Biodegradable polymer blends of poly(3-hydroxybutyrate) and poly(DL-lactide)-co-poly(ethylene glycol)

The melting and crystallization behavior and phase morphology of poly(3-hydroxybutyrate) (PHB) and poly(DL-lactide)-co-poly(ethylene glycol) (PELA) blends were studied by DSC, SEM, and polarizing optical microscopy. The melting temperatures of PHB in the blends showed a slight shift, and the melting enthalpy of the blends decreased linearly with the increase of PELA content. The glass transition temperatures of PHB/PELA (60/40), (40/60), and (20/80) blends were found at about 30°C, close to that of the pure PELA component, during DSC heating runs for the original samples and samples after cooling from the melt at a rate of 20°C/min. After a DSC cooling run at a rate of 100°C/min, the blends showed glass transitions in the range of 10–30°C. Uniform distribution of two phases in the blends was observed by SEM. The crystallization of PHB in the blends from both the melt and the glassy state was affected by the PELA component. When crystallized from the melt during the DSC nonisothermal crystallization run at a rate of 20°C/min, the temperatures of crystallization decreased with the increase of PELA content. Compared with pure PHB, the cold crystallization peaks of PHB in the blends shifted to higher temperatures. Well-defined spherulites of PHB were found in both pure PHB and the blends with PHB content of 80 or 60%. The growth of spherulites of PHB in the blends was affected significantly by 60% PELA content. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1849–1856, 1997     

Study on miscibility of PEO and PCL in blends with PHB by solution viscometry

Viscometric studies were carried out for polymer-blend solutions in chloroform, i.e. for solutions of two polymers in a common solvent. Polymer blends comprised poly(3-hydroxy butyrate) (PHB) in combination with poly(ethylene oxide) (PEO) and poly(ε-caprolactone) (PCL), respectively. Experimental results obey the Huggins equation to an excellent approximation in the concentration range studied. Intrinsic viscosities vary linearly with blend composition to a good approximation. Huggins coefficients display generally nonlinear dependencies on blend composition. Positive deviations from perfect behaviour are attributed to attractions between different chain molecules or miscibility of the constituents. The viscometric study demonstrates that PEO is miscible with PHB, whereas PCL is immiscible.     

Miscibility of block copolymers of poly(ε‐caprolactone) and poly(ethylene glycol) with poly(3‐hydroxybutyrate) as well as the compatibilizing effect of these copolymers in blends of poly(ε‐caprolactone) and poly(3‐hydroxybutyrate)

Atactic poly(3‐hydroxybutyrate) (a‐PHB) and block copolymers of poly(ethylene glycol) (PEG) with poly(ε‐caprolactone) (PCL‐b‐PEG) were synthesized through anionic polymerization and coordination polymerization, respectively. As demonstrated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) measurements, both chemosynthesized a‐PHB and biosynthesized isotactic PHB (i‐PHB) are miscible with the PEG segment phase of PCL‐b‐PEGs. However, there is no evidence showing miscibility between both PHBs and the PCL segment phase of the copolymer even though PCL has been block‐copolymerized with PEG. Based on these results, PCL‐b‐PEG was added, as a compatibilizer, to both the PCL/a‐PHB blends and the PCL i‐PHB blends. The blend films were obtained through the evaporation of chloroform solutions of mixed components. Excitingly, the improvement in mechanical properties of PCL/PHB blends was achieved as anticipated initially upon the addition of PCL‐b‐PEG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2600–2608, 2001     

Compatibility behavior in thermoplastic polymer blends containing poly(t-butylstyrene-co-acrylonitrile)

The phase behavior of a series of binary component polymer blends of poly(ε-caprolactone) (PCL) and poly(t-butylstyrene-co-acrylonitrile) (TBSAN) containing varying contents of acrylonitrile (AN) was examined to determine the influence of copolymer composition and PCL content on blend miscibility or immiscibility. Thermal measurements were extensively used to determine phase behavior, i.e., a single compositionally dependent glass transition temperature implies blend miscibility. Otherwise, immiscibility is assumed to dominant blend behavior. It was determined that TBSAN and PCL form miscible blends over a broad range of AN content, i.e., spanning from below 43.2 mol % (19.8 wt %) to about 66.4 mol % (39.6 wt %), a range considerably different from that found in poly(styrene-co-acrylonitrile) copolymers. TBSAN-containing blends were found to be immiscible when the AN content is less than about 43 mol % or greater than about 67 mol %. Small-angle light-scattering and polarized light microscopy was used to probe the substantial morphological changes in the miscible blends. Little change was observed in the immiscible blends. These results clarify the phase separation observed in these blend systems. © 1993 John Wiley & Sons, Inc.     

