Patent Application
20240425650
The present invention relates to the technology of polymers. In particular the present invention relates to a triblock copolymer, in particular wherein a functional polymacrolactone (PML) is located on the mid-block and polylactic acid on the side-blocks, a process for obtaining thereof and uses thereof.
Polylactic acid (PLA), a biobased, biocompatible, and biodegradable polyester, is a promising polymer with good properties for diverse applications such as packaging, agriculture, or medicine among others. However, it also has deficiencies that must be improved to really have an impact on these fields. Firstly, the lack of functional groups in PLA really limits its application, especially in advanced fields such as biomedical or electronic. For instance, the functional groups could be used to bind bioactive molecules or drugs and use it as drug delivery system. Another example could be the incorporation of hydrophilic molecules that would increase the biodegradation rate. Thus, the addition of extra functional sites would really improve PLA performance and extend its application scope. Secondly, and regarding the mechanical properties, PLA is a rigid and brittle material. That means it can tolerate moderate forces, but it barely deforms before breaking-down (<10%). These are good properties, but some applications may demand the material could undergo plastic deformation or perform flexible behaviour prior to failure. For instance, the design of biomedical temporary implants would rather involve tough and deformable materials instead of a brittle one which could collapse into small pieces inside the body.
Therefore, providing functional sites and improving mechanical properties has been an essential task in the research and development of advanced PLAs. In fact, multiple solutions have been proposed in the literature to modify PLA properties.
Several strategies to provide new functional groups to PLA were proposed. In general, these strategies are based on the use of a functional co-monomer as initiator or on the reaction of functional molecules with PLA end-chain groups. The former approach, as mentioned, involves the use of functional monomers or initiators with the target characteristics. For instance, PEG has been used as initiator in the lactide polymerization to obtain hydrophilic scaffolds of PLA with enhanced degradation rate [1]. The other strategies comprise the grafting of hydrophilic or bioactive molecules into PLA, frequently at the surface, by the end-chain groups. For instance, PLA has been grafted with amine-terminated architectures [2] or with osteoinductive growth factors [3] to improve its hydrophilic and biomedical performance.
Similarly, modification of PLA mechanical properties has already been addressed. A well-known strategy is the synthesis of thermoplastic elastomers (TPEs), which typically have a triblock structure. This solution, owing to the physical crosslinking induced by separated block microphases, combines the rubbery behaviour of soft polymers, the mechanical strength of the hard segments, and the easy processability of thermoplastics. In the literature, there are several examples of PLA copolymerized with softer and more flexible polyesters. Some examples are poly(butylene succinate) (PBS) [4], poly(butylene adipate terephthalate) (PBAT) [5] and lactones such as poly(ε-caprolactone) (PCL) [6], poly(δ-valerolactone) [7] or poly(ε-decalactone) [8]. However, many of these solutions involve high crystalline polymers with saturated long backbones which may difficult the polymer biodegradation. In addition, neither PLA nor these copolymers have more than two functionalities, both located at the end-chain. This is a great limitation in case a further modification is required. For instance, depending on the final application, it might be required to increase the degradation rate or even to add new functional-molecules (bioactive, conductive, barrier . . . ).
In view of above, the problem to be solved by the present invention is to provide a biobased and biocompatible synthetic polymer in the form of a triblock copolymer which has multiple functionalization sites, thus polymers with tunable biodegradation behaviour and mechanical properties can be prepared. Owing to the wide functionalization possibilities, this polymer could be directed towards many application fields such as biomedical, packaging, electronic or agriculture among others.
The inventors have surprisingly found a triblock copolymer which overcomes the previous drawbacks. This triblock copolymer has an ABA structure of a biobased and biodegradable segment A (PLLA or PDLLA) and a biobased, biodegradable, and unsaturated soft segment B (PML). The synergistic effect of combining the functionalization of PLA and the synthesis of TPEs with tunable mechanical properties in a single strategy was surprisingly achieved by using an unsaturated PML as macroinitiator in the lactide ring-opening polymerization (ROP). Moreover, the synthesis pathway and the processing methods for obtaining the triblock copolymer of the invention are cost-effective and easily transferable to the industrial scale.
