WO2014135727A1

WO2014135727A1 - Novel random terpolymers based on d-lactide, l-lactide and ε-caprolactone

Info

Publication number: WO2014135727A1
Application number: PCT/ES2014/070156
Authority: WO
Inventors: Jorge FERNÁNDEZ HERNÁNDEZ; Aitor LARRAÑAGA ESPARTERO; José Ramón SARASUA OIZ
Original assignee: Universidad Del País Vasco
Priority date: 2013-03-04
Filing date: 2014-03-03
Publication date: 2014-09-12
Also published as: ES2504666B1; ES2504666A1

Abstract

The invention relates to random terpolymers based on D-lactide, L-lactide and ε-caprolactone with limited or no crystallisation capacity during hydrolytic degradation.

Description

NEW TERPOLÍ RANDOM MEROS BASED ON D-LACTIDA, L-LACTIDA and ε- CAPROLACTONA

OBJECT OF THE INVENTION

The present invention relates to the chemical synthesis of thermoplastic, bioabsorbable and biocompatible biopolymers for application preferably in the medical field and more especially to random terpolymers based on D-lactide, L-lactide and ε-caprolactone with little or no crystallization capacity during hydrolytic degradation.

BACKGROUND OF THE INVENTION

During the last decades the synthesis of biodegradable polymers has been stimulated by the need for new materials for applications in the medical field. These biomaterials are designed to degrade in a controlled manner over a predetermined period of time, decomposing into small non-toxic molecules that can be reabsorbed or excreted by the human organism, and, therefore, do not have to be removed clinically once their function but they must maintain their performance (mechanical properties and biocompatibility) during the time in which they are used.

The most studied absorbable homopolymers, such as polyglycolide (PGA) or polylactides (PLAs), have a similar mechanical behavior, characterized by a high Young's modulus and low elongation at break values, and have inappropriate degradation times for numerous clinical applications that require resistant biodegradable materials of great flexibility that degrade in a certain period of time. Among the applications in the medical field of these thermoplastic elastomers required are included cell therapy for soft tissue reconstruction and use in the surgical field as implants, stents or catheters.

Mixtures or chemical synthesis allow obtaining new biodegradable materials with improved properties. By polymerization with other monomers that give rise to low-temperature glass transition homopolymers, which are more thermally resistant or having a greater hydrophilic character, new materials can be developed that improve flexibility, mechanical and thermal resistance and the degradation rate with respect to the corresponding homopolymers. Lactide, glycolide, ε-caprolactone, ethylene glycol, trimethylene carbonate or p-dioxanone-based copolymers and terpolymers are receiving increased attention and offer a wide range of properties depending on their composition.

The crystallization capacity of the most commonly used copolymers and terpolymers is still high and due to improper adjustments in the composition and underestimation of their sequence distribution are materials prone to structural changes during storage or hydrolytic degradation. In their storage, some of these biomaterials undergo an aging process that involves supramolecular rearrangements until they reach thermodynamic equilibrium that can affect the mechanical behavior of the material by increasing its stiffness and / or decreasing its elongation at break (Fernández J, Etxeberría A, Sarasua JR. Synthesis, structure and properties of poly (L-lactide-co-£ - caprolactone) statistical copolymers. Journal of the Mechanical Behavior of Biomedical Materials 2012; 9: 100-1 12; [20] Tsuji H, Mizuno A, Ikada Y. Enhanced Crystallization of Poly (L-lactide-co-ε-caprolactone) During Storage at Room Temperature. Journal of Applied Polymer Science 2000; 76: 947-953)

On the other hand, the majority of biodegradable elastomers available that are degraded while preserving their amorphous character, have very low transition temperatures (less than 15-20 ° C) resulting in materials with very low elastic moduli (<5 MPa). This makes them difficult to handle materials at room temperature that exhibit insufficient mechanical support at 37 ° C (human body temperature). In hydrolytic degradation at 37 ° C, these changes in the morphology of the polymer are more relevant and are accelerated due to the plasticizing effect of water molecules that favors the mobility of polymer chains (Saha SK, Tsuji H. Effects of rapid crystallization on hydrolytic degradation and mechanical properties of poly (L-lactide-co-ε-caprolactone. Reactive & Functional Polymers 2006; 66: 1362-1372; Saha SK, Tsuji H. Enhanced crystallization of poly (L-lactide-co- £ - caprolactone) in the presence of water. Journal of Applied Polymer Science 2009; 112: 715-720). Degradation occurs preferentially in the amorphous regions of the material, being the most resistant crystalline regions (Albertsson AC, Eklund M. Influence of molecular structure on the degradation mechanism of degradable polymers: In vitro degradation of poly (trimethylene carbonate), poly (trimethylene carbonate-co-caprolactone) and poly (adipic anhydride) Journal of Applied Polymer Science 1995; 57: 87-103). Therefore, high crystallization inhibits the homogeneous degradation of the material and contributes to the deterioration of its properties, favoring fragile breakage (Fernández J, Larrañaga A, Etxeberría A, Sarasua JR. Effects of chain microstructures and derived crystallization capability on hydrolytic degradation of poly (L-lactide / £ - caprolactone) copolymers Polymer Degradation and Stability 2013: 98: 481-489). In addition, low molecular weight crystalline residues are formed in the degradation process that can remain in the human body for years, once the material has already lost its properties and has fulfilled its function (Tsuji H, Ikarashi K. In vitro hydrolysis of poly (L-lactide) crystalline residues as extended-chain crystallites Part I: long-term hydrolysis in phosphate-buffered solution at 37 ° C. Biomaterials 2004; 25: 5449-5455).

The conformation of reliable medical devices requires materials that have stability, durability and predictability of their macroscopic and microscopic properties. Through better control of the composition and microstructure, as well as molecular weight, it is possible to make new thermoplastic materials with custom properties, which improve the properties of commercial absorbable polymers, being able to adapt their mechanical properties and degradation times to needs of specific medical applications.

The medical field requires highly flexible resistant biodegradable materials that degrade over a certain period of time and preferably have transition temperatures above 15 ° C. However, the crystallization capacity of the most commonly used copolymers and terpolymers is still high and due to poor adjustments in the composition and underestimation of their sequence distribution are materials prone to structural changes during storage or hydrolytic degradation. In addition, low molecular weight crystalline residues are formed in the degradation process that can remain in the human body for years, once the material has already lost its properties and has fulfilled its function

In response to this need, random terpolymers (R greater than 0.9) are synthesized in the present invention by polymerization of L-lactide and D-lactide, to provide consistency and mechanical strength to the material, and ε-caprolactone to provide elastomeric character. These materials show little or no crystallization capacity during storage or degradation thanks to the control of the average lengths of L-lactide or D-lactide and ε-caprolactone. They are thermoplastic materials of different mechanical behaviors that exhibit a homogeneous degradation without the formation of crystalline residues of high hydrolytic resistance and that have a glass transition temperature greater than 15 ° C.

