BIODEGRADABLE THERMOPLASTIC COPOLYESTER ELASTOMERS: METHYL BRANCHED PBAMT
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e-Polymers 2021; 21: 336–345
Research Article
Wen-Bo Neng, Wen-Guang Xie, Bo Lu, Zhi-Chao Zhen, Jun-Long Zhao*, Ge-Xia Wang*, and
Jun-Hui Ji*
Biodegradable thermoplastic copolyester
elastomers: Methyl branched PBAmT
https://doi.org/10.1515/epoly-2021-0024 (PBAT) copolymer chains may well explore the potential
received December 18, 2020; accepted February 08, 2021 application of biodegradable PBAT-based material.
Abstract: A series of novel biodegradable copolyesters Keywords: poly(butylene 3-methyl adipate co-terephtha-
named poly(butylene 3-methyl adipate co-terephthalate) late), 3-methyl adipic acid, thermoplastic copolyester
(PBAmT) were synthesized from the monomers of 3-methyl elastomers, biodegradable, crystallizability
adipic acid (AAm), 1,4-butanediol (BDO), and terephthalic
acid (TPA) through a process of esterification and poly-
condensation. 1H NMR analysis shows that they are
random copolymers whose composition can be well con- 1 Introduction
trolled by the feed ratio of monomers. From the results of
DSC and XRD, the introduction of methyl group success- Recently, the development and application of biodegrad-
fully destroys the crystallizability of the PBAm chains, able plastics are more and more concerned by researchers
thus making it become a relative soft segment compared and enterprises attributed to the problem of “white pol-
to PBA, while these random PBAmT copolymers con- lution” caused by the plastic products (1–4). From the
structed by soft segment PBAm and rigid segment PBT first generation of biologically fermentated poly(hydroxy-
change from semi-crystalline polymers to nearly amor- valerate)s (PHAs) (5,6) to the later chemically synthesized
phous polymers as the feed ratio of Am increases. biodegradable polyester poly(lactic acid) (PLA) (7–9), poly-
Especially, mechanical tests reveal that the copolymers show caprolactone (PCL) (10), and poly(butylene succinate) (PBS)
outstanding elasticity and rebound resilience with excellent (11,12), etc. (13–15), the biodegradable polyester family is
strength. These thermoplastic copolyester elastomers with booming. While all these polyesters are kinds of rigid
good performance by simply introduction of branched degradable plastic, people pay little attention on the soft
methyl group on polybutylene adipate terephthalate degradable thermoplastic copolyester elastomers (TPEE).
As a novel class of thermoplastic elastomers, TPEE
are copolyesters consisting of glassy or crystalline hard
segments and amorphous soft segments. In the past few
* Corresponding author: Jun-Long Zhao, Key Laboratory of Synthetic decades, the commercial growth of TPEE has continu-
and Natural Functional Molecule of the Ministry of Education,
ously increased because of their unique advantages: first,
College of Chemistry and Materials Science, Northwest University,
Xi’an 710127, China, e-mail: 20134631@nwu.edu.cn
TPEE have a similar synthetic feature as polyesters, which
* Corresponding author: Ge-Xia Wang, National Engineering can be easily synthesized through a process of esterifica-
Research Center of Engineering Plastics, Technical Institute of tion and polycondensation (16–18); second, TPEE with
Physics and Chemistry, Chinese Academy of Sciences, different physical properties can be easily designed by
Beijing 100190, China, e-mail: gxwang@mail.ipc.ac.cn variation in the species of the hard and soft segments
* Corresponding author: Jun-Hui Ji, National Engineering Research
and their ratios (13–15,19,20). Generally speaking, in the
Center of Engineering Plastics, Technical Institute of Physics and
Chemistry, Chinese Academy of Sciences, Beijing 100190, China, TPEE, the hard segments are generally aromatic polyesters
e-mail: jhji@mail.ipc.ac.cn such as poly(ethylene terephthalate) (PET), poly(trimethy-
Wen-Bo Neng: Key Laboratory of Synthetic and Natural Functional lene terephthalate) (PTT), and poly(butylene terephtha-
Molecule of the Ministry of Education, College of Chemistry and late) (PBT) while the soft segments are aliphatic polyethers
Materials Science, Northwest University, Xi’an 710127, China
or polyesters with long chains such as poly(ethylene
Wen-Guang Xie, Bo Lu, Zhi-Chao Zhen: National Engineering
Research Center of Engineering Plastics, Technical Institute of
glycol) (PEG), poly(tetramethylene glycol) (PTMG), and
Physics and Chemistry, Chinese Academy of Sciences, poly(sebacate ethylene glycol) (21–24). The introduction
Beijing 100190, China of long aliphatic flexible soft segments is the most common
Open Access. © 2021 Wen-Bo Neng et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0
International License.Biodegradable thermoplastic copolyester elastomers 337
strategy to construct polyester elastomers although very few purchased from Aladdin Reagent Co. Ltd and used as
TPEE are also constructed by introducing branched chain or received. Lipase from porcine pancreas (30–90 units mg−1)
stereo isomers (25–28). was purchased from Sigma Aldrich Co. Ltd.
