Synthesis of novel biodegradable poly(butylene succinate) copolyesters composing of isosorbide and poly(ethylene glycol)

A series of biodegradable isosorbide‐based copolyesters poly(butylene succinate‐co‐isosorbide succinate‐co‐polyethyleneoxide succinate) (PB_xI_yE_zS) were synthesized via bulk polycondensation in the presence of dimethyl succinate (DMS), 1,4‐butanediol (BDO), poly(ethylene glycol) (PEG) and isosorbide (ISO). The crystallization behaviors, crystal structure and spherulite morphology of the copolyesters were analyzed by differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD) and polarizing optical microscopy (POM), respectively. The results indicate that the crystallization behavior of the copolyesters was influenced by the content of isosorbide succinate (IS) and polyethyleneoxide succinate (PEOS) units, which further tuned the mechanical and biodegradable properties of the copolyesters. The PB_xI_yE_zS copolyesters, compared to pure poly(butylene succinate), showed lower crystallization temperature, melting temperature, degree of crystallinity and degradation rate while a significant increase in glass transition temperature with increasing isosorbide content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of biodegradable poly(butylene succinate‐co‐propylene succinate)s

Biodegradable polyesters such as poly(butylene succinate) (PBS), poly(propylene succinate) (PPS), and poly(butylene succinate‐co‐propylene succinate)s (PBSPSs) were synthesized respectively, from 1,4‐succinic acid with 1,4‐butanediol and 1,3‐propanediol through a two‐step process of esterification and polycondensation in this article. The composition and physical properties of both homopolyesters and copolyesters were investigated via ¹H NMR, DSC, TGA, POM, AFM, and WAXD. The copolymer composition was in good agreement with that expected from the feed composition of the reactants. The melting temperature (T_m), crystallization temperature (T_c), crystallinity (X), and thermal decomposition temperature (T_d) of these polyesters decreased gradually as the content of propylene succinate unit increased. PBSPS copolyesters showed the same crystal structure as the PBS homopolyester. Besides the normal extinction crosses under the polarizing optical microscope, the double‐banded extinction patterns with periodic distance along the radial direction were also observed in the spherulites of PBS and PBSPS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization kinetics of poly(1,4‐butylene‐co‐ethylene terephthalate)

The crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and their copolymers poly(1,4‐butylene‐co‐ethylene terephthalate) (PBET) containing 70/30, 65/35 and 60/40 molar ratios of 1,4‐butanediol/ethylene glycol were investigated using differential scanning calorimetry (DSC) at crystallization temperatures (T_c) which were 35–90 °C below equilibrium melting temperature . Although these copolymers contain both monomers in high proportion, DSC data revealed for copolymer crystallization behaviour. The reason for such copolymers being able to crystallize could be due to the similar chemical structures of 1,4‐butanediol and ethylene glycol. DSC results for isothermal crystallization revealed that random copolymers had a lower degree of crystallinity and lower crystallite growth rate than those of homopolymers. DSC heating scans, after completion of isothermal crystallization, showed triple melting endotherms for all these polyesters, similar to those of other polymers as reported in the literature. The crystallization isotherms followed the Avrami equation with an exponent n of 2–2.5 for PET and 2.5–3.0 for PBT and PBETs. Analyses of the Lauritzen–Hoffman equation for DSC isothermal crystallization data revealed that PBT and PET had higher growth rate constant G_o, and nucleation constant K_g than those of PBET copolymers. © 2001 Society of Chemical Industry     

Sulfonated poly(butylene succinate) as a pseudo‐random copolymer: effect of sulfonate groups on microstructure and thermal behavior