DESCRIPTION OF THE INVENTION

These and other features and advantages of the invention will become more clearly apparent from the following detailed description of preferred embodiments, given solely by way of illustrative and non-limiting examples, with reference to the accompanying figures.

DETAILED EXHIBITION OF THE INVENTION

In one of its aspects the present invention is directed to random terpolymers (R> 0.85) obtainable by mass polymerization (without solvent use) in a single stage of:

a) ε-caprolactone of formula (I)

(I)

b) L-lactide of formula (II)

(II)

and e) D-lactide of formula (III)

These terpolymers can be synthesized in a single stage by adding the comonomers (I) to (III) at the same time. The catalyst is added once the mixture has been melted and the medium has been inerted. These polymers have a marked random character in the distribution of lactide and caprolactone units (short sequences of L-lactide, D-lactide and ε-caprolactone). Although the sequences of L-lactide or D-lactide and of ε-caprolactone have the ability to crystallize during degradation, the materials of the present invention exhibit little or no crystallization capacity during storage or degradation thanks to the control of average lengths of L-lactide or D-lactide and ε-caprolactone. They are thermoplastic materials of different mechanical behaviors that exhibit a homogeneous degradation without the formation of crystalline residues of high hydrolytic resistance and that have a glass transition temperature greater than 15 ° C.

In the terpolymers of the present invention the presence of L-lactide and D-lactide contributes to increase the consistency and mechanical strength of the material, and the presence of ε-caprolactone contributes to providing elastomeric character.

In one embodiment of the present invention, random terpolymers are obtained by reacting a mixture of comonomers having a molar content of ε-caprolactone between 5 and 30 mol% with respect to the total of comonomers (I), (II) and ( III). For values of less than 5%, the material becomes very susceptible to brittle breakage and its mechanical behavior resembles that of the most common semicrystalline homopolymers. On the contrary, for values greater than 30% the glass transition temperature will be very low (less than 15 ° -20C) and although their elastomeric character is very high the consistency of these will be insufficient (very low elastic modules, <5 MPa) being difficult to work with them at temperatures higher than their glass transition temperature, as is the case with the temperature of the human body (37 ° C).

In another embodiment of the present invention, random terpolymers are obtained by reacting a mixture of comonomers having a molar content of a ε-caprolactone molar content between 5 and 25 mol% with respect to the total comonomers (I), (II ) and (III) and preferably having the same amount of L-Lactide and D-Lactide.

In another embodiment of the present invention, random terpolymers are obtained by reacting a mixture of comonomers having a molar content of a ε-caprolactone molar content between 5 and 15 mol% with respect to the total comonomers (I), (II ) and (III). Such polymers have exceptional properties for applications in which the stiffness of the terpolymers is important, being an alternative to the rigid biodegradable materials currently used that are very susceptible to brittle breakage (vitreous behavior) and / or have a high crystallization capacity during the degradation resulting in crystalline residues of low molecular weight that, due to their high hydrolytic resistance, can remain in the human body for years, once the material has already lost its properties and has fulfilled its function.

In another embodiment of the present invention the random terpolymers are obtained by reacting a mixture of comonomers having a molar content of a ε-caprolactone molar content between 15 and 30 mol% with respect to the total comonomers (I), (II ) and (III). Such polymers have exceptional properties for applications in which the elastomeric properties of the terpolymers are important, being an alternative to the currently used elastomeric biodegradable materials that have a very low T _g , presenting insufficient consistency, and / or have a high capacity of crystallization during degradation. In another embodiment of the present invention, random terpolymers are obtained by reacting a mixture of comonomers having a molar content of L-lactide between 3 and 72%, preferably between 5 and 72% with respect to the total comonomers ( I), (II) and (III) and a D-lactide content between 3 and 72%, preferably between 5 and 72% of the total comonomers (I), (II) and (III). In another embodiment of the present invention, random terpolymers are obtained by reacting a mixture of comonomers having a molar content of ε-caprolactone (II) between 5 and 30% with respect to the total comonomers (I), (II) and (III) an L-lactide content between 3 and 72%, preferably between 5 and 72% of the total comonomers (I), (II) and (III) and a D-lactide content between 3 and 72%, preferably between 5 and 72% of the total comonomers (I), (II) and (III).

In another embodiment of the present invention, random terpolymers are obtained by reacting a mixture of comonomers in which the enantiomeric excess of L-lactide or D-lactide is greater than 5%, preferably greater than 7.5% and more preferably greater than 10%.

Another aspect of the present invention is the method of synthesis of the random terpolymers described above which consists in reacting the catalyst and the comonomers in a single stage:

a) ε-caprolactone of formula (I)

b) L-lactide of formula (II)

and e) D-lactide of formula (III)

In one embodiment of the present invention the polymerization reaction proceeds by ring opening polymerization (ROP) being carried out in bulk at temperatures between 120 and 140 ° C for 2 or 3 days of reaction. Once the reaction is finished, it is necessary to remove impurities from the catalyst, oligomers and monomers that have not reacted. This is done by dissolution-precipitation in chloroform-methanol but there are other alternatives such as the use of other solvent-precipitating pairs or vaporization under pressure.

The polymerization reaction is carried out in a single stage by adding the comonomers at the same time, while the catalyst is added once the mixture has been melted and the medium has been inerted thus giving rise to random polymer structures (R> 0.85).

In one embodiment of the present invention the polymerization reaction is carried out in a single step in the presence of a catalyst that is selected from the group consisting of bismuth 2-ethylhexanoate, bismuth hexanoate (BiHex ₃ ), the triflate of bismuth (Bi (OTf) ₃ ), bismuth diphenyl ethoxide (Ph ₂ BiOEt), bismuth subsalicylate (BiSS) and bismuth triphenyl (Ph ₃ Bi), more preferably from the group consisting of bismuth subsalicylate ( BiSS) and bismuth triphenyl (PH ₃ Bi).

In a preferred embodiment the catalysts are used so that the molar ratio of the total monomers (I), (II) and (III) to the catalyst is between 250: 1 and 10,000: 1, preferably between 750: 1 and 2000 : 1, more preferably between 1000: 1 and 1500: 1 and the reaction is preferably carried out in an inert atmosphere, eg in an N ₂ atmosphere.

In a more preferred embodiment the reaction is carried out at temperatures between 120 and 150 ° C, more preferably between 130 and 140 ° C and the reaction time is between 8 and 96 hours depending on the reaction temperature. Thus when the temperature is 130 ° C the reaction time can be between 48 and 72 hours and when the temperature is 140 ° C the reaction time can be between 32 and 48 hours. Another aspect of the present invention relates to mixtures of one or more of the random terpolymers described above.

