Patent Application
20240174807
This application claims priority to Korean Patent Application No. 10-2022-0152851 filed on Nov. 15, 2022, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which is incorporated by reference in its entirety.
The present invention relates to a multiblock copolymer containing polylactic acid and polyamide for toughening polylactic acid and a method for preparing the same.
Recently, in order to solve problems such as global warming and secure sustainable growth, many studies are being actively conducted to reduce greenhouse gases and replace petrochemical raw materials. As a solution thereof, since biomass-derived monomer polymerized bioplastics have similar physical properties and application fields to existing plastics, the bioplastics have easy market entry during development, so that its commercialization potential is higher than any other bioplastic.
Among these bioplastics, polylactide (PLA) is repolymerized using lactide depolymerized from oligomeric polylactic acid initially polymerized by lactic acid converted from glucose through a fermentation process. Among brittle general polymers, polylactide (PLA) is generally recognized as one of the most promising plastics to replace petrochemical-based polymers, such as polystyrene (PS) for injection molding and polypropylene (PP) for fiber extrusion, due to bioperformance including high yield stress of 50 to 60 MPa due to the presence of ester linkages in PLA, and compatibility and degradability for end-user industries based on thermoplastic processing and packaging, biomedics, textiles, and transportation.
However, despite the advantages for commercial plastics, the inherent brittleness of PLA has poor toughness of 8 to 9 MJ m−3 and an elongation at break of less than 10%, and limits the use of ductility that requires plastic deformation at increased stress and flexibility at increased strain.
There have been extensive efforts in academia and industry to overcome such brittleness and expand the application range of PLA. These efforts may be divided into two main strategies: a single-phase based approach for achieving a plasticizing effect by introducing plasticizers that are fully mixed with PLA, and a micro/nano phase separation method for improving toughening behavior by preparing a physically and chemically mixed PLA system or block copolymer.
Sustainable organic small molecules with molar masses of <1000 g mol−1 such as lactide-derived ester oligomers, tartaric acid esters, levulinic acid esters, ethoxylated esters from waste frying oil, and ferulic acid esters have recently been reported and used as plasticizers. The sustainable organic small molecules induced a single-phase system with improved PLA flexibility having a reduced E value of 1299-11 MPa, an a yield value of 74-7 MPa, and an increased ε value of 243-658% compared to original PLA.
In contrast, a PLA enrichment scheme driven by phase separation, and micrometer-scale phase separation is generally involved with a polymer mixing system that physically combines PLA and its immiscible counterparts with the following materials: 1) a non-reactive compatibilizer located at an interface between two components to lower an interfacial tension, or 2) a chemically reactive compatibilizer having a functional group such as epoxy, carboxylic acid, and thiol-ene to covalently link an incompatible polymer with PLA and exhibit a large increase in fracture (toughness) in a tensile strain-stress curve.
Another method for reinforcing PLA may synthesize polymer structures such as diblocks, triblocks, terpolymers and graft copolymers, which are repeating block units consisting of PLA as a major part and an immiscible polymer that provides ductility, which may also be achieved with nano-scale phase separation. In particular, a multiblock copolymer derived from an ABA triblock in which a soft (or rubbery) B phase is cross-linked to a hard A phase (PLA or PLLA block) exhibits improved mechanical properties, including elastomer and toughening performance. However, these PLA multiblock copolymers have a disadvantage in that yield stress and Young's modulus are lower than those of commercially available PLA homopolymers.
An object of the present invention is to overcome the brittleness of PLA used as bioplastic and provide improved toughening.
Another object of the present invention is to provide a copolymer including PLA for toughening PLA and a method for preparing the same.
The objects to be solved by the present invention are not limited to the aforementioned object(s), and other object(s), which are not mentioned above, will be apparent to those skilled in the art from the following description.
For the object of the present invention described above, the present inventors prepared a polyamide 11-polylactide multiblock copolymer by preparing polyamide 11 having a diamine end group by copolymerizing 11-amino undecanoic acid derivatives derived from vegetable oil in the presence of a small amount of diamine, preparing hydroxyl telechelic polylactide-polyamide 11-polylactide by ring-opening polymerization of lactide with the polyamide 11, and then preparing polyamide 11-polylactide multiblock copolymer by urethane bonding of diisocyanate to the polylactide-polyamide 11-polylactide. It is developed a multiblock copolymer containing PLA and PA for toughening PLA by confirming that the polyamide 11-polylactide multiblock copolymer prepared as described above solved a problem of brittleness of PLA and significantly improved toughness.
