SAXS analysis of the morphology of biocompatible and biodegradable poly(ε-caprolactone-b-glycolide) copolymers

Abstract

Poly(ε-caprolacrone-b-glycolide) diblock copolyesters have been synthesized by the sequential polymerization of ε-caprolactone and glycolide as initiated by aluminium alkoxides. Copolymerization is typically "living" and yields copolyesters of perfectly controlled molecular weight and composition. Diblock molecular weight (Mn PGA +Mn PCL ) ranges from 5700 to 42 000 and the ρ = Mn PCL /Mn PGA ratio varies from 1.5 to 13.1. Due to the inherent insolubility of the polyglycolide (PGA) segment in common organic solvent, the diblock copolyesters form stable non-aqueous colloidal dispersions e.g. in toluene, the stability of which results from the soluble poly(ε-caprolactone) (PCL) block. Combining all the experimental observations (PCS, TEM, WAXS, SAXS, AFM), a micelle model has been proposed which consists of a polyglycolide core surrounded with a corona of polycaprolactone (PCL). Both constituents are semi crystalline. From SAXS observations, the PGA core is better described by two concentric spheres. The internal sphere of a 5-6.7 nm diameter would essentially contain crystalline PGA. The diameter of the external sphere, D PGA , is in the range from 6.2 to 9.6 nm, at least for the investigated diblock copolymers. As a rule, this diameter increases as ρ decreases at constant molecular weight and as the diblock molecular weight increases at constant ρ. A scattering peak (weak) is observed in the range from 10.8 to 15.5 nm and the Bragg distance is close ΜD PGA > where µ is equal to (l+3ρ/2) 1/3 . From steric considerations, µ is the ratio between the diameter of the micelle and the diameter of the PGA core, so that this peak has been assigned to the characteristic intermicellar distance. At very small angles, several additional peaks are the signature of a hyperstructure which is possibly lamellar.

Microstructure analysis and thermal property of copolymers made of glycolide and ϵ‐caprolactone by stannous octoate

“…Therefore, copolymers based on PGL and PCL can be expected to produce a wide range of physical and mechanical properties that depend on the chemical composition. Thus, P(GL/CL) copolymer is of particular interest in terms of modifying the rigidity of PGL, which has been the subject of many studies 8, 11, 12. GL and CL have different polymerization rates in copolymerization, and this tends to result in block structures.…”

Macromolecular Engineering of Polylactones and Polylactides. 22. Copolymerization of ε-Caprolactone and 1,4,8-Trioxaspiro[4.6]-9-undecanone Initiated by Aluminum Isopropoxide

“…This is a valuable method to finely tune one property to the value needed for a specific application. Copolymerization of ε-CL with LA or GL yields biodegradable and biocompatible polyesters with a large range of chemical and physical properties. − The biodegradable sutures, commercially available under the trademark Vicryl, are nothing but random copolymers of PGL and PLA. In the recent past, increasing attention has been paid to some synthetic aliphatic polyesters bearing functional pendent groups because they provide the unique opportunity of attaching drugs, regulating cell function, and improving the desirable hydrophilicity.…”

Novel Macromolecular Architectures Based on Aliphatic Polyesters: Relevance of the “Coordination-Insertion” Ring-Opening Polymerization

“…A typical example of nanoparticles based on the aliphatic polyester engineering by living ROP is provided by the poly(CL-b-GA) copolymers which form stable colloidal dispersions in organic solvents such as toluene and THF without the need of any additional surfactant [27]. The poly(CL-b-GA) particles form a new class of stable non-aqueous dispersions in which a PGA core is stabilized by a PCL shell [122]. The copolymer micelles were characterized by TEM and PCS that show a bimodal distribution.…”