Nonisothermal crystallization behaviors of biodegradable double crystalline poly(butylene succinate)‐poly(ethylene glycol) multiblock copolymers

Nonisothermal crystallization behaviors of both poly(butylene succinate) (PBS) and poly(ethylene glycol) (PEG) segments within PBS‐PEG (PBSEG) multiblock copolymers were investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization kinetics of both PBS and PEG segments were analyzed by Avrami, Ozawa, and Mo methods. The results showed that both of Avrami and Mo methods were successful to describe the nonisothermal crystallization kinetics of PBS and PEG segments. The results of crystallization kinetics indicated that the crystallization rate of PBS segment decreased with PBS segment content and/or L_PBS, while that of PEG segment decreased with M_n,PEG or F_PEG. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40940.     

Crystallization behavior and morphology of double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers

Double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers (PTT/PEOT), with PTT content ranging from 16.5 to 65.5 wt%, were synthesized by melt copolycondensation. The morphological transformation of samples from microphase separation to macrophase separation was investigated by gel permeation chromatography and transmission electron microscopy. Differential scanning calorimetry and in situ wide‐angle X‐ray diffraction suggested that all copolycondensation samples displayed double crystalline behavior. The melt‐crystallization peak temperatures (T_{m, c} values) of PTT chains monotonously increased with increasing PTT content and were higher than that of homo‐PTT when the content of PTT was above 30.6 wt%. Interestingly, T_{m, c} values of PEOT chains were also increased with increasing PTT content. Polarized optical microscopy revealed that all copolycondensation samples studied could form ring‐banded spherulites and band spacing increased with increasing T_c values. In addition, band spacing decreased with increasing PTT content at a given T_c. Strangely, although PEOT was the main component in all copolycondensation samples, spherulitic morphology formed by the advance crystallization of PTT did not change after PEOT crystallization. Only a subtle change of quadrant tones was detected. © 2012 Society of Chemical Industry     

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     

聚丁二酸丁二醇酯/聚乙二醇硬脂酸酯共混物非等温结晶行为

以聚丁二酸丁二醇酯（PBS）和聚乙二醇硬脂酸酯（PEOST）为原料,采用溶液共混法制备了PEOST质量分数分别为10%（POS-10）和30%（POS-30）的两种合金材料。通过差示扫描量热法（DSC）研究了合金材料的非等温结晶行为,用莫志深（Mo）法分析了PBS的非等温结晶动力学,采用Kissinger法和Friedman法计算PBS的结晶活化能,并用红外（FTIR）和偏光显微镜（POM）进行表征。研究结果表明：PBS先结晶形成结晶微区不利于PEOST结晶,而较高含量的PEOST有利于PBS的结晶。受PBS先结晶的影响,POS-10降温DSC曲线没有出现PEOST的结晶峰,而POS-30在低的降温速率情况下出现了PEOST双结晶峰;升温DSC曲线中两试样均出现了PEOST的熔融峰。在相同的冷却速率下,POS-30的PEOST熔融温度（T_m）和熔融焓（△H_m）大于POS-10;POS-30的PBS结晶峰温度（T_p）、结晶焓（△H_c）大于POS-10,而结晶半峰宽（D）值更小;但两者的T_m和△H_m相当。随冷却速率的增加,PBS的D值增大,而PEOST的D值却降低;冷却速率的增加对PBS的T_m值影响不大,但使PEOST的T_m略有减小。Mo法适合用于共混物中PBS的非等温结晶动力学分析。POS-30的PBS绝对值结晶活化能要大于POS-10。POS-30在红外光谱谱图中出现了PEOST结晶的红外响应峰（1109cm^-1和841cm^-1）而POS-10没有。     

Biodegradable poly(ethylene succinate) blends and copolymers containing minor amounts of poly(butylene succinate)