Study on the Crystallization,Miscibility, Morphology,Properties of Poly(lactic acid)/Poly(ε-caprolactone) Blends

A series of blends of poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA₇₀PCL₃₀ blend. This result reveals that the PLA₇₀PCL₃₀ blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the T_g. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA₇₀PCL₃₀ blend gave the largest growth rate of PLA spherulite. Finally, the mechanical property of PLA/PCL blends indicated that PLA can easily be tuned from rigid to ductile by the addition of PCL.     

可完全生物降解的聚乳酸共混体系研究进展

综述了国内外以聚乳酸（PLA）为基础的完全生物降解共混体系的研究进展,主要包括不同光学活性的PLA共混、PLA与脂肪族聚脂共混、PLA与天然高分子共混、PLA与聚己内酯共混、PLA与聚乙二醇共混、PLA与聚乙烯醇共混以及PLA与聚乙烯基吡咯烷酮共混等。目前的研究表明,将PLA与另一种完全生物降解组分共混,通过不同组分分子间的相互作用,使PLA材料在保持环境友好性的同时提高了力学性能、增加了韧性、并降低了生产成本等,从而扩展了PLA在工程塑料领域和包装等领域的应用。     

A review on the potential biodegradability of poly(ethylene terephthalate)

This paper reviews the state of the art in the field of the hydrolytic degradation of poly(ethylene terephthalate) (PET) under bio-environmental conditions. Most of the papers published so far on this subject have been focused on the hydrolysis of PET at high temperatures. Although some authors claim to enhance the biodegradation properties of this aromatic polyester by copolymerization with readily hydrolysable aliphatic polyesters, no clear and satisfying conclusions can yet be formulated. Poly(ethylene terephthalate-co-lactic acid), poly(ethylene terephthalate-co-ethylene glycol), and poly(ethylene terephthalate-co-ε-caprolactone) block and random copolymers are the modifications mainly investigated for biodegradable applications. The hydrodegradability and biodegradability of PET, PET copolymers and PET blends are detailed in this review. A total of 89 references including 16 patents are cited. © 1999 Society of Chemical Industry     

Miscibility and crystallization behavior of biodegradable blends of two aliphatic polyesters. Poly(3-hydroxybutyrate-co-hydroxyvalerate) and poly(ε-caprolactone)

Biodegradable polymer blends of poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL) blends were prepared with the ratio of PHBV/PCL ranging from 80/20-20/80 by co-dissolving the two polyesters in chloroform and casting the mixture. Differential scanning calorimetry (DSC) and optical microscopy (OM) were used to investigate the miscibility and crystallization of PHBV/PCL blends. Experimental results indicated that PHBV showed no miscibility with PCL for PHBV/PCL blends as evidenced by the existence of unchanged composition independent glass transition temperature and the biphasic melt. Crystallization of PHBV and PCL was studied with DSC and analyzed by the Avrami equation by using two-step crystallization in the PHBV/PCL blends. The crystallization rate of PHBV at 70 °C decreased with the increase of PCL in the blends, while the crystallization mechanism did not change. In the case of the isothermal crystallization of PCL at 42 °C, the crystallization rate increased with the addition of PHBV, and the crystallization mechanism changed, too, indicating that the crystallization of PHBV at 70 °C had an apparent influence on the crystallization of PCL at 42 °C.     

