Poly(P-Dioxanone) (PPDO), and Its Copolymers
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http://www.paper.edu.cn MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016 ©2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc. JOURNAL OF MACROMOLECULAR SCIENCE Part C—Polymer Reviews Vol. C42, No. 3, pp. 373–398, 2002 POLY( p-DIOXANONE) AND ITS COPOLYMERS Ke-Ke Yang, Xiu-Li Wang, and Yu-Zhong Wang* Center for Degradable and Flame-Retardant Polymeric Materials, School of Chemistry, Sichuan University, Chengdu 610064, P. R. China CONTENTS 1. Introduction ............................................................ 374 2. Synthesis of PDO ....................................................... 374 2.1. Physical Properties of PDO ........................................374 2.2. Synthesis of PDO ..................................................375 3. Ring-Opening Polymerization of PDO . ................................ 376 3.1. Catalyst............................................................376 3.2. Copolymerization Based on PDO ..................................381 4. Properties of PPDO ..................................................... 383 4.1. Solubility ..........................................................384 4.2. Biodegradability ...................................................384 4.3. Thermal Properties.................................................386 4.4. Crystallization and Morphology ....................................386 4.5. Mechanical Properties. ...........................................390 5. Application of PPDO ................................................... 390 5.1. Surgical Suture.....................................................390 5.2. Bone and Tissue Fixation Device ...................................391 5.3. Drug Delivery System. ...........................................391 *Corresponding author. Fax: þ86-28-5412907; E-mail: [email protected] 373 DOI: 10.1081/MC-120006453 1532-1797 (Print); 1532-9038 (Online) Copyright # 2002 by Marcel Dekker, Inc. www.dekker.com 中国科技论文在线 http://www.paper.edu.cn MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016 ©2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc. 374 YANG, WANG, AND WANG 6. Conclusion .............................................................. 391 References .............................................................. 392 ABSTRACT This paper reviews the synthesis, properties, and applications of bio- degradable polymer, poly(p-dioxanone) (PPDO), and its copolymers. Recent progress in ring-opening polymerization of p-dioxanone employ- ing several effective catalysts is described. Properties of PPDO are given. The copolymers based on PPDO are also discussed. Key Words: Poly(p-dioxanone); Copolymers; Ring-opening polymeri- zation; Biodegradable 1. INTRODUCTION Aliphatic polyesters, with outstanding biodegradability, bioabsorb- ability, and biocompatibility, have attracted great interest from researchers in recent decades. The related papers and patents increased sharply in a very short period, and remarkable progress has been achieved in this field.[1–9] As a result, a series of polyesters and copolyesters have been synthesized success- fully from the lactone monomers including glycolide (GA),[10] lactide (LA),[3,7–9] e-caprolactone (CL),[2,11,12] p-dioxanone (PDO),[4,5,13,14] 1,5-diox- epan-2-one (DXO),[15] 1,3-dioxan-2-one (TMC),[16–18] and so on. Most of them have been applied to make biodegradable products, especially surgical devices such as surgical suture, anchors, staples, tacks, clips, plates, screws, and bone fixation devices.[7,8,14] Compared with other aliphatic polyesters, poly( p-dioxanone) (PPDO) has its own special characteristics. Except for its ultimate biodegradability due to the existence of ester bonds in polymer chains, the unique ether bonds endow it with good flexibility.[19] It has also received the approval of the Food and Drug Administration (FDA) to be used as suture material in gynecology.[19,20] However, PPDO did not become the focus of polyesters for quite a long period. There are two main reasons for this. One reason is that the monomer PDO was not commercially available in the past. The other reason is that the activity of the PDO monomer is comparatively low, and most catalysts that have been mentioned in the available infor- mation are not effective enough to produce the polymer at reasonable cost. Fortunately, the synthetic method of producing PDO has been sim- plified greatly, and studies on PPDO have made rapid development in recent years. 