Another aspect of the present invention relates to composite materials comprising mixtures of the terpolymers of the invention. In the context of the present invention, composite material is understood as those materials that are formed by mixing the terpolymers of the invention and one or more materials to achieve the combination of properties that cannot be obtained in the original materials. Said composite materials are formed by two or more physically distinguishable and mechanically separable components and have several chemically distinct phases, completely insoluble to each other and separated by one inferred. Examples of composite materials are those consisting of terpolymers of the invention with mechanical reinforcement, that is to say they comprise terpolymers of the invention and fibers or particles (inorganic fillers and nano-charges such as glass fibers, carbon fibers or carbon nanotubes; organic fillers). such as aramid fibers or high density polyethylene fibers; and natural fillers such as fibers of plant origin) in order to improve the mechanical properties of the polymer matrix. Another example of composite materials are those comprising terpolymers of the invention and bioactive fillers such as bioactive inorganic particles (bioglass, hydroxyapatite etc.) or bioactive molecules such as growth factors (set of substances, most of a protein nature) that stimulate the cell proliferation by regulating the cell cycle by initiating mitosis and, in addition, regulating cell survival and stimulating cell migration, cell differentiation and even apoptosis) in order to improve cell activity and growth in the polymer matrix. Another example of composite materials are composite materials comprising terpolymers of the invention and antibiotic agents (phosphamycin, gentamicin, etc.) in order to improve the antibacterial activity of the polymer matrix. Another aspect of the present invention relates to medical devices or implants such as catheters; the probes; nerve guides (tubular grafts that bridge two ends of a damaged nerve); stents (devices of different designs, usually meshes, that are introduced into the coronary arteries (cases of atherosclerosis), esophagus (cases of esophageal stenosis) etc, and act by pointing at its wall); sutures, fixations, inserts and / or bone substitutes; the capsules for drug release, scaffolds or cell anchors (anchoring matrices of porous three-dimensional structure) comprising the random terpolymers described above. Rigid terpolymers will preferably be used in hard tissues (bone tissues) and the most flexible terpolymers in soft tissues (cardiology, urology, digestive system, nervous system, respiratory system ...).

Another aspect of the present invention relates to plastics comprising the random terpolymers described above and other biodegradable and biocompatible polymeric materials together with additives for plastics such as flame retardants, antioxidants, foaming, plasticizers, ultraviolet light absorbers, antistatic, antibacterial and other additives for plastics such as those described in the Encyclopedia of Plastics (Volume 3). pp. 1-28.

The molar content of the set formed L-lactide and D-lactide influences stiffness, mechanical strength and consistency. If in an L-lactide-ε-caprolactone copolymer we substitute D-lactide for e-caprolactone, the mechanical properties associated with the tension (elastic modulus and tensile stress) are increased and the elongation at break is somewhat reduced. The glass transition temperature of the material is increased. On the other hand, by replacing L-lactide with D-lactide, we managed to break the microstructural order of L-lactide units by limiting their crystallization capacity. The molar content in ε-caprolactone can vary between 5 and 30% depending on the elastomeric properties required.

When the molar content of ε-caprolactone is between 5 and 15 mol% with respect to total comonomers (I), (II) and (III). Said terpolymers have exceptional properties for applications in which the stiffness of the terpolymers is important while when the molar content of ε-caprolactone is between more than 15 and 30 mol% with respect to the total comonomers (I), (II) and (III) the terpolymers have exceptional properties for applications in which the elastomeric properties of the terpolymers are important, being an alternative to the currently used elastomeric biodegradable materials that have a very low T _g , presenting insufficient consistency, and / or have a high crystallization capacity during degradation. The materials of the present invention exhibit little or no crystallization capacity during their degradation thanks to the control of the average lengths of L-lactide or D-lactide and ε-caprolactone. They are thermoplastic materials of different mechanical behaviors that exhibit a homogeneous degradation without the formation of crystalline residues of high hydrolytic resistance.

DESCRIPTION OF THE FIGURES Figure 1. Curves of the first sweep of differential scanning calorimetry (DSC) at different degradation times corresponding to PLCL 008515 synthesized in example 1.

Figure 2. Curves of the first differential scanning calorimetry (DSC) scan at different degradation times corresponding to PLCL 502525 synthesized in Example 2.

Figure 3. Curves of the first differential scanning calorimetry (DSC) scan at different degradation times corresponding to PLCL 504010 synthesized in example 3.

Figure 4. Curves of the first differential scanning calorimetry (DSC) scan at different degradation times corresponding to the PLCL 602515 synthesized in Example 4.

Figure 5. Representation of the neperian logarithm of the molecular weights by weight (Mw) versus the degradation time to obtain the degradation kinetic constants of each poly (lactide / £ -caprolactone) (PLCL) used as an example.

Figure 6. Evolution of the remaining weight during the degradation of the poly (lactide / £ -caprolactone) (PLCLs) synthesized in Examples 1-4.

Figure 7. Evolution of water absorption during the degradation of poly (lactide / £ -caprolactone) (PLCLs) synthesized in examples 1-4.

Figure 8. Representative stress-strain curves of poly (lactide / £ - caprolactone) (PLCLs) synthesized in Examples 1-4.

Definitions In the context of the present invention, random terpolymers are understood as the polymers resulting from the ring opening reaction of three monomers in which the distribution of the repeating units derived from said monomers along the polymeric chain has a character markedly random, that is, very close to the Bernouilli statistical distribution and more specifically terpolymers having a value of R, determined as explained below, greater than 0.85, more preferably greater than 0.90 and still more preferably greater than 0.95. In the context of the present invention, it is understood that a material has an elastomeric character when it shows an elastic behavior, that is, when it is capable of undergoing reversible deformations when it is subject to the action of external forces and to recover the original shape if these external forces They are removed. Materials with an elastomeric character also typically have high values of strain at break, have no yield point (creep stress) and typically have a high elastic recovery.

In the context of the present invention thermoplastic material is understood to be that which, at relatively high temperatures, becomes plastic, deformable or flexible, melts when heated and hardens in a glass transition state when it is allowed to cool sufficiently. Thermopastic materials have a thermodynamic pseudotransition when heated (the glass transition temperature (T _g ) being the temperature at which said thermodynamic pseudotransition occurs). Thermoplastic polymers differ from thermosetting polymers or thermofixes in that after heating and molding they can overheat and form other objects, while in the case of thermosets or thermofixes, after initial cooling, their shape does not change when heated but they are combusted before achieving a change of form. In the context of the present invention, enantiomeric excess is understood as the percentage obtained by performing the following arithmetic operation:

(Molar% of D-lactide) - (Molar% of L-lactide)

EE (%) =

(Molar% of D-lactide) + (Molar% of L-lactide) In the context of the present invention, the consistency of a material at the working temperature of said material is understood as the ability of the material to retain its shape at said temperature without softening so that it maintains its ability to act as a mechanical support. Thus, for example, if the material is used to form a probe that must be used at 37 ° C, it will be considered to be consistent at that temperature when maintaining its initial shape, thus maintaining its light and adequate mechanical support. In the context of the present invention, mechanical strength of a material is understood as the mechanical properties associated with the tension and in particular the elastic modulus (or the 2% secant modulus) and the breaking stress.