Effect of block copolymer containing ionic liquid moiety on interfacial polarization in PLA/PCL blends

Compared with poly(?‐caprolactone)‐b‐poly(ethylene glycol) block copolymer (BC), a systematic study of the effect of the concentration of the compatibilizer, poly(?‐caprolactone)‐b‐poly(ethylene glycol) BC containing ionic liquid moiety (BCIL), on the interfacial properties of a phase separating blend of poly(l ‐lactic acid)/poly(?‐caprolactone) (PLA/PCL) was performed. BCIL copolymer as a compatibilizer for immiscible PLA/PCL blend can reinforce the interactions between the two polymeric phases by the IL electrostatic interaction at interphase, and the particle size of PCL decreases because of interfacial reinforced‐compatibilization of IL moiety. Ion mobility of IL moiety at interphase and PCL phase for PLA/PCL/BCIL blend can induce interfacial blocking of charge carriers, and IL moiety segregating mainly at the interface can decrease the relaxation rate and increase the dielectric strength of interfacial polarization. Our results provide a methodology to characterize and tune the morphology and blocking of charge carriers with the aim of tailoring the dielectric interfacial properties of blends. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46161.     

Effects of hetero-armed star-shaped PCL-PLA polymers with POSS core on thermal,mechanical, and morphological properties of PLA

In this study, AB type-heteroarm star-shaped poly(ε-caprolactone)-poly(lactic acid) (PCL-PLA) polymers with polyhedral oligomeric silsesquioxane (POSS) core ((PCL)₄-POSS-(PLA)₄, coded as SPLA) were synthesized successfully by using ring opening polymerization and click chemistry techniques together. The synthesized polymers were compounded with commercial PLA at different blending ratios (PLA/SPLA = 100/0, 95/5, 90/10, and 80/20% wt). The effects of heteroarm SPLA polymers having different arm lengths (n = 10, 20, 30, and 50) on morphological, mechanical, and thermal behaviors of PLA were investigated. It is determined that SPLA polymers with four PLA and four PCL arms on its structure enhanced mechanical properties of PLA. The tensile modulus decreased, and lowest modulus values were observed with blends prepared at 80/20 ratio. Elongation at break values increased in all blends, maximum increment was observed with 1,4-phenylene diisocyanate (PDI) containing SPLA20 blends prepared at 90/10 ratio. This result showed that SPLA20 had optimum chain length for chain extension reactions of between PLA chains. Besides, a trade compatibilizer PDI was utilized to enhance the intercompatibility of binary polymer blends.     

Miscibility windows in ternary polymer blends of a polyester,polymethacrylate and poly(styrene‐co‐acrylonitrile)

Miscibility, phase diagrams and morphology of poly(ε‐caprolactone) (PCL)/poly(benzyl methacrylate) (PBzMA)/poly(styrene‐co‐acrylonitrile) (SAN) ternary blends were investigated by differential scanning calorimetry (DSC), optical microscopy (OM), and scanning electron microscopy (SEM). The miscibility window of PCL/PBzMA/SAN ternary blends is influenced by the acrylonitrile (AN) content in the SAN copolymers. At ambient temperature, the ternary polymer blend is completely miscible within a closed‐loop miscibility window. DSC showed only one glass transition temperature (T_g) for PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 ternary blends; furthermore, OM and SEM results showed that PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 were homogeneous for any composition of the ternary phase diagram. Hence, it demonstrated that miscibility exists for PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 ternary blends, but that the ternary system becomes phase‐separated outside these AN contents. Copyright © 2003 Society of Chemical Industry     

Miscibility and crystallization of poly(ethylene oxide) and poly(ε-caprolactone) blends

Blends of poly(ethylene oxide) (PEO) with poly(ε-caprolactone) (PCL), both semicrystalline polymers, were prepared by co-dissolving the two polyesters in chloroform and casting the mixture. Phase contrast microscopy was used to probe the miscibility of PEOB/PCL blends. Experimental results indicated that PEO was immiscible with PCL because the melt was biphasic. Crystallization of PEO/PCL blends was studied by differential scanning calorimetry and analyzed by the Avrami equation. The crystallization rate of PEO decreased with the increase of PCL in the blends while the crystallization mechanism did not change. In the case of the isothermal crystallization of PCL, the crystallization mechanism did not change, and the change in the crystallization rate was not very big, or almost constant with the addition of PEO, compared with the change of the crystallization rate of PEO.     