In a first aspect the present invention relates to a triblock copolymer comprising or consisting of the following structure (I):
Polylactic acid(PLA)-X-polylactic acid(PLA) (I)
wherein X is an unsaturated polymacrolactone (PML) or a copolymer containing the PML and a polyester.
In a second aspect, the present invention relates to a process for obtaining a triblock copolymer according to the first aspect of the invention.
In a third aspect, the present invention relates to the use of the triblock copolymer according to the first aspect of the invention.
In a first aspect, the present invention relates to a triblock copolymer comprising the following structure (I):
Polylactic acid(PLA)-X-polylactic acid(PLA) (I)
wherein X is an unsaturated polymacrolactone (PML) or a copolymer containing the PML and a polyester.
In a particular embodiment, the present invention relates to a triblock copolymer consisting of the following structure (I):
Polylactic acid(PLA)-X-polylactic acid(PLA) (I)
wherein X is an unsaturated polymacrolactone (PML) or a copolymer containing the PML and a polyester.
In this disclosure and in the claims, terms such as “comprises,” “comprising,” “containing” and “having” are open-ended terms and can mean “includes,” “including,” and the like; while terms like “consisting of” or “consists of” refer to the mentioned elements after these terms and others which are not mentioned are excluded.
Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The singular terms “a”, “an”, and “the” include plural referents unless context clearly indicates otherwise. For example, “an unsaturated polymacrolactone” or “the PML” includes the option of one unsaturated polymacrolactone and the option of more than one, identical or different, unsaturated polymacrolactone. Likewise, “a copolymer” includes the option of one copolymer and the option of more than one, identical or different, copolymer, having this copolymer one or more than one, identical or different, PML and one or more than one, identical or different, polyester. Accordingly, there is the option to have a combination of different molecules of PML acting as the PML, as well as a combination of different molecules of polyester acting as the polyester in structure (I). Similarly, the word “or” is intended to include “and” unless the context clearly indicate otherwise.
In a preferred embodiment of the first aspect, the PML is selected from polyglobalide (PGI), poly(ambrettolide) (PAmb), poly(6-ω-hexadecenlactone) (P6HDL) and a combination thereof. In another preferred embodiment of the first aspect, the PML is a combination of any of polyglobalide (PGI), poly(ambrettolide) (PAmb) and poly(6-ω-hexadecenlactone) (P6HDL).
In another preferred embodiment of the first aspect, the polyester is selected from polypentadecalactone (PPDL), polycaprolactone (PCL), polyglycolic acid (PGA), and poly(para-dioxanone). In another preferred embodiment of the first aspect, the polyester is a combination of any of polypentadecalactone (PPDL), polycaprolactone (PCL), polyglycolic acid (PGA) and poly(para-dioxanone).
In another preferred embodiment, “X” in structure (I) is a copolymer consisting of a PML and a polyester.
In another preferred embodiment of the first aspect, the triblock copolymer is end-functionalized or grafted through PML double bonds with molecules containing hydroxyl (—OH), carboxyl (—COOH) or —NH2 (amine) moieties.
In another preferred embodiment of the first aspect, the triblock copolymer is crosslinked through the self-crosslinking reaction of PML double bonds or through the crosslinking reaction of PML double bonds and other crosslinking molecules such as thiols, amines, maleimides, vinyl sulfones or acrylates.