The positional effect of sulfonate groups on poly(butylene succinate) (PBS) microstructure was investigated. In this regard, unsaturated poly(butylene fumarate) (PBF) and poly(butylene succinate‐ran‐fumarate) copolymers, synthesized via esterification/polycondensation reactions, were modified through post‐polymerization modification. The progress of the PBF sulfonation reaction was analyzed via ¹H NMR, dynamic light scattering and field emission SEM. The microstructure and thermal behavior of the functional polyesters were studied through DSC, TGA, elemental analysis and ¹H NMR. Based on the results, the sulfonation reaction of unsaturated polymer chains, which are not experiencing a phase separation, is instantaneous, but sulfonation of the chains that have formed colloidal particles is a time‐consuming process. Surprisingly, the outcomes of ¹H NMR analysis revealed a kind of heterogeneity along the fully sulfonated PBS backbone, similar to what is usually observed for copolymers. This is due to the ability of sulfonate groups to locate in different sites and create various block types. Due to the attraction between sulfonate groups, they tend to attach to the chain such that they provide the greatest number of second type blocks (containing two sulfonate groups). The randomness of sulfonated polymers after the sulfonation reaction was increased compared to that of the corresponding unsaturated copolymers. Increasing the content of sulfonate groups also led to a significant decrease in the thermal resistance (ca 120 °C) and crystallinity, along with a dramatic increase in ash content and T_g (up to 156 °C). © 2018 Society of Chemical Industry     

Effects of shearing and comonomer content on the crystallization behavior of poly(butylene succinate‐co‐butylene 2‐ethyl‐2‐methyl succinate)

Poly(butylene succinate‐co‐butylene 2‐ethyl‐2‐methyl succinate) (PBSEMS) random copolymers were prepared with different comonomer compositions. The effects of shearing and comonomer content on the crystallization behavior of these copolymers were investigated at 80 °C. The thermal and morphological properties of the resulting samples were also discussed. The copolymers showed a longer induction time and a slower crystallization rate with increasing comonomer content. The promoting effect of shear on the overall crystallization behavior was more notable for those copolymers containing more 2‐ethyl‐2‐methyl succinic acid (EMSA) units. The melting temperature of ‘as‐prepared’ poly(butylene succinate) (PBS) was ca. 115 °C, while that of the copolymers varied from 112 to 102 °C. Higher comonomer contents in the copolymers gave rise to lower melting temperatures and broader melting peaks. In addition, the isothermally crystallized samples showed multiple melting endothermic behavior, the extent of which depended on the comonomer content. The copolymers showed different wide‐angle X‐ray diffraction (WAXD) patterns from that of neat PBS, depending on the comonomer content and shear applied during crystallization. With increasing comonomer content, the copolymers crystallized without shearing, showing the shifting of a diffraction peak to a higher angle, while those crystallized under shear did not show any peak shift. Copyright © 2004 Society of Chemical Industry     

Characterization of the mechanical properties,crystallization, and enzymatic degradation behavior of poly(butylene succinate‐co‐ethyleneoxide‐co‐DL‐lactide) copolyesters

A series of aliphatic biodegradable poly (butylene succinate‐co‐ethyleneoxide‐co‐DL ‐lactide) copolyesters were synthesized by the polycondensation in the presence of dimethyl succinate, 1,4‐butanediol, poly(ethylene glycol), and DL ‐oligo(lactic acid) (OLA). The composition, as well as the sequential structure of the copolyesters, was carefully investigated by ¹H‐NMR. The crystallization behaviors, crystal structure, and spherulite morphology of the copolyesters were analyzed by differential scanning calorimetry, wide angle X‐ray diffraction, and polarizing optical microscopy, respectively. The results indicate that the sequence length of butylene succinate (BS) decreased as the OLA feed molar ratio increasing. The crystallization behavior of the copolyesters was influenced by the composition and sequence length of BS, which further tuned the mechanical properties of the copolyesters. The copolyesters formed the crystal structures and spherulites similar to those of PBS. The incorporation of more content of ethylene oxide (EO) units into the copolyesters led to the enhanced hydrophilicity. The more content of lactide units in the copolyesters facilitated the degradation in the presence of enzymes. The morphology of the copolyester films after degradation was also studied by the scanning electron microscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,characterization and properties of poly(butylene succinate) modified with rosin maleopimaric acid anhydride

