Polyether diol structures

Table 1.2 List of common polyether diol structures used in resorbable polyurethanes...

Polyethers. Three structurally different polyether diols are mainly used poly(1,2-oxypropylene)diol (PPG), poly(1,2-oxybutylene)diol (B-2000), both terminated essentially by secondary hydroxyl groups, and poly (l,4-oxybutylene)diol, a considerably more reactive component owing to primary hydroxyl termination. Of these the poly(oxypropylenes)... 

Figure 4.5 shows some structural possibilities for polyether diols and polyether triols [1-13]. 

Figure 4.5 Various structures of polyether diols and triols...

Lights stability of polyurethanes depends to a large extent on their chemical structure, and both components (Le., isocyanate and polyol) have an influence. Polyurethanes based on aliphatic isocyanates and polyester diols show the best light stability if yellowing is considered, whereas polyurethanes based on aromatic isocyanates and polyether diols are worst in this respect. 

Only one example of TPU based on a polyether diol from derivatives of vegetable oils has been reported the structure shown in Scheme 4.2 [9]. This structure was polymerised with a conventional aromatic diissocynate. The ensuing material had a Tg of 15 °C and good thermal stability, with only 5% weight loss at 305 °C. 

The blocked isocyanate function of aminimides also allows their use as polyurethane adhesives. Thus bis(aminimides) crosslink with polyester or polyether diols to yield a range of elastomers dependent upon the structure of the bis(aminimide) and the co-reactant chosen. For example, bis(aminimides) mixed with polyhydroxyl components can provide stable, single-package prepolymer compositions which yield polyurethanes on heating without the problem of isocyanate moisture sensitivity which can plague polyurethane applications. 

Thus, the rearrangement of cyclic vinyl acetals of type 1 yields tetrahydrofuran-3-carbaldehydes 2, 3), which are useful precursors in the synthesis of polyether antibiotics. The rearrangement of acyclic vinyl acetals (4) produces the aldol ethers Sand 6 stereoselectively. E. g., star-tingwiththe 1,3-dioxolanyl vinyl acetal7or the 1,3-dioxanyl vinyl acetalft the aldehydes 12are obtained, which contain the 1,2- and the 1,3-diol structural subunit... 

In a,o)-siloxanes, a uniform structure is synthesized that is denoted ABA. When a bifunctional polyether, e.g., a polyether diol, reacts with a,co-siloxanes, polyether siloxanes with A[BA] , structure are obtained. Evidently there is no difference in the amount of modifications per molecule for the latter two structures. Trisiloxane copolymers based on HMTS differ insignificantly in their chain length. 

Macrocyclic polyethers containing the 2.2-paracyclophane unit are interesting structures and several such compounds have been prepared . Despite the diverse structural possibilities, the syntheses of these molecules have generally been accomplished by straightforward Williamson ether syntheses. The only unusual aspect of the syntheses appears to be a novel approach to certain paracyclophanes developed by Helgeson (see footnote 7a in Ref. 91). The first step of Eq. (3.28) illustrates the formation of the required tetrol, which is then treated with base (KOH or KO-t-Bu) and the appropriate diol dito-sylate to afford the macrocycle. 

SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF T1TANOCENE-CONTAINING POLYETHERS BASED ON REACTION WITH ETHYLENE OXIDE-CONTAINING DIOLS, INCLUDING POLY (ETHYLENE GLYCOL)... 

We have previously synthesized a number of titanium polyethers of the following general structure (3,4). A variety of aromatic and aliphatic diols were successfully incorporated as the fundamental backbone units of the polyethers. These materials are insoluble and do not soften prior to thermal-induced degradation. 

Multiple sequential AD gave access to interesting dendritic structures as shown by Sharpless [19], Thus, dihydroxylations of 3- and 4-vinylbenzyl chlorides followed by coupling of the products with other chiral diols in a double-exponential manner afforded novel dendrimers with chiral polyether subunits. 

Physical properties are related to ester-segment structure and concentration in thermoplastic polyether-ester elastomers prepared hy melt transesterification of poly(tetra-methylene ether) glycol with various diols and aromatic diesters. Diols used were 1,4-benzenedimethanol, 1,4-cyclo-hexanedimethanol, and the linear, aliphatic a,m-diols from ethylene glycol to 1,10-decane-diol. Esters used were terephthalate, isophthalate, 4,4 -biphenyldicarboxylate, 2,6-naphthalenedicarboxylate, and m-terphenyl-4,4"-dicarboxyl-ate. Ester-segment structure was found to affect many copolymer properties including ease of synthesis, molecular weight obtained, crystallization rate, elastic recovery, and tensile and tear strengths. 

Figure 1. Synthesis and structure of polyether-ester block copolymers (D — hydrocarbon portion of diol Ar = aromatic portion of the ester x,y = the number of repeat units in the respective ester and polyether-ester blocks)...

Up to this point the discussion has been concerned with alkylene terephthalate/PTME terephthalate copolymers in which the concentration of alkylene terephthalate and the chemical structure of the alkylene groups have been varied. The next section of this report is concerned with polyether-ester copolymers in which aromatic esters other than terephthalate are used in combination with PTME glycol and various diols. The objective is the same, to correlate changes in copolymer structure with changes in copolymerization results and copolymer properties. Once again the 50% tetramethylene terephthalate/PTME terephthalate copolymer (Tables I and II) with its excellent properties and relative ease of synthesis will be used as the point of reference to which the other polymers will be compared. 

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