In a second aspect, the present invention relates to a process for obtaining a triblock copolymer as defined according to the first aspect, i.e. with the following structure (I)
Polylactic acid(PLA)-X-polylactic acid(PLA) (I)
wherein X is an unsaturated polymacrolactone (PML) or a copolymer containing the PML and a polyester,
comprising the steps of:
wherein in case of X being a block copolymer containing the PML and a polyester, there is an additional step (b-i) or (b-ii) after step (a) and before next step (c) consisting of:
c) polymerizing lactide with a ring-opening polymerization (ROP) using the unsaturated polymacrolactones obtained in step (a) or the copolymers obtained in step (b) as macroinitiators and catalysed by tin (II) 2-ethylhexanoate.
In an alternative embodiment when X in formula (I) is a copolymer, the process for obtaining a triblock copolymer as defined according to the first aspect, i.e. with the following structure (I), comprises the steps of:
(II) 2-ethylhexanoate.
In a further embodiment, after the step of polymerization of the lactide (i.e. step (c) or step (2) depending on the embodiment for the process), there is an additional step consisting of:
In a preferred embodiment of the second aspect, the PML is selected from polyglobalide (PGI), poly(ambrettolide) (PAmb) and poly(6-ω-hexadecenlactone) (P6HDL). In another preferred embodiment of the second aspect, the PML is a combination of any of polyglobalide (PGI), poly(ambrettolide) (PAmb) and poly(6-ω-hexadecenlactone) (P6HDL).
In another preferred embodiment of the second aspect, the polyester is selected from polypentadecalactone (PPDL), polycaprolactone (PCL), polyglycolic acid (PGA) and poly(para-dioxanone). In another preferred embodiment of the second aspect, the polyester is a combination of any of polypentadecalactone (PPDL), polycaprolactone (PCL), polyglycolic acid (PGA) and poly(para-dioxanone).
In another preferred embodiment, the lactide used in step (c) or step (2) is L-lactide or a mixture of L-lactide and D-lactide.
In another preferred embodiment, the step (a) or steps (1a) or (1b) is carried out in bulk under inert atmosphere.
In another preferred embodiment, the step (a) or steps (1a) or (1b) is carried out with a catalyst. In a further preferred embodiment said catalyst is Candida Antarctica Lipase B (CALB) enzyme.
In another preferred embodiment, the step (b-i) or (b-ii) is carried out in bulk under inert atmosphere.
In another preferred embodiment, the step (b-i) or (b-ii) is carried out with a catalyst. In a further preferred embodiment said catalyst is Candida Antarctica Lipase B (CALB) enzyme.
In another preferred embodiment, the step (c) or step (2) is carried out in bulk under inert atmosphere in the range of 120-190° C.
In another preferred embodiment, the concentration of tin (II) 2-ethylhexanoate is in the range of 0.025-0.10% wt.
In another preferred embodiment, the concentration of the macroinitiator PML or the copolymer consisting of PML and a polyester is in the range of 10-50% mol.
In another preferred embodiment, the unreacted monomer is removed and the catalyst is removed or inactivated at the end of each polymerization. There are several ways to carry out such removal or inactivation. In a further preferred embodiment, said removal is carried out by dissolving the reaction mixture in a solvent (for example, chloroform) and precipitating in cold methanol. Nevertheless, when high amounts of reactants are used (for example 1 kg) said removal/inactivation can be carried out without solvents and under vacuum.
In a third aspect, the present invention relates to the use of the triblock copolymer as defined according to the first aspect of the invention in the preparation of:
Block copolymers, particularly with diblock and triblock structures, are frequently used as compatibilizers in immiscible polymer blends. The immiscibility of polymer blends is due to the high interfacial tension between the components, thus the poor interfacial adhesion lead to phase separation and deficient physicochemical properties in comparison to the separated components. Block copolymers play a key role in the compatibilization of immiscible blends because they can be placed at the interface of the separated phases reducing the interfacial tension, thus improving interfacial adhesion. Each block of the copolymer is rather concentrated in one of the separated phases serving as physical bonding between them. As a result, compatibilized blends show improved properties.