Huge hydrogenated phenanthrene ring segments were introduced into the main chain of poly(butylene succinate) by polymerization of succinic acid (SA), 1,4‐butanediol (BD) and rosin maleopimaric acid anhydride (RMA), which was obtained from maleic rosin. The chemical structure and composition of the copolyesters were determined with the aid of ¹H‐NMR, FTIR and elemental analysis. The thermal properties, crystallization behaviour and mechanical properties of the copolyester were then investigated using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), polarized light microscopy (PLM) and mechanical testing. With increasing content of hydrogenated phenanthrene ring segments, the melting temperature, the crystallization temperature and the relative degree of crystallinity decreased gradually, but the elongation at break and the notched impact strength of poly(butylene succinate) were enhanced without a significant deterioration of tensile strength. Copyright © 2006 Society of Chemical Industry     

The effect of 60Co γ‐rays on the crystal structure,melting and crystallization behavior of poly(butylene succinate)

The results obtained for poly(butylene succinate) (PBS) after ⁶⁰Co γ‐ray irradiation, studied by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimeter (DSC) and polarizing optical microscopy (POM), revealed that the degree of crystallinity, melting temperature and enthalpy decreased with increasing irradiation dose, but that the crystal structure of PBS did not vary when compared to non‐irradiated PBS. By using Scherrer equation, small changes occurred in the crystal sizes of L₀₂₀, L₁₁₀ and L₁₁₁. The spherulitic morphology of PBS was strongly dependent on irradiation dose and changed significantly at higher irradiation dosages. The crystallization kinetics of PBS indicated that the Avrami exponent (n) for irradiated PBS was reduced to 2.3, when compared to non‐irradiated PBS (3.3). Copyright © 2004 Society of Chemical Industry     

Synthesis,characterization and properties of biodegradable poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyesters

BACKGROUND: To obtain a biodegradable thermoplastic elastomer, a series of poly(ester‐ether)s based on poly(butylene succinate) (PBS) and poly(propylene glycol) (PPG), with various mass fractions and molecular weights of PPG, were synthesized through melt polycondensation. RESULTS: The copolyesters were characterized using ¹H NMR, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, mechanical testing and enzymatic degradation. The results indicated that poly(ester‐ether)s with high molecular weights were successfully synthesized. The composition of the copolyesters agreed very well with the feed ratio. With increasing content of the soft PPG segment, the glass transition temperature decreased gradually while the melting temperature, the crystallization temperature and the relative degree of crystallinity decreased. Mechanical testing demonstrated that the toughness of PBS was improved significantly. The elongation at break of the copolyesters was 2–5 times that of the original PBS. Most of the poly(ester‐ether) specimens were so flexible that they were not broken in Izod impact experiments. At the same time, the enzymatic degradation rate of PBS was enhanced. Also, the difference in molecular weight of PPG led to properties being changed to some extent among the copolyesters. CONCLUSION: The synthesized poly(ester‐ether)s having excellent flexibility and biodegradability extend the application of PBS into the areas where biodegradable thermoplastic elastomers are needed. Copyright © 2009 Society of Chemical Industry     

Synthesis and characterizations of branched poly(butylene succinate) copolymers with 1,2‐octanediol segments

