Structure Changes of Silk Fibroin(SF) by Blending with Poly(ε-caprolactone)(PCL):Characterization of SF and PCL Blended Electrospinning Films

The mechanical properties and water solubility of electrospinning SF films limit their use as biomaterials. In order to develop a tissue engineering biomaterial with both satisfying biological properties and sufficient biomechanical properties,blended films composed of silk fibroin( SF) and poly( ε-caprolactone)( PCL) were fabricated by electrospinning in this study. Scanning electron microscope( SEM), X-ray diffraction( XRD),thermal analysis,Fourier transform-infrared( FT-IR),Raman spectra,mechanical testing,and water solubility were used to characterize the morphological, structural and mechanical properties of the blended electrospinning films. Results showed that the diameter of the blended fiber was distributed between 600 and1000 nm,and the fiber diameter increased as the PCL content increased. There is no obvious phase separation due to the similarity and intermiscibility,as well as the interactions( mainly hydrogen bonds), between the two polymers. Meanwhile, the secondary structures of SF changed from random coils and Silk I to Silk II because of the interactions between SF and PCL. For this reason,the tensile strength and elongation at break of the electrospinning films improved significantly,and the water solubility decreased. In conclusion,the blended electrospinning films fabricated in this study showed satisfying mechanical properties and water insolubilities,and they may be promising biomaterials for applications in tissue engineering for blood vessels,nerve conduits,tendons,ligaments and other tissues.

Effect of Poly(ε-caprolactone-b-tetrahydrofuran)Triblock Copolymer Concentration on Morphological,Thermal and Mechanical Properties of Immiscible PLA/PCL Blends

In this study a low molecular weight triblock copolymer derived fromε-caprolactone and tetrahydrofuran was used as a non-reactive compatibilizer of immiscible PLA/PCL blends.Ternary blends with 0,1.5 wt%,3 wt%and 5 wt% copolymer and about 75 wt%PLA were prepared by single screw extrusion and characterized by scanning electron microscopy(SEM),differential scanning calorimetry(DSC),dynamic mechanical analysis(DMA),tensile and Izod impact testing.SEM micrographs showed that the size of the dispersed PCL domains was practically constant regardless of copolymer concentration.This result can be explained by the low shear rate employed during processing step and a decrease of PCL viscosity by presence of the triblock copolymer.However,when the copolymer concentration increased,strain at break of PLA/PCL blends also increased.PLA/PCL blend with 0 wt% copolymer presented 2%strain at break,whereas PLA/PCL blend with 5 wt%copolymer exhibited 90%.

“Polymer-in-ceramic” based poly(ε-caprolactone)/ceramic composite electrolyte for all-solid-state batteries

Inspired by the concept of "polymer-in-ceramic",a composite poly(ε-caprolactone)(PCL)/ceramic containing LiTFSI is prepared and investigated as a solid electrolyte for all-solid-state batteries.The composite with the optimum concentration of 45 wt% LiTFSI and 75 wt% Li1.5Al0.5Ge1.5(PO4)3(LAGP,NASICON-type structure) exhibits a high ionic conductivity(σi=0.17 mS cm-1) at 30℃,a transference number of 0.30,and is stable up to 5.0 V.The composite electrolyte is a flexible and self-standing membrane.Solid-state LiFePO4//Li batteries with this composite electrolyte demonstrate excellent cycling stability with high discharge capacity of 157 mA h g-1,high capacity retention of 96% and coulombic efficiency of 98.5% after 130 cycles at 30℃ and 0.1 C rate.These electrochemical properties are better than other PCL-based allsolid-lithium batteries,and validate the concept of "polymer-in-ceramic" by avoiding the drawback of lower conductivity in prior "polymer-in-ceramic" electrolyte at high concentration of the ceramic.