Polybutylene adipate terephthalate (PBAT) is a new
generation of bio-degradable aliphatic-aromatic copolye-
sters synthetic from the monomers of adipic acid (AA),
1,4-butanediol (BDO), and terephthalic acid (TPA). Combin- 2.2 Synthesis
ing the biodegradability of aliphatic polyester with excellent
mechanical properties and thermal stability of aromatic The synthesis of PBAmT was performed via a two-stage
polyester, PBAT possesses excellent strengths both on melt polycondensation adapted as easterification at
softness and toughness (29–32). The mechanical proper- atmospheric pressure and polycondensation at reduced
ties of PBAT are similar to that of low-density polyethylene, pressure. According to the molar percentage of AAm in
thus making it suitable for biodegradable and flexible total acid feed, the PBAmT were labeled as PBAmT55,
applications such as agricultural films and various PBAmT60, PBAmT70, PBAmT75, and PBAmT80. Melt ester-
packaging material. The contents of aromatic TPA and ification and polycondensation were performed in a
aliphatic AA have a significant influence on the solid- 250 mL four-neck round bottom flask with mechanical
state structures and properties of PBAT copolyester stirring. In a typical experiment of preparing PBAmT70,
(33,34). As the content of aromatic TPA increases, the 19.94 g PTA, 44.85 g AAm, 54.07 g BDO (diol:diacid molar
rigidity and crystallinity of PBAT increase, while as the ratio 1.5:1), 0.07 g TBT (0.5 mmol mol−1 diacid, TBT is
content of AA increases, the elasticity of PBAT increases, proved to significantly accelerate the esterification reac-
which indicates that it is very possible to make PBAT into tion of aromatic dicarboxylic acid), and 0.07 g PPA
thermoplastic elastomer, where PBA unit can act as a role (0.5 mmol mol−1 diacid, PPA is believed to prevent side
of soft segment, and PBT acts as a role of hard segment. reactions such as etherification and thermal decomposi-
As we know, common PBA and PBT are both crystallized tion) were added into the flask. In the first step, the ester-
polymers, while to guarantee the resilience, the soft segment ification reaction was conducted at 190–210°C for 4 h
in elastomer should be noncrystallizable (21–24). A well- with a N2 inlet. In the second step, another part of
performance elastomer based on PBAT structure can only 0.14 g TBT (1.0 mmol mol−1 diacid) was added, and the
be obtained if the crystallization of PBA or PBT segments is polycondensation reaction was conducted at 220–250°C
destroyed. To realize the idea in this paper, a short branched for 4 h under a reduced pressure of 30 Pa.
3-methyl AA (AAm) was introduced instead of AA to synthe-
size a series of novel poly(butylene 3-methyl adipate co-ter-
ephthalate) (PBAmT) copolymers with different mole ratio of
BAm and BT. We expect that the short branch 3-methyl in AA 2.3 Characterization
can effectively decrease the crystallizability of PBAm seg-
ment. Then the flexible soft PBAm segments together with Gel permeation chromatography (GPC) was used to mea-
PBT rigid segments can construct a thermoplastic elastomer sure material molecular weight and polydispersity at a
with good mechanical property and elastic resilience. The rate of 1 mL min−1 at 35°C. Chloroform was used as the
copolyesters are characterized by 1H NMR, GPC, DSC, XRD, solvent and the data were calibrated with polystyrene
tensile tests, and their enzymatic degradation test. The standard samples.
experimental results confirm our assumption, and we get a On the Bruker-AMX-300 device, with CDCl3 as the
series of TPEE with good performance by simply introducing solvent of PBAmT, the 1H NMR spectrum was recorded.
branched methyl group on PBAT copolymer chains. The chemical shift was based on one part per million of
tetramethylsilane.
