Synthesis and properties of new polyesters having tetrahydrofuran rings in their main chains

Abstract

SYNOPSISNew polyesters 6a-6c consisting of 2,4-linked tetrahydrofuran rings were synthesized by bulk polycondensation of methyl trans-and cis-4-hydroxytetrahydrofuran-2-carboxyla~s ( 5a and 5b) and a stereoisomeric mixture of methyl 4-hydroxy-5-methyltetrahydrofuran-2-carboxylate ( 5 c ) at high temperature. These monomers were prepared from methyl glycolate or methyl lactate and diethyl maleate through a four-step reaction sequence. The polycondensation was carried out without solvent at different temperatures ranging from 150 to 220°C. Titanium isopropoxide was most effective among the catalysts examined, giving polyesters with number-average molecular weights up to 2 X lo4. Polyester 6a consisting of trans-2,4-linked tetrahydrofuran rings was soluble in trifluoroacetic acid and a mixed solvent of chloroform and methanol (lO/l, v / v ) . Polyester 6b composed of cis-2,4-linked tetrahydrofuran rings was soluble in dimethyl sulfoxide and dimethylformamide in addition to the two solvents for 6a. Polyester 6c with 5-methyl-substituted tetrahydrofuran rings was composed of a mixture of stereoisomeric units and thus was soluble in a variety of solvents including chloroform, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and dimethylformamide. The glass transition temperatures of 6a, 6b, and 6c determined by DSC were 109, 88, and 66°C. These polyesters were found to be very slowly hydrolyzed in a neutral phosphate buffer solution at ambient temperature. 0 1993 John Wiley & Sons, Inc. 0 817 (1983).16. The symbols (t, c, and r ) are used according to the IUPAC nomenclature for cyclic compounds having three or more substituents. The symbol "r" indicates the reference substituent having the lowest position number. The symbol "t" or " c " denotes trans or cis configuration of a substituent in other position with respect to the reference substituent. (1978).

Terpene-Based Renewable Monomers and Polymers via Thiol–Ene Additions

“…Titanium isopropoxide was also tried in an attempt to reach higher molecular weights. Titanium alkoxides are known to act as efficient transesterification catalysts and have been successfully used for polyester synthesis being compatible with a variety of functional groups . Moreover, titanates are recognized as extremely powerful for ester-exchange reactions .…”

Chemical Synthesis of Atactic Poly-3-hydroxybutyrate (a-P3HB) by Self-Polycondensation: Catalyst Screening and Characterization

“…Tin catalysts, as well as zinc acetate, have been reported to be effective in the polymerization of lactic acid and glycolic acid, resulting in high molecular weight polymers with controlled properties [14,15]. Moreover, titanium isopropoxide and iron chloride have also been shown to promote polycondensation by increasing the electrophilic character of the carbonyl group of an ester, resulting in polyesters with molecular weights up to 2 × 10 4 g/mol, such as the reaction product of methyl 4-4hydroxytetrahydrofuran-2-carboxylate with linked tetrahydrofuran rings [16,17]. While the chemical synthesis of polyhydroxyalkanoates can produce polymers with certain properties that cannot yet be achieved by biotechnology, it is more expensive and laborious than biotechnological production.…”