Synthetic polymers of, III

Mani R., Bhattacharya M., Properties of injection moulded starch/synthetic polymers blends-III. Effect of amylopectin to amylose ratio in starch, Eur. Polym. J., 34, 1998,1467-1475. 

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

Unlike other synthetic polymers, PVDF has a wealth of polymorphs at least four chain conformations are known and a fifth has been suggested (119). The four known distinct forms or phases are alpha (II), beta (I), gamma (III), and delta (IV). The most common a-phase is the trans-gauche (tgtg ) chain conformation placing hydrogen and fluorine atoms alternately on each side of the chain (120,121). It forms during polymerization and crystallizes from the melt at all temperatures (122,123). The other forms have also been well characterized (124—128). The density of the a polymorph crystals is 1.92 g/cm and that of the P polymorph crystals 1.97 g/cm (129) the density of amorphous PVDF is 1.68 g/cm (130). 

Leather Tanning and Textiles. Although chromium (VT) compounds are the most important commercially, the bulk of the appHcations in the textile and tanning industries depend on the abiUty of Cr(III) to form stable complexes with proteins, ceUulosic materials, dyestuffs, and various synthetic polymers. The chemistry is complex and not well understood in many cases, but a common denominator is the coordinating abiUty of chromium (ITT) (see LEATHER Textiles). 

For the results reported in both Table 7.2-3 and Table 7.2-4, the only reported detail concerning the ionic liquid was that it was [EMIM][C1-A1C13]. No details of the aluminium(III) chloride content were forthcoming. As with most of the work presented in this chapter, data are taken from the patent literature and not from peer reviewed journals, and so many experimental details are not available. This lack of clear reporting complicates issues for the synthetic polymer chemist. Simpler and cheaper chloroaluminate(III) ionic liquids prepared by using cations derived from the reaction between a simple amine and hydrochloric acid (e.g., Me3N-E3Cl and... 

Whereas cellulose structure is now known in considerable detail [18,19], and the introduction of new solvent systems for dissolving cellulose has intensified the interest in studying point (ii), less is known about point (iii). Such knowledge, however, is a pre-requisite to control the properties of these polymers, hence increase their competitiveness as possible substitutes for synthetic polymers. 

Different classifications for the chiral CSPs have been described. They are based on the chemical structure of the chiral selectors and on the chiral recognition mechanism involved. In this chapter we will use a classification based mainly on the chemical structure of the selectors. The selectors are classified in three groups (i) CSPs with low-molecular-weight selectors, such as Pirkle type CSPs, ionic and ligand exchange CSPs, (ii) CSPs with macrocyclic selectors, such as CDs, crown-ethers and macrocyclic antibiotics, and (iii) CSPs with macromolecular selectors, such as polysaccharides, synthetic polymers, molecular imprinted polymers and proteins. These different types of CSPs, frequently used for the analysis of chiral pharmaceuticals, are discussed in more detail later. 

The scope of the living cationic polymerizations and synthetic applications of these functionalized monomers will be treated in the next chapter on polymer synthesis (see Chapter 5, Section III.B). One should note that the feasibility of living processes for these polar monomers further attests to the formation of controlled and stabilized growing species. Conventional nonliving polymerizations, esters, ethers, and other nucleophiles are known to function as chain transfer agents and sometimes as terminators. In addition, the absence of other acid-catalyzed side reactions of the polar substituents, often sensitive to hydrolysis, acidolysis, etc., demonstrates that these polymerization systems are free from free protons that could arise either from incomplete initiation (via addition of protonic acids to monomer) or from chain transfer reactions (/3-proton elimination from the growing end). 

Polymethacrylates are synthetic cationic and anionic polymers of dimethylaminoethyl methacrylates, methacrylic acid, and methacrylic acid esters in varying ratios. Several different types are commercially available and may be obtained as the dry powder, as an aqueous dispersion, or as an organic solution. A (60 40) mixture of acetone and propan-2-ol is most commonly used as the organic solvent. See Tables I and III. 

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