Hydroxylated polyesters synthesis

Chemical Properties. The chemistry of 1,4-cyclohexanedimethanol is characteristic of general glycol reactions however, its two primary hydroxyl groups give very rapid reaction rates, especially in polyester synthesis. 

On the other hand, highly selective enzymatic catalysis has been used to modify sugars containing multiple hydroxyl groups in microaqueous media. Enzymes are non-harmful catalysts which catalyze under mild conditions. Recent advances in enzymatic catalysts would be useful tools not only for polyester synthesis but also for vinyl monomer synthesis (96). 

Chemical Properties. Trimethylpentanediol, with a primary and a secondary hydroxyl group, enters into reactions characteristic of other glycols. It reacts readily with various carboxyUc acids and diacids to form esters, diesters, and polyesters (40). Some organometaUic catalysts have proven satisfactory for these reactions, the most versatile being dibutyltin oxide. Several weak bases such as triethanolamine, potassium acetate, lithium acetate, and borax are effective as stabilizers for the glycol during synthesis (41). 

Due to the high reaction temperatures required during the last stages of these syntheses, side reactions cannot be avoided. Acetaldehyde, carboxyl endgroups, and vinyl endgroups are formed during PET and PEN synthesis. The formation of 2,2/-oxydiethylene moieties in polymer chains by etherification of hydroxyl endgroups is also a well-known side reaction of EG polyester syntheses.264 These reactions should be carefully controlled since they can exert an important influence on polymer properties such as Ts, mechanical properties, hydrolytic stability, and discoloration. 

The synthesis of block copolymers of polysaccharides and aliphatic polyesters has also been tried. But, many successful results were not reported because the reactivity of many hydroxyl groups on polysaccharides was an obstacle to the ROP of cyclic polyester or coupling reactions using terminal-activated polysaccharides. Li and Zhang reported the synthesis of maltoheptaose-b-PCL copolymers by ROP... 

Finally, Lecomte and coworkers reported the synthesis of mikto-arm star-shaped aliphatic polyesters by implementing a strategy based on click chemistry (Fig. 36) [162]. Firstly, the polymerization of sCL was initiated by a diol bearing an alkyne function. The chain-ends were protected from any further undesired reaction by the esterification reaction with acetyl chloride. The alkyne was then reacted with 3-azidopropan-l-ol. The hydroxyl function located at the middle of the chain was then used to initiate the ROP of sCL and y-bromo-s-caprolactone. Finally, pendant bromides were reacted successfully with sodium azide and then with N, N-dimethylprop-2-yn-l-amine to obtain pendant amines. Under acidic conditions, pendant amines were protonated and the polymer turned out to exhibit amphiphilic properties. 

Parzuchowski PG, Grabowska M, Tryznowski M, Rokicki G (2006) Synthesis of glycerol based hyperbranched polyesters with primary hydroxyl groups. Macromolecules 39 7181-7186... 

Biela T, Duda A, Pash H, Rode K (2005) Star-shaped poly(L-lactide)s with variable numbers of hydroxyl groups at polyester arms chain-ends and directly attached to the star-shaped core -controlled synthesis and characterization. J Polym Sci Part A Polym Chem 43 6116-6133... 

Tetrabromobisphenol A (TBBPA) is primarily used as a reactive flame retardant in epoxy resin circuit boards. Both hydroxyl groups on TBBPA can be reacted with epichlorohydrin under basic conditions to form the diglycidyl ether, which is widely used in epoxy resin formulations. TBBPA is also used in polycarbonate and ether polyester resins and is used as a chemical intermediate for the synthesis of tetrabromobisphenol A allyl ether, -bis(2-hydroxyethyl ether), -carbonate oligomer, and -diglycidyl ether. TBBA is also used as a flame retardant in plastics, paper, and textiles, and as a plasticizer in adhesives and coatings. 

There are two classes of polyols used in PU synthesis polyesters and polyethers. Approximately 90% of all PUs are manufactured using polyether polyols. Many polyols can be modified to have a higher degree of primary hydroxyl groups, or to contain one of polyurea or PU dispersions.The primary polyols are more reactive and the dispersed polyurea and PU segments serve to increase the crosslinking of the finished PU. Most of the polyether polyols... 

In condensation polymerization, the use of NIR to follow the reactant concentrations at elevated temperatures (200-300 °C) has been applied to the synthesis of aromatic and aliphatic polyesters (Dallin, 1997). This provides an accurate alternative to the routine measurement of acid values, hydroxyl number and viscosity, with the added advantage of providing continuous data throughout the polyesterification, which allows optimum conversion. Related examples of the use of NIR include studies of esterification of low-molar-mass analogues (Blanco and Serrano, 2000) or transesterification of an existing polymer or copolymer (Sasic et al, 2000). The NIR method allowed quantitative determination of rate constants, end points and yield and equilibrium constants as well as mechanistic information, which allowed the esterification to be optimized through the use of higher temperatures and an excess of acetic acid (Blanco and Serrano, 2000). 

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