According to the present invention, the multiblock copolymer containing PLA and PA has a significantly improved toughening effect compared to PLA.
In addition, the multiblock copolymer containing PLA and PA has an effect of having a bio-carbon content of 97% or more.
In addition, the method for preparing the multiblock copolymer containing PLA and PA has an eco-friendly effect without using a solvent.
It should be understood that the effects of the present invention are not limited to the effects, but include all effects that can be deduced from the detailed description of the present invention or configurations of the present invention described in appended claims.
Before describing the present invention in detail, terms or words used in this specification should not be construed as unconditionally limited to a conventional or dictionary meaning, and the inventors of the present invention can appropriately define and use the concept of various terms in order to describe their invention in the best method. Furthermore, it should be understood that these terms or words should be interpreted as meanings and concepts consistent with the technical idea of the present invention.
That is, the terms used in the present invention are only used to describe a preferred embodiment of the present invention, and are not intended to specifically limit the contents of the present invention, and it should be noted that these terms are terms defined in consideration with various possibilities of the present invention.
In addition, in this specification, it should be understood that the singular expression may include a plural expression unless clearly indicated in another meaning in the context, and even if similarly expressed in the plural, the singular expression may include the meaning of the singular number.
Throughout the present invention, when a component is described as “including” the other component, the component does not exclude any other component, but may further include any other component unless otherwise indicated in contrary.
Further, hereinafter, in the following description of the present invention, a detailed description of a configuration determined to unnecessarily obscure the subject matter of the present invention, for example, known technologies including the related arts may be omitted.
Hereinafter, the present invention will be described in more detail.
The present invention provides a method for preparing a polyamide 11-polylactide multiblock copolymer as a multiblock copolymer containing PLA and PA for toughening PLA.
The polyamide 11-polylactide multiblock copolymer according to the present invention may be prepared by including (a) preparing polyamide 11 [NH2-PA11-NH2] having a diamine end group; (b) preparing hydroxyl telechelic polylactide-polyamide 11-polylactide [OH-PLA-PA11-PLA-OH] by adding lactide to the polyamide 11 [NH2-PA11-NH2] having the diamine end group and performing ring-opening polymerization; and (c) preparing a polyamide 11-polylactide multiblock copolymer [(PA11-PLA)n, wherein n is an integer or prime number of 1 to 10] by adding diisocyanate to the hydroxyl telechelic polylactide-polyamide 11-polylactide [OH-PLA-PA11-PLA-OH] and forming a urethane bond.
The method for preparing the polyamide 11-polylactide multiblock copolymer according to the present invention was shown in Table 1 below and will be described in detail below with reference to Table 1.
The polyamide 11 [NH2-PA11-NH2] having the diamine end group may be prepared by polycondensation of an 11-amino undecanoic acid derivative of Formula 2 below and diamine of Formula 3 below.
In Formula 2, R1 is selected from H or a C1-C10 straight-chain, branched-chain or cyclic alkyl group, or a C6-C10 aryl group or a C7-C10 aralkyl group.
In Formula 3, R2 is selected from C1-C20 straight-chain or branched-chain alkylene, C3-C20 cycloalkylene, C6-C20 arylene,
The polyamide 11 [NH2-PA11-NH2] having the diamine end group may be represented by Formula 4 below.
In Formula 4, R2 is selected from C1-C20 straight-chain or branched-chain alkylene, C3-C20 cycloalkylene, C6-C20 arylene,
and x is an integer of 1 to 200.
In step (b), (b-1) lactide may be added to the polyamide 11 [NH2-PA11-NH2] having the diamine end group and subjected to ring-opening polymerization to form hydroxyl telechelic lactide-polyamide 11-lactide [OH-LA-PA11-LA-OH] (step {circle around (1)} in Table 1), and (b-2) lactide may be continuously subjected to ring-opening polymerization to prepare hydroxyl telechelic polylactide-polyamide 11-polylactide [OH-PLA-PA11-PLA-OH] (step {circle around (2)} in Table 1).
