Polyol linear

Polyols. Linear polyols containing two carbon to seven carbon atoms all evoked neural responses. Two important results were observed (Figure 8)s (1) The effectiveness (CR q.) of the polyols increased as the chain length increased up to five carbon atoms (2) In contrast to monosaccharides, the configurations of linear polyol may not play a role in the taste response. This is indicated by the identical responses to the four pentitols D-arabinitol, L-arabinitol, D-ribitol, or D-xylitol. 

Hydrogen donors for hydroesterification may be primary or secondary alcohols, cyclohexanol, phenol or polyols. Linear or branched primary alcohols react similarly secondary alcohols are less active and tertiary alcohols are not suitable. The reactivity of various olefins has been compared. ... 

In these glycosylated derivatives, the aglycones are not exclnsively alcohols or terpene polyols. Linear or cyclic alcohols (hexanol, phenylethanol and benzyl alcohol) and some Ci3-norisoprenoids, as well as, probably, volatile phenols such as vanillin, may also be present (Section 7.3.1). 

Synonyms Polyester polyol, aromatic Polyester polyol, crosslinked Polyester polyol, linear Polyester polyol, slightly branched Polyol, flexible Properties Vise. liqs. to waxy solids... 

Polyols. Analogous to the use of linear a,C0-dibasic acids, such as adipic and sebacic, polyols with long, flexible chains between hydroxyl groups, such as 1,4-butanediol [110-63-4] 1,6-hexanediol [629-11-8J, and diethylene glycol [111-46-6] may also be used to impart greater flexibiUty ia the resia. 

Polyester polyols are based on saturated aHphatic or aromatic carboxyHc acids and diols or mixtures of diols. The carboxyHc acid of choice is adipic acid (qv) because of its favorable cost/performance ratio. For elastomers, linear polyester polyols of ca 2000 mol wt are preferred. Branched polyester polyols, formulated from higher functional glycols, are used for foam and coatings appHcations. Phthalates and terephthalates are also used. 

Two-component systems consist of (1) polyol or polyamine, and (2) isocyanate. The hardening starts with the mixing of the two components. Due to the low viscosities of the two components, they can be used without addition of solvents. The mass ratio between the two components determines the properties of the bond line. Linear polyols and a lower surplus of isocyanates give flexible bond lines, whereas branched polyols and higher amounts of isocyanates lead to hard and brittle bond lines. The pot life of the two-component systems is determined by the reactivity of the two components, the temperature and the addition of catalysts. The pot life can vary between 0.5 and 24 h. The cure at room temperature is completed within 3 to 20 h. 

Recently, Brich and coworkers (40) reported the synthesis of lactide/glycolide polymers branched with different polyols. Polyvinyl-alcohol and dextran acetate were used to afford polymers exhibiting degradation profiles significantly different from that of linear poly-lactides. The biphasic release profile often observed with the linear polyesters was smoothened somewhat to a monophasic profile. Further, the overall degradation rate is accelerated. It was speculated that these polymers can potentially afford more uniform drug release kinetics. This potential has not yet been fully demonstrated. 

The linear oligoester diol was heated with salycilic acid and with MHBA using a similar procedure to yield modified polyols. Only 60% to 80% of theoretical distillate was obtained. 

A direct esterification procedure by which a linear polyester diol can be modified with p-hydroxybenzoic acid (PHBA) was demonstrated. The products are oligomers in which phenolic end-groups appear to predominate. They are heterogeneous and are probably liquid-crystalline when 30 wt% or more of PHBA is incorporated. The procedure has the advantage that appears adaptable to large scale production but the disadvantages that the polyols are predominately phenolic and are contaminated with small amounts of phenol and unreacted PHBA. 

Selective modification of polyols such as ethylene glycol, 1,3-propylene glycol, or glycerol with butadiene (1) has been studied [7-10]. The monosubstituted compounds are preferred due to their potential applications as surfactants, PVC plasticizers, or even in cosmetics. The telomerization of 1 with ethylene glycol yields a complex mixture including linear and branched mono- and ditelomers, as well as 1,3,7-octatriene and vinyl cyclohexene (Fig. 2) [11]. 

For polyurethane production, Donnelly [109] has carried out the synthesis of copolyurethanes based on mixtures of commercial poly(THF diol)s with glucose. Complex products resulted, which can be represented by mono- or bis(glucoside) structures. From a variety of polyol blends, solid polyurethanes were prepared which ranged from linear, soluble, weak elastomers to polymers of higher transition temperature and stiffness, low solubility, and low extension under tensile load [110]. 

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