The thermal behaviors of materials were character-
ized by a Mettler-DSC1 differential scanning calorimeter
2 Materials and methods (DSC) model. Five milligrams of sample was used to test
through conventional heating/cooling/heating proce-
dures from −70°C to 120°C at a temperature change rate
2.1 Materials of 10°C min−1, and the first heating run served to erase the
thermal history.
AAm, TPA, BDO, tetrabutyl titanate (TBT), polyphosphoric At room temperature, wide-angle X-ray diffraction
acid (PPA), and other reagents were analytically pure and (WAXD) patterns were recorded on the Rigaku RAD-IIIB338 Wen-Bo Neng et al.
system, nickel filtered Cu-Kα radiation (λ = 0.154 nm, applied to the sample is 0, and Rn is based on two con-
40 kV, and 110 mA) in the 2θ range from 6° to 60°, and secutive cycles.
the step size was 0.02° s−1. Using a 0.1 mm thick polyte- The enzymatic degradation performance was studied
trafluoroethylene film as a spacer layer, the polymer using lipase in porcine pancreas. Using the same molding
sample was sandwiched between polytetrafluoroethylene method as above, samples of 10 × 10 × 0.3 mm films were
sheets, and then heated at a temperature of about 2°C prepared by melting and pressing in a square mold
higher than the melting temperature under a pressure (thickness of 0.3 mm), and then placed in a phosphate
of 15 kg cm2 for 2 min to prepare melt crystallized PBAmT buffer solution (pH = 7.2) with 0.1 mg mL−1 lipase at 37°C.
copolyester film. The molded polymer film was then After a specific incubation period, the film was removed,
transferred to an oven at the desired temperature for iso- rinsed with distilled water, and weighed until a constant
thermal crystallization. After the crystallization was com- weight was reached. The degree of biodegradation was
pleted, the polymer film was separated and subjected to estimated by weight loss. Hitachi S-4300 scanning elec-
X-ray diffraction. tron microscope was used to observe the morphology of
Tensile testing and cyclic tensile testing were per- the film before and after enzyme degradation.
formed at room temperature (25°C) using an Instron ten-
sile testing machine. The dumbbell-shaped samples with
effective length 25 mm, width 4.0 mm, and thickness
2.0 mm were prepared by melt-pressing under a hot press
3 Results and discussion
at 30 MPa for 30 s and the temperatures ranged from
100°C to 190°C. In the tensile testing, all samples were
stretched at a stretching rate of 50 mm min−1 at 25°C. At 3.1 Chain structure and sequence of PBAmT
least five specimens were tested for each sample, and the
average values were reported. As the physical properties of PBAmT copolymers depend
In the cyclic tensile test, dumbbell-shaped samples strongly on their chain structure and sequence includ-
were stretched to 100% strain at a tensile rate of 20 ing molecular weight and composition, they have been
mm min−1 at room temperature. Then, the clamp began synthesized by a two-stage melt polycondensation from
to return at a speed of 20 mm min−1 until the force acting TPA, AA, and BDO, through the same and efficient pro-
on the sample is 0. After the above two steps, a cycle was cess, which can guarantee a relatively high molecular
completed. Three samples were tested to calculate the weight and well-controlled composition. The chemical
mean and standard deviation. Each sample was sub- activity of the branched dicarboxylic acid AAm shows
jected to five cycles, and the shape recovery rate (Rn) no significant difference with AA. All the copolyesters
was calculated according to Eq. 1: with different proportion of BAm and BT were synthesized
within an identical time.