The hydroxyl telechelic polylactide-polyamide 11-polylactide [OH-PLA-PA11-PLA-OH] may be represented by Formula 5 below.
In Formula 5, R2 is selected from C1-C20 straight-chain or branched-chain alkylene, C3-C20 cycloalkylene, C6-C20 arylene,
x is an integer of 1 to 200, and y and z are the same as or different from each other and are integers of 1 to 500.
The ring-opening polymerization in steps (b-1) and (b-2) may be performed by a mechanochemical method. Preferably, the ring-opening polymerization may be performed by a ball milling method, but is not limited thereto.
In step (b-2), Sn(Oct)2 may be used as a catalyst.
The lactide may be D-lactide or L-lactide.
The diisocyanate may be represented by Formula 6 below.
In Formula 6, R3 is selected from C1-C20 straight-chain or branched-chain alkylene, C3-C20 cycloalkylene, and C6-C20 arylene.
The forming of the urethane bond in step (c) may be performed by a mechanochemical method. Preferably, the forming of the urethane bond may be performed by a ball milling method, but is not limited thereto.
The present invention provides a polyamide 11-polylactide multiblock copolymer represented by Formula 1 below as a multiblock copolymer containing PLA and PA for toughening PLA.
In Formula 1, R2 is selected from C1-C20 straight-chain or branched-chain alkylene, C3-C20 cycloalkylene, C6-C20 arylene,
R3 is selected from C1-C20 straight-chain or branched-chain alkylene, C3-C20 cycloalkylene, or C6-C20 arylene, x is an integer of 1 to 200, y and z are the same as or different from each other and integers of 1 to 500, and n is an integer or a prime number of 1 to 10.
The polyamide 11-polylactide multiblock copolymer according to the present invention may be prepared by the above-described preparing method. Specifically, the polyamide 11-polylactide multiblock copolymer may be prepared by urethane bonding of diisocyanate to the hydroxyl telechelic polylactide-polyamide 11-polylactide [OH-PLA-PA11-PLA-OH] prepared by ring-opening polymerization of lactide with the polyamide 11 [NH2-PA11-NH2] having the diamine end group. The preparing process for each step duplicates with the method for preparing the aforementioned polyamide 11-polylactide multiblock copolymer and thus will be omitted.
The method for preparing the polyamide 11-polylactide multiblock copolymer according to the present invention may be performed only by a mechanochemical method without using an organic solvent harmful to the human body or the environment.
The polyamide 11-polylactide multiblock copolymer according to the present invention has a very high bio-based carbon content, and the bio-based carbon content may be 90% or more, preferably 95% or more, and more preferably 97% or more.
The polyamide 11-polylactide multiblock copolymer according to the present invention may include 30 to 90 vol % of polylactide and 5 to 70 vol% of polyamide 11 having the diamine end group. In the present invention, four types of polyamide 11-polylactide multiblock copolymers containing 50, 60, 70, and 80 vol % of polylactide were prepared and their mechanical properties were confirmed.
Specifically, the polyamide 11-polylactide multiblock copolymer according to the present invention has Young's modulus (E=758-903 MPa), yield stress (σyield=57-63 MPa), elongation (εb=380-493%) and toughness (γ=124-171 MJ m−3), and exhibits excellent mechanical properties compared to commercial PLA.
As a conventional toughening PLA technology, there was a method of implementing toughening PLA by preparing a polybutadiene-polylactide multiblock copolymer.
Hereinafter, the present invention will be described in detail with reference to Examples for specific description. However, Examples according to the present invention may be modified in various forms, and it is not interpreted that the scope of the present invention is limited to the following Examples. Examples of the present invention will be provided for more completely explaining the present invention to those skilled in the art.