Furthermore, this functional triblock copolymers can be directed towards the biomedical field to prepare tissue regeneration scaffolds or drug delivery systems. The control of each block length, the composition and the molecular weight allows the preparation of short-term or long-term medical devices. Moreover, the functionalization of the triblock copolymer by the ending groups or the double bond of PMLs gives the chance of adding hydrophilic and non-fouling molecules such as PEG. The amphiphilic structure of these PEG-containing triblock copolymers would facilitate the encapsulation of drugs, while the non-fouling properties of PEG would reduce the inflammation body response in implantable medical devices. Additionally, drugs or other bioactive molecules could be covalently linked to the triblock copolymer by the unsaturation of PML blocks.
Additionally, PLA has been widely researched as a biobased solution for the packaging industry. However, neat PLA has not the right properties to compete against the current standard polymers such as PET or PE. The mechanical properties, barrier properties and transparency are the main constrains. The triblock copolymer proposed by this invention allow the obtention of flexible materials with good barrier properties, while the transparency could be achieved by functionalization of PML double bonds to decrease the polymer crystallinity.
As mentioned before, the proposed triblock copolymer, apart from having tunable mechanical and physical properties, is also biocompatible. Thus, it offers a competitive advantage to other polymeric substrates traditionally used in the electronic or textile sector. For instance, by adjusting the block length ratio (A/B), our triblock copolymer could meet the flexibility requirements to be used in electronics, where flexibility is an unresolved claim in regard to bio-based and biocompatible polymers. Thereby, it could be used as substrate in domestic electronics or as substrate for the development of sensors and biosensors. Indeed, PLA has shown to provide advanced properties in microfluidic devices such as Organ on a Chips [9], improving the properties of PDMS.
The properties of our triblock copolymer are also compatible within the sectors where fibers are required, such as the textile sector. Moreover, since our triblock copolymer has multiple functionalization sites, it could deliver high added value products for example in sportswear, or in other technical applications related to any biology, human, animal or plant (Smart Agro).
It is noted that any of the embodiments disclosed herein for the product or the process according to the first or second aspect of the invention can be taken alone or combined with any other embodiment disclosed herein unless the context specifies otherwise.
A number of examples will be provided below that are intended to illustrate the invention and in no way limit the scope of the invention, which is established by the attached claims.
Triblock copolymers were synthetized in two steps. First, PMLs were obtained by enzymatic ring-opening polymerization (e-ROP) of macrolactones (MLs) in bulk, using 1,4-butanediol as initiator. Then, in a second step, PMLs were used as macroinitiators in the lactide bulk ROP catalyzed by tin (II) 2-ethylhexanoate. Alternatively, random or block copolymers of PMLs and a polyester could be prepared in a single or sequential polymerizations, respectively, by ROP or polycondensation methods. Furthermore, triblock copolymers might be functionalized with hydroxyl (—OH), carboxyl (—COOH) or amine (—NH2) moieties. Functionalization might be performed to the end-groups using carbodiimide chemistry or to the double bonds of PML blocks by thiol-ene “click” chemistry.
PMLs with molecular weight (Mn) ranging from 10 to 25 kg·mol−1 were obtained from unsaturated MLs such as globalide (GI) and 6-ω-hexadecenlactone (6HDL).
A series of triblock copolymers were synthetized following a single reaction pathway, which is depicted in
At the end of each polymerization, reaction mixture was dissolved in chloroform and precipitated in cold methanol to remove the unreacted monomer and the catalyst. Next, the precipitated was filtered, washed repeatedly with fresh solvent and dried under vacuum for 48 h.
Hereinbelow 3 non-limitative examples of synthesis involving L-lactide, D,L-lactide, globalide and 6-ω-hexadecenlactone are described.