In the context of the present invention, catalyst is understood as those metal compounds and enzymes that make possible the polymerization reactions of the cyclic esters. Particularly suitable as catalysts in the present invention are organic bismuth salts such as bismuth 2-ethylhexanoate, bismuth hexanoate (BiHex ₃ ), bismuth triflate (Bi (OTf) ₃ ), bismuth diphenyl ethoxide (Ph ₂ BiOEt), bismuth subsalicylate (BiSS) and bismuth triphenyl (Ph ₃ Bi) and even more preferred bismuth subsalicylate (BiSS) and bismuth triphenyl (Ph ₃ Bi).

In the context of the present invention, cell anchoring to porous polymeric matrices is understood on the surface of which one or more cells are joined by any means of attachment including covalent, non-ionic bonds, Van der Waals forces.

In the context of the present invention, medical implants are understood as any medical device manufactured to replace a missing biological structure, supplant a damaged biological structure, or improve an existing biological structure. Medical implants are man-made devices, unlike transplants, which are biomedical tissues. Examples of medical implants are pacemakers, cochlear implants, drug delivery devices, cannulas and stents. Determination of the average length of Lactide and ε-caprolactone sequences

To determine the degree of randomness of the terpolymers of the present invention, the average lengths of Lactide and ε-caprolactone sequences are calculated from the areas of the signals corresponding to the methine groups of the repeating units derived from the lactides (-CH-) and the average value of the signal areas corresponding to the methylenes of the repeating units derived from ε-caprolactone (ε and a-CH ₂ ) in proton nuclear magnetic resonance spectra ( ¹ H-NMR).

Proton nuclear magnetic resonance spectra ( ¹ H-NMR) are performed on a Bruker Avance DPX 300 to 300.16 MHz resonance frequency using 5 mm OD sample tubes. All spectra were recorded at room temperature at 0.7 mL solutions of deuterated chloroform (CDCI ₃ ) using the following experimental conditions:

10 mg sample

3 s acquisition time

1 s delay time

8,5 S pulse

Spectral width 5000 H

32 sweeps

Ε-Caprolactone Lactide repeat unit repeat unit

The signal corresponding to the methine of the repeating units derived from the lactide is found at chemical shifts between 5.0 ppm and 5.3 ppm. Due to the existence of HH couplings there is an overlap of the signals corresponding to the repeat units that derive from the lactide and that are adjacent to other repeat units that derive from the lactide on the one hand and the signals corresponding to the repeat units that derive from the lactide and that are adjacent to units Repeat derived from ε-caprolactone on the other hand. Therefore, the set of both signals is integrated together and the resulting area is designated as A.

In the case of the ε-caprolactone repeating units the chemical displacement of the protons of the methylenes in ε and α depend on the adjacent repeating unit in the polymer.

Thus the signal of the methylene protons in α is found in the area with chemical shifts around 4.1 ppm being divided into 2 groups: a) the one with the greatest displacement (with an area B) corresponds to the protons of the α-methylenes of those ε-caprolactone repeat units that have, with the carbonyl end of ε-caprolactone, a lactide repeat unit and b) the one with the lowest displacement (with an area C) corresponds to the protons of α-methylenes of those ε-caprolactone repeat units that have, ε-caprolactone attached to the carbonyl end, a ε-caprolactone repeat unit.

Similarly, the signal of the protons of the methylenes in ε is found in the zone with displacements around 2.3 being also divided into 2 groups: the one with the greatest displacement (with an area D) corresponds to the protons of the methylenes in ε of those ε-caprolactone repeating units that have, together with the ether end of ε-caprolactone, a repeating unit of lactide and the one with the least displacement (with an area D) corresponds to the protons of the methylenes in ε of those ε-caprolactone repeating units that have a ε-caprolactone repeating unit attached to the ether end of ε-caprolactone. The average length of Lactide and ε-caprolactone (/ ¡) sequences, the average Bernoulli (/ ¡) random-Bemouiii¡ sequences and the random character (R) were calculated by applying the following equations: The parameters LA, CL _L A, CL _C L and CL can be calculated from areas A, B, C, D and E as follows:

LA is a parameter proportional to the number of lactide repeat units of the copolymer and is calculated as LA = (LACL + LALA) = A / 2.

LA _L A is a parameter proportional to the number of lactide repeat units of the copolymer having an adjacent unit of lactide and LA _C L is a parameter proportional to the number of repeat units of lactide of the copolymer having an adjacent unit of ε- caprolactone What is determined is the sum of LA _L A and

CL _L A is a parameter proportional to the number of repeat units of ε-caprolactone in the copolymer having an adjacent unit of lactide and is calculated as CL _LA = (B + D) / 4.

By definition CL _L A (copolymer ε-caprolactone repeat units having an adjacent lactide unit) and LA _C L (number of copolymer lactide repeat units having an adjacent ε-caprolactone unit) have the same value, that is LA _C L = CL _L A-

CLCL is a parameter proportional to the number of repeat units of ε-caprolactone in the copolymer having an adjacent ε-caprolactone unit and is calculated as CL _C L = (C + E) / 4.

CL is a parameter proportional to the total number of repeating units of ε-caprolac-tone in the copolymer and is calculated as CL = CL _L A + CL _C L = (B + C + D + E) / 4.

From the parameters LA, CL _L A, CL _C L and CL the molar fraction of the lactide repeat units [LA], the molar fraction of the ε-caprolactone repeat units [CL] and the fraction are calculated molars of ε-caprolactone-lactide (or lactide ^ -caprolactone) [LA-CL] dyads as follows:

[LA] = LA / (LA + CL)

[CL] = CL / (LA + CL) [LA-CL] = (LACL + CL _LA ) / (LA _LA + LA _C L + LALA + CL _CL ) = 2 * CL _LA / (LA + CL)

Finally, with the molar fractions previously calculated, the average length of the lactide / _{L A} repeat unit sequences and the average length of the ε-caprolactone / _C i_ repeat unit sequences can be calculated.

