Polymers with Carbon Backbones

Vinyl polymers are mostly susceptible to hydrolysis, except a few. For biodegradation, they require an oxidation process, and most 

Generally, vinyl polymers are, with some exceptions, not susceptible to hydrolysis. For their biodegradation, if any at all, an oxidation process is needed. Most of the biodegradable vinyl polymers contain readily oxidizable function groups. 

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A polymer is a very large, chain-like molecule made up of simple chemical units called monomers. It can be naturally occurring or synthetic. Polymers have a wide range of applications and can be classified into three major groups biopolymers, polymers with hydrolyzable backbones, and polymers with carbon backbones [9,10]. 

Another category involves the polymers with carbon backbones which are not susceptible to hydrolysis, like vinyl polymers. Their biodegradation, if it occurs at all, requires an oxidation process. Most of the biodegradable vinyl polymers contain an easily oxidizable functional group. Approaches to improve the biodegradability of vinyl polymers often include the addition of catalysts to promote their oxidation or photooxidation [9,10]. This category includes ... 

A simple rule is that polar bonds yield strong IR absorption and weak Raman effect, and nonpolar bonds are weak or absent in IR but strong in the Raman. If this rule is applied to polymer molecules, it can be determined that for hydrocarbon polymers with carbon backbones, the IR absorption of the backbone will be weak, and this result has been observed under experimental conditions. However, substituted groups like C—H, C—F, and C=0 will have polar bonds because of differences in electronegativity, and the IR absorption will be strong. Again this speculation has been observed under experimental conditions. 

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

DNA is a polymer with a backbone built of repeating units derived from the sugar ribose (20). For DNA, the ribose molecule has been modified by removing the oxygen atom at carbon atom 2, the second carbon atom clockwise from the ether oxygen atom in the five-membered ring. Therefore, the repeating unit—the monomer—is called deoxyribose (21). 

It seems likely that phosphazene polymers with carbon or sulfur in the backbone are the forerunners of many new polymer systems that will be investigated in the coming years. 

In this chapter, a selective overview of technological and historical background is followed by a general discussion of the microscopic details of the transport phenomenon and experimental techniques. Key results of earlier studies on carbon-based systems are presented and then compared with corresponding data on poly(methylphenylsilylene) (PMPS), which has been taken as the prototype for studies of transport system in polymers with silicon backbones. Key points are then summarized. Those wishing to omit the extensive background section may proceed directly to the section on electronic transport in polysilylenes (page 492). 

Polyolefins are hydrocarbon polymers with the backbone formed from a chain of aliphatic carbon atoms. These polymers are typically obtained in a reaction shown schematically as follows ... 

Polymers with carbon-carbon double bonds in their backbone can undergo two types of metathesis, both leading to degradation. In an intramolecular reaction cyclic oligomers are formed, while many unsaturated polymers can be degraded by intermolecular cross-metathesis with low-molecular-weight olefins. Identification of the degradation products provides valuable information on the microstructure of the polymer [7] (cf Section 3.3.10.1). 

Polymers with carbon single bonds making up their backbone have a bond angle of 0 = 68°. 

Polymers containing all metal backbones of Ru-Ru or Os-Os bonds have been prepared via the electrochemical reduction of ruthenium and osmium complexes containing /ram-chloride ligands.81,82 Scheme 2.6 shows the synthesis of polymers with their backbones comprised solely of metal-metal bonds. The polymers were prepared by reducing [Mn(/ran.s-Cl2)(bipyXCO)2] (M = Ru, Os), 33, to M° complexes and forming the polymer after the loss of the chloride ligands. In both cases, the polymers were selective for the reduction of carbon dioxide. 

Numerous other types of carbon-based polymers with conjugated backbones have been prepared and investigated in addition to the ones already discussed. Tateishi et al. [387] produced freestanding, doped films of poly(p-phenylene xylylidene) with conductivities up to 70 S cm . 

Poly(carbosilane)s are organosilicon polymers with a backbone structure composed essentially of Si-C bonds. They represent the most widely studied class of precursors to silicon carbide fibre, and are the starting polymers in the manufacture of the Nicalon silicon carbide fibre produced by Nippon Carbon Co. 

The chemical degradation takes place when a polymer is exposed to reacting fluids, such as gaseous O2,03, CI2, H2S, H2O, etc. In polymers with carbon-carbon backbone, oxidation is the principal chemical degradative mechanism that results in formation of peroxides and/or hydroxy peroxides, chain scission and accompanying it the free radical grafting (which may be absent in high vacuum). Polymers with tertiary carbons (e.g., PP or hnear low density PE, LED PE) oxidize readily for PO the process is autocatalytic. ... 

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