Lm − Ln
Rn = × 100%, (1) The molecular weights of PBAmT were measured by
Lm − Ln − 1
GPC. As listed in Table 1, number average molecular
where n is the number of cycles, Lm is the maximum weight (Mn) ranging from 40,689 to 49,614 g mol−1 and
strain applied to the material, Ln and Ln−1 are the strain weight average molecular weight (Mw) ranging from
of the sample in two consecutive cycles when the force 71,539 to 80,946 g mol−1 are obtained with polydispersity
Table 1: Molecular weight and polydispersity characteristics of PBAm and PBAmT
1
Sample GPC BAm ratio H NMR
−1 −1
Mn (g mol ) Mw (g mol ) PI Feed (%) Calculated (%) Ln,BAm Ln,BT R
PBAmT55 49,614 80,946 1.63 55 54.12 2.15 1.84 1.01
PBAmT60 47,866 78,971 1.65 60 59.55 2.35 1.70 1.01
PBAmT70 45,738 78,311 1.72 70 71.15 2.83 1.53 1.01
PBAmT75 44,016 71,539 1.63 75 74.55 3.03 1.49 1.00
PBAmT80 41,811 71,605 1.72 80 79.85 4.32 1.27 1.02
PBAm 40,689 78,068 1.92 100 100.00 — — —Biodegradable thermoplastic copolyester elastomers 339
(PI = Mw/Mn) from 1.63 to 1.92, as expected for the syn- 2Ia
Ln,BAm = 1 + , (2)
thetic method used. This result indicates that a high Ih + Ik
molecular weight of copolymer can be obtained using 2Ie
the two-stage melt polycondensation method.
Ln,BT = 1 + , (3)
Ih + Ik
To better understand the sequence structures of
R = 1/ Ln,BT + 1/ Ln,BAm . (4)
polymer chains, 1H NMR was conducted for all the
PBAmT copolymers. The 1H NMR spectrum of PBAmT70
is shown as the example in Figure 1. The two different
dicarboxylic acids both have their typical proton with 3.2 Thermal properties of PBAmT
totally different chemical shifts. The shift appearing at
8.09 ppm belongs to C6H6 units of TPA and 0.96 ppm The thermal properties and melt crystallization behaviors
belongs to CH3 units of AA. The composition of BAm of the copolymers have direct influence on their using
and BT can be easily calculated by the integrated inten- and processing performance, which can also reflect their
sity of peaks c and d. The mole ratio of calculated 1H NMR crystallization properties. The glass transition tempera-
are well fitted with the feed ratio of AA when synthesis. ture (Tg), melting temperature (Tm), and crystallization
The chemical shifts of –CH2– in BDO close to different temperature (Tc) of PBAmT copolymers as well as PBAm
ester bonds resulting from copolycondensation show dif- were investigated by DSC as seen in Figure 2. Different
ferent chemical shifts appear at 4.09 ppm (a), 4.14 ppm from the semi-crystalline PBA that shows obvious melt
(h), 4.37 ppm (k), and 4.43 ppm (e), respectively. From and crystallization peaks as reported by literature, the
the spectrum, the number-average sequence length methyl branched PBAm is amorphous and shows that
of BT and BAm units (Ln,BT and Ln,BAm ), and the degree the glass transition point is only −55°C. The introduction
of randomness (R) are calculated using Eqs 2–4, respec- of methyl group significantly reduces the crystallinity of
tively, where the integrated intensity of chemical shift I is the PBAm chain, so that it becomes flexible chains com-
abbreviated as Ii. The multipeaks fitting function of Mes- pared to rigid PBA chains. With the introduction of more
tReNova software was used to calculate the integrated and more PBT blocks that play a role as hard segment
intensity of the partially peaks: a, h, k, e. The results into the copolymer, the Tg increases continuously and
of PBAmT70 are listed as Ln,BT = 1.53 and Ln,BAm = 2.83, reaches to a higher temperature of −30°C when the con-
R = 1.01. The 1H NMR data and the calculated results of tent of PBT increases to 45%. The increase in Tg is prob-
other copolymer are listed in Table 1. The degree of ran- ably because of that the flexibility of the copolymer
domness close to 1.0 indicates a random structure of all chains are restricted greatly. All the copolyesters with
the synthesized copolyesters (35). only one glass transition temperature means that they
Figure 1: 1H NMR spectrum and chain structures of PBAmT70.340 Wen-Bo Neng et al.
