymerization is an important one, with both practical and fundamental applications. Practical uses are primarily in the area of light-induced curing of coatings, a process which is expected to be energy-conservative in comparison with conventional thermal curing (4). 

Abstract This chapter describes the influence of three-dimensional nanofillers used in elastomers on the nonlinear viscoelastic properties. In particular, this part focuses and investigates the most important three-dimensional nanoparticles, which are used to produce rubber nanocomposites. The rheological and the dynamic mechanical properties of elastomeric polymers, reinforced with spherical nanoparticles, like POSS, titanium dioxide and nanosdica, were described. These (3D) nanofillers in are used polymeric matrices, to create new, improved rubber nanocomposites, and these affect many of the system s parameters (mechanical, chemical, physical) in comparison with conventional composites. The distribution of the nanosized fillers and interaction between nanofUler-nanofiUer and nanofiller-matrix, in nanocomposite systems, is crucial for understanding their behavior under dynamic-mechanical conditions. 

Applications of microparticles can be found in medicine, biochemistry, colloid chemistry, and aerosol research [48]. Some uses include separation media for chromatographic application, high surface area substrates for immobilized enzymes, standards for calibration, spacers in optical cavities and liquid crystal displays, and three-dimensional microenvironments for cell encapsulation. It should be stressed that even a scaled-up MF synthesis enables generation of a relatively small amount of particles, in comparison with conventional emulsion, dispersions, or suspension polymerizations. Thus, most practical applications of such microbeads should utilize their high-value unique properties, for example, a uniform distribution of sizes and control of morphology, structure, and shape. Therefore, some of the demonstrated applications of polymer microbeads are still in the proof-of-concept stage. 

In contrast, it was also reported that under microwave conditions the ATRP of MMA in a p-xylene solution did not give any rate enhancement in comparison with conventional conditions. The polymerization reaction exhibited a good... 

The synthesis of poly (ether imide) s in the condensation of disodium salt of PBA and bis(chlorophthalimide)s was also described under microwave irradiation (Figure 55). The polymerization reactions were performed under PTC conditions in an o-dichlorobenzene solution. The polymerization reactions, in comparison with conventional heating polycondensation, proceeded rapidly (25 min vs. 4h at 200 °C), and polymers with inherent viscosities in the range of 0.55-0.90 dlg" were obtained. 

Comparison with Conventional Emnlsion Polymerization. Let us eonsider two series of experiments with different KPS concentrations. One of these series is a conventional emulsion polymerization (involving a surfactant) and the second is a soap-free proeess involving Laponite and PEGMA. 

Monodispersed poly (methyl methacrylate-ethyleneglycol dimethacrylate) is prepared by a multistep swelling and polymerization method. When a good solvent such as toluene is applied as a porogen, the seed polymer severely affects the pore structure, whereas no effects are observed with poor solvents, such as cyclohexanol, as a porogen, in comparison with the conventional suspension polymerization (68,69). 

In vitro synthesis of polyesters using isolated enzymes as catalyst via non-biosynthetic pathways is reviewed. In most cases, lipase was used as catalyst and various monomer combinations, typically oxyacids or their esters, dicarboxylic acids or their derivatives/glycols, and lactones, afforded the polyesters. The enzymatic polymerization often proceeded under mild reaction conditions in comparison with chemical processes. By utilizing characteristic properties of lipases, regio- and enantioselective polymerizations proceeded to give functional polymers, most of which are difficult to synthesize by conventional methodologies. 

Template polymerization can be used for production of polymers with much higher molecular weights in comparison with those obtained by conventional process (in the last case a degradative addition frequently takes place). It was shown based on the example of N-vinylimidazole polymerization. By the template process, polymers with up to 70 times higher molecular weight than in conventional polymerization were obtained. 

Table II. Yield Comparison of Conventional Fixed-Bed Hydroforming with Thermal Reforming Plus Catalytic Polymerization...

So far, a great number of well-defined macromonomers as branch candidates have been prepared as will be described in Sect. 3. Then a problem is how to control their polymerization and copolymerization, that is how to design the backbone length, the backbone/branch composition, and their distribution. This will be discussed in Sect. 4. In brief, radical homopolymerization and copolymerization of macromonomers to poly(macromonomers) and statistical graft copolymers, respectively, have been fairly well understood in comparison with those of conventional monomers. However, a more precise control over the backbone length and distribution by, e.g., a living (co)polymerization is still an unsolved challenge. 

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