Degradation of nonalternating poly(ester amides)

Abstract

Introduction.Aliphatic polyesters are an important class of biodegradable and hydrolyzable synthetic polymers.'" A series of a-hydroxypolyesters, such as poly-(glycolic acid) (PGA), poly(1actic acid) (PLA), and their copolymers, have been successfully used as bioabsorbable sutures and surgical implants.lt3 Other types of polyesters,415 such as poly(caprolactone), poly(@-propiolactone), and poly(butyrolactone), can also be potentially used as biodegradable polymers in drug delivery and agricultural uses.On the other hand, commercial aliphatic polyamides (nylon 6 and nylon 66) are nonbiodegradable. The large concentration of hydrogen bonds and the high regularity of the polyamide structure are the possible reasons for the inertness of these nylons to biodegradation. On the basis of the above facts, poly(ester-amides) (PEAS) composed of esters and amides could potentially be a class of biodegradable polymers which would have better physical properties than polyesters.6-11Recently, aliphatic poly(ester-amides) containing ahydroxy or a-amino acid moieties have been studied for their potential biomedical applications. Helder and coworkers6 studied the in vitro degradation of nonalternating glycine/DL-lactic acid copolymers. Barrows and cow o r k e r~~~~ also synthesized a series of alternating poly-(ester-amides) by using a two-step polycondensation reaction from glycolic acid, diamine, and diacoyl chloride and investigated the in vivo degradation of the copolymers for the purpose of developing new surgical implants. However, very few studies on the degradation of poly-(ester-amides) have been reported. Tokiwa et al. 9JO showed that poly(ester-amides), made by amide-ester interchange reactions of nylons and polycaprolactone, were degraded by lipase. To develop degradable materials for general applications, two types of nonalternating PEAS were synthesized by anionic" and interfacial12 polymerizations. The hydrolysis (in buffer solution) and biodegradation (under attack of fungi) of these polymers were studied.Experimental Section. Nylon 6 was obtained from Polysciences Inc. and low-density polyethylene (LDPE) from Union Carbide (No. 6201). 1,6-Hexanediamine was purified by vacuum sublimation. t-Caprolactone, l,&hex-anediol, and adipoyl chloride were distilled at reduced pressure. e-Caprolactam was recrystallized from reagentgrade acetone three times and dried in vacuum. Alcoholfree chloroform was prepared by washing with distilled water three times, followed by drying with anhydrous CaClz and distillation. Dry methanol was prepared from absolute-grade methanol by drying with potassium methoxide followed by distillation. The catalyst, sodiocaprolactam, was made by reacting e-caprolactam with sodium methoxide in anhydrous methanol under argon. Excess methanol was distilled off and the residue heated under reduced pressure at 120-130 OC for 2 h to remove any remaining methanol and lactam.The intrinsic viscosities of the polymers were measured in a 0.5 g/dL solution of 90% formic acid at 25 "C. The infrared spectra of th...

Microflora dynamics in earthworms casts in an artificial soil (biosynthesol) containing lactic acid oligomers

“…In conclusion, the slight decrease of the number of fungi in the earthworms casts compared to the population found in biosynthesol shows that earthworms regulate the number of fungi mostly by eating them. Among those fungi, Fusarium and Aspergillus strains known as able to bioassimilate PLA (Fusarium, Torres et al, 1996c) or other aliphatic esters (Aspergillus, Nishida et Tokiwa, 1993, Gonsalves et al, 1992 were found. It is thus probable that OLA is first degraded by those fungi and also by bacteria, and then earthworms eat them.…”

Microwave syntheses of poly(?-caprolactam-co-?-caprolactone)

“…However, polyester-amides composed of esters and amides could potentially have better physical and mechanical properties than polyester with retention of biodegradability characteristics of the polyesters. 4 -8 Synthesis of such materials via anionic copolymerization of -caprolactam with -caprolactone has been investigated by Goodman et al 9 -12 Gonsalves et al, 13 and Nakayama et al 14 Goodman et al 9 showed that, in anionic copolymerization studies using N-sodium caprolactam as a catalyst, at both high and low initial -caprolactam/-caprolactone feed ratio (70/30 or 25/ 75), incorporation of -caprolactam units into the copolymer increased at higher catalyst concentrations (1 and 2%) and with reaction time. For a catalyst level of 0.5%, at the same feed ratios, -caprolactone is the major component in copolymers.…”

Concept and Synthesis of Poly(ester amide)s with One Isolated, Two or Three Consecutive Amide Bonds Randomly Distributed Along the Polyester Backbone

“…Such PEAs can be prepared by condensing either (i) lactones with lactams or (ii) lactones and lactams with diamines, diols and diacid derivatives [1][2][3][4][5][6][7][8][9][10][11]. BAK ® 1095, a commercial product from Bayer is a random semi-crystalline PEA based on ε-caprolactam, 1,4-butanediol and adipic acid [1,2].…”

“…Ringopening co-polymerization of lactones and lactams affords random co-polymers [1,2,[4][5][6][7][8][9][10][11][104][105][106][107]. Aliphatic and/or aromatic dicarboxylic acids and diols with varying number of methylene groups give rise to various microstructures and architectures.…”