Poly(ethylene succinate) (PES), poly(butylene succinate) (PBS), and PES‐rich copolyesters were synthesized using an effective catalyst, titanium tetraisopropoxide. PES was blended with minor amounts of PBS for the comparison. The compositions of the copolyesters and the blends were determined from NMR spectra. Their thermal properties were studied using a differential scanning calorimeter (DSC), a temperature modulated DSC (TMDSC), and a thermogravimetric analyzer. No significant difference exists among the thermal stabilities of these polyesters and blends. For the blends, the reversible curves of TMDSC showed a distinct glass‐rubber transition temperature (T_g), however, the variation of the T_g values with the blend compositions was small. Isothermal crystallization kinetics and the melting behavior after crystallization were examined using DSC. Wide‐angle X‐ray diffractograms (WAXD) were obtained for the isothermally crystallized specimens. The results of DSC and WAXD indicate that the blends have a higher degree of crystallinity and a higher melting temperature than those of the corresponding copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

脂肪族聚丁二酸丁二醇-聚乙二醇嵌段共聚物的制备及性能研究

采用熔融缩聚法以钛酸四丁酯为催化剂,使单体发生酯交换反应,成功制备了一系列以聚乙二醇(PEG)为亲水软段,以聚丁二酸丁二醇酯(PBS)为硬段的嵌段共聚物,采用1H-NMR确定了共聚物的结构组成;采用DSC、吸水性测试及水解降解试验对嵌段共聚物性能表征,结果表明共聚物中两种链段的含量与原料投料比一致,具有可调控性。由于PEG的引入,使共聚物结晶性下降,亲水性和降解性得到显著改善。     

Crystallization kinetics,melting behavior,and morphologies of poly(butylene succinate) and poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyester

This article investigated the crystallization kinetics, melting behavior, and morphologies of poly(butylene succinate)(PBS) and its segmented copolyester poly(butylene succinate)‐block‐poly(propylene glycol)(PBSP) by means of differential scanning calorimetry, polarized light microscopy, and wide angle X‐ray diffraction. Avrami equation was used to describe the isothermal crystallization kinetics. For nonisothermal crystallization studies, the Avrami equation modified by Jeziorny, and the model combining Avrami equation and Ozawa equation were employed. The results showed that the introduction of poly(propylene glycol) soft segment led to suppression of crystallization of PBS hard segment. The melting behavior of the isothermally and nonisothermally crystallized samples was also studied. Results showed that the isothermally crystallized samples exhibited two melting endotherms, whereas only one melting endotherm was shown after nonisothermal crystallization. The spherulitic morphology of PBSP and wide angle X‐ray diffraction showed that the polyether segments were excluded from the crystals and resided in between crystalline PBS lamellae and mixed with amorphous PBS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crystallization kinetics and morphology of poly(butylene succinate)/poly(vinyl phenol) blend

Biodegradable crystalline poly(butylene succinate) (PBSU) can form miscible polymer blends with amorphous poly(vinyl phenol) (PVPh). The isothermal crystallization kinetics and morphology of neat and blended PBSU with PVPh were studied by differential scanning calorimetry (DSC), optical microscopy (OM), wide angle X-ray diffraction (WAXD), and small angle X-ray scattering (SAXS) in this work. The overall isothermal crystallization kinetics of neat and blended PBSU was studied with DSC in the crystallization temperature range of 80-88 °C and analyzed by applying the Avrami equation. It was found that blending with PVPh did not change the crystallization mechanism of PBSU, but reduced the crystallization rate compared with that of neat PBSU at the same crystallization temperature. The crystallization rate decreased with increasing crystallization temperature, while the crystallization mechanism did not change for both neat and blended PBSU irrespective of the crystallization temperature. The spherulitic morphology and growth were observed with hot stage OM in a wide crystallization temperature range of 75-100 °C. The spherulitic morphology of PBSU was influenced apparently by the crystallization temperature and the addition of PVPh. The linear spherulitic growth rate was measured and analyzed by the secondary nucleation theory. Through the Lauritzen-Hoffman equation, some parameters of neat and blended PBSU were derived and compared with each other including the nucleation parameter (K_g), the lateral surface free energy (σ), the end-surface free energy (σ_e), and the work of chain folding (q). Blending with PVPh decreased all the aforementioned parameters compared with those of neat PBSU; however, the decrease extent was limited. WAXD result showed that the crystal structure of PBSU was not modified after blending with PVPh. SAXS result showed that the long period of blended PBSU increased, possibly indicating that the amorphous PVPh might reside mainly in the interlamellar region of PBSU.     

