Urethane-ester

Asphalt, unmodified Coal tar Coal tar— epoxy Coal tar— nretlianes Epoxy phenolic- baked Epoxy amine- cnred Epoxy ester Fnrfnryl alcohol Phenolics, baked Polyesters (nnsati i-rated) Polyvinyl cliloracetates Vinyl ester Urethanes Vinylidene cliloride Clilorinated rubber... 

TPEs associating both rigid and soft polyester blocks have also been described. They cannot be obtained by the melt polyesterification used for polyesterether TPEs, since interchange reactions would yield random—rather than block — copolyesters. The preferred method involves the reaction of OH-terminated aliphatic and aromatic-aliphatic polyesters with chain extenders such as diisocyanates and results in copoly(ester-ester-urethane)s. 

A series of poly(ester-urethane) urea triblock copolymers have been synthesized and characterized by Wagner et al/ using PCL, polyethylene glycol, and 1,4 diisocyanatobutane with either lysine ethyl ester or putrescine, as the chain extender. These materials have shown the elongation at break from 325% to 560% and tensile strengths from 8 to 20 MPa. Degradation products of this kind of materials did not show any toxicity on cells. 

Guan JJ, Sacks MS, Beckman EJ, and Wagner WR. Synthesis, characterizadon, and cytocompadbility of elastomeric, biodegradable poly(ester-urethane) ureas based on poly(caprolactone) and pudescine. J Biomed Mater Res, 2002, 61, 493-503. 

Bmin P, Veensda GJ, Nijenhuis AJ, and Pennings AJ. Design and synthesis of biodegradable poly(ester-urethane) elastomer networks composed of non toxic building blocks. Makromol Chem Rapid Common, 1988, 9, 589. 

Apparently there are no mild chemical reactions that can be used to transform the amide linkages in the backbone of conventional poly-(amino acids) into nonamide linkages such as ester, urethane, or carbonate bonds. Consequently, it is usually not possible to simply replace the backbone amide bonds of conventional poly (amino acids) by nonamide linkages. Pseudopoly(amino acids) must therefore be prepared from scratch by suitably designed polymerization reactions. 

In addition to esterification, these oils can also be reacted with isocyanates to make polyurethanes. Some of the most interesting products to be described below consist of mixed ester-urethane compositions, where the ester portion is made before gelation where the water can be evaporated easily, and the urethane component is added as a type of postcure. 

Another approach was attempted by Seppala and Kylma who reported the synthesis of poly(ester-urethane)s by condensation of hydroxyl terminated tel-echelic poly(CL-co-LA) oligomers with 1,6-hexamethylene diisocyanate (Scheme 33) [94]. The diisocyanate acts as chain extender producing an increase in molecular weight of the preformed oligomers. The authors claim that some of the copolymers present elastomeric properties. Using a similar method. Storey described the synthesis of polyurethane networks based on D,L-LA, GA, eCL,... 

The chain-extended, linear poly(ester urethanes) so obtained can now be crosslinked in a second stage, involving reaction with - water - or glycols - or diamines. 

A synthetic approach to poly(ester-urethanes) was recently published by Xue et al. [48]. Glycerol was employed as a trifunctional initiator in the enzymatic ROP of CL. The three-arm PCL triol was then reacted with methylene-diphenyl diisocyanate (MDI) and hexanediol to yield a three-arm PCL-based poly(ester-urethane) with shape-memory properties. 

Research Focus Synthesis of biodegradable and biocompatible polyethylene oxide derivatives containing poly(ester-urethanes) for use as medical implants. 

Biodegradable and Biocompatible Peg-Based Poly (Ester-Urethanes)... 

Additional poly(ester-urethane) derivatives were prepared by reacting the step 1 prepolymer diol with selected diisocyanate as indicated below ... 

Other poly(ester-urethanes) derivatives were prepared by the authors (1) in an earlier investigation and are discussed. 

In water and in. hydrophilic solvents nitrourea dearranges rapidly into cyanic acid and nitroamide. Alkalis promote the reaction. If an aqueous solution of nitrourea is warmed, bubbles of nitrous oxide begin to come off at about 60°. If it is allowed to stand over night at room temperature, the nitrourea disappears completely and the liquid is found to be a solution of cyanic acid. Indeed, nitrourea is equivalent to cyanic acid for purposes of synthesis. It reacts with alcohols to form carbamic esters (urethanes) and with primary and second amines to form mono-and unsym-di-substituted ureas. 

Z-Menthyl Isocyanate. Pickard and Littlebury 20-21 found that Z-menthyl isocyanate forms crystalline esters (urethanes) with many alcohols and phenols. The two diastereoisomeric urethanes from cZZ-l-phenyl-1-p-hydroxyphenylethane and from dZ-oc-tetrahydro-/3-naphthol were separated readily.2 The method has not been applied widely. Z-Men-thyl isocyanate is the most readily available resolving agent of this type but is difficult to prepare. The urethanes are not easily hydrolyzed, and the isocyanate is not recovered in the hydrolysis but is converted to the amine. 

Keywords. Monomers from renewable resources, Polymers from renewable resources, 1,3-Propanediol, Succinic acid, Lactones, Cyclohexanedimethanol, Polyethyleneglycol, Chain-extension, Poly(ester-urethane)s, Poly(ester-carbonate)s... 

PEU Poly(ester-urethane)s PHB Poly-(3-hydroxybutyrate ROP Ring-opening polymerization SEC Size exclusion chromatography SP Oligo(l,3-propylene succinate)... 

Two different types of chain-extending agents were used, namely 4,4 -di-isophenylmethane diisocyanate (MDI) and phosgene, which lead to two different classes of copolymers, poly(ester-urethane)s and poly(ester-carbonate)s respectively. High molecular weight poly(ester-carbonate)s have earlier been prepared by the dichloroformate synthesis [12-13]. 

Table 3. Molecular weights of poly(ester urethane)s ...

The series of ten different segmented poly(ester-urethane)s obtained was characterized by SEC (molecular weight, polydispersity), DMA (thermo-mechanical properties), DSC (thermal properties) and Instron (mechanical properties). Before the mechanical testing could be performed, it was necessary to establish procedures for film production. 

The isocyanate (2270 cm"1) uretedinedione ring carbonyl (1780 cm"1) and urea carbonyl (1660 cm"1) groups can usually be identified. Carbonyls from ester, urethane, allophanate, isocyanuric acid ring and Biuret groups all absorb near 1730 cm 1 and are difficult to distinguish. Hydrogen bonds which can function as physical crosslinks in PU have been... 

The rate of reversion, or hydrolytic instability, depends on the chemical structure of the base polymer, its degree of crosslinking, and the permeability of the adhesive or sealant. Certain chemical linkages such as ester, urethane, amide, and urea can be hydrolyzed. The rate of attack is fastest for ester-based linkages. Ester linkages are present in certain types of polyurethanes and anhydride cured epoxies. Generally, amine cured epoxies offer better hydrolytic stability than anhydride cured types. 

Carbamate esters (urethanes) are the stable esters of the unstable carbamic acid, the monoamide of carbonic acid. 

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