The copolymer was prepared in two steps. First, polyglobalide (PGI) was synthetized in a Schlenk tube by enzymatic ring-opening polymerization (e-ROP) at 80° C. in bulk. The tube, provided with a magnetic stirrer, was fluxed with N2 gas to yield an innert atmosphere. The reactor was heated to 80° C. and a 5% w/w of the enzyme Candida Antarctica Lipase B (CALB) with 0.95% mol of 1,4-butanediol were added. After closing the tube with a septum and stopping N2 gas, the monomer globalide (2 g) was injected to start polymerization. The total reaction time was 5 h. After that time, the reaction product was dissolved in chloroform and filtered to remove enzymes. Filtrated was then precipitated in excess of methanol and washed repeatedly in fresh solvent. Finally, it was dried under vacuum for 48 h at room temperature. The obtained PGI reached a molecular weight of 24.6 kg·mol−1 as determined by 1H NMR. DSC studies revealed a melting temperature of 48° C. and a crystallization temperature of 32° C.
PGI was then used as macroinitiator in lactide ROP. A 50 mL 3-necked reactor equipped with a mechanical stirrer was heated to 80° C. and vacuumed at 20 mbar for 15 minutes. Then, aided by N2 gas to keep the innert atmosphere, PGI (2.5 g) and L-lactide (1.5 g) were supplied to the reactor. Vacuum at 50 mbar was applied again for 15 minutes. Pressure was returned to 1 bar and temperature was increased to 180° C. At that temperature, 0.05% w/w of stannous octoate respect to lactide were added to start the copolymerization. The total reaction time was 2 h. The resulting polymer was dissolved in chloroform and precipitated in excess of methanol. Precipitated copolymer was dried under vacuum for 48 h. The triblock formation was confirmed by 1H NMR. It reached a number average molecular weight (Mn) of 34.2 kg·mol−1 and a weight average molecular weight (Mw) of 66.5 kg·mol−1 as determined by GPC. The copolymer presented two melting peaks at 46.0° C. (PGI block) and 159.8° C. (PLLA blocks) by DSC. PGI block crystallized at 27.4 and −7.2° C., while PLLA blocks could not crystallize from the melting. The copolymer displayed an elastomeric behaviour at tensile tests reaching 250% elongation at failure, with an elastic modulus of 158 MPa and maximal tensile strength of 4.58 MPa.
The copolymer was prepared in two steps. First, polyglobalide (PGI) was synthetized in a Schlenk tube by enzymatic ring-opening polymerization (e-ROP) at 80° C. in bulk. The tube, provided with a magnetic stirrer, was fluxed with N2 gas to yield an innert atmosphere. The reactor was heated to 80° C. and a 5% w/w of the enzyme Candida Antarctica Lipase B (CALB) with 1.18% mol of 1,4-butanediol were added. After closing the tube with a septum and stopping N2 gas, the monomer globalide (2 g) was injected to start polymerization. The total reaction time was 5 h. After that time, the reaction product was dissolved in chloroform and filtered to remove enzymes. Filtrated was then precipitated in excess of methanol and washed repeatedly in fresh solvent. Finally, it was dried under vacuum for 48 h at room temperature. The obtained PGI reached a molecular weight of 21.5 kg·mol−1 as determined by 1H NMR.
PGI was then used as macroinitiator in lactide ROP. A 50 mL 3-necked reactor equipped with a mechanical stirrer was heated to 80° C. and vacuumed at 20 mbar for 15 minutes. Then, aided by N2 gas to keep the innert atmosphere, PGI (2.0 g) and D,L-lactide (2.0 g) were supplied to the reactor. Vacuum at 50 mbar was applied again for 15 minutes. Pressure was returned to 1 bar and temperature was increased to 180° C. At that temperature, 0.05% w/w of stannous octoate respect to lactide were added to start the copolymerization. The total reaction time was 2 h. The resulting polymer was dissolved in chloroform and precipitated in excess of methanol. Precipitated copolymer was dried under vacuum for 48 h. The triblock formation was confirmed by 1H NMR. It reached a number average molecular weight (Mn) of 37.0 kg mol−1 and a weight average molecular weight (Mw) of 65.4 kg·mol−1 as determined by GPC. The copolymer presented only one melting peak at 41.0° C. due to PGI block, which crystallized in two steps at 23.1° C. and −3.9° C. PDLLA blocks were amorphous. The copolymer displayed an elastomeric behaviour at tensile tests reaching 230% elongation at failure, with an elastic modulus of 553 MPa and maximal tensile strength of 11.9 MPa.
