Dilute solution and bulk properties

Long,V.C. Thesis The effect of branching on the dilute solution and bulk properties of polyvinyl acetate. University of Michigan 1958. 

Whereas the above examples focused on end-capped polybetaines, the other molecular structural extreme is polymers end-capped with betaine groups, which are known, too. The dilute solution and bulk properties of such polymers with zwitterionic end groups were reviewed by Hadjichristidis et al. [237]. 

This presentation summarizes results on the synthesis, the dilute solution and bulk properties of dimethylamine and sulfozwitterionic end-functionalized polymers having different architectures (linear homopolymers, diblock and triblock copolymers and star polymers with different number of fimctional groups). 

All isotopes of element 85, astatine, are intensely radioactive with very short half-lives (p. 795). As a consequence weighable amounts of the element or its compounds cannot be prepared and no bulk properties are known. The chemistry of the element must, of necessity, be studied by tracer techniques on extremely dilute solutions, and this introduces the risk of experimental errors and the consequent possibility of erroneous... 

The synthesis of well-defined LCB polymers have progressed considerably beyond the original star polymers prepared by anionic polymerization between 1970 and 1980. Characterization of these new polymers has often been limited to NMR and SEC analysis. The physical properties of these polymers in dilute solution and in the bulk merit attention, especially in the case of completely new architectures such as the dendritic polymers. Many other branched polymers have been prepared, e.g. rigid polymers like nylon [123], polyimide [124] poly(aspartite) [125] and branched poly(thiophene) [126], There seems to be ample room for further development via the use of dendrimers and hyperbran-... 

The synthesis of end-functionalized (telechelic or semitelechelic) polymers has been the subject of numerous studies over the last decades due to both the academic and industrial interest developed for these polymers (1 4). The incorporation of end groups is capable to lead to dramatic changes in the dilute solution (5-7) and bulk properties (8,9) of the parent materials giving rise to practically and potentially numerous applications. 

Attempts to restrict the definition of SPs have been made. The most restrictive definition was proposed by Meijer and coworkers [2] to regard SPs as only those systems exhibiting chainlike behavior in diluted solutions. Such a definition is of interest since linear SPs do have peculiar properties (e.g., rheological ones) that widen possible applications of conventional polymers. However, a significant degree of supramolecular polymerization (DP) may not occur in dilute solutions while novel properties may appear in concentrated phases or in the bulk. Moreover, a less restrictive definition of SPs may highlight important features of supramolecular polymer chemistry better, in particular the use of approaches that cut across traditional boundaries between colloid, polymer, and solid-state science. 

These data are quoted from systematic studies on dilute solutions where bulk susceptibility effects have been taken into account and the solvents used were chosen to encompass a broad range of properties. 

Relationships between the synthesis and molecular properties of polymers (Chapter 2), and between their molecular and bulk properties (Chapters 4 and 5), provide the foundations of Polymer Science. In order to establish these relationships, and to test theories, it is essential to accurately and thoroughly characterize the polymers under investigation. Furthermore, use of these relationships to predict and understand the in-use performance of a particular polymer depends upon the availability of good characterization data for that polymer. Thus polymer characterization is of great importance, both academically and commercially. The current chapter is concerned with molecular characterization of polymer samples, by which is meant the determination of their average molar masses, molar mass distributions, molecular dimensions, overall compositions, basic chemical structures and detailed molecular microstructures. Since most methods of molecular characterization involve analysis of polymers in dilute solution (<20gdm ), the relevant theories for polymers in solution will be introduced before considering the individual methods. 

Although a discussion of the properties of crystals formed in dilute solution is not a major topic in this chapter, they are of great importance, both as entities in themselves and in relation to bulk crystallized systems. Of particular importance in the present context is the level of crystallinity that is attained and the structure of the non-crystalline region. The lamellar-like platelets that are formed in dilute solution and the chain orientation within the crystallites is well established. Based almost solely on the observation of lamellae, and the concept of regularly folded chains, a completely... 

Compared to dilute solution viscometry and to some extent to bulk rheology, the flow properties of dendrimers in concentrated solutions have been the least investigated area of dendrimer rheology. In fact, with the notable exception of some recent data on generation 4 PPI in water [22] the only [32] reported... 

The need for well defined polymer species of low polydls-perelty and of known structure arises from the Increasing Interest In structure-properties relationship In dilute solution as well as In the bulk. A great variety of methods have been attempted, to synthesize so-called model macromolecules or tailor made polymers-over the past 20 years. The techniques based on anionic polymerization, when carried out In aprotic solvents, have proved best suited for such synthesis, because of the absence of spontaneous transfer and termination reactions that characterize such systems. The "living 1 polymers obtained are fitted at chain end with carbanionic sites, which can either Initiate further polymerization, or react with various electrophilic compounds, intentionally added to achieve functionalizations. Another advantage of anionic polymerizations is that di-functlonal Initiators are available, yielding linear polymers fitted at both chain ends with carbanionic sites. In this paper we shall review the various utility of anionic polymerization to the synthesis of tailor made well defined macromolecules of various types. 

Trace impurities in noble metal nanoclusters, used for the fabrication of highly oriented arrays on crystalline bacterial surface layers on a substrate for future nanoelectronic applications, can influence the material properties.25 Reliable and sensitive analytical methods are required for fast multi-element determination of trace contaminants in small amounts of high purity platinum or palladium nanoclusters, because the physical, electrical and chemical properties of nanoelectronic arrays (thin layered systems or bulk) can be influenced by impurities due to contamination during device production25 The results of impurities in platinum or palladium nanoclusters measured directly by LA-ICP-MS are compared in Figure 9.5. As a quantification procedure, the isotope dilution technique in solution based calibration was developed as discussed in Chapter 6. 

It is much easier to demonstrate the existence of the kinks in the properties of aqueous solutions than in the properties of pure (bulk) water. The kinks do, however, seem to occur in the properties of both. For this reason, it is believed that the kinks (at least in dilute solutions) owe their existence to some phenomena associated with the structure of water itself and that the existence of the kinks in aqueous solutions are caused by the persistence of some particular structural features of pure water, even in the presence of ionic solutes. 

In a dilute solution, when the polymer is in a coil state (Fig. 6a), the diffusion of hydrophobic particles into the coil is normally faster than the chemical reaction [53]. In this case, the local concentration of particles H inside the coil is practically the same as in the bulk. Therefore, we expect that at the initial stage, the reaction will lead to a random copolymer some of the P monomeric units will attach to H reagent and thereby they will acquire amphiphilic (A) properties P + H —A (Fig. 6b). As long as the number of modified A units is not too large, the chain remains in a swollen coillike conformation (Fig. 6b). However, when this number becomes sufficiently large, the hydrophobically modified polymer segments would tend to form... 

The synthesis and the properties, both in bulk and in solution, of asymmetric star polymers are reviewed. Asymmetry is introduced when arms of different molecular weight, chemical nature or topology are incorporated into the same molecule. The phase separation, aggregation phenomena, dilute solution properties etc. are examined from a theoretical and experimental point of view. Recent applications of these materials show their importance in modern technologies. 

Homopolymerization of macromonomer provides regular star- or comb-shaped polymers with a very high branch density as shown in Fig. 1 a,c,e. Such polymacromonomers, therefore, are considered to be one of the best models for understanding of branched architecture-property relationships. Their properties are expected to be very different from the corresponding linear polymers of the same MW both in solution and the bulk state. Indeed, during the past decade, remarkable progress has been accomplished in the field of static, dynamic, and hydrodynamic properties of the polymacromonomers in dilute and concentrated solutions, as well as by direct observation of the polymers in bulk. 

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