You can also calculate the theoretical average length of the repeat unit sequences of a fully random polymer or Bernouilli

(/ LA) random-Bernouilh _j ; (/ CL) / rraanndaoomm - Bneerrnn oouuii Uttii - _{and *} -,

L LJ LL ^A J (2)

Finally, it is possible to calculate the R parameter that gives an idea of the degree of randomness of the copolymer. For a block copolymer in which the sequences are long, the random character (R) tends to 0 while for random distributions Bernouilli type the random character (R) tends to 1. hA ^ random-Bernouilli (cL) ^ random- Bernouilli [LA CL] (3)

/ _LA ^" / _CL ^" 2 [LA] [CL]

EXAMPLES

In the examples that follow the codes assigned to the synthesized copolymers begin with the name "PLCL" followed by a 6-digit number in which the first 2 figures represent the molar percentage of L-lactide in the reaction mixture, the third and fourth figures represent the molar percentage of D, L-lactide in the reaction mixture and the last two figures represent the molar percentage of ε-caprolactone in the reaction mixture.

COMPARATIVE EXAMPLE 1: Synthesis of PLCL 008515

The synthesis is carried out at 130 ° C in a 50mL balloon with magnetic stirring and with a thermocouple for temperature control. 21.25 g of m-lactide and 3.75g of ε-caprolactone are weighed and added to the balloon. The mixture is melted and a gentle flow of nitrogen is applied for half an hour to achieve an inert atmosphere in the means, medium. After that time, 0.0435g of bismuth subsalicylate (BiSS) is added and the reaction time is counted. The magnetic stirring is maintained at 100 rpm. After 72 hours of reaction, the balloon is removed from the oil bath and allowed to cool to room temperature. It is necessary to remove impurities from the catalyst, oligomers and monomers that have not reacted, and, for this reason, dissolve in chloroform and subsequently precipitate in methanol. EXAMPLE 2: Synthesis of PLCL 502525

The synthesis is carried out at 140 ° C in a 50mL balloon with magnetic stirring and with a thermocouple for temperature control. 12.50 g of L-lactide, 6.25 g of m-lactide and 6.25 g of ε-caprolactone are weighed and added to the balloon. The mixture is melted and a gentle flow of nitrogen is applied for half an hour to achieve an inert atmosphere in the medium. After that time, 0.0446g of bismuth subsalicylate (BiSS) is added and the reaction time is counted. The magnetic stirring is maintained at 100 rpm. After 48 hours of reaction, the balloon is removed from the oil bath and allowed to cool to room temperature. It is necessary to remove impurities from the catalyst, oligomers and monomers that have not reacted, and, for this reason, dissolve in chloroform and subsequently precipitate in methanol. EXAMPLE 3: Synthesis of PLCL 504010

The synthesis is carried out at 140 ° C in a 50mL balloon with magnetic stirring and with a thermocouple for temperature control. 12.50 g of L-lactide, 10.00 g of m-lactide and 2.50 g of ε-caprolactone are weighed and added to the balloon. The mixture is melted and a gentle flow of nitrogen is applied for half an hour to achieve an inert atmosphere in the medium. After that time, 0.0430g of bismuth subsalicylate (BiSS) is added and the reaction time is counted. The magnetic stirring is maintained at 100 rpm. After 48 hours of reaction, the balloon is removed from the oil bath and allowed to cool to room temperature. It is necessary to remove impurities from the catalyst, oligomers and monomers that have not reacted, and, for this reason, dissolve in chloroform and subsequently precipitate in methanol.

EXAMPLE 4: Synthesis of PLCL 602515

The synthesis is carried out at 140 ° C in a 50mL balloon with magnetic stirring and with a thermocouple for temperature control. 15.00 g of L-lactide, 6.25 g of m-lactide and 3.75 g of ε-caprolactone are weighed and added to the balloon. The mixture is melted and a gentle flow of nitrogen is applied for half an hour to achieve an inert atmosphere in the medium. After that time, 0.0435g of bismuth subsalicylate (BiSS) is added and the reaction time is counted. The magnetic stirring is maintained at 100 rpm.

After 72 hours of reaction, the balloon is removed from the oil bath and allowed to cool to room temperature. It is necessary to remove impurities from the catalyst, oligomers and monomers that have not reacted, and, for this reason, dissolve in chloroform and subsequently precipitate in methanol.

The terpolymers of Examples 1 to 4 were analyzed by Differential Scanning Calorimetry (DSC), to obtain information on their thermal transitions related to their structure and morphology, and Size Exclusion Chromatography (SEC-GPC), to obtain their distribution of molecular weights Nuclear Magnetic Resonance Spectroscopy ( ¹ H-NMR) was used to confirm the composition and sequence distribution of the polymers obtained.

Likewise, mechanical and biodegradation tests were carried out to define the possible applications of these materials. Biodegradation studies are carried out at 37 ° C (temperature of the human organism) in a phosphate buffered solution (PBS) (pH = 7.2), monitoring the following parameters: mechanical properties, mass loss, water absorption , glass transition temperature (T _g ), enthalpy of fusion (AH _m ), melting temperature (T _m ) and molecular weight distribution (molecular weight by weight and polydispersity index). The aforementioned in vitro biodegradation study was carried out by tripled with samples of about 20mg. These were obtained from films of 150-200 μηι of the different materials prepared by the method of dissolution-evaporation in chloroform followed by a heat treatment (1 min at 180 ° C) with rapid cooling. The 1x1 cm ² samples were distributed in Falcon tubes with PBS maintaining a surface area-volume ratio of 0.1 cm-1. At different degradation times, 3 samples of each material were extracted from the temperature controlled oven.

Tables 1 and 2 provide the results of the characterization using ¹ H-RM N (composition and microstructural parameters) and molecular weight measurements of the poly (lactide / £ -caprolactone) (PLCLs) synthesized in Examples 1-4 . As you can see the sequence distribution is random and the random character (R) is approximately 1. The molecular weights of the terpolymers synthesized in Examples 1-4 were measured by size exclusion chromatography (SEC or GPC) in a Waters 1515 equipped with two Styragel columns calibrated with polystyrene standards. Chloroform was used as eluent, the flow being 1 ml / min. From the molecular weight distribution the average molecular weights in number (M _n ), in weight (M _w ) and the polydispersity index (ratio) were obtained

M _w / Mn) "

The composition of the terpolymers expressed as a percentage of molar content of ε-caprolactone and lactide is obtained from the ¹ H-NMR spectrum. Since it is impossible to offer the exact content of L-Lactide and D-Lactide (they are indistinguishable in the NMR spectrum) approximate values are given under the assumption of an equal reactivity of L-Lactide and D-Lactide. Under this assumption and taking into account the L-LA / D-LA ratio of the feed, we can obtain its molar fraction in the polymer because we know the content of caprolactone [CL] and lactide [LA]. Subsequently we obtain approximate values of the sequence lengths of L-LA and D-LA using the following formula

/ ₌ l · / ₌ l

^{L LA} ((D - LA) + (CL)) R ' ^{D LA} ((L - LA) + (CL)) R where (L-LA) and (D-LA) are the approximate molar fractions of L-LA and D-LA and R the random character already calculated.

