Monomer composition

Similar patterns of property differentiation are clearly recognized at the macromolecular level. For example, dramatic changes in physical and chemical properties are observed by simply converting a linear topology of common composition to a cross-linked architecture. In traditional macromolecular science, these issues were considered apparent and obvious. However, as novel architectures emerged, new architecture-property relationships have not been so clearly articulated and exploited. Prompted by the synthetic accessibility of many new polymeric architectures based on common compositional monomers... 

The ability to determine which copolymerization model best describes the behavior of a particular comonomer pair depends on the quality of the experimental data. There are many reports in the literature where different workers conclude that a different model describes the same comonomer pair. This occurs when the accuracy and precision of the composition data are insufficient to easily discriminate between the different models or composition data are not obtained over a wide range of experimental conditions (feed composition, monomer concentration, temperature). There are comonomer pairs where the behavior is not sufficiently extreme in terms of depropagation or complex participation or penultimate effect such that even with the best composition data it may not be possible to conclude that only one model fits the composition data [Hill et al., 1985 Moad et al., 1989]. 

Geurtsen W,Lehmann F Spahl W, Leyhausen G. Cytotoxicity of 35 dental resin composite monomers/additives in permanent 3T3 and three human primary fibroblast cultures. J Biomed Mater Res 1998. 4L474-80. 

The properties of a copolymer depend on its composition, monomer sequence and stereochemical structure. Although compositional analysis can be achieved by several methods other than NMR spectroscopy, quantitative data on monomer sequence distribution can only be obtained from NMR spectroscopy. I3C NMR chemical shifts of C=0 carbons of PMMA are sensitive to pentad to heptad stereochemical sequences. The C=0 carbon signals for the copolymers of methacrylates are also sensitive to triad comonomer sequence. Thus it should be difficult to assign both tactic and comonomer sequence signals, especially in the case of copolymers with low stereoregularity. 

Copolymer of Compositions, % monomer Copolymer of Compositions, % monomer... 

Certain cyclic monomers are build up from two or more other simpler compounds which can serve as monomers by themselves. Thus, during the polymerization of more complex cyclic monomers simpler structures may emerge during the polymerization process. Szwarc 83) for the first time quantitatively treated the thermodynamics of polymerization of such a composite monomer, reevaluating the experimental data of Schulz et al. M). Below we follow Szwarc s reasoning applied for the cationic polymerization of 1,3,5-trioxepane (TXP), a monomer comprising formaldehyde (FA) and 1,3-dioxolane (DXL). Under equilibrium conditions besides the unreacted monomer both FA and DXL are also present ... 

The difficulties in forming copolymers of certain olefins with SO2 have been discussed in a number of papers [61d]. The highest copolymerization rates were found in systems containing an electron-donor monomer with low resonance stabilization and gave alternating copolymer compositions. Monomers with high resonance stabilization with elechon-acceptor groups result mainly in homopolymerization under normal conditions. For example, styrene forms only a... 

Plant polysaccharides tend to be heterogeneous in nature, with distributions of molecular weight, composition, monomer sequence, and functional groups. Monomer sequence distribution is often a critical parameter in determining the functional properties of the polysaccharide. While the spectroscopic analysis of these materials may produce an accurate assessment of the monomer composition, the monomer sequence distribution is a statistical average of the... 

Polymers are found in such a large variety of products that they have shaped modern life. The extraordinary versatility of polymers in terms of end-use properties is due to the variety and complexity of the microstructure of the polymeric material. The polymeric material includes both the polymer and the additives with which it is compounded. The microstructure of the polymeric material is determined by the molecular and morphological characteristics of the polymer itself, the way in which the polymer is processed and the additives used for compounding (Figure 1.1). The molecular characteristics of the polymer include chemical composition, monomer sequence distribution (MSD), molecular weight distribution (MWD), polymer architecture, chain configuration and morphology. 

Figure 6.1 presents some important microstructural features of the emulsion polymers. They include copolymer composition, monomer sequence distribution (MSD),... 

The entire range of properties of a synthetic fiber depends especially on the molecular composition (monomers and tacticity tacticity means the geometric regularity of polymer side chains) and the... 

FIGURE 16.8 Dependence of the refractive index at 532 nm on the copolymer composition (monomers A and C). 

The practical volume in which polymerization is carried out is also important. In this respect, one should mention isobutene polymerization in a tubular reactor (L = 0.7 m, < ) = 0.02 to 0.03 m) without stirring under adiabatic conditions—that is, reaction heat is used for preheating reaction mass [38]. The small diameter of the tubular reactor and the small reaction mass circulation rate (0.01 to 0.02 m/s) ensure the laminar character of the flow. Reaction mass constant composition (monomer and catalyst concentration) is ensured by mixer 4 (Fig. 4). Mean residence time of reaction mixture in the reactor is 35 to 70 s. Its adiabatic character does not provide an even temperature throughout the reactor... 

Just like the determination of MMDs requires separation of polymers according to molar mass (or molecular size in solution, e.g. by SEC) the determination of CCDs requires separation of polymers according to chemical composition (PhilHpsen, 2004). A distinction can be made between the overall chemical composition (monomer ratio) of a copolymer... 

Details are given of a method for monitoring the realtime curing dynamics of composite monomers, exploiting site specific information provided by high resolution NMR. Data using polyvinylpyrrolidone, polyhydroxy-ethyl methacrylate and polybutylhydroxycyclohexyl methacrylate are compared with results from a computer simulation based on a multicomponent kinetic model. 7 refs. 

Kapur and Brar [192] report the C-NMR spectra of a series of acrylonitrile-methyl methacrylate copolymers. The primary structure, including monomer composition, monomer sequence distribution and triad tacticity of A/M copolymers were determined on the basis of C[ H]-NMR analysis and compared with the calculated fractions. The resonance of carbonyl and nitrile carbons were assigned to different cotactic triads by considering the possible electronic interactions between the central monomer unit and its immediate neighbours. 

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