Heteroatom chain polymers

For ease of discussion, this section is divided into three broad classifications — natural, synthetic, and modified natural based biodegradable polymers and plastics. Natural polymers indicate no modification of isolated polymer, synthetic poisoners include carbon chain and heteroatom chain polymers, and modified natural polymers encompass grafts and blends, and chemical modifications such as oxidations and esterifications. 

Biodegradable polymers and plastics are readily divided into three broad classifications (/) natural, (2) synthetic, and (J) modified natural. These classes may be further subdivided for ease of discussion, as follows (/) natural polymers (2) synthetic polymers may have carbon chain backbones or heteroatom chain backbones and (J) modified natural may be blends and grafts or involve chemical modifications, oxidation, esterification, etc. 

Heteroatom Chain Backbone Polymers. This class of polymers includes polyesters, which have been widely studied from the initial period of research on biodegradable polymers, polyamides, polyethers, polyacetals, and other condensation polymers. Their linkages are quite frequendy found in nature and these polymers are more likely to biodegrade than hydrocarbon-based polymers. 

A.P. Monkman, L.-O. Palsson, R.W.T. Higgins, C. Wang, M.R. Bryce, A.S. Batsanov, and J.A.K. Howard, Protonation and subsequent intramolecular hydrogen bonding as a method to control chain structure and tune luminescence in heteroatomic conjugated polymers, J. Am. Chem. Soc., 124 6049-6055, 2002. 

Chap. 14 Aliphatic Polymers with Heteroatom Chains... 

Polystyrene (PS) is the simplest carbon-chain polymer, which contains a phenyl ring. This polymer contains no heteroatoms and is readily soluble in most organic solvents this makes it possible to use its solutions to assess the effect of the spatial organization of macromolecules (conformation) on the micro structure of the carbon obtained, for it is known that the change in fumed carbon structure may be caused by a difference in the supramolecular structure of carbonization precursors [12]. According to Ref.[13], the mean size of aggregates for solutions of PS in ethyl acetate with a concentration of 0.25 g/100 mL is 1000 A at 1.5g/100 mL concentration, it is 4000 A, and for 5.0 g/100 mL it is 890 A, their number (N10"9/sm"3) being 0.017, 0.27 and 6.88 respectively. 

Polymers with Heteroatom Chain Structure (Heteropolymers)... 

Inorganic polymers or macromolecules contain no carbon but nonmetals, semimetals and/or metals in the main chain or network. Examples are polysiloxanes, polysilanes, polyphosphacenes and several polymers with metal-heteroatom chains (organometallic polymers). 

This is not true for heteroatomic chains - CH2C HX 0 such as where C is a true asymmetric center, and these polymers are optically active. In this case, an absolute configuration can be assigned, using preferably the Cahn-Ingold-Prelog system, referring either to the R-(rectus) or to the S-(sinister) form. 

The synthetics may be sub-divided into addition polymers and condensation polymers, the former being mostly carbon-chain backbone polymers and the latter being chiefly heteroatom chain backbone polymers. Poly(acrylic acid) and poly(vinyl alcohol)... 

Other polyamides produced experimentally include polymers with active lateral groups (hydroxy, keto groups etc.), polymers with heteroatoms (sulphur and oxygen) in the polyamide-forming intermediates, polymers with tertiary amino groups in the main chain and polymers with unsaturation in the main chain. There does not, however, appear to have been any serious attempt to develop unsaturated polyamide analogues to the polyester laminating resins. 

Acrylate polymers also have fully saturated polymer backbones free of any heteroatoms in the main chain. This makes the polymers highly resistant to oxidation, photo-degradation and chemical attack. The acrylate groups are esters, which could be hydrolyzed under severe conditions. However, the hydrophobic nature of most acrylic polymers minimizes the risk for hydrolysis and, even if this reaction happened to some extent, the polymer backbone would still be intact. Other desirable acrylate properties include the following ... 

---