Polyamide 11 (NH2-PA11-NH2, that is, PA11) having a diamino end group was synthesized by bulk self-polycondensation of biomass-derived 11-aminoundecanoic acid (AUDA) and petroleum-based hexamethylene diamine (HMDA). A mixture of 11-AUDA (80 g, 397.40 mmol) and HMDA (1.39 g, 11.96 mmol) was charged at ambient temperature in a round bottom flask (500 mL) equipped with an overhead mechanical stirrer, an N2 inlet and a distillation apparatus. Thereafter, a reactor was put in a hot oil bath and purged with N2 while stirring for 30 minutes. The temperature was increased up to 250° C. under stirring, and the polycondensation was performed without any catalyst for 6 h with a continuous nitrogen flow (200 mL min−1), until HMDA (Tb 204° C.) of ca. 50% was evaporated and disappeared. After cooling, a reaction crude material was dissolved in N-methyl-2-pyrrolidone (NMP) (33% w/v) at 160° C., and precipitated in cold water to remove residual monomers and obtain a solid product. After repeating the purification process three times, the recovered PA11 was dried in a vacuum oven at 120° C. for 3 days (90-95% isolated yields). 1H NMR (400 MHz, TFA-d) for PA11: δ 3.61 (t, Ha, the methylene protons (2H) adjacent to the amine of the amide units), δ 3.29 (m, Hb, the methylene protons (4H) of connected with terminal amine), δ 2.78 (t, Hc, the methylene protons (2H) at the α-position of amide units), δ 1.91-1.70 (m, the methylene protons (4H) of amide repeating units), and δ 1.56-1.32 (m, the methylene protons (12H) of amide repeating units).
For the (PA11-PLA)n multiblock, four types of HO-PLA-PA11-PLA-OH (i.e., PLA-PA11-PLA) triblock copolymers with fPLA (polylactide volume fraction) of 0.5, 0.6, 0.7, and 0.8 were synthesized. The triblock copolymers were synthesized by bulk ring-opening polymerization (ROP) of D,L-lactide with the diamine-terminated PA11 (Mn,NMR 12 kmol−1) prepared in Preparation Example 1 as a macroinitiator using ball milling. D,L-lactide (e.g., 16.05 g, 111.36 mmol for fPLA0.7) and a PA11 midblock (5.0 g, 0.41 mmol) were filled into a ball milling reactor (250 mL) in a nitrogen-filled glove box, and added with stainless steel balls (25 mm D.×3 ea, 10 mm D.×10 ea).
The sealed reactor filled with nitrogen was taken to a mixer mill (Retsch MIXER MILL MM 500 NANO) and in order to cap or hydroxyl-functionalize the terminal diamine of PA11 with one lactide molecule, a ring-opening initiation step was performed under 30 Hz vibration for 10 minutes. Then, a Sn(Oct)2 (66 mg, 0.16 mmol) catalyst was added to the reactor in the glove box, and an ROP growth step of residual lactide was continuously performed for 1 hour with 30 Hz vibration. The reaction was quenched by exposure to ambient air, diluted with HFIP/chloroform (50/50% v/v), and precipitated into cold methanol. After repeating the precipitation three times, the recovered triblocks (white solid) were dried at 120° C. in a vacuum oven for 1 day (80-85% isolated yields). 1H NMR (400 MHz, TFA-d) for PLA-PA11-PLA triblock copolymers: δ 5.47 (m, Hd1, methine protons (1H) of PLA repeating units), δ 4.78 (m, He1, methine protons (2H) of the PLA end units connected with hydroxyl group), δ 3.61 (t, Ha, methylene protons (2H) adjacent to the amine of the amide units), δ 3.45 (m, Hb2, methylene protons (4H) beside an amide group connected with a PLA unit), δ 2.78 (t, Hc, methylene protons (2H) at the α-position of amide units) δ 1.95-1.60 (m, the methylene protons (4H) of amide repeating units and the methyl protons (3H) of PLA repeating units), and δ 1.54-1.32 (m, the methylene protons (12H) of amide repeating units).