Figure 2: DSC thermograms of PBAm and PBAmT copolyesters. The curves were obtained during the second heating (a) and cooling runs (b),
while the first heating run was to erase thermal history.
are all random copolymers, which is in agreement with and shows no diffraction peaks compare to PBA. On the
the results of the proton NMR spectra (36,37). contrary, PBT units are crystallizable. When the BAm con-
For Tc and Tm, there are no melting and melt crystal- tent is less than 40%, both PBAmT60 and PBAmT55
lization peaks appearing for PBAm, PBAmT80, PBAmT75, behave as semi-crystalline polyesters and show five dif-
and PBAmT70 during the heating and cooling scan when fraction peaks at 16.1°, 17.2°, 20.2°, 23.2°, and 25.1°, which
composition of PBAm is higher. As explained above, the can be assigned to (011), (010), (101), (100), and (111)
copolymers show nearly amorphous condition when the reflection planes of PBT, according to the literature
proportion of PBAm is high, and the crystallization rate is (36,37). The intensity of diffraction peaks decreases as
so slow that we cannot observe the peaks within the BAm content increases but still appear at the same posi-
experimental time region. As the content of PBT increases tion, indicating that the branched BAm segment shows
further, the crystallization of PBAmT60 is improved, no significant effect on the crystal form of PBT segment.
leading to a melting peak appearing at 90°C. Although On the contrary, as BAm content increases, PBAmT80,
the cooling scan curve still shows no peaks under this PBAmT75, and PBAmT70 show no diffraction peaks in
condition, a cold crystallization peak at 21°C is clearly their XRD patterns indicating that the crystallinity of
observed in the next heating run (38,39). As the PBT copolyesters decreases dramatically. The decreased crys-
composition increases higher, the crystallization of tallization ability attributes a large part to the randomi-
PBAmT55 increases further and shows obvious melting zation of the main chain structure and the influence of
peak at 108°C and melt crystallization peak at 62°C. These amorphous PBAm units. The introduction of branched
results well support our explanations about the influence
of methyl group of PBAm on the crystallization property
of copolymers. With the increase in PBAm content, the
crystallinity of copolyester transfers from semi-crystal-
line to amorphous, and it tends to become a better ther-
moplastic elastomer.
3.3 Crystal structure
To further understand the influence of methyl branched
AA on the crystallization property of the copolyesters,
XRD was investigated for all of the synthesized PBAmT.
According to the XRD patterns shown in Figure 3, PBAm
segment with methyl branch is proved to be amorphous Figure 3: XRD patterns of PBAmT copolyesters and PBAm.Biodegradable thermoplastic copolyester elastomers 341
Table 2: Mechanical performance parameters of PBAmT
Sample Strength (MPa) Elongation (%)
PBAmT55 20.8 ± 0.5 1,071 ± 70
PBAmT60 16.0 ± 0.3 1,295 ± 93
PBAmT70 5.7 ± 0.3 1,244 ± 24
PBAmT75 5.4 ± 0.1 1,480 ± 2
PBAmT80 5.3 ± 0.1 1,399 ± 34
PBAm — —
PBAm chain reduces the regularity of the main chain,
ultimately leading to the decrease in the degree of crys-
Figure 4: Stress (σ)–strain (ε) curves of PBAmT.
tallinity of the copolyester, in which the microcrystalline
structure acts as the cross-linking point to form thermo-
plastic. These results validate the DSC results mutually. is much better with the recoverable strain close to 1,500%
and tensile strength of nearly 5.4 MPa.
To further study the elasticity of PBAmT, we took
3.4 Mechanical properties PBAmT70 as an example and carried out five times of
tension recovery cyclic loading under 100% strain. The
The mechanical properties of PBAmT copolymers depend stress–strain curve for cyclic tension is shown in Figure 5,
mainly on the ratio of PBAm segments to PBT segments, and the shape recovery rate data for the samples are
and the crystallinity of PBT segments as the two segments summarized in Table 3. In the first cycle, the shape
are miscible in amorphous phase. Therefore, the effect of recovery rate of the sample is 82.6%, and it gradually
different contents of PBAm on their mechanical properties increases above 97.6% in the following four cycles. These
was checked by tensile strength measurements. Tensile results confirm the sufficient level of elastic recovery of
strength and elongation at break are tested and presented PBAmT. It is found that the tensile and recovery curves of
in Table 2. The PBAm samples are amorphous polymers the samples form a nonlinear hysteresis loop. In the first
and almost have no available mechanical properties. cyclic tension, the samples show a large hysteresis loop
For PBAmT, when the content of BAm decreases from and a large residual strain. With the increase in the
80% to 55%, the tensile strength increases from 5.3 MPa number of cycles, the tensile and recovery trajectories
to 20.8 MPa, which is because of not only the greater almost coincide, the hysteresis loop gradually decreases,
flexibility of PBAm chains than that of PBT, but also the and the total residual strain tends to be constant.
low crystallinity of the copolymers. In contrast, the elon- In fact, the area of hysteresis loop is equivalent to the
gation at break obviously decreases from 1,480% to work lost in the stretching recovery process of elastomer.