TABLE 1

TABLE 2

The microstructural parameters / LA and / c. are the average lengths of Lactide and ε-caprolactone sequences obtained from the ¹ H-NMR spectrum. These values are compared with the Bernoulli random sequence lengths (/ _L A = 1 / [CL] and / _C L = 1 / [LA]), obtaining the random character coefficient (R) defined below: R = (//./ random-Bernouilli I {¡LA)) = {¡CL) random-Bernouilli I {¡CL)) - YES R tends to 0 ί ^β φθΙίΐΤΙ ^β - ro will be diblock (long unit sequences structural) and if R tends to 1 the Terpolymer will be random (short sequences of structural units) and follow the Bernouilli sequence distribution. The structural parameters / L-LA and ta- _LA are approximate values of the average sequence lengths of L-Lactide and D-Lactide obtained under the assumption of an equal reactivity of L-Lactide and D-Lactide.

EXAMPLE 5: Thermal analysis during degradation of poly (lactide / £ - caprolactone) (PLCLs) synthesized in examples 1-4 The equipment used for scanning differential calorimetry analysis is a DSC Q200 from the calibrated TA Instruments commercial house with Indian and sapphire patterns. A sample between 5 and 9 mg is cooled to -85 ° C and heated to 185 ° C at 20 ° / min. During this first scan, information about the current physical and morphological state of the sample is obtained. The glass transition temperature of the material (T _g ), enthalpy relaxation δ (J g ^"1 ), the enthalpy of fusion ΔΗΓΤΙ (J g ^{" 1} ) and the temperature of temperature are obtained from the calorimetric flow vs. temperature curve. crystalline fusion (T _m ) of the polymer. Subsequently, through a second scan, information is obtained on the properties of the polymer, independent of the thermal history.

Figure 1 shows the curves of the first differential scanning calorimetry (DSC) scan at different degradation times corresponding to the PLCL 008515 synthesized in Example 1. It can be seen how as the degradation progresses the transition temperature of the material, which is initially of 28.7 ° C, decreases. The PLCL 008515 remains amorphous throughout the study and no fusion is seen by not having crystallizable sequences of L-lactide being the sequences of ε-caprolactone short enough to not be able to crystallize. In the first week of in vitro degradation, a small enthalpy relaxation associated with the glass transition temperature can be distinguished.

Figure 2 shows the curves of the first sweep differential scanning calorimetry (DSC) at different degradation times corresponding to the PLCL 502525 synthesized in example 2. It can be seen how as the degradation progresses the transition temperature of the material, which initially is of 20.8 ° C, decreases. The PLCL 502525 remains amorphous throughout the study and is not appreciated no fusion associated with the crystallizable sequences of L-lactide and ε-caprolactone since their sequence lengths are short enough.

Figure 3 shows the curves of the first scanning differential scanning calorimetry (DSC) at different degradation times corresponding to the PLCL 504010 synthesized in example 3. It can be seen how as the degradation progresses the transition temperature of the material, which is initially of 38.0 ° C, decreases. The PLCL 504010 remains amorphous until day 49 of degradation, in which a small fusion (T _m ~ 80 ° C) associated with crystallizable sequences of L-lactide is observed, which increases until reaching a value of about 8 J / g on the final day of the study. It should be noted the presence of a marked enthalpy relaxation associated with the glass transition temperature. The intensity of the peak falls to high degradation times as the glass transition temperature of the material decreases. Figure 4 shows the curves of the first scan of differential scanning calorimetry (DSC) at different degradation times corresponding to the PLCL 602515 synthesized in Example 4. It can be seen how as the degradation progresses the transition temperature of the material, which is initially of 36, 1 ° C, decreases. PLCL 602515 remains amorphous until day 35 of degradation, in which a small fusion (T _m ~ 80 ° C) associated with crystallizable L-lactide sequences is observed, which increases until reaching a value of about 18 J / g on the final day of the study. It should be noted the presence of a marked enthalpy relaxation, lower than that of PLCL 504010, associated with the glass transition temperature. The intensity of the peak falls to high degradation times as the glass transition temperature of the material decreases.

Table 3 collects the evolution data during the study of degradation of molecular weights in weight (M _w ), polydispersity index (IP) and thermal properties, obtained in two DSC scans, of the poly (lactide / £ - caprolactone) (PLCLs) synthesized in examples 1-4.

TABLE 3

^1st Sweep

Time sweep M _w (g mor ¹ ) IP T _g1 (° C) δ (J g ¹ ) T _m AH _m (J g T _g (° C)

56 12.0 ± 0.4 * 33.4 1.3 79.0 3.0 24.7

70 9.0 ± 0.1 * 35.7 ** **

1.1 22.2

84 7.4 ± 0.2 * 30.0 - ** ** 17.1

98 6.5 ± 0.0 * 30.1 - 80.2 8.0 17.7

0 76.8 ± 0.0 1.96 34.3 0.3 - - 36.1

3 68.3 ± 0.5 2.01 33.1 0.1 - - 35.4

7 62.6 ± 0.8 2.05 34.9 0.8 - - 34.1

14 52.4 ± 1.6 2.06 34.4 1.2 - - 34.8

21 38.8 ± 1.0 2.27 35.7 1.1 - - 35.4

28 27.2 ± 0.6 3.17 31.7 0.6 - - 30.2

35 19.9 ± 0.3 3.95 29.1 - 77.6 2.4 30.6

49 11.0 ± 0.05 * 32.6 - 81.8 10.6 26.4

56 9.4 ± 0.09 * 26.8 - 81.6 11.4 25.9

70 8.2 ± 0.4 * 23.0 - 81.8 10.5 18.5

84 6.8 ± 0.2 * 22.7 - 84.7 18.6 14.8

98 6.0 ± 0.0 * 18.0 - 82.7 17.8 10.6

Not measurable due to uncertainty in the measures of the average molecular weight in number (M _n ) It could not be measured due to the presence of traces of water in the sample for DSC.

EXAMPLE 6: Evolution of molecular weights and calculation of degradation kinetics during degradation of poly (lactide / £ -caprolactone) (PLCLs) synthesized in examples 1-4

Molecular weights at different degradation times of the terpolymers synthesized in Examples 1-4 and collected in Table 3 were measured by size exclusion chromatography (SEC or GPC) on a Waters 1515 set equipped with two Styragel columns calibrated with standards of polystyrene. It can be seen how as the degradation progresses the polydispersity index (IP) becomes greater as the molecular weight distribution of the polymer chains becomes wider.