A (PA11-PLA)n multiblock copolymers were prepared by self-coupling of α,ω-hydroxyl-terminated PLA-PA11-PLA triblock copolymers with fPLA of 0.5, 0.6, 0.7, and 0.8 using 4,4′-methylenebis(phenyl isocyanate) (MDI). In a nitrogen-filled glove box, a triblock with fPLA of 0.7 (2.0 g, 0.042 mmol), MDI (13 mg, 0.051 mmol) and Sn (Oct)2 (17 mg, 0.042 mmol) were filled into a ball milling reactor (50 mL) and stainless steel balls (20 mm D.×2 ea) were added. The sealed reactor filled with nitrogen was transported to a mixer mill (Retsch MIXER MILL MM 400), and then a mechanochemical urethane coupling reaction was performed with 20 Hz vibration for 1 hour. The reaction was quenched by exposure to ambient air, diluted with HFIP/chloroform (50/50% v/v), and precipitated into cold methanol. After repeating the purification three times, the recovered multiblocks (gray solid) were dried at 120° C. in a vacuum oven for 1 day (90-95% isolated yields). 1H NMR (400 MHz, TFA-d) for (PA11-PLA)n multiblock copolymers: δ 7.26 (m, Hg, aromatic protons (8H) of MDI), δ 5.47 (m, Hd1, methine protons (1H) of PLA repeating units), δ 4.01 (m, Hh, methylene protons (2H) of MDI), δ 3.61 (t, Ha, methylene protons (2H) adjacent to the amine of the amide units), δ 3.45 (m, Hb2, methylene protons (4H) beside an amide group connected to a PLA unit), δ 2.78 (t, Hc, methylene protons (2H) at the α-position of amide units) δ 1.93-1.59 (m, the methylene protons (4H) of amide repeating units and the methyl protons (3H) of PLA repeating units), and δ 1.55-1.28 (m, the methylene protons (12H) of amide repeating units).
A [poly(amide11)-block-poly(lactide)]n, that is, (PA11-PLA)n multiblock copolymer was prepared by using biomass-derived monomers 11-aminoundecanoic acid (11-AUDA) and D,L-lactide (LA) and petroleum-based hexamethylene diamine (HMDA) and by bulk self-condensation, bulk ring-opening polymerization (ROP) using mechanochemical ball milling and subsequent alcohol-isocyanate coupling reactions.
First, a series of diamino-terminated PA11 samples as polyamide blocks in the multiblock copolymers were synthesized through the bulk self-condensation of 11-AUDA with varying amounts (1.5, 2.9, 4.8, 15, 23, and 36 mol %) of HMDA as a chain-reducing agent to target the molar masses of 12, 6.2, 3.8, 1.2, 0.7, and 0.4 kg mol−1. For irreversible equilibration of the polycondensation, a continuous nitrogen flow (200 mL min−1) was applied to remove by-product water, but simultaneously to induce HMDA blowing. This was also supported by sublimation, which occurred at a fairly high polymerization temperature (250° C.) and by the relatively low boiling condition of HMDA (204° C.). The resultant PA11 showed lower HMDA molar amounts of 0.9, 1.5, 3.3, 8.1, 16, and 21 mol % and higher molar masses of 22, 12, 5.4, 2.2, 1.1, and 0.8 kg mol−1 than the theoretical weights calculated with the above-targeted molar ratios, which were determined by 1H NMR analysis using trifluoroacetic acid-d (TFA-d) (
In order to introduce an acceptable molar mass of PA11 as a semi-crystalline block in the (PA11-PLA)n multiblock copolymer synthesis and maximize the PLA toughening effect, PA11 with an Mn,NMR value of 12 kg mol−1 was selected (>99% conversion of AUDA, 95% segregated yield at 80 g scale and >99% bio-based carbon) (Tables 1 and 2). The formation of the amide linkages was confirmed by two chemical shifts of methylene protons Ha and Hc at δ 3.61 and 2.78. The Mn,NMR value of PA11 may be determined using a ratio of the methylene proton Ha or Hc to the methylene protons Hb adjacent to the terminal amine of PA11 (