Miscibility and crystallization in crystalline/crystalline blends of poly(butylene succinate)/poly(ethylene oxide)

Miscibility and crystallization behavior have been investigated in blends of poly(butylene succinate) (PBSU) and poly(ethylene oxide) (PEO), both semicrystalline polymers, by differential scanning calorimetry and optical microscopy. Experimental results indicate that PBSU is miscible with PEO as shown by the existence of single composition dependent glass transition temperature over the entire composition range. In addition, the polymer-polymer interaction parameter, obtained from the melting depression of the high-T_m component PBSU using the Flory-Huggins equation, is composition dependent, and its value is always negative. This indicates that PBSU/PEO blends are thermodynamically miscible in the melt. The morphological study of the isothermal crystallization at 95 °C (where only PBSU crystallized) showed the similar crystallization behavior as in amorphous/crystalline blends. Much more attention has been paid to the crystallization and morphology of the low-T_m component PEO, which was studied through both one-step and two-step crystallization. It was found that the crystallization of PEO was affected clearly by the presence of the crystals of PBSU formed through different crystallization processes. The two components crystallized sequentially not simultaneously when the blends were quenched from the melt directly to 50 °C (one-step crystallization), and the PEO spherulites crystallized within the matrix of the crystals of the preexisted PBSU phase. Crystallization at 95 °C followed by quenching to 50 °C (two-step crystallization) also showed the similar crystallization behavior as in one-step crystallization. However, the radial growth rate of the PEO spherulites was reduced significantly in two-step crystallization than in one-step crystallization.     

Crystallization behavior of plasticized poly(lactide) film by poly(l-lactic acid)-poly(ethylene glycol)-poly(l-lactic acid) triblock copolymer

Polymer Bulletin - Poly(l-lactic acid)-poly(ethylene glycol)-poly(l-lactic acid) triblock copolymer (PLLA-PEG-PLLA) prepared by simple esterification of l-lactic acid (l-LA) and diol-polyethylene...     

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     

Bamboo fibers @ poly(ethylene glycol)‐reinforced poly(butylene succinate) biocomposites

The poly(poly(ethylene glycol) methyl ether methacrylate)‐ (PPEGMA)‐grafted bamboo fiber (BF) (BF@PPEGMA) was successfully synthesized via the esterification and atom transfer radical polymerization (ATRP) methods. The poly(butylenes succinate) (PBS) matrix‐based composites including BF and BF@PPEGMA were prepared by a twin‐screw extruder. The structure, morphology, as well as the properties of BF@PPEGMA and composites was investigated. The results indicated that PPEGMA was successfully grafted onto the BF surfaces, making BF surfaces rough and less thermally stable. The BF@PPEGMA showed of stronger interactions with PBS matrix than pristine BF, leading to the improvement of tensile modulus, tensile strength, and elongation at break of the composites. The PBS/BF@PPEGMA composites absorbed less water than PBS/BF composites due to the existence of less content of hydroxyl groups after surface modification. Incorporation of BF and BF@PPEGMA facilitated the crystallization of PBS at higher temperatures, leading to formation of regular spherulites without appearance of transcrystallization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Crystallization behaviour of random block copolymers of poly(butylene terephthalate) and poly(tetramethylene ether glycol)

The morphology and crystallization behaviour of random block copolymers of poly(butylene terephthalate) and poly(tetramethylene ether glycol) have been investigated. Single crystals have been grown in thin films crystallized from the melt. Well defined lamellae, exhibiting (hkO) single crystal electron diffraction patterns have been observed in copolymers containing down to 49 wt% (0.83 mole fraction) poly(butylene terephthalate). WAXS and electron diffraction support a model of a relatively pure poly(butylene terephthalate) crystal core with the poly(tetramethylene ether glycol) (soft segment) sequences and short hard segments being rejected to the lamellar surface and the soft segment rich matrix. The lateral dimensions of the lamellae are determined by the number of hard segment sequences long enough to traverse the stable crystal size at the crystallization temperature. This leads to an initial population of crystals formed at T_c and a second set of smaller crystals that grow from the short hard segment sequences upon cooling to room temperature. The result is fractionation by sequence length due to a coupling of the sequence distribution with the stable crystal size at the crystallization temperature.     