Figure 5 shows the evolution of the Neperian logarithm of the molecular weight by weight (M _w ) versus the degradation time of the PLCLs synthesized in Examples 1-4. The Relationship between the Neperian logarithm of molecular weight in weight and time is approximated by the equation:

In M _w = In M _w0 - K _Mw t (3) in which M _w is the average molecular weight averaged by weight, M _w0 is the initial average molecular weight averaged by weight and K _Mw is the apparent degradation kinetic constant By another part from K _Mw, the average degradation time t _{1 2} can be calculated using the equation :.

t _1/2 = ln 2 / K _Mw (4)

The values of the kinetic constant K _Mw were calculated from the slope of the adjustment curve of the molecular weight data versus time in the first 35 days of study for the PLCLs 008515 and 502525 and in the first 49 days for the PLCLs 504010 and 602515, since at higher times surface erosion becomes the dominant mechanism. Based on these results, the order of degradation rate is PLCL 008515> PLCL 502525> PLCL 602515> PLCL 504010. These PLCLs in Examples 1-4 show rapid degradation. The PLCL 008515 has a kinetic constant of 0.066 days ^"1 and an average life time of 10.5 days. The PLCL 502525 has a kinetic constant of 0.056 days ^{" 1} and an average life time of 12.4 days. The PLCL 504010 has a kinetic constant of 0.030 days ^"1 and an average life time of 23.1 days. Finally, the PLCL 602515 has a kinetic constant of 0.040 days ^{" 1} and an average life time of 17.3 days.

EXAMPLE 7: Weight loss and water absorption during degradation of poly (lactide / £ -caprolactone) (PLCLs) synthesized in examples 1-4

The weight loss or remaining weight of polymer (% RW) and water absorption (% WA) values were obtained at different degradation times from the wet weights (W _w ), measured immediately after taking the samples and remove surface water, wrapping the sample in blotting paper and measuring dry weight (W _d ), carried out after subjecting the samples to a drying process overnight followed by drying in a vacuum oven (800-900 bar) at room temperature for 24 hours, taking into account the initial weight of each sample (W ₀ ) and using the equations :.

W ^YV W - W ^YV d

% WA 100

O) w.

% RW 100

Figure 6 shows the evolution of the remaining weight during the degradation of the PLCLs synthesized in Examples 1-4.

Figure 7 shows the evolution of water absorption during the degradation of PLCLs synthesized in Examples 1-4. Biomaterials begin to lose mass when they reach a molecular weight by weight limit. At that time the solubility of the oligomers is favored and the water absorption is already very high. The weight loss of the PLCL 008515 and the PLCL 502525 begins on day 35 when their respective M _w are 8400 and 1 1800 g / mol. In contrast, in the higher glass transition temperature PLCLs, the PLCL 504010 and the PLCL 602515, the weight loss is evident on day 56 of degradation, in which their respective M _w are 12000 and 9400 g / mol.

The samples undergo changes in their morphology throughout the degradation. All of them, due to their high amorphous character, lose consistency becoming more viscous.

None of the materials give rise to crystalline residues of high hydrolytic resistance during their degradation, nor do they form whitish fragments of high fragility. Thus, in an advanced state of degradation the remains have a pasty appearance thanks to their high water absorption. EXAMPLE 8: Evolution of mechanical properties during degradation of poly (lactide / £ -caprolactone) (PLCLs) synthesized in examples 1-4

The mechanical tests of the non-degraded samples and of the submerged samples for 7, 14 and 21 days belonging to the PLCLs synthesized in Examples 1-4 were carried out in an Instron 5565 unit at a speed of 10 mm min ^"1 . Tests were carried out with a controlled temperature of 21 ± 2 ° C and a relative humidity of 50 ± 5% according to ISO 527-3 / 1995. The mechanical properties offered correspond to average values of at least 5 specimens. from 150-200 μηι films prepared by him method of dissolution-evaporation in chloroform followed by a thermal treatment with rapid cooling.

Figure 8 shows the most representative stress-strain curves of the PLCLs synthesized in Examples 1-4. As can be seen, the PLCL 502525 has a clearly elastomeric behavior (2% secant modulus of 5.7 MPa and 994% elongation at break) without the presence of a creep point. On the contrary, in the curves of the PLCL 008515, PLCL 504010 and PLCL 602515 a yield point can be seen. The PLCL 008515 has a 2% secant module of 146.5 MPa and an elongation at break of 361%. The PLCLs synthesized in Examples 3 and 4 are more rigid with secant modules of 336.7MPa and 331.3 MPa, respectively. The PLCL 504010 has a more vitreous behavior with an elongation at break of 59%. Instead, the PLCL 602515 deforms up to 230%.

Table 4 shows the mechanical properties (2% secant modulus, creep stress, breaking stress, elongation at break and elastic recovery) of the PLCLs synthesized in Examples 1-4 at different degradation times.

In the first week of degradation, the PLCL 008515 undergoes a small change in its properties towards a more rigid behavior, related to the small enthalpy relaxation observed in the DSC scan (Figure 1). Then, as the glass transition temperature of the material decreases and the mobility of the chains increases, the PLCL 008515 gains elastomeric character but suffers a deterioration in its mechanical properties (2% secant modulus and tensile stress) The PLCL 502525 could only be tested prior to the start of the degradation study. After a week submerged at 37 ° C in PBS, it lost consistency and it was impossible to carry out mechanical tests. In the first week of degradation, the PLCL 504010 undergoes a significant change in its properties towards a more rigid behavior, related to the enthalpy relaxation observed in the DSC scan (Figure 3). Elongation at break goes from 59% to 4%. On day 14, mechanical tests could no longer be carried out due to the fragility of the material.

In the first two weeks of degradation, the PLCL 602515 undergoes a change in its properties towards a more rigid behavior, related to the enthalpy relaxation observed in the DSC scan (Figure 4). On day 21 there is a deterioration in the mechanical properties (2% secant modulus, tensile strength, elongation at breakage) of PLCL 602515 as a consequence of its loss of molecular weight.

TABLE 4

Tension

creep

Module or

Tension Elongation Drying recovery Limit

Name 1 at break to elastic break at 2% elastic

conventional

at 10% ²

(MPa) (MPa) (MPa) (%) (%)

Day 146.5 ± 5.38 ± 361, 2 ±

3.68 ± 0.39 96.4 ± 1 0 8.9 0.56 1 1, 1

Day 189.6 ± 7.97 ± 257.7 ±

8.14 ± 0.34 95.4 ± 1

PLCL ⁷ 19.4 1, 00 15.9

008515 ° ia 169.1 ± 4.98 ± 167.2 ±

5.37 ± 0.36 97.8 ± 1 14 1 1, 2.54 14.6

Day 32.2 ± 4.0 1, 27 ± 0, 12 1, 56 ± 422.0 ± 91, 0 ± 1 21 0.16 24.0

PLCL Day 2.34 ± 993.6 ±

5.7 ± 0.3 0.44 ± 0.02 94.1 ± 1 502525 0 0.19 33.5

Day 336.7 ± 5.06 ±

7.41 ± 0.80 59.2 ± 7.1 80.9 ± 8 0 39.8 0.42

PLCL

Day 742.8 ± 23.62 ±

504010 - 3.8 ± 0.4 - 7 37.3 1.31

Day 331.3 ± 9.21 ± 229.9 ±

7.91 ± 0.89 95.1 ± 2 0 41.3 0.55 11.8

Day 374.1 ± 11.43 ± 234.9 ±

12.12 ± 1.39 86.8 ± 2

PLCL 7 30.2 0.48 25.4

602515 Day 455.4 ± 8.22 ± 134.3 ±

12.87 ± 1.07 96.3 ± 1 14 48.5 0.85 11.2

Day 225.6 ± 5.71 ±

7.97 ± 1.03 38.1 ± 4.2 95.3 ± 2 21 11.0 0.62

¹ PLCL 502525 became too viscous during degradation and no mechanical tests could be made due to its lack of consistency. The PLCL 504010 became very fragile from day 7 of degradation and mechanical tests could not be carried out at other degradation times.