Second, in order to introduce a glassy PLA block into the (PA11-PLA)n multiblock copolymer, a poly(lactide)-block-poly(amide11)-block-poly(lactide) (PLA-PA11-PLA) triblock copolymer, composed of PA11 as an midblock and PLA as end blocks, was prepared using bulk ring-opening polymerization (ROP) through mechanochemical ball milling. The triblocks were prepared by an intermediate synthesis of PA11 amide end-capped LA without the addition of Sn(Oct)2. This is because the insertion of LA into tin-nitrogen bonds is much slower than insertion of LA into tin-oxygen bonds, and thus, such synthesis may cause faster propagation(step {circle around (2)} in Table 1) than initiation (step {circle around (1)} in Table 1) and then uncontrolled PLA homo-polymerization. After complete conversion of H2-PA11-NH2 to HO-LA-PA11-LA-OH, four types of PLA-PA11-PLA were prepared by sequential one-pot ball milling by adding a small amount of Sn(Oct)2 for PLA propagation (>98% conversion rate, LA and 85-90% isolated yields at 20 g scale). The ratio of LA to one terminal hydroxyl unit of a HO-LA-PA11-LA-OH macroinitiator (including 58, 87, 136 and 232:1) was selected to design Mn,theo values of 8.2, 12, 19 and 31 kg mol−1 for one PLA block, hereafter referred as PLA-PA11-PLA (0.5, 0.6, 0.7, 0.8), respectively (Table 2). 1H NMR spectroscopy [
In order to completely connect glassy PLA blocks in the (PA11-PLA)n multiblock copolymer, self-coupling α,ω-hydroxyl terminated PLA-PA11-PLA triblock copolymer was achieved using 4,4′-methylenebis(phenyl isocyanate) (MDI) as a coupling reagent and Sn(Oct)2 as a catalyst in a ball milling system. The ratio of hydroxyl (—OH) to isocyanate (—NCO) was fixed at 1:1.2 to facilitate the contact between the triblock terminus and MDI in the vibratory ball mill to obtain multiblocks with sufficient molar masses for PLA toughening. This is the first approach to synthesize a multiblock copolymer by forming urethane bonds between hydroxyl-terminated triblock copolymers based on mechanochemical reactions at ambient temperature (90-95% isolated yield and to 97% bio-based carbon) (Table 1). It is well known that a bulk polyamide (PA) process requires an operating temperature of 180° C. or higher and there may be transesterification reactions in the presence of Sn(Oct)2 in a melt process. In addition, a polymerization method using a solvent to prepare a copolymer containing PA is limited in practice due to the low solubility of PA in most common organic solvents. Four multiblocks with fPLA of 0.5, 0.6, 0.7, and 0.8 were prepared and the molecular properties were listed in Table 2.
The methine peak H e i next to the terminal hydroxyl of the triblock disappeared, but resonances of an aromatic ring proton Hg and a methylene proton Hh of MDI integrated into the multiblock were observed together at δ 7.26 and δ 4.01 (
/
bM and I indicate 11-AUDA and HMDA monomer.
cM and I indicate D,L-lactide (LA) monomer and one terminal hydroxyl unit of HO-LA-PA11-LA-OH.
dM and I indicate 4,4′-methylenebis(phenyl isocyanate) (MDI) and α,ω-hydroxyl terminated PLA-PA11-PLA triblock copolymer.
eA-B-A values indicate the targeted Mn values for PLA-PA11-PLA triblock copolymers.
fConversions of AUDA and HMDA for preparing PA11.
gConversion of D,L-lactide for producing PLA-PA11-PLA triblock based on mechanochemical ball milling process (20 g scale).
hIsolated yields of multiblocks through precipitation.
iTheoretical molar masses of PA11 midblock and PLA end-blocks based on the conversions of 11-AUDA/HMDA and LA monomers by 1H NMR analysis.
jCalculated by the integration ratios of the repeating units of the PLA side chains using 1H NMR analysis, plus PA11 molar mass of 12 kg mol−1.
kDetermined by multiplying the Mn, NMR values of the triblock copolymers by n.
lDetermined by size-exclusion chromatography (SEC) in hexafluoroisopropanol (HFIP) with 0.01N sodium trifluoroacetate (NaTFA) relative to poly(methyl methacrylate) standards.
mVolume fractions of PLA calculated using the densities of the PA11 and PLA homopolymers (ρPA11 = 1.03 and ρPLA = 1.24).
nAverage number of (PLA-PA11-PLA) units in the triblock copolymers.
oAverage number of triblocks in the multiblock based on the ratio of the Mn, SEC values corresponding to the triblocks and the multiblocks.
pDetermined by the second heating cycle of differential scanning calorimetry (DSC) at 10° C. min−1 under nitrogen.
qTg value of PLA block in the triblock and multiblock, because the PA11 block in the triblock and multiblock homopolymer might have a relatively weak and broad Tg range around 40-60° C., which was overlapped with that of PLA.
