Synthesis of Degradable Polyesters Having Pendant Ester Groups by Ring-Opening Polymerization of 4-Substituted 2,6-Dioxabicyclo[2.2.2]octan-3-one Derivatives

Ito

J of Applied Polymer Sci

et al. 1994

SYNOPSISHomo-and copolyesters, containing 2,5-linked tetrahydropyran rings in their backbones, were prepared by cationic ring-opening polymerization of bicyclic lactones, 2,g-dioxabicyclo [ 2.2.21 octan-3-one ( 1 ), and its 4-methoxy-carbonyl and 4-benzyloxycarbonyl derivatives ( 3 and 4 ) . Copolyesters, having pendant carboxyl groups, were derived from the copolymers containing 4 as one of the comonomers by the catalytic hydrogenolysis of the pendant benzyloxyxarbonyl groups. Copolyesters, containing both 2,5-linked and 2,6-linked tetrahydropyran rings in the main chains, were obtained by the copolymerization of 1 with 6,8-dioxabicyclo [ 3.2.11 octan-7-one ( 13 ) , which is a structural isomer of 1. Spontaneous hydrolytic degradability of these polyesters was investigated in a phosphate buffer solution (pH 7.5) at 27°C. The degradability of the polyesters markedly depended on the molecular structure: hydrophobic pendant groups retarded the hydrolytic degradation, whereas hydrophilic pendant groups accelerated it. In particular, a small amount of pendant carboxyl groups significantly enhanced the hydrolytic degradability of the copolyesters from 1. Polyesters, containing 2,6-linked tetrahydropyran rings in their backbones, underwent hydrolytic degradation more readily than those entirely consisting of 2,5-linked tetrahydropyran rings. INTRODUCTIONPollution by wasted plastics is one of the major factors that are worsening the ecological environment on the earth. There are two approaches to solving this troublesome problem: one is the material design of readily recyclable polymers; the other is the development of spontaneously degradable polymeric materials. As for the latter approach, one of the most promising materials is a class of photodegradable polymers. A variety of photodegradable polymers have been designed and synthesized, and some of them are commercialized.' Polymers, which are spontaneously hydrolyzable under neutral conditions to yield harmless low molecular weight compounds, would be of practical value if they were * To whom correspondence should be addressed. CCC OOZ1-8995/94/061035-09 readily processable and had the desirable mechanical and thermal properties. Of particular importance are biodegradable polymers, which are hydrolyzed and catabolized by microorganisms in a natural environment.On the other hand, from the viewpoint of biomedical materials, considerable attention has been directed toward spontaneously hydrolyzable, biodegradable, synthetic polymers, especially poly (a-hydroxy acid) s, such as poly (glycolic acid), poly ( lactic acid), and their analogues.2 Since the hydrolysis rates of these polyesters are relatively low, because of their high crystallinity and low hydrophilicity, several biodegradable polyesters with pendant carboxyl groups have been synthesized in order to impart higher hydrophilicity. Lenz et al.3'4 prepared homo-and copolymers of p-malic acid and its alkyl esters by ring-opening polymerization of benzyl malolactonate, followed by hydrogenolytic debenzylation. O...

Spontaneous hydrolytic degradability of copolyesters having tetrahydropyran rings in their backbones

Ito

J of Applied Polymer Sci

et al. 1994

Biodegradability of polyesters having tetrahydropyran rings in their backbones

Ito

J of Applied Polymer Sci

et al. 1994

SYNOPSISBiodegradability of several homo-and copolyesters, containing tetrahydropyran rings in their backbones with or without pendant groups, was investigated by degradation tests, both in soil and in an activated sludge. These polyesters were hydrolytically degraded to lower molecular weight compounds, and eventually to hydroxytetrahydropyran carboxylic acids, at different rates, depending on their molecular structure. Quantitative determination of carbon dioxide, generated during the treatment with the activated sludge, showed that the hydrolysates from polyesters 2 and 10, without pendant alkoxycarbonyl groups, were catabolized by microorganisms. It was concluded from these results that at least the polyesters without pendant groups were biodegradable, and that polyester 10, consisting of 2,g-linked tetrahydropyran rings, underwent biodegradation more readily than polyester 2, consisting of 2,5-linked tetrahydropyran rings.

Synthesis and degradabilities of polyesters from 1,4:3,6‐dianhydrohexitols and aliphatic dicarboxylic acids

J. Polym. Sci. A Polym. Chem.

1995

SYNOPSISSix different polyesters (6a-6c and 7a-7c) were prepared by the bulk polycondensations of the respective combinations of 1,4:3,6-dianhydro-~-glucitol (3) and 1,4:3,6-dianhydro-D-mannitol(4) with succinyl dichloride (5a), glutaryl dichloride (5b), and adipoyl dichloride (5c) a t 140-180°C. Polyesters having number average molecular weights up to 2.6 X lo4 were obtained in high yields. Only polyester 7a based on 4 and 5a was partially crystalline, whereas all the other polyesters were amorphous. Thin films of these polyesters except that of 7a were spontaneously hydrolyzed in a neutral phosphate buffer solution a t 50"C, whereas they were reluctant to be hydrolyzed a t 27°C. The polyesters were more or less degraded at 27°C by treatment with an activated sludge or by prolonged burial in soil. 0 CCC 0887-624X/95/162813-08 as well as spontaneous hydrolytic degradation in a neutral phosphate buffer These polyesters were prepared by cationic ring-opening polymerization of bicyclic lactones, 6,g-dioxabicyclo[3.2.l]octan -7 -one and 2,6 -dioxabicyclo [2.2.2]octan-3-one, respectively.