Branched poly(butylene succinate) (PBS) copolymers were synthesized, from succinic acid (SA), 1,4‐butanediol (1,4‐BD), and 1,2‐octanediol (1,2‐OD) through a two‐step process containing esterification and polycondensation, with different mole fractions of 1,2‐OD segments. The branched PBS copolymers were characterized with ¹H‐NMR, differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), thermogravimetric analysis (TGA), dynamic rheological testing, and tensile properties analysis. The results of DSC and WAXD show that, with the increasing of the 1,2‐OD segments content, the glass transition temperature (T_g), melting temperature (T_m), crystallization temperature (T_c), and the degree of crystallinity (X_c) decrease. While the crystal structure of PBS does not change by introducing 1,2‐OD segments. The results of TGA and dynamic rheological testing indicate that the thermal stability of neat PBS is improved with the addition of 1,2‐OD segments. The incorporation of 1,2‐OD segments has some effects on the rheological properties of PBS, such as complex viscosities (|η*|), storage modulus (G′), and loss modulus (G″). Tensile testing demonstrates that the elongation at break is improved significantly with increasing 1,2‐OD segments content, but without a notable decrease of tensile strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Investigation on isothermal crystallization,melting behaviors,and spherulitic morphologies of multiblock copolymers containing poly(butylene succinate) and poly(1,2‐propylene succinate)

In this article, isothermal crystallization, melting behaviors, and spherulitic morphologies of high‐impact multiblock copolymers, comprising of PBS as hard segment and poly(1,2‐propylene succinate) (PPSu) as soft segment with hexamethylene diisocyanate as a chain extender, were investigated. The results from differential scanning calorimetry (DSC) suggest that the two segments of multiblock copolymers are miscible in amorphous region. The crystallization kinetics were analyzed by the Avrami equation. The effect of PBS segment length as well as the introduction of PPSu segment on the crystallization kinetics and melting bebaviors of block copolymers was studied. Both crystallization rate (G) and spherulitic growth rate (g) are markedly increased with the increase of PBS segment length or decreased with the incorporation of PPSu segment. All the multiblock copolymers show the multiple melting behaviors, whose position and area depend on PBS segment length and the presence of PPSu segment. The melting peaks shift to higher temperature region with increasing PBS segment length. Spherulitic morphologies of the multiblock copolymers after being isothermally crystallized were examined by polarized optical microscopy. It is the first time to investigate the effect of one segment length on crystallization bebavior of block copolymers based on a fixed weight ratio systematically. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Peroxide modification of poly(butylene adipate‐co‐succinate)

We attempted to introduce crosslinking into poly(butylene adipate‐co‐succinate) (PBAS) to improve the properties, such as the mechanical strength and elasticity, by a simple addition of dicumyl peroxide (DCP). Prior to curing, the thermal stability of PBAS was investigated. Above 170°C PBAS was severely degraded, and the degradation could not be successfully stabilized by an antioxidant. The PBAS was effectively crosslinked by DCP, and the gel fraction increased as the DCP content increased. A major structure of the crosslinked PBAS was an ester and aliphatic group. The tensile strength and elongation of PBAS were improved with an increasing content of DCP, but there was little affect on the tear strength. The biodegradability of crosslinked PBAS was not seriously deteriorated. A higher degree of crosslinking gave a lower heat of crystallization and heat of fusion. However, the melt crystallization temperatures of the crosslinked PBAS were higher than that of PBAS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 637–645, 2001     

Reactive blending of poly(butylene succinate) and poly(triethylene succinate): characterization of the copolymers obtained

Poly[butylene‐co‐(triethylene succinate)] block copolymers (PBSPTES), prepared by reactive blending of the parent homopolymers (PBS and PTES) in the presence of Ti(OBu)₄, were analysed by nuclear magnetic resonance (NMR), wide angle X‐ray diffraction, thermogravimetric analysis and differential scanning calorimetry techniques, in order to investigate the effects of the transesterification reactions on the molecular structure and thermal properties. ¹H‐NMR analysis evidenced the formation of copolymers whose degree of randomness increased with mixing time. After melt quenching, all the copolymers were found to be semicrystalline with the exception of a random copolymer. The results obtained indicated that the block size has a fundamental role in determining the rate of crystallization and therefore the phase behavior of the block copolymers. Copyright © 2012 Society of Chemical Industry     

