Poly diol molecular weight

The synthesis of aliphatic poly(carbonate-co-ester)s with about 1 1 molar ratio of the ester-to-carbonate repeat units was reported by CALB-catalyzed transesterification among diethyl carbonate, a diester, and a diol. Molecular weight Mw values reached 59000 at a reaction temperature of 90 °C. A carbonate-ester transesterification reaction between poly(butylene carbonate) and poly(butylene succinate) was also catalyzed by CALB at 95 °C to result in a block copolymer [57]. 

In addition, polyester polyols are made by the reaction of caprolactone with diols. Poly(caprolactone diols) are used in the manufacture of thermoplastic polyurethane elastomers with improved hydrolytic stabiHty (22). The hydrolytic stabiHty of the poly(caprolactone diol)-derived TPUs is comparable to TPUs based on the more expensive long-chain diol adipates (23). Polyether/polyester polyol hybrids are synthesized from low molecular weight polyester diols, which are extended with propylene oxide. 

Plasticizers can be classified according to their chemical nature. The most important classes of plasticizers used in rubber adhesives are phthalates, polymeric plasticizers, and esters. The group phthalate plasticizers constitutes the biggest and most widely used plasticizers. The linear alkyl phthalates impart improved low-temperature performance and have reduced volatility. Most of the polymeric plasticizers are saturated polyesters obtained by reaction of a diol with a dicarboxylic acid. The most common diols are propanediol, 1,3- and 1,4-butanediol, and 1,6-hexanediol. Adipic, phthalic and sebacic acids are common carboxylic acids used in the manufacture of polymeric plasticizers. Some poly-hydroxybutyrates are used in rubber adhesive formulations. Both the molecular weight and the chemical nature determine the performance of the polymeric plasticizers. Increasing the molecular weight reduces the volatility of the plasticizer but reduces the plasticizing efficiency and low-temperature properties. Typical esters used as plasticizers are n-butyl acetate and cellulose acetobutyrate. 

Poly(tetramethylene oxide) polyols (PTMEG) are high performance polyethers that are crystalline waxes at molecular weights above 650 and liquids at lower molecular weights. They are only available as diols, but they produce adhesives with good hydrolysis resistance and moisture resistance, which is why these adhesives are even used in medical devices, blood bags, catheters, and heart-assist devices [25]. Certain thermoplastic polyurethane adhesives and solvent-borne adhesives are also based on PTMEG s. 

Initiators such as (306) initiate the ROP of CL to form telechelic triblock diols.478 Molecular weights approach theoretical values with polydispersities <1.3 and no significant level of transesterification was detected at up to 95% conversions. Alternative bimetallic samarium initiators have been used to synthesize aromatic, cumulene and amine/imine link-functionalized poly(lactones).479... 

Rafler el al. [105] applied the two-film model to the mass transfer of different alkane diols in poly(alkylene terephthalate) melts and demonstrated a pressure dependency of the mass-transfer coefficient in experiments at 280 °C in a small 3.6L stirred reactor. They concluded that the mass-transfer coefficient kij is proportional to the reciprocal of the molecular weight of the evaporating molecule. 

Poly(vinyl acetate) of number-average molecular weight 100,000 is hydrolyzed to poly(vinyl alcohol). Oxidation of the latter with periodic acid to cleave 1,2-diol linkages yields a poly(vinyl alcohol) with Xn = 200. Calculate the percentages of head-to-tail and head-to-head linkages in the poly(vinyl acetate). 

Table VI. Comparison of Calculated and Observed Molecular Weights of Poly (propylene ether) Diols...

Figure 8 shows the characterization of these poly (propylene ether) diols by gel-permeation chromatography. There is a shift in the peak position to lower elution volumes, in accord with an increase in molecular weight with each monomer increment polymerized. The molecular-weight distributions of the three diols are similar and remain narrow after the addition of monomer increments. Since all of the molecules apparently continued to grow, this polymerization must proceed with very little chain termination under these conditions. 

Figure 9 shows that the unsaturation of poly (propylene ether) diols and triols remained constant as the molecular weight was varied. By comparison, the unsaturation of commercial polyols (presumably made with potassium hydroxide) increased appreciably as the molecular weight increased. Figure 10 shows that upon varying the amount of diiso-... 

Combining whole-cell biocatalysis and radical polymerization, researchers at Imperial Chemical Industries (ICI) published a chemoenzymatic route to high-molecular-weight poly(phenylene) [86], This polymer is used in the fibers and coatings industry. However, since it is practically insoluble, the challenge was to make a soluble polymer precursor that could first be coated or spun, and only then converted to poly(phenylene). The ICI process starts from benzene, which is oxidized by Pseudomonas putida cells to cyclohexa-3,5-diene-l,2-diol (see Figure 5.17). The... 

Harris, R.F., M.D. Joseph, C. Davidson, C.D. Deporter, and V.A. Dais. Polyurethane Elastomers Based on Molecular Weight Advanced Poly(Ethylene Ether Carbonate) Diols. Comparison to Commercial Diols. Journal of Applied Polymer Science 41 (1990) 487-507. 

Polyesterification. High molecular weight linear polyester resins, such as poly(ethylene terephthalate) (PET), poly(propylene terephthalate) (PPT), and poly(butylene terephthalate) (PBT), can be produced by either transesterification of dimethyl terephthalate (DMT) with an excess of the corresponding diol or by direct esterification of terephthalic acid (TPA). Tetraalkyl titanates, such as TYZOR TPT or —TYZOR TBT, have been found to be excellent catalysts for either of these reactions. However, in the case of PET, the residual titanate catalyst reacts with trace quantities of aldehydic impurities produced in the polymerization process to generate a yellow discoloration of the polymer (468,469). In the case of PPT and PBT, where the color of polymer is not as critical, organic titanates are the catalyst of choice because of their greater reactivity than antimony or tin (470). Numerous processing variations have been described in the literature to minimize formation of tetrahydrofuran in the PBT process (471—472). 

Soft blocks are composed of linear, dihydroxy poly ethers or polyesters with molecular weights between 600 and 3000. In a typical polymerization of a thermoplastic polyurethane elastomer, the macroglycol is end capped with the full amount of aromatic diisocyanate required in the final composition. Subsequently, the end-capped prepolymer and excess diisocyanate mixture reacts further with the required stoichiometric amount of monomeric diol to complete the reaction. The diol links the prepolymer segments together while excess diol and diisocyanate form short hard-block sements, leading to the (AB)n structure illustrated in Figure 1. Block lengths in (AB)n polymers are frequently much shorter than those in anionically synthesized ABA block copolymers. 

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. 

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