1,071%, which is also because of the formation of greater
phase separation with higher BAm contents.
The crystallized PBT hard segments give strength to
the copolymers, and the branched soft PBAm segments
provide flexibility to the system. Furthermore, crystal-
lized PBT segments act as junctions of a labile physical
network in the materials to guarantee the elastic recovery.
The PBAmT copolyesters obtain excellent elasticity and
flexibility. Figure 4 shows the stress (δ)–strain (ε) curves.
For PBAmT copolymers, their curves are typical elastic
curves with large elongation at break but without
yielding behaviors, and actually the deformation is rever-
sible to some extent. Besides, their strain hardening is
obvious, which is caused by the strain-induced crystal-
lization and chain alignment. PBAmT exhibits obvious
rebound resilience, while the rebound resilience of PBAmT75 Figure 5: Cyclic stretching curve of PBAmT70.342 Wen-Bo Neng et al.
Table 3: Tensile properties of PBAmT70 kind of elastomer with excellent elasticity and great
development potential.
Sample R1 (%) R2 (%) R3 (%) R4 (%) R5 (%)
PBAmT70 82.6 97.6 98.7 99.1 99.3
± 1.8 ± 0.2 ± 0.3 ± 0.2 ± 0.3
3.5 Enzymatic degradation
It is an obvious relaxation phenomenon when the polymer The study of the enzymatic degradation behaviors of the
chain is hindered by the change in internal friction and copolyesters is indispensable to develop novel bio-based
strain, which cannot keep up with the change in stress. biodegradable. In this work, the enzymatic degradation
In addition to the large lag cycle in the first cycle, the behaviors of the copolymer by lipase from porcine pan-
tension recovery curves of the following cycles almost creas were detected in phosphate buffer solution (pH 7.2)
overlap, indicating that the friction to be overcome in at 40°C. Figure 6 shows the SEM micrographs of PBAmT
the process is small, and the tension recovery process during enzymatic degradation after 0, 2, and 6 weeks.
has obvious reversibility. In conclusion, PBAmT is a The surfaces of all the samples appear smooth initially.
Figure 6: SEM micrographs of PBAmT80 (a1–a3), PBAmT75 (b1–b3), PBAmT70 (c1–c3), PBAmT60 (d1–d3), and PBAmT55 (e1–e3), during enzy-
matic degradation at several times; (a1–e1) 0 days, (a2–e2) 2 weeks, and (a3–e3) 6 weeks.Biodegradable thermoplastic copolyester elastomers 343
As time goes on, there is apparently a degradation emer- Plastics, Technical Institute of Physics and Chemistry,
ging. After 2 weeks, they show some holes because of Chinese Academy of Sciences, China, for her help in
the degradation, and then small fragments because of experimental testing.
extended surface erosion are revealed and large parts
of the film surface are removed at last. It should be noted Funding information: The authors would like to thank the
that the degradation behaviors of all PBAmT copolymers National Natural Science Foundation of China (Project
show apparently no difference in our experiments. They No. 51973228) and Youth Innovation Promotion Association,
all behave as the characteristics of amorphous polymers CAS (2018033) for financial support.
and can degrade completely. The relatively higher biode-
gradation rate compared with PBAT can be well explained Author contributions: Wen-Bo Neng: writing – original
that the introduction of branched BAm decreases the crys- draft, writing – review and editing, methodology, formal
talline and melting point. analysis; Wen-Guang Xie, Bo-Lu, and Zhi-Chao Zhen:
In other words, the acceleration to degradation caused writing – original draft, formal analysis, visualization,
by the decrease in crystalline and melting point exceeds project administration; Jun-Long Zhao, Ge-Xia Wang,
the resistance to degradation caused by increasing the and Jun-Hui Ji: resources.
BT units, thus accelerating the adsorptive binding of the
lipase at the PBAmT surface. Conflict of interest: The authors state no conflict of
interest.
Data availability statement: All data generated or analysed
4 Conclusion during this study are included in this published article.
High molecular weight poly(butylene adipate co-tere-
phthalate) thermoplastic elastomer with methyl branch
introduced into the main chains were obtained by an References
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