The copolymer was prepared in two steps. First, polyglobalide (PGI) was synthetized in a Schlenk tube by enzymatic ring-opening polymerization (e-ROP) at 80° C. in bulk. The tube, provided with a magnetic stirrer, was fluxed with N2 gas to yield an innert atmosphere. The reactor was heated to 80° C. and a 5% w/w of the enzyme Candida Antarctica Lipase B (CALB) with 2.36% mol of 1,4-butanediol were added. After closing the tube with a septum and stopping N2 gas, the monomer 6-ω-hexadecenlactone (2 g) was injected to start polymerization. The total reaction time was 5 h. After that time, the reaction product was dissolved in chloroform and filtered to remove enzymes. Filtrated was then precipitated in excess of methanol and washed repeatedly in fresh solvent. Finally, it was dried under vacuum for 48 h at room temperature. The obtained P6HDL reached a molecular weight of 10.5 kg·mol−1 as determined by 1H NMR. P6HDL was then used as macroinitiator in lactide ROP. A 50 mL 3-necked reactor equipped with a mechanical stirrer was heated to 80° C. and vacuumed at 20 mbar for 15 minutes. Then, aided by N2 gas to keep the innert atmosphere, P6HDL (1.0 g) and L-lactide (3.0 g) were supplied to the reactor. Vacuum at 50 mbar was applied again for 15 minutes. Pressure was returned to 1 bar and temperature was increased to 180° C. At that temperature, 0.05% w/w of stannous octoate respect to lactide were added to start the copolymerization. The total reaction time was 2 h. The resulting polymer was dissolved in chloroform and precipitated in excess of methanol. Precipitated copolymer was dried under vacuum for 48 h. The triblock formation was confirmed by 1H NMR. It reached a number average molecular weight (Mn) of 43.0 kg·mol−1 and a weight average molecular weight (Mw) of 68.0 kg mol−1as determined by GPC. The copolymer presented two melting peaks at 44.5° C. (P6HDL block) and 1636° C. (PLLA blocks) by DSC. PGI block crystallized at −10.4° C., while PLLA blocks did it at 99.8° C. The copolymer displayed an elastomeric behaviour at tensile tests reaching 34% elongation at failure, with an elastic modulus of 491 MPa and maximal tensile strength of 25.5 MPa.
PEG-functionalized triblock copolymers were prepared by esterification of the triblock copolymers and carboxyl-terminated PEG (COOH-PEG24-COOH). As an example, the mixture containing the triblock copolymer PDLLA139-PGI85-PDLLA139 prepared as described in Example 2 (3.00 g, 0.075 mmol) and a 5-fold excess of the carboxyl-terminated PEG (Mn≈1,000 g·mol−1, 0.75 g, 0.75 mmol) were added to a round flask provided with a magnetic stirrer. The mixture was dissolved with 20 mL of DCM for 30 min. Then, DCC (0.774 g, 3.75 mmol) and DMAP (0.018 g, 0.15 mmol) were added to the solution and reaction was left to proceed for 24 h at room temperature. Then, reaction mixture was poured into an excess of cold methanol. The precipitate was filtrated, washed repeatedly with fresh methanol, washed with cold diethyl ether (−18° C.) to remove methanol, dried under vacuum for 48 h and stored in a desiccator until further use.