PREPARATION AND CHARACTERIZATION OF INCLUSION COMPLEXES OF TWO-ARM LINEAR AND FOUR-ARM STAR-SHAPED POLY(ε-CAPROLACTONE)S WITHα-CYCLODEXTRIN

Both four-ann star-shaped poly（ε-caprolactone） （4sPCL） and two-ann linear PCL （2LPCL） were synthesized and their inclusion complexation with α-cyclodextrin （α-CD） were studied. The inclusion complexes （ICs） formed between the PCL polymers and α-CD were characterized by ^1H-NMR, DSC, TGA, WAXD, and FT-1R, respectively. Both branch ann number and molecular weight of the PCL polymers have apparent effect on the stoichiometry （CL：CD, mol：mol） of these ICs. All these analytical results indicate that the branch arms of the PCL polymers are incorporated into the hydrophobic α-CD cavities and their original crystalline properties are completely suppressed. Moreover, the inclusion complexation between two-ann linear or four-ann star-shaped PCL polymers and α-CD not only enhances the thermal stability of the guest PCL polymers but also improves that of α-CD.

MOLECULAR WEIGHT DEPENDENCE OF THE MELTING BEHAVIOR OF POLY(ε-CAPROLACTONE)

Poly(ε-caprolactone) (PCL) with different molecular weights was synthesized and characterized by a gelpermeation chromatograph equipped with multiple detector. The melting behavior of PCL was also studied. It was found thatthe equilibrium melting points (T_m^0) of PCL samples depend on their molecular weights. Wide angle X-ray diffractionmeasurements (WAXD) and DSC measurements showed that the crystals of the high molecular weight PCLs were moreperfect than those of the low molecular weigh ones. These results demonstrate that the concentration of the end groups ofPCL chains is the main factor that influences the melting behavior. The fusion enthalpy per repeating unit (ΔH_u) wasdetermined to be 11.3 kJ/mol for PCL.

HETEROCYCLIC SCHIFF BASE NEODYMIUM COMPLEX AS CATALYST FOR RING-OPENING POLYMERIZATION OF ε-CAPROLACTONE

An aromatic heterocyclic Schiff base neodymium complex bearing thiazole was synthesized and its activity in the ring-opening polymerization ofε-caprolactone(CL)was examined.The conditions of the CL/Nd molar ratio,monomer concentration,polymerization time and temperature were investigated.Activities of ca.171 kg/Nd·h were obtained under the optimum condition(CL/Nd=1600(molar ratio),[CL]=2.26 mol L^(-1),1 h at 50℃),giving a poly(ε-caprolactone)(PCL)of number-average molecular weight M_n=5.4×10~4 and molecular...

Novel electrospun poly(ε-caprolactone)/type Ⅰ collagen nanofiber conduits for repair of peripheral nerve injury

Recent studies have shown the potential of artificially synthesized conduits in the repair of peripheral nerve injury. Natural biopolymers have received much attention because of their biocompatibility. To investigate the effects of novel electrospun absorbable poly(ε-caprolactone)/type Ⅰ collagen nanofiber conduits(biopolymer nanofiber conduits) on the repair of peripheral nerve injury, we bridged 10-mm-long sciatic nerve defects with electrospun absorbable biopolymer nanofiber conduits, poly(ε-caprolactone) or silicone conduits in Sprague-Dawley rats. Rat neurologica1 function was weekly evaluated using sciatic function index within8 weeks after repair. Eight weeks after repair, sciatic nerve myelin sheaths and axon morphology were observed by osmium tetroxide staining, hematoxylin-eosin staining, and transmission electron microscopy.S-100(Schwann cell marker) and CD4(inflammatory marker) immunoreactivities in sciatic nerve were detected by immunohistochemistry. In rats subjected to repair with electrospun absorbable biopolymer nanofiber conduits, no serious inflammatory reactions were observed in rat hind limbs, the morphology of myelin sheaths in the injured sciatic nerve was close to normal. CD4 immunoreactivity was obviously weaker in rats subjected to repair with electrospun absorbable biopolymer nanofiber conduits than in those subjected to repair with poly(ε-caprolactone) or silicone. Rats subjected to repair with electrospun absorbable biopolymer nanofiber conduits tended to have greater sciatic nerve function recovery than those receiving poly(ε-caprolactone) or silicone repair. These results suggest that electrospun absorbable poly(ε-caprolactone)/type Ⅰ collagen nanofiber conduits have the potential of repairing sciatic nerve defects and exhibit good biocompatibility. All experimental procedures were approved by Institutional Animal Care and Use Committee of Taichung Veteran General Hospital, Taiwan, China(La-1031218) on October 2, 2014.