Synthesis of novel temperature responsive PEG-b-[PCL-g-P(MEO2MA-co-OEGMA)]-b-PEG (tBG) triblock-graft copolymers and preparation of tBG/graphene oxide composite hydrogels via click chemistry

Novel triblock-graft copolymers, poly ethylene glycol-b-[poly(ε-caprolactone)-g-poly(2-(2-methoxyethoxy) ethyl methacrylate-co-oligo (ethylene glycol) methacrylate)]-b-poly ethylene glycol (PEG-b-[PCL-g-P(MEO₂MA-co-OEGMA)]-b-PEG) (tBG), were synthesized via ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). In the synthesis process, temperature responsive P(MEO₂MA-co-OEGMA) chains were grafted onto the PCL block of triblock copolymer PEG-b-PCL-b-PEG to improve its hydrophilicity. This method succeeded in increasing the solubility of PEG-b-PCL-b-PEG in water, and more importantly, endowing PEG-b-PCL-b-PEG with temperature sensitivity. By adjusting the feed ratio of 2-(2-methoxy ethoxy) ethyl methacrylate (MEO₂MA) and oligo (ethylene glycol) methacrylate (OEGMA) monomers, the lower critical solution temperature (LCST) of the tBG can be realized at about 37 °C. Taking advantage of the excellent mechanical property of graphene sheets, alkyne-functionalized graphene oxide (alkyne-GO) was introduced to cross-link tBGs and prepare tBG/GO composite hydrogel through click reaction between tBG-N₃ and alkyne-GO. Different from traditional cross-linkers, alkyne-GO acts as reinforcing filler in the composite hydrogel. Benefiting from superior properties of PCL, PEG, P(MEO₂MA-co-OEGMA) and GO, the as-prepared temperature responsive tBG/GO hydrogel exhibits excellent mechanical strength and toughness, demonstrating future potential applications in tissue engineering and biotechnology fields.     

Miscibility and rheologically determined phase diagram of poly(ethylene oxide)/poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone) blends

Poly(ethylene oxide)/poly(ε-caprolactone) (PEO/PCL) blends can be widely used in lithium rechargeable battery area or as medical materials, while the miscibility and phase diagram of the blends are still unclear. The present work attempted to establish the blends’ phase diagram using rheometry and investigated the miscibility. The results showed that a miscibility window of upper critical solution temperature character of the blends is revealed. Meanwhile, the abnormal rheological behavior of PEO at temperatures higher than 130 °C has little influence on the phase diagram determination. Different rheological properties of PEO/PCL blends from those of PEO revealed the existence of interactions between PEO and PCL molecular chains. Whereas shear-induced mixing or shear-induced phase separation might occur in phase diagram determination of PEO/PCL blends using rheometry.     

The crystallization behavior of poly(ethylene glycol)-poly(ε-caprolactone) diblock copolymers with asymmetric block compositions

Crystallization behavior, structural development and morphology evolution of a series of poly (ethylene glycol)-poly(ε-caprolactone) diblock copolymers (PEG-b-PCL) were investigated via differential scanning calorimetry (DSC), X-ray diffraction (XRD) and atomic force microscopy (AFM). In these copolymers, both blocks were crystallizable and biocompatible. The mutual effects between the PEG and PCL blocks were significant, leading to the obvious block composition dependence of the crystallization behavior and morphology of the PEG-b-PCL copolymers. The relative block length determined which block crystallized first. The temperature-dependent XRD measurements confirmed which block crystallized first from the copolymer during the cooling procedure. Single crystals of the PCL and PEG homopolymers and the PEG-b-PCL copolymers were obtained and observed by AFM. The block (PCL or PEG) crystallized first would determine the crystal morphology. The block crystallized later acted as a solvent, which was advantageous to forming perfect single crystals of the whole block copolymers.     