² Since the PLCL 008515 on day 21 of degradation and the PLCL 502525 did not show creep, values of the conventional elastic limit at 10% are given using the secant modulus at 2% deformation.

Claims

one . A process for obtaining random terpolymers by mass polymerization a single stage of:

a) ε-caprolactone of formula (I)

b) L-lactide of formula (II)

c) D-lactide of formula (III)

random terpolymers are understood to be those that have a higher R value

TLA - CL1

that 0.85 calculating R by the formula R = - - being [LA] and [CL]

2 [LA] [CL]

respectively the molar fractions of the lactide and ε-caprolactone repeat units and [LA-CL] being the molar fraction of the ε-caprolactone-lactide (or lactide-e-caprolactone) dyads.

2. Method according to claim 1 characterized in that the polymerization reaction is carried out in a single step in the presence of a catalyst that is selected from the group consisting of bismuth 2-ethylhexanoate, hexanoate bismuth (BiHex ₃ ), bismuth triflate (Bi (OTf) ₃ ), bismuth diphenyl ethoxide (Ph ₂ BiOEt), bismuth subsalicylate (BiSS) and bismuth triphenyl (PH ₃ Bi) which is added to the mixture of reaction in molten state. 3. Method according to claim 2 characterized in that the catalyst is selected from the group consisting of bismuth subsalicylate (BiSS) and bismuth triphenyl (PH ₃ Bi).

4. Method according to any of the preceding claims characterized in that the molar ratio of the total monomers (I), (II) and (III) to the catalyst is comprised between 250: 1 and 10,000: 1.

Method according to any of the preceding claims, characterized in that the mixture of comonomers (I) to (III) comprises between 5 and 30 mol%, with respect to the total of comonomers (I), (II) and (III), of ε-caprolactone.

Method according to any one of the preceding claims, characterized in that the mixture of comonomers (I), (II) and (III) comprises an amount of D-lactide between 5 mol% and 72 mol% and an amount of L-lactide. between 5 mol% and 72 mol% with respect to the total of comonomers (I), (II) and (III).

7. Method according to any of the preceding claims characterized in that the random terpolymers are obtained by reacting a mixture of comonomers in which the enantiomeric excess of L-lactide or D-lactide exceeds 5 mol%.

Method according to any one of claims 1 to 6, characterized in that the mixture of comonomers (I) to (III) has a molar content of ε-caprolactone molar content between 5 mol% and 25 mol% with respect to the total comonomers (I), (II) and (III) and has the same molar percentage of L-Lactide and D-Lactide

Method according to any of the preceding claims, characterized in that the polymerization reaction takes place by ring opening polymerization (ROP) being carried out in bulk at temperatures between 120 and 140 ° C for 2 or 3 days of reaction.

Method according to any of the preceding claims characterized in that it is carried out in an inert atmosphere, preferably in an N ₂ atmosphere.

. A random terpolymer obtainable by single stage polymerization of: ε-caprolactone of formula (I)

(I)

b) L-lactide of formula (II)

ιο (ll)

Y

c) D-lactide of formula (III)

(Neither)

understood as random terpolymers those that have a value of R, greater

TLA - CL1

15 than 0.85 with R being calculated using the formula R = - - where [LA] and [CL]

2 [LA] [CL]

12. Terpolymer according to claim 1 characterized in that in the process of obtaining the polymerization reaction is carried out in a single step in the presence of a catalyst that is selected from the group consisting of bismuth 2- ethylhexanoate, bismuth hexanoate (BiHex ₃ ), bismuth triflate (Bi (OTf) ₃ ), bismuth diphenyl ethoxide (Ph ₂ BiOEt), bismuth subsalicylate (BiSS) and bismuth triphenyl (PH ₃ Bi).

13. Terpolymer according to claim 12 characterized in that the catalyst is selected from the group consisting of bismuth subsalicylate (BiSS) and bismuth triphenyl (PH ₃ Bi).

14. Terpolymer according to any of claims 1 to 13, characterized in that the molar ratio of the total monomers (I), (II) and (III) to the catalyst is between 250: 1 and 10,000: 1.

15. Terpolymer according to any of claims 1 to 14, characterized in that in the process of obtaining the mixture of comonomers (I) to (IV) it comprises between 5 and 30 mol%, with respect to the total of comonomers (I), ( II) and (III), of ε-caprolactone.

16. Terpolymer according to any of claims 1 to 15, characterized in that in the process of obtaining the mixture of comonomers (I), (II) and (III) it comprises an amount of D-lactide between 5 and 72 and an amount of L-lactide between 5 and 72% with respect to total comonomers (I), (II) and (III).

17. Terpolymer according to any of claims 1 to 14, characterized in that a mixture of comonomers in which the enantiomeric excess of L-lactide or D-lactide exceeds 5% is used in the process of obtaining.

18. Terpolymer according to any of claims 11 to 16, characterized in that the mixture of comonomers (I) to (III) has a molar content of a molar content of ε-caprolactone between 5 and 25 mol% with respect to the total comonomers ( I), (II) and (III) and has the same molar percentage of L-Lactide and D-Lactide

19. Terpolymer according to any of claims 1 to 18 characterized in that in the process of obtaining the polymerization reaction takes place by ring opening polymerization (ROP) being carried out in bulk at temperatures between 120 and 140 ° C for 2 or 3 reaction days

20. Mixtures of one or more of the terpolymers as defined in any of claims 9 to 19.

21. Composite materials comprising one or more terpolymers as defined in any one of claims 9 to 19.

22. Composite materials according to claim 21 which comprise in addition to the terpolymer one or more materials selected from the group consisting of mechanical reinforcement materials, materials capable of conferring bioactivity, materials capable of conferring antibacterial activity.

23. Medical devices or implants comprising one or more terpolymers as defined in any of claims 9 to 22. 24. Cellular anchors comprising one or more terpolymers as defined in any of claims 9 to 22.

25. Plastics comprising one or more terpolymers as defined in any of claims 9 to 22 and other biodegradable and biocompatible polymeric materials.