Morphology and hydrogen‐bond restricted crystallization of poly(butylene succinate)/cellulose diacetate blends

Poly(butylene succinate)/cellulose diacetate (PBS/CDA) blends were prepared by the solution blending method from poly(butylene succinate) (PBS) and cellulose diacetate (CDA). The influence of hydrogen bond on the structure, morphology, crystallization, as well as the physical properties of PBS/CDA blends was significantly investigated. The fourier transform infrared spectroscopy (FTIR) results indicated that the carbonyl groups of PBS shifted to higher wavenumbers and disappeared at the content of 60% CDA, due to the formation of hydrogen bond between PBS and CDA. The wide‐angle X‐ray diffractometer (WAXD) and differential scanning calorimeter (DSC) analysis suggest that the crystallization of PBS was significantly restricted by the incorporation of CDA, which is also attributed to the hydrogen bonding. The scanning electron miscroscope (SEM) and polarized optical microscopy (POM) results revealed that PBS and CDA were miscible without appearance of obvious phase separation. The hydrogen bonding interaction led to the change of decomposing mechanism of blends as determined by thermogravimetric analysis (TGA), as well as the increase of the elongation at break due to the reduced crystallinity of PBS. The existence of CDA led to the decrease of water contact angle, showing of the improved hydrophilicity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sulfur‐containing polymers: Effect of composition on melting behavior and crystallization kinetics of poly(butylene terephthalate)

The melting behavior and crystallization kinetics of poly(butylene terephthalate/thiodipropionate) (PBT) copolymers were investigated using the differential scanning calorimetry technique. Multiple endotherms typical of PBT were observed in the copolymers under investigation and were found to be influenced both by crystallization temperature (T_c) and composition. Wide‐angle X‐ray diffraction measurements permitted the identification of the crystalline structure of PBT in all the copolymers investigated. By applying the Hoffman–Weeks method, the equilibrium melting temperature of the copolymers was derived. Isothermal crystallization kinetics were analyzed according to Avrami's treatment. Values of the exponent n close to 3 were obtained, independent of T_c and composition, results in agreement with it being a crystallization process originating from predetermined nuclei and characterized by three‐dimensional spherulitic growth. The introduction of butylene thiodipropionate units was found to decrease the PBT crystallization rate. The heat of fusion (ΔH_m) was correlated to the specific heat increment (Δc_p) of samples of different degrees of crystallinity, and the results were interpreted based on there being an interphase, whose amount was found to increase as the sulfur‐containing unit content was increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2003–2009, 2003     

Crystallization behaviour of poly(butylene succinate) copolymers

Poly(butylene succinate‐co‐butylene 2‐methyl succinate) (PBSMS) random copolymers were synthesized with various comonomer compositions and their crystallization behaviour and morphology were investigated by differential scanning calorimeter, small angle X‐ray scattering and polarized optical microscopy. The equilibrium melting temperature obtained by the Hoffman–Weeks plot significantly decreased with increasing comonomer concentration containing methyl side‐groups. Spherulitic growth rates were strongly dependent on comonomer concentration and were analyzed using the Lauritzen–Hoffman kinetic theory. The surface free energy (σσ_e) dramatically decreased with comonomer contents. From analysis of the SAXS data, the dependence of the lamellar thickness on crystallization temperature decreased with increasing comonomer concentration. © 2002 Society of Chemical Industry     

Macromolecular design of novel sulfur‐containing copolyesters with promising mechanical properties