Melt‐state miscibility of poly(ethylene‐co‐1‐octene) and linear polyethylene

On purpose to examine the effect of branch length on the miscibility of polyolefin blends, miscibility behavior of linear polyethylene/poly(ethylene‐co‐1‐octene) blend was studied and compared to that of linear polyethylene/poly(ethylene‐co‐1‐butene) blend. Miscibility of the blend was determined by observing the morphology quenched from the melt, and by using the relation between interaction parameter and copolymer composition. When the weight composition and molecular weight was the same, poly(ethylene‐co‐1‐octene) was slightly more miscible with linear polyethylene than poly(ethylene‐co‐1‐butene) was. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Compatibilization of polypropylene/ poly(3‐hydroxybutyrate) blends

Blending polypropylene (PP) with biodegradable poly(3‐hydroxybutyrate) (PHB) can be a nice alternative to minimize the disposal problem of PP and the intrinsic brittleness that restricts PHB applications. However, to achieve acceptable engineering properties, the blend needs to be compatibilized because of the immiscibility between PP and PHB. In this work, PP/PHB blends were prepared with different types of copolymers as possible compatibilizers: poly(propylene‐g‐maleic anhydride) (PP–MAH), poly (ethylene‐co‐methyl acrylate) [P(E–MA)], poly(ethylene‐co‐glycidyl methacrylate) [P(E–GMA)], and poly(ethylene‐co‐methyl acrylate‐co‐glycidyl methacrylate) [P(E–MA–GMA)]. The effect of each copolymer on the morphology and mechanical properties of the blends was investigated. The results show that the compatibilizers efficiency decreased in this order: P(E–MA–GMA) > P(E–MA) > P(E–GMA) > PP–MAH; we explained this by taking into consideration the affinity degree of the compatibilizers with the PP matrix, the compatibilizers properties, and their ability to provide physical and/or reactive compatibilization with PHB. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Blending Modification of PHBV/PBS/PEG and its Biodegradation

This study used poly(butylene succinate) and poly(ethylene glycol) to modify poly(3-hydroxybutyrate-co-3-hydroxyvalerate). The results showed that the incorporation of poly(butylene succinate) and poly(ethylene glycol) improved the mechanical properties of blends. The results showed that crystallinity of the poly(ethylene glycol)-containing blends decreased, so do the crystallization temperature and melting temperature of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) component of blends. Poly(butylene succinate)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(ethylene glycol) ratio of 50:20:30 was chosen owing to its good properties. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) component of blends can be degraded completely by Pseudomonas mendocina DS04-T, whereas this strain cannot degrade poly(butylene succinate) and poly(ethylene glycol). Apart from poly(butylene succinate), Fusarium sp. FS1301 can also biodegrade poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(ethylene glycol).     

不同分子量PCL增韧PLA的结构与性能

采用两种不同分子量的聚(ε-己内酯)(PCL)(粘均分子量60 000和3 000)与聚乳酸(PLA)在175℃下共混10 min制备PLA/PCL共混物。通过动态流变、扫描电子显微镜(SEM)和力学性能等研究了PLA/PCL共混物的结构和性能。动态流变显示,在PCL低含量(质量分数小于15%)时,PCL与PLA是相容的,质量分数为15%时PCL与PLA表现出明显的相分离行为。SEM显示,随着PCL含量的增加,PCL相的尺寸变大;低分子量PCL(L-PCL)的相尺寸明显大于高分子量PCL(H-PCL),而且相形态不是规则的球状。随着PCL含量的增加,共混物的拉伸强度下降,而断裂伸长率增加。当H-PCL质量分数为8.3%时,PLA/H-PCL共混物的断裂伸长率为137.32%。当H-PCL质量分数为15%时,其断裂伸长率高达232.76%。在添加相同含量PCL时,PLA/H-PCL共混物的拉伸强度高于PLA/L-PCL;而PCL质量分数8%时,共混物的断裂伸长率相差不多,当PCL质量分数大于8%时,PLA/H-PCL共混物的断裂伸长率明显比PLA/L-PCL共混物的高。     

Phase behavior of poly(ε-caprolactone)/ poly (vinylidene fluoride) blends

The miscibility of blends of poly (ε-caprolactone) (PCL)/poly(vinylidene fluoride) (PVDF) was studied by measuring the cloud point, melting point depression and crystallization kinetics. Lower critical solution temperature (LCST) behavior was observed at PCL-rich compositions, whilst it was not observed at high compositions of PVDF. However it is possible that an LCST could exist below the melting point of PVDF. From analysis of the melting point depression, the Flory interaction parameter x₁₂, was calculated from the Nishi-Wang equation and the value was found to be-1.5. The crystallization rate of PCL increased with increasing amount of PVDF in the blend. The spinodal curve for PCL/PVDF blends was simulated by using the lattice-fluid theory.