中国科技论文在线 http://www.paper.edu.cn MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016 ©2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc. POLY( p-DIOXANONE) AND ITS COPOLYMERS 375 This article presents a review of the synthesis, properties, and applica- tions of PPDO and its copolymers. 2. SYNTHESIS OF PDO 2.1. Physical Properties of PDO p-Dioxanone or 1,4-dioxan-2-one, abbreviated as PDO, is a colorless crystal or liquid. Its molecular weight is 102, and melt point is 24C.[21] Boiling points are 220C, 213–214C, 109–110C, and 92–93C, respectively, under different pressures [760 mmHg (calculated value), 747 mmHg, 22 mmHg, and 10 mmHg].[13,22] There are many ways to characterize its molecular structure, such as nuclear magnetic resonance (NMR) spectroscopy (1H-NMR spectrum), infrared (IR) spectroscopy, and mass spectrometry (MS).[22] The NMR spectrum of PDO exhibits a sharp singlet at d4.40 and two multiplets of equal intensity centered at d3.9 and 4.5. The IR spectrum shows the following absorptions: CH stretching at À1 À1 2900 cm ,C¼O stretching at 1740 cm ,CH2 bending at 1455 and 1432 cmÀ1, CO stretching at 1200, 1130, and 1053 cmÀ1, and other weaker bands at 876, 853, 726 cmÀ1. The mass spectrum of PDO, including parent, Pþ1, and major peaks, appear at 103, 102, 101, 87, 86, 75, 73, 58, 57, 45, 44, 43, 42, 32 m/e, respectively.[22] 2.2. Synthesis of PDO In the early 1970s, Doddi et al.[14] had used ethylene glycol, metallic sodium, and chloroacetic acid to synthesize PDO (Scheme 1). However, the procedure was so complex and the yield so low that it caused a high cost of PDO and seriously hampered the application of PPDO. So this method was substituted in the last decade by a simple method that prepared PDO by oxidative dehydrogenation of diethylene glycol over Cu(O) catalyst supported on silica particles (Scheme 2).[23] Because the resource, diethylene glycol, was very cheap, this one-step reaction sharply decreased the cost of PDO. Purification of PDO is also an important step in order to achieve high molecular weight PPDO. Distillation and recrystallization are both effective ways to purify the monomer. Distillation is usually conducted under high vacuum, considering the rather high boiling point of PDO at normal pressure. Commonly, ethylacetate has been chosen as the recrystallizing solvent. However, the yield of recrystallization is lower than that of distillation. Jiang[24] supplied a method to gain excellent purified PDO by double recrystallization using ethylacetate as solvent with a yield of 30%. 中国科技论文在线 http://www.paper.edu.cn MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016 ©2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc. 376 YANG, WANG, AND WANG HOCH2CH2OH + Na HOCH2CH2ONa + H2 + HOCH2CH2OH 1/2ClCH2COOH HOCH2CH2OCH2OONa + NaCl + HOCH2CH2OH distillation HOCH2CH2OCH2COONa + NaCl HOCH2CH2OH washing by acetone HOCH CH OCH COONa 2 2 2 CH3COCH3 + NaCl + - H3O + Cl HOCH2CH2OCH2COOH + H2O + NaCl precipitation with ethanol and filtration HOCH2CH2OCH2COOH ++ H2O C2H5OH NaCl + C2H5OH distillation HOCH2CH2OCH2COOH H2O + C2H5OH O O O Scheme 2. O Catalyst O HOCH2CH2OCH2CH2OH O Scheme 1. 3. RING-OPENING POLYMERIZATION OF PDO 3.1. Catalyst The polyester PPDO is synthesized by ring-opening polymerization from the monomer PDO. In this polymerization process, the catalyst plays an important role, which influences not only the polymeric parameters such as reaction rate, conversion, and yield, but also the properties of the polymer such as molecular weight and polydispersity. Several catalysts, especially organometallics, have been found effective to initiate the ring-opening polymerization of lactone, even if some of them have not been reported to apply to PDO. Most catalysts are the derivatives of organometallics of heavy metals such as Ti, Zr, Sn, Cd, Al, Zn, Y, La, and Yb. Thereafter, the catalysts that have been used frequently will be listed in detail. 中国科技论文在线 http://www.paper.edu.cn MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016 ©2002 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc. POLY( p-DIOXANONE) AND ITS COPOLYMERS 377 3.1.1. Organic Tin Compounds Organic tin compounds, including stannous octoate,[25–29] stannous oxalate,[30] dibutyltin oxide,[31] stannic bromide, stannic chloride, stannous bromide, stannous chloride,[32–34] stannous acetylacetonate,[35] and [16] Bu2SnOct2, have been used most frequently in ring-opening polymeriza- tion of lactone. Among these, stannous octoate (SnOct2) has been found the most effective catalyst. Moreover,