The miscibility of poly(butylene succinate) (PBS)/poly(butylene thiodiglycolate) (PBTDG) blends was investigated by DSC technique. PBS and PBTDG were completely immiscible in as blended‐state, as evidenced by the presence of two T_gs at ?34 and ?48°C, respectively. The miscibility changes upon mixing at elevated temperature: the original two phases merged into a single one because of transesterification reactions. Poly(butylene succinate/thiodiglycolate) block copolymers, prepared by reactive blending of the parent homopolymers, were studied to investigate the effects of transesterification reactions on the molecular structure and solid‐state properties. ¹³C‐NMR analysis evidenced the formation of copolymers whose degree of randomness increased with mixing time. Thermal characterization results showed that all the samples were semicrystalline, with a soft rubbery amorphous phase and a rigid crystal phase whose amount decreased by introducing BTDG units into the PBS chain (20 ≤ χ_c ≤ 41). Lastly, the mechanical properties were found strictly related to crystallinity degree (χ_c), the random copolymer, exhibiting the lowest elastic modulus (E = 61 MPa) and the highest deformation at break (ε_b (%) = 713). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,characterization and properties of novel biodegradable multiblock copolymers comprising poly(butylene succinate) and poly(1,2‐propylene terephthalate) with hexamethylene diisocyanate as a chain extender

In this exploration of novel biodegradable polyesters, multiblock copolymers based on poly(butylene succinate) (PBS) and poly(1,2‐propylene terephthalate) (PPT) were successfully synthesized with hexamethylene diisocyanate as a chain extender. The amorphous and rigid PPT segment was chosen to modify PBS. The structures of the polymers were characterized using ¹H NMR and ¹³C NMR spectroscopy, gel permeation chromatography and wide‐angle X‐ray diffraction; the physical properties were investigated using thermogravimetric analysis, differential scanning calorimetry, mechanical testing and enzymatic degradation. The results indicate that the copolymers possess satisfactory mechanical and thermal properties, with impact strength 186% higher than that of PBS homopolymer, while tensile strength, flexural strength, thermal stability and melting point (T_m) are slightly decreased. Crystallization and biodegradation rates are still acceptable at 5 wt% PPT, although they are decreased by the introduction of PPT. The addition of appropriate amounts of PPT can improve the impact strength effectively without an obviously deleterious effect on tensile strength, flexural strength, thermal stability, T_m, crystallization rate and biodegradability. This study describes a convenient route to novel multiblock copolymers comprising crystallizable aliphatic and amorphous aromatic polyesters, which are promising for commercialization as biodegradable materials. Copyright © 2011 Society of Chemical Industry     

聚丁二酸丁二酯的结晶动力学研究

采用氯仿溶解聚丁二酸丁二酯（PBS）,然后利用甲醇逐级沉淀分离获得不同相对分子质量及其分布的PBS级分,分别采用差示扫描量热仪、广角X射线衍射仪、偏光显微镜等对不同级分PBS的等温和非等温结晶动力学、晶体形态及结构进行了系统研究。结果表明,随着相对分子质量的增加和相对分子质量分布的变宽,各级分的半结晶时间逐渐降低,结晶半峰宽逐渐变窄,结晶度逐渐增加;但各级分PBS的晶型和晶貌并未发生明显的转变。     

Preparation and thermal behavior of random poly(butylene terephthalate/azelate) copolyesters

Poly(butylene terephthalate), poly(butylene azelate), and poly(butylene terephthalate/butylene azelate) random copolymers of various compositions were synthesized in bulk using the well‐known two‐stage polycondensation procedure, and characterized in terms of chemical structure and molecular weight. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. As far as the thermal stability is concerned, it was found to be rather similar for all copolymers and homopolymers investigated. All the copolymers were found to be partially crystalline, and the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of melting temperature with respect to pure homopolymers. Flory's equation was found to describe the T_m–composition data and permitted to calculate the melting temperatures (T^°_m ) and the heats of fusion (ΔH_u) of both the completely crystalline homopolymers. Owing to the high crystallization rate, the glass transition was observable only for the copolymers containing from 30 to 70 mol % of the terephthalate units; even though the samples cannot be frozen in a completely amorphous state, the data obtained confirmed that the introduction of the aromatic units gave rise to an increase of T_g, due to a chain stiffening. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2694–2702, 1999