rCrystallinity (%) based on the theoretical heat of fusion (ΔHf) calculated by 100% crystallinity of PA11 (i.e., ΔHf° = 189.05 J g−1)
sNormalized PA11 crystallinity (XPA11) calculated with Xpolymer and the molar mass fraction of PA11 block in the multiblock.
t5% weight loss (Td, 5%) estimated by thermogravimetric analysis (TGA, 10° C. min−1 under nitrogen).
uPrincipal domain spacing of the bulk triblock and multiblock samples evaluated by SAXS analysis (25° C.).
indicates data missing or illegible when filed
15
The thermal characteristics of the PA11 midblock, the PLA-PA11-PLA triblocks and the (PA11-PLA)n multiblocks, such as glass transition and melting transition temperatures Tg and Tm, were characterized by differential scanning calorimetry (DSC) [
A dynamic mechanical analysis (DMA) in torsion mode was used to determine the phase separated structure and the thermoplastic properties of the (PA11-PLA)n multiblocks, including the transitions of storage modulus (G′) and the sharp peaks in tan δ (=G″/G′) as temperature increased at a rate of 3° C. min−1 at a frequency of 1 Hz [
The behavior of dissimilar components microphase-separated into ordered morphologies in block copolymers was determined by the total number of repeating units (N), the volume percentage of each component (f), and the interaction parameter between the two segments in various architectures (χ). The temperature dependent χ value is expressed by the following Equation 1:
where, α is an excess enthalpic coefficient and β is an excess entropic coefficient. The PA11-PLA Flory-Huggins χ interaction parameter was measured using TODT values observed by DMA in a torsion mode of the PLA-PA11-PLA triblocks with three different molar masses 7.7-12-7.7, 12-17-12 and 16-24-16 kg mol−1 and an fPLA of 0.5. The degree of polymerization N could be calculated based on the ambient temperature densities of PA11 and PLA homopolymers (1.03 and 1.24 g cm−3, respectively) with a standard reference volume of 71.1 cm3 mol−1 (118 A3 per repeat unit), resulting in the N values of 335, 496 and 699 for the three triblocks. According to the mean-field theory, a lamellar position in the order-to-disorder transition of compositionally symmetric ABA triblocks may be predicted at (χN)ODT=17.996. Considering the factors obtained from the triblock copolymer, the temperature dependence of χ between PA11 and PLA was described by Equation 2 below.
For comparison with the literature on common block copolymer systems having χPLA-PB=0.21 and 0.17, χPLA-PDL=0.11 and 0.10, χPLA-PCHE=0.31 and 0.25, χPLA-PDMS=1.18 and 1.08, χPLA-PMCL=0.06 and 0.05, χPLA-PS=0.15 and 0.13, χPS-PMMA=0.04 and 0.04, χPS-PDHS=0.78 and 0.73, χPCL-PB=0.17 and 0.15, χP3HS-PDMS=0.40 and 0.39 at 100 and 140° C., ↔PA11-PLA values were calculated to be 0.24 and 0.13 [PB=polybutadiene, PDL=Poly(ε-decalactone), PCHE=poly(cyclohexylethylene), PDMS=poly(dimethylsiloxane), PMCL=poly(6-methyl-ε-caprolactone), PS=polystyrene, PMMA=poly(methyl methacrylate), PDHS=poly(3,4-dihydroxystyrene), PCL=polycaprolactone, P3HS=poly(3-hydroxystyrene)]. This was a first complete approach to investigate the Flory-Huggins χ interaction parameter of PA11-PLA, each of which has been used as a commodity plastic.
The nanophase-separated structures of the bulk PLA-PA11-PLA triblocks and the (PA11-PLA)n multiblocks were confirmed using small-angle X-ray scattering (SAXS) at room temperature (
bIngeo ™ 4060D is an amorphous PLA product from NatureWorks LLC and (98) means the Mn, sec value of 98 kg mol−1.
cAs-prepared (15) and (50) indicate amorphous PLA homopolymers with Mn, NMR = 15 and 50 kg mol−1 for this study, which was similar to the molar masses of a PLA block in (PA11-PLA(0.5 and 0.8))2.0 and 1.4.
