A. Alla

Degradable poly(ester amide)s based on l-tartaric acid

Abstract A series of poly(ester amide)s with ester/amide group ratios ranging from 1 99 to 1 4 were obtained using 1,6-hexanediamine, 1,6-hexanediol and 2,3-di-O-methoxy- l -tartaric and succinic acids as building blocks. The ester linkages were introduced in pairs using as comonomer the diacid resulting from the esterification of 1,6-hexanediol with 2 mol of succinic anhydride. Polycondensastion reactions were carried out in solution at room temperature with the diamine activated as the N,N′-bis(trimethylsilyl) derivative and the two diacids as bis(pentachlorophenyl) esters. The prepared poly(ester amide)s have number average molecular weights in the range 10 000–40 000, display optical activity and are soluble in chloroform. These copolymers were found to be highly crystalline with melting points above 200°C and mechanical moduli comparable to those reported for the parent polyamide poly(hexamethylene-di-O-methyl- l -tartaramide). They were degraded by aqueous buffer of pH 7.4 at a rate that increased with the content of the copolymer in succinic acid units. 1H n.m.r. evidenced that no reactions other than those entailing the hydrolysis of the main chain ester bonds appear to take place at polymer degradation.

PET copolyesters made from a D-mannitol-derived bicyclic diol

The carbohydrate-based bicyclic diol 2,4:3,5-di-O-methylene-D-mannitol (Manx) was made to react in the melt with ethylene glycol and dimethyl terephthalate to produce random PExManxyT copolyesters covering the whole range of molar compositions. The copolyesters had weight-average molecular weights in the 33000–41000 g mol−1 interval and were thermally stable up to nearly 380 °C. They displayed Tg in the 81 to 137 °C range with values largely increasing with the content in Manx units. Copolyesters containing minor amounts of Manx were semicrystalline whereas those with contents equal to or more than 30% of Manx were amorphous. Stress–strain parameters were affected by composition, increasing tensile strength and elastic modulus and reducing elongation at break when introducing Manx units. These bio-based PET copolyesters showed enhanced susceptibility to hydrolysis.

Hydrolytic and enzymatic degradation of copoly(ester amide)s based on l-tartaric and succinic acids

Abstract The hydrolytic and enzymatic degradation of a series of crystalline copoly(ester amide)s derived from l -tartaric and succinic acids, 1,6 hexanediamine and 1,6-hexanediol with ester/amide groups ratios 3/97, 10/90, 15/85 and 20/80 was investigated. The hydrolytic degradation study was carried out at 37°C in buffered solution at pH 7.4. Changes taking place in sample weight, molecular weight, chemical constitution and thermal properties of the polymer were evaluated. Degradation proceeded with a notable increment in crystallinity and entailing slight but significant changes in the Tg and Tm temperatures. It was found that copoly(ester amide)s degraded faster than the parent poly(hexamethylene-di-O-methyl- l -tartaramide) and that the rate of degradation increased with the content in ester groups. It was also showed that degradation is accompanied by formation of cyclic succinimide units indicative of a scission mechanism based on the occurrence of intramolecular imidation reactions. The enzymatic degradation of these copoly(ester amide)s with papain was comparatively examined for a preliminary evaluation of their potential biodegradability.

Hydrolyzable Aromatic Copolyesters of p-Dioxanone

Entropically driven ring-opening copolymerization of mixtures of a fraction of cyclic oligo(hexamethylene terephthalate)s composed of cycle sizes from 2 to 5 and p-dioxanone was used to prepare random copolyesters covering a range of aromatic (HT) to aliphatic (DO) units ratios from 9 to 1.3. The composition and microstructure of the copolyesters were accurately determined by (1)H and (13)C NMR, respectively. The copolyesters showed thermal degradation and glass transition temperatures in good agreement with their comonomeric composition and microstructure, and they crystallized for contents in DO less than 30%, adopting the same crystal structure as poly(hexamethylene terephthalate). The copolyesters appeared to be sensitive to hydrolytic degradation, which was observed to take place superficially with the generation of non-water-soluble degraded fragments and with the release of water-soluble dioxanoic acid to the aqueous medium.