EPITAXIAL CRYSTALLIZATION OF POLY(ε-CAPROLACTONE)ON HIGHLY ORIENTED ISOTACTIC POLYPROPYLENE

Electron microscope and electron diffraction have been used to study epitaxial crystallization of poly(ε-caprolactone)(PCL).on highly oriented film of isotactic polypropylene(iPP).The results obtained from bright field(BF)electron micrograph and electron diffraction indicate that the PCL can epitaxially grow on iPP substrate and form cross-hatched lamellar texture.The c axes of PCL are ±500 apart from the c axes of iPP. The contact planes of the two kinds of crystals are(010)of iPP and(100) of PCL,respectively.

AN APPROACH TO SYNTHESIZE POLY(ETHYLENE GLYCOL)-b-POLY(ε-CAPROLACTONE) WITH TERMINAL AMINO GROUP via SCHIFF'S BASE AS AN INITIATOR

A new method to synthesize a degradable terminal amino group-containing copolymer,poly(ethylene glycol)-b- poly(ε-caprolactone)(MPEG-PCL-NH_2),was developed in the following three steps:(1)the ring-opening polymerization (ROP)ofε-caprolactone from the Schiff base prepared from benzatdehyde and ethanolamine(Ph-CH=NCH_2CH_2OH)used as an initiator to obtain heterobifunctional poly(ε-caprolactone)with one terminal Schiff base group and one hydroxyl group (HO-PCL-CH_2CH_2N=CH-Ph);(2)the coupling reaction of two ...

TRANSESTERIFICATION OF POLY(ETHYLENE TEREPHTHALATE) WITH POLY(ε-CAPROLACTONE)

Transesterification of poly（ethylene terephthalate） （PET） with poly（ε-caprolactone） （PCL） was investigated bymeans of NMR spectroscopy, extraction experiments, differential scanning calorimetry （DSC） and phase contrast microscopy（PCM）. The;H-NMR results show that transesterification takes place in the melt blends and leads to the formation of thePET-PCL copolyester with a chemical structure similar to ethylene terephthalate-ε-caprolactonc copolycster （TCL）synthesized directly from monomers. However, even in the blend that has been transesterified for 8 h, the random PET-PCLcopolyester, PET-PCL copolyester with long PET or long PCL segments and the unreacted PET and PCL homopolymersmay coexist. Due to the low mobility of PET and PCL chains and the high viscosity of the two macromolecules, thetransesterification proceeds with difficulty. Furthermore, PET is incompatible with PCL, the transesterification can onlyoccur at the interface or in the interfacial region between two phases, and finally the reaction can only reach a localequilibrium. These results indicate that in fact the transesterification in the melt blend between two incompatiblehomopolymers could not lead to the formation of completely random or typical block copolyesters.

Synthesis and Characterization of ABBA Block Copolymer of Glycolide and ε-Caprolactone

A biodegradable ABBA block copolymer was synthesized via the ring-opening co-polymerization of ~ε-caprolactone(CL, B) and glycolide(A) by means of step polymerization in the presence of ethylene glycol as an initiator and stannous octanoate as a catalyst at 110 ℃ for 48 h. The molecular length of the PCL pre-polymer(BB) could be adjusted by controlling the molar ratio of the ethylene glycol initiator to ε-caprolactone monomer. The structure and the composition of the block copolymer were determined by the weight ratio of the monomer glycolide(A) to PCL pre-polymer(BB). The block copolymers were characterized by ~ 1H NMR, GPC, DSC and X-ray. The results confirm the successful synthesis of an ABBA block copolymer.

