Poly molecular structures

It is not the purpose of this book to discuss in detail the contributions of NMR spectroscopy to the determination of molecular structure. This is a specialized field in itself and a great deal has been written on the subject. In this section we shall consider only the application of NMR to the elucidation of stereoregularity in polymers. Numerous other applications of this powerful technique have also been made in polymer chemistry, including the study of positional and geometrical isomerism (Sec. 1.6), copolymers (Sec. 7.7), and helix-coil transitions (Sec. 1.11). We shall also make no attempt to compare the NMR spectra of various different polymers instead, we shall examine only the NMR spectra of different poly (methyl methacrylate) preparations to illustrate the capabilities of the method, using the first system that was investigated by this technique as the example. 

Fig. 2. Molecular structures of selected photoconductive polymers with pendent groups (1) poly(A/-vinylcarba2ole) [25067-59-8] (PVK), (2) A/-polysiloxane carbazole, (3) bisphenol A polycarbonate [24936-68-3] (4) polystyrene [9003-53-6] (5) polyvin5i(l,2-/n7 j -bis(9H-carba2ol-9-yl)cyclobutane) [80218-52-6]...

Much work has been carried out in order to elucidate the molecular structure of poly(vinyl chloride). In 1939, Marvel, Sample and Roy dechlorinated PVC with zinc dust to give linked cyclic structures (Figure 12.9). 

Amorphous thermoplastics These are made from polymers which have a sufficiently irregular molecular structure to prevent them from crystallising in any way. Examples of such materials are polystyrene, poly methyl methacrylate and polyvinyl chloride. 

Poly(p-pheny lene)s, PPPs, constitute the prototype of rigid-rod polymers and are currently being intensively investigated [1]. The key role of PPPs follows from their conceptually simple and appealing molecular structure, from their chemical stability, and from their superior physical properties [2], In turn, this is the result of important advances made in aromatic chemistry over the last few years. The following section gives an overview of the most common methods to generate poly(p-phenylene)s via different synthetic approaches. 

This polymer has one of the simplest molecular structures ([CH2CH2— ] ) and is at present the largest toimage plastic material, having first been produced commercially in 1939 for use in electrical insulation. There is a difficulty over the nomenclature of this polymer. The lUPAC recommended name for the monomer is ethene, rather than the older ethylene. Hence the lUPAC name for the polymer is poly (ethene). However, this name is almost never used by chemists working with the material throughout this book, therefore, this polymer will be referred to by its more widespread name, poly(ethylene). 

Molecular structural changes in polyphosphazenes are achieved mainly by macromolecular substitution reactions rather than by variations in monomer types or monomer ratios (1-4). The method makes use of a reactive macromolecular intermediate, poly(dichlorophosphazene) structure (3), that allows the facile replacement of chloro side groups by reactions of this macromolecule with a wide range of chemical reagents. The overall pathway is summarized in Scheme I. 

FIGURE 5 Molecular structures of poly(Bisphenol A carbonate) and poly(Bisphenol A iminocarbonate). The poly(iminocarbonates) are, in a formal sense, derived from polycarbonates by replacement of the carbonyl oxygen by an imino group. 

FIGURE 6 Molecular structures of poIy(CTTE), poly(CTTH), and poly(CTTP), a homologous series of tyrosine-derived polymers used in a study of the effect of the C-terminus protecting group on the materials properties of the resulting polymers. Cbz" stands for the benzyloxycarbonyl group (47). 

The thermal properties of tyrosine-derived poly(iminocarbonates) were also investigated. Based on analysis by DSC and thermogravi-metric analysis, all poly(iminocarbonates) decompose between 140 and 220 C. The thermal decomposition is due to the inherent instability of the iminocarbonate bond above 150°C and is not related to the presence of tyrosine derivatives in the polymer backbone. The molecular structure of the monomer has no significant influence on the degradation temperature as indicated by the fact that poly(BPA.-iminocarbonate) also decomposed at about 170 C, while the structurally analogous poly(BPA-carbonate) is thermally stable up to 350 C. 

Figure 2. Molecular structures of poly(Bisphenol A carbonate) and poly(Bisphenol A iminocarbonate).

Fig. 9 (a) Molecular structures of novel ESIPT dyes, 2,5,-bis[5-(4-t-butylphenyl)-[l,3,4]oxadia-zol-2-yl]-phenol (SOX), and 2,5-bis[5-(4-t-butylphenyl)-[l,3,4]oxadiazol-2-yl]-benzene-l,4,-diol (DOX). (b) Emission colors in the Commission Internationale de L Eclariage (CEE) chromaticity diagram. The inner oval and the filled circle at coordinate (x,y) of (0.33, 0.33) indicate the white region and the ideal color, respectively. Note that PS and PVK denote polystyrene and poly (N-vinylcarbazole) film (reprint from ref. [91], Copyright 2005 Wiley-VCH)... 

Figure 3 Molecular structure of acetonitrile and poly(acrylonitrile).

Figure 16 Molecular structure of a dimer of poly(bis phenol A carbonate) used in a study of degradation pathways [110].

Figure 29 Some of the molecular structures used to interpret the EPR spectra of poly(aniline) oligomers. The molecules are labelled 1 and 4 in the same fashion as Ref. [149].

Figure 13.1.2 The molecular structure of glycolic acid, lized species. Lactic acid (Fig. 13.1.3) has also been polymerized into poly(lactic...

The material system is a Langmuir-Blodgett film of the S enantiomer of a chiral polymer deposited on a glass substrate. The polymer is a poly(isocyanide)30 functionalized with a nonlinear optical chromophore (see Figure 9.14). In this particular system the optical nonlinearity and chirality are present on two different levels of the molecular structure. The chirality of the polymer is located in the helical backbone whereas the nonlinearity is present in the attached chromophores. Hence, this opens the possibility to optimize both properties independently. 

Poly(4-phenoxybenzoyl-1,4-phenylene) (PPBP), sulfonated, 23 718 Polyacetal, antioxidant applications, 3 121 Polyacetaldehyde, 1 103 Polyacetal fiber, 13 392 Polyacetylene, 7 514-515 26 953 conduction in, 7 527 22 208 molecular structure of, 22 211 optical band gap, 7 529t Peierls distortion in, 22 203, 208 room temperature conductivity, 7 532 synthesis of, 22 213... 

Polyphthalamides (PPA), 10 216-217 ASTM standards for, 19 793 Poly(p-phenylene) (PPP), 22 207t 23 717 conducting, 7 523, 527 molecular structure of, 22 211 optical band gap, 7 529t room temperature conductivity, 7 532 water-soluble, electroactive, self-doped sulfonatoalkoxy-substituted, 23 720 Poly(p-phenylene benzobisoxazole) (PBO), 19 714... 

Acetylated poly(phenylsilsesquioxane) characterization, 176-177 molecular structure determination, 176 29Si-NMR spectra, 176,178/ synthesis, 176... 

Orchard B, Tripathy S (1986) Molecular-structure and electronic property modification of poly(diacetylenes). Macromolecules 19 1844—1850... 

Fig. 5.12 Molecular structure of atactic poly(propylene oxide).

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