Crystallization behavior and morphology of poly(ethylene 2,6-naphthalate)

The crystallization behavior and morphology of poly(ethylene 2,6-naphthalte) (PEN) were investigated by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and transmission electron microscopy (TEM). POM results revealed that PEN crystallized at 240 °C shows the coexistence of α and β-form spherulite morphology with different growth rates. In particular, when PEN crystallized at 250 °C, the morphology of spherulites showed a squeezed peanut shape. The Avrami exponents decreased from 3 to 2.8 above the crystallization temperature of 220 °C, indicating a decrease in growth dimension. Analysis from the secondary nucleation theory suggests that PEN crystallized at 240 °C has crystals with both regime I and regime II. In TEM observation, the ultra-thin PEN film crystallized at 200 °C showed the spherulitic texture with characteristic diffractions of α-form, while PEN crystallized at 240 °C generated an axialite structure with only β-form diffraction patterns. In addition, despite a long crystallization time of 24 h, amorphous regions were also observed in the same specimen. It was inferred that the initiation of PEN at 240 °C generates only β-form crystals from axialite structures.     

Synthesis and characterization of poly(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol) segmented block copolymers

Poly(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol) segmented random copolymers, with poly(butylene succinate) (PBS) molar fraction (M_PBS) varying from 10 to 60 %, were synthesized through a melt polycondensation process and characterized by means of GPC, NMR, DSC and mechanical testing. The number‐average relative molecular mass of the copolymers was higher than 4 × 10⁴ g mol^?1 with polydispersity below 1.9. Sequence distribution analysis on the two types of hard segments by means of ¹H NMR revealed that the number‐average sequence length of PBT decreased from 2.80 to 1.23, while that of PBS increased from 1.27 to 4.76 with increasing M_PBS. The random distribution of hard segments was also justified because of the degree of randomness around 1.0. Micro‐phase separation structure was verified for the appearance of two glass transition temperatures and two melting points, respectively, in DSC thermograms of most samples. The crystallinity of hard segments changed with the crystallizability controlled by the average sequence length and reached the minimum value at an M_PBS of about 50–60 mol%. The results can also be ascribed to the co‐crystallization between two structurally analogous hard segments. Mechanical testing results demonstrated that incorporating a certain amount of PBS moieties (less than 30 mol%), at the expense of a minute depression of the elastic modulus, that higher relative elongation and more flexibility of polymer chain could be expected. Maximum equilibrium water absorption and faster degradation rates were observed on samples with higher M_PBS values and lower crystallinity of hard segments were better hydrophilicity of the polymer chain, through in vitro degradation experiments. Copyright © 2003 Society of Chemical Industry     

Crystallization behavior of poly(butylene succinate)/corn starch biodegradable composite

The effects of corn starch (CS) filler and lysine diisocyanate (LDI) as a coupling agent on the crystallization behavior of a poly(butylene succinate) (PBS)/CS ecocomposite were investigated using differential scanning calorimetry. In isothermal crystallization, n values for pure PBS were from 2.33 to 2.82. On the other hand, both composites showed values of 3 < n < 4. In nonisothermal crystallization, the Avrami exponent varied from 2.12 to 2.55 for pure PBS, from 1.58 to 1.96 for the composite without LDI, and from 1.79 to 1.91 for the composite with LDI, depending on the cooling rate. There was not a large difference of the crystallization rate constant (k) as adjusted by the Jeziornay suggestion. The activation energy for nonisothermal crystallization was also calculated on the basis of three different equations (Augis–Bennett, Kissinger, and Takhor equations). However, the values of the activation energy were in contradiction with the results of the kinetics. The addition of the filler (CS) and coupling agent (LDI) affected the morphological structure of PBS spherulites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1107–1114, 2005     