dRilsan ® BMNO is a semicrystalline PA11 product from Arkema and (50) means the Mw value of 50 kg mol−1.
eAs-prepared (12) indicates a semicrystalline PA11 homopolymer with Mn, NMR = 12 kg mol−1 for this study, which was similar to the molar mass of a PA11 block incorporated in all the multiblocks.
fPerformed by dynamic mechanical analysis (DMA) in torsion mode.
gMeasured by tensile testing on ASTM D1708 standard.
hDetermined by X-ray diffraction (XRD) analysis for Ingeo ™ 4060D, Rilsan ® BMNO, and the multiblock samples before and after stretching.
indicates data missing or illegible when filed
To evaluate the mechanical properties of a (PA11-PLA)n multiblock copolymer, a dog bone-shaped specimen was prepared by performing compression molding around Tm (to 190° C.) of PA11 and then cooling at ambient temperature, that is, below Tg of PLA (50 to 60° C.). It was elongated with constant crosshead speed (50 mm min−1) during uniaxial tensile testing. The tensile data of glassy PLA including two samples prepared for this study (Mn,NMR=15 and 50 kg mol−1) and a commercial product (Mn,SEC=98 kg mol−1), 15 semi-crystalline PA11 (Mn,NMR=12 kg mol−1) including the specimens polymerized for this operation, an industrial product (Mw,SEC=50 kg mol−1) and multiblocks were disclosed in Table 3 along with stress-strain plots (
A series of multiblock copolymers consisting of amorphous PLA produced by D,L-lactide (LA) and semi-crystalline PA11 produced by hexamethylene diamine (HMDA) and reproducible 11-aminoundecanoic acid (11-AUDA) have been developed to achieve superior mechanical properties that perfectly reproduce the initial modulus and lasting ductility with subsequent strain-hardening. First, amine-terminated PA11 (H2N-PA11-NH2) was prepared by bulk self-condensation and then capped with LA without a catalyst through mechanochemical ball milling to be converted to HO-LA-PA11-LA-OH. After introducing a small amount of Sn(Oct)2, unreacted LA was rapidly propagated to prepare PLA-PA11-PLA triblocks with fPLA of 0.5 to 0.8, based on the controlled ROP. Here, the terminal hydroxyl groups were subsequently coupled with a diisocyanate reagent to finally prepare (PA11-PLA)n multiblocks by ball milling. Molecular properties of the triblocks and multiblocks were studied by 1H NMR and SEC. Thermal analysis including DSC, DMA and TGA determined the phase separation between PA11 and PLA based on Tg,PLA and Tm,PA11, and demonstrated that there are two transitions to thermal degradation (Td). The SAXS profiles of the triblocks and multiblocks also confirmed the microphase-separated morphology. The PA11-PLA χ interaction parameter may be calculated using TODT values obtained from DMA of the three PLA-PA11-PLA triblock copolymers with fPLA of 0.5. A multiblock covalently linked by the triblocks displayed impressive tensile behaviors, still having their initial modulus and additionally showing toughness, even with stain-hardening, compared to the fragile precursor triblocks. This may be attributed to the formation of PLA phase bridged by PA11 and the enhanced crystallinity of the PA11 block in the multiblock after stretching, which was confirmed by comparing the XRD patterns. Interestingly, the mechanical behaviors of the multiblocks were exactly similar with what to merge those of each commercial PLA and PA11. Through the excellent mechanical behavior of the semicrystalline-glassy (PA11-PLA)n multiblocks, it may be confirmed that a sustainable approach of the present invention is effective to prepare tough PLA.
So far, specific embodiments of the multiblock copolymer containing PLA and PA for toughening PLA according to an embodiment of the present invention and the method for preparing the same have been described, but it is obvious that various modifications are possible within the limits without deviating from the scope of the present invention.
Therefore, the scope of the present invention should not be limited to the exemplary embodiments and should be defined by the appended claims and equivalents to the appended claims.
In other words, the exemplary embodiments described above are illustrative in all aspects and should be understood as not being restrictive, and the scope of the present invention is represented by appended claims to be described below rather than the detailed description, and it is to be interpreted that the meaning and scope of the appended claims and all changed or modified forms derived from the equivalents thereof are included within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0152851 | Nov 2022 | KR | national |
