Polyether, aliphatic

Various types of condensation polymers such as aromatic polysulfonates and polysulfides, aromatic polyethers, aliphatic and aromatic polysulfides, and carbon-carbon chain polymers of high molecular weights by the phase-transfer catalyzed polycondensation fi-om combinations of aromatic disulfonyl chlorides, phosphonic dichlorides, activated aromatic dichlorides, and aliphatic dihalides, withbisphenol, aliphatic and aromatic dithiols, and active ethylene compounds. The two-phase polycondensation was generally carried out in a water-immiscible organic solvent-aqueous alkaline solution system at room temperature. The method of polycondensation offers a highly versatile and convenient synthetic method for a variety of condensation polymers. 

Synthetic polymers are an integral part of everyday life. Synthetic polymers in the form of polyolefins such as polypropylene and polyethylene and other synthetic polymers such as poly(acrylate)s and poly(styrene)s (PSs) are predominantly used in packaging materials. Condensation polymers are produced in smaller amounts than addition polymers. Nevertheless, some condensation polymers such as polyesters with specific reference to poly(ethylene terephthalate) (PET) and aliphatic polyethers, aliphatic polyamides (i.e., nylons), and polysiloxanes are quite important. 

Linear polyethers derived from three or more molecules of aliphatic dihydroxy compounds, particularly when the chain length exceeds ten units, are most conveniently named by open-chain replacement nomenclature. For example, CH3CH2—O—CH2CH2—O—CH2CH3 could be 3,6-dioxaoctane or (2-ethoxy)ethoxyethane. 

The tendency of aliphatic ethers toward oxidation requires the use of antioxidants such as hindered phenoHcs (eg, BHT), secondary aromatic amines, and phosphites. This is especially tme in polyether polyols used in making polyurethanes (PUR) because they may become discolored and the increase in acid number affects PUR production. The antioxidants also reduce oxidation during PUR production where the temperature could reach 230°C. A number of new antioxidant products and combinations have become available (115,120,124—139) (see Antioxidants). 

Multiblock systems. A somewhat similar approach is involved in the production of thermoplastic polyurethane elastomers. In this case the chain contains soft segments that are largely aliphatic polyether in nature and also hard segments that are primarily polyurea (see Chapter 27). 

Besides being commercially referred to as polyacetal materials polyformaldehydes are also often known as polyoxymethylenes and are the simplest type of a family of aliphatic polyethers. 

Of the many other aliphatic polyethers, polythioethers and polysulphides prepared in the laboratory, some have become commercially available. Those of interest to the plastics industry are dealt with later in this chapter. 

The flexible backbone of an aliphatic polyether chain can lead to polymers with a low glass transition temperature. Providing crystallisation can be inhibited by... 

Polyacetals are among the aliphatic polyether family and are produced by the polymerization of formaldehyde. They are termed polyacetals to distinguish them from polyethers produced by polymerizing ethylene oxide, which has two -CH2- groups between the ether group. The polymerization reaction occurs in the presence of a Lewis acid and a small amount of water at room temperature. It could also be catalyzed with amines ... 

A reiterative application of a two-carbon elongation reaction of a chiral carbonyl compound (Homer-Emmonds reaction), reduction (DIBAL) of the obtained trans unsaturated ester, asymmetric epoxidation (SAE or MCPBA) of the resulting allylic alcohol, and then C-2 regioselective addition of a cuprate (Me2CuLi) to the corresponding chiral epoxy alcohol has been utilized for the construction of the polypropionate-derived chain ]R-CH(Me)CH(OH)CH(Me)-R ], present as a partial structure in important natural products such as polyether, ansamycin, or macro-lide antibiotics [52]. A seminal application of this procedure is offered by Kishi s synthesis of the C19-C26 polyketide-type aliphatic segment of rifamycin S, starting from aldehyde 105 (Scheme 8.29) [53]. 

Aliphatic carboxylic acids Alkyl ethyl ethers Cyclic polyethers Phosphorous compounds Rearrangement peak in dioxanes... 

Polyester block copolymers can be defined as (AB) -type alternating multiblock copolymers composed of flexible aliphatic polyester or polyether blocks (A-type blocks) and rigid high-melting aromatic-aliphatic polyester blocks IB-type blocks) (Formula 2.2). 

Yang and coworkers did the most efforts on the development of network polyester based on citric acid. " They investigated the reaction of citric acid with a series of aliphatic diols (from 3-16 carbon chains) and polyether diols such as polyethylene oxide (PEG), in which 1,8-octanediol (POC) and 1,10 decanediol (PDC) have been studied the most. 

F.D. Konstandakopoulou, K.G. Gravalos, and J.K. Kallitsis, Synthesis and characterization of processible aromatic-aliphatic polyethers with quinquephenyl segments in the main chain for light-emitting applications, Macromolecules, 31 5264-5271, 1998. 

Cyclic peptides, self-assembly of, 24 59-60 Cyclic peroxides, 18 436, 447-448, 459 Cyclic poly(aliphatic disulfide)s, 23 712 Cyclic poly(disulfide)s, available information related to, 23 713 Cyclic polyethers, 12 658 chelating agents, 5 710 Cyclic reforming operations, 25 166 Cyclic sesquiterpenoids, biosynthetic routes to, 24 472 Cyclic siloxanes... 

Telechelic polymers rank among the oldest designed precursors. The position of reactive groups at the ends of a sequence of repeating units makes it possible to incorporate various chemical structures into the network (polyether, polyester, polyamide, aliphatic, cycloaliphatic or aromatic hydrocarbon, etc.). The cross-linking density can be controlled by the length of precursor chain and functionality of the crosslinker, by molar ratio of functional groups, or by addition of a monofunctional component. Formation of elastically inactive loops is usually weak. Typical polyurethane systems composed of a macromolecular triol and a diisocyanate are statistically simple and when different theories listed above are... 

The usefulness of the PTP concept was further demonstrated by Frechet et al. [30] in a study where hyperbranched aliphatic polyethers were synthesized from a diepoxide and a tri-functional alcohol, utilizing an A2-B3 monomer concept. 

Preparation of Frechet-type Polyether Dendrons and Aliphatic Polyester Dendrimers by Convergent Growth An Experimental Primer... 

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