Poly[(4‐hydroxybutyric acid)‐alt‐(glycolic acid)]: Synthesis by Thermal Polycondensation of Metal Salts of 4‐Chlorobutyric Acid Carboxymethyl Ester

Abstract

Summary: A new sequential copolyester consisting of glycolic acid and 4‐hydroxybutyric acid units was prepared by a thermal polycondensation method that uses the formation of metal chloride salts as a driving force. The polymerization conditions (time, temperature) were studied in order to obtain appropriate molecular weights and high yields. Thermal properties and thermal stability were also determined. The polymerization kinetics of sodium, potassium and cesium monomer derivatives were studied by differential scanning calorimetry and the results compared. Non‐isothermal data and an isoconversional procedure (free model) were applied to determine the Arrhenius parameters (activation energy and pre‐exponential factor). The kinetic model was selected according to both the Coats‐Redfern method and the evaluation of isokinetic parameters.

Isothermal crystallization kinetics and spherulitic morphology of poly(4‐hydroxybutyric acid‐alt‐glycolic acid)

“…Poly(4Hb‐ alt ‐Glc) was synthesized with an 80% yield by thermal polyesterification of the potassium salt of 4‐chlorobutyric acid carboxymethyl ester, as previously reported12 (Scheme ). The intrinsic viscosity measured in dichloroacetic acid at 25 °C was 0.46 dL/g.…”

“…Recently, we have demonstrated that this kind of thermal polycondensation reaction is especially useful for preparation of alternating poly(ester amide)s containing glycolic acid units 10, 11. This procedure has also been extended to the production of alternating polyesters such as those derived by polymerization of Cl(CH 2 ) 3 COOCH 2 COO − K + and ClCH 2 COO(CH 2 ) n −1 COO − K + monomer salts 12. In this way, it is possible to obtain a set of biodegradable materials whose properties can be tuned by changing the number of methylene groups of the glycolic acid comonomer.…”

Some tentative explanations for the enthalpy–entropy compensation effect in chemical kinetics: from experimental errors to the Hinshelwood-like model

“…Thus, if we accept that, as confirmed by many experimental data reported in the published literature [3][4][5], there exists a linear correlation between the standard activation enthalpies and entropies for a family of related chemical reactions (differing usually either in the inert substituent of one of the reactants, provided that this is an organic species, or in the solvent used): plot, respectively, we must also accept (and confirmed by experimental results [6]) that there also exists a linear correlation between the Arrhenius parameters that can be expressed as: …”

Microspheres of new alternating copolyesters derived from glycolic acid units for controlled drug release

“…Poly(Glc‐ alt ‐6HH) was synthesized by the thermal polyesterification of the potassium salt of 6‐(2‐chloroacetate)hexanoic acid, as previously reported,13 with an 80% yield [Scheme (a)]. Poly(4Hb‐ alt ‐Glc) was synthesized by the thermal polyesterification of the potassium salt of 4‐chlorobutyric acid carboxymethyl ester, as previously reported,12 with an 80% yield [Scheme (b)].…”