The esterification of carboxyl-terminated PEG and the triblock copolymers succeeded a 95% yield as determined by 1H NMR. The number average and weight average molecular weights were Mn=37 kg·mol−1 and Mw=65 kg·mol−1, respectively. The contact angle of PEG-functionalized triblock copolymers was reduced from 90° to 86° because of the PEG addition. Additionally, elongation at break increased from 230% to 380% because of PEG, while the ultimate tensile strength and the elastic modulus decreased from 11.9 MPa to 4.4 MPa and from 553 MPa to 140 MPa, respectively.
Following the same method as the described in Example 1, Example 2 and Example 3, up to 12 syntheses were performed to validate the triblock copolymer properties. Table 1 shows all the synthetized triblock copolymers grouped by their PLA and PML composition.
1H
1H NMR
In all cases, the conversion of the monomer into polymer overpassed the 90% and the triblock copolymers were recovered at high yields (>85%). The theoretical molecular weight in an ideal reaction was targeted at 40 kg·mol−1. Moreover, since copolymers with different PLA/PML compositions were planned, the block length of PLA (segment A) and PML (segment B) were adjusted proportionally. Composition and molecular weights of the triblock copolymers were calculated by 1H NMR and GPC. Table 1 shows that copolymers were obtained with a PLA composition within the 50-90% mol range. Moreover, molecular weights were in the range of 30-40 kg·mol−1. There are samples with slightly lower molecular weights, which were probably due to the presence of undesired hydroxyl or carboxyl initiating species in the reaction system. On the other hand, deviations in PLA composition were attributed to the loss of lactide by reverse sublimation before starting the reaction.
That loss, milligrams, was almost constant, but it became more significant when lower lactide contents were used.
Nevertheless, the triblock structure was confirmed by 1H and 13C NMR.
Table 2 shows the mechanical properties of the triblock copolymers. These results evidenced that block length played an important role. The film of neat PLLA, having replicated the molecular weight of the copolymers (40 kg·mol−1), was too brittle even to obtain the specimens for testing. Meanwhile, even those copolymers with only 9-10% mol of PML improved the mechanical performance respect to PLLA. In general, elongation at break (Ep) clearly improved with increasing PML, but at the same time involved a reduction on the ultimate tensile strength (σmax) and the elastic modulus (E). Therefore, PLA-based materials with tunable properties ranging from stiff to ductile could be prepared by simply adjusting the PLA/PML composition.
Since the neat PLLA with 40 kg·mol−1 molecular weight was too brittle to be tested, a PLLA with higher molecular weight (Mn=72 kg·mol−1, Mw=144 kg·mol−1) was synthetized.
The composition of the triblock structure also influenced the melting temperatures (Tm) of the copolymers. Table 3 summarizes the thermal properties of the triblock copolymers. As the composition of either PML or PLA increased, the Tm of the respective block increased as well. Differences on Tm were about 10° C. On the contrary, there was not a significant change on the Tg, degradation onset temperature at 5% (° Td,5%) and residual weight (Rw).
Thermal characterization confirmed the triblock structure as well.
PEG-functionalization of PDLLA139-PGI85-PDLLA139 was successful. The comparison of 1H NMR spectra depicted in
The contact angle of PEG-functionalized triblock copolymers was reduced from 90° to 86° because of the PEG addition. The apparently slight decrease of the contact angle was fundamental to change the surface of triblock copolymers from relatively hydrophobic (>=) 90° to hydrophilic (<) 90°. The influence of that small change became more significant when rough surfaces were compared as the roughness intensifies the hydrophobicity or hydrophilicity of flat surfaces.
Regarding the mechanical properties, PEG-functionalized copolymers displayed more ductile and flexible properties in comparison to neat triblock copolymers.
All the synthetized PLA-PML-PLA were analysed using the following techniques:
| Number | Date | Country | Kind |
|---|---|---|---|
| 21383008.6 | Nov 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/080298 | 10/28/2022 | WO |