Hydrolytic degradation behavior of poly(butylene succinate)s with different crystalline morphologies

The effect of crystalline morphology on the hydrolytic degradation behavior of poly(butylene succinate) (PBS) in an alkaline solution was investigated by using scanning electron microscopy, gel permeation chromatography, and weight loss measurement. Morphological changes were induced on PBS samples by different thermal treatments (i.e., melt quenching or isothermal crystallization) at a constant overall degree of crystallinity. It was found that even with a similar degree of crystallinity, the hydrolytic degradation rate of an isothermally crystallized sample at 60°C was higher than that of a melt‐quenched sample. This was due to the difference in the internal morphology of the spherulites: the internal structure of spherulite in an isothermally crystallized sample consists of coarse and loosely packed fibrils whereas a melt‐quenched sample contains finer and tightly packed fibrils. This result suggested that the internal structure of the spherulite of PBS samples plays an important role in the hydrolytic degradation for this experimental condition. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1025–1033, 2001     

Crystallization,morphology, and mechanical properties of poly(butylene succinate)/poly(ethylene oxide)‐polyhedral oligomeric silsesquioxane nanocomposites

The biodegradable poly(butylene succinate) (PBS)/poly(ethylene oxide)‐polyhedral oligomeric silsesquioxane (PEO‐POSS) nanocomposites were prepared by the solution blending and melt‐injection methods. The effect of PEO‐POSS on the non‐isothermal and isothermal crystallization, morphology, as well as mechanical properties of PBS was carefully investigated. The PEO‐POSS nanoparticles dispersed well in the PBS matrix, with the diameters around 30 nm. From isothermal crystallization analysis, the incorporation of PEO‐POSS enhanced the crystallization of PBS due to the heterogeneous nucleation effect while the crystal structure of PBS remained. PBS/PEO‐POSS nanocomposites showed of higher glass transition temperatures than that of neat PBS, attributing to the existence of PEO‐POSS decreasing the flexibility of PBS chains. The elongation at break of the PBS/PEO‐POSS nanocomposites reached the maximum value with PEO‐POSS content of 5 wt%. However, the elastic modulus of PBS decreased after the incorporation of PEO‐POSS. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Crystallization behavior of biodegradable amphiphilic poly(ethylene glycol)‐poly(L‐lactide) block copolymers

Poly(ethylene glycol)‐poly(L ‐lactide) diblock and triblock copolymers were prepared by ring‐opening polymerization of L ‐lactide with poly(ethylene glycol) methyl ether or with poly(ethylene glycol) in the presence of stannous octoate. Molecular weight, thermal properties, and crystalline structure of block copolymers were analyzed by ¹H‐NMR, FTIR, GPC, DSC, and wide‐angle X‐ray diffraction (WAXD). The composition of the block copolymer was found to be comparable to those of the reactants. Each block of the PEG–PLLA copolymer was phase separated at room temperature, as determined by DSC and WAXD. For the asymmetric block copolymers, the crystallization of one block influenced much the crystalline structure of the other block that was chemically connected to it. Time‐resolved WAXD analyses also showed the crystallization of the PLLA block became retarded due to the presence of the PEG block. According to the biodegradability test using the activated sludge, PEG–PLLA block copolymer degraded much faster than PLLA homopolymers of the same molecular weight. © 1999 John Wiley amp; Sons, Inc. J Appl Polym Sci 72: 341–348, 1999     

The effect of poly(ethylene glycol) as plasticizer in blends of poly(lactic acid) and poly(butylene succinate)

The effect of polyethylene glycol (PEG) on the mechanical and thermal properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends was examined. Overall, it was found that PEG acted as an effective plasticizer for the PLA phase in these microphase‐separated blends, increasing the elongation at break in all blends and decreasing the T_g of the PLA phase. Significant effects on other properties were also observed. The tensile strength and Young's modulus both decreased with increasing PEG content in the blends. In contrast, the elongation at break increased with the addition of PEG, suggesting that PEG acted as a plasticizer in the polymer blends. Scanning electron microscope images showed that the fracture mode of PLA changed from brittle to ductile with the addition of PEG in the polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43044.