Melt-Spinning of Nano-Hydroxyapatite/Poly(ε-caprolactone)Composite Fibers for Potential Application in Bone Tissue Engineering

Nano-hydroxyapatite/poly（e-caprolactone） （nHA/PCL） composite materials are among the best candidates for application in bone tissue engineering. As the main technique to fabricate porous scaffolds, electrospilming produce scaffolds with unsatisfactory mechanical strength and limited pore size for cdi infiltration. Micron-sized fiber assembly with higher mechanical strength is qualified to structure hybrid scaffolds. In this study, nHA/PCL monofilament fibers with different mass ratios were fabricated through melt-spinning. Transmission electron microscope （TEM） was used to observe the aggregation between nHA parfides. Other characterizations including scanning electron microscopy （SEM）, attenuated total reflection Fourier transform infrared spectroscopy （ATR.FTIR） and X-ray diffraction （XRD） were done to discuss the morphology, components and crystallization of the nHA/PCL composite fibers, respectively. The influence of nHA/PCL mass ratio on the tensile properties and water contact angle of composite fibers was also studied. The SEM images show the homogeneous dispersion of nano partides in the polymer matrix. Besides, nHA content increases the tensile strength, initial modulus and hydrophillcity of the composite fibers under the premise of spinnability. This kind of fibers is strong enough to fabricate fiber assembly which may have potential application in bone tissue engineering.

Synthesis of Highly Branched Poly(ε-caprolactone) by Self-condensing Atom Transfer Radical Polymerization of Macroinimers

Branched poly（ε-capmlactone） was synthesized by self-condensing atom transfer radical polymerization of macroinimer, α-acryloyoxy-ω-2-bromopropionyloxy poly（ε-caprolactone）, which was prepared by enzyme-catalyzed ring-opening polymerization of ε-caprolactone with 2-hydroxylethyl acrylate as initiator and esterification of the ω-hydroxyl group of the obtained poly（ε-caprolactone） by 2-bromopropionyl bromide.

Study on two kinds of degradation mechanisms for biomaterials poly(ε-caprolactone)

The in vitro and in vivo degradation behaviour of poly (ε-caprolactone) (PCL) has been examined in terms of degree of degradation and morphological change during an inclibation period of up to 300 d. Gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) were employed to character ize their degradation profiles. The observation of the changes in intrinsic viscosity and average molecular weight as well as the crystallinity of PCL leads to the findings that 2 degradation mechanisms of PCL exist. The subcutaneous implant test shows that the rate of degradation in the rabbit body is much higher than in vitro. This illustrated that in vivo, the mechanism of bioerosion is more important than hydrolytic cleavage of ester linkage, especially in the second stage of degradation. Regardless of the initial Mn of specimens, a lin ear relationship between Mn and degradation time has been observed until the Mn decreased to be about 5 ooo D. Above this figure, the main degradation mechanism was hydrolytic cleavage of ester group accompa nied by enzymatic surface erosion, below this point, the bioerosion with weight loss plays a more significant role than hydrolytic reaction in their degradation. Comparison between the morphology of PCL materials af ter and before erosion was made by means of scanning electron microscopy (SEM).

溶剂浇铸-粒子沥滤法制备PBS/PCL组织工程支架

选用聚丁二酸丁二醇酯(PBS)/聚ε-己内酯(PCL)共混材料作为组织工程支架材料基质,氯化钠和葡萄糖颗粒作为致孔剂,在传统的溶剂浇铸-粒子沥滤法的基础上,通过调节PBS/PCL的质量分数制得了不同尺寸且孔径、孔隙率满足组织工程支架要求的PBS/PCL多孔支架.对多孔支架的微结构、孔径、孔形态和亲水性进行了表征,研究了PBS/PCL的质量分数、致孔剂粒径对支架成型及孔隙率的影响.结果表明,PBS/PCL的质量分数对支架成型影响较大,过低或过高的质量分数都会导致支架成型性差,质量分数在6%～10%时支架成型较好.利用质量分数为8%的PBS/PCL溶液可以制备形状复杂的多孔支架.所制支架内部孔洞分布均匀,贯通性好,孔径可由致孔剂的粒径来调控,支架孔隙率为86%～93%.支架亲水性良好,吸水率随孔隙率的增大而上升.

激光熔融静电纺丝法制备PLLA/PCL/nHA复合纤维支架及细胞相容性评价

利用激光熔融静电纺丝技术制备了PLLA/PCL及PLLA/PCL/nHA复合纤维,热压后形成层压复合纤维支架。利用扫描电镜对纤维支架进行了表征,同时对其进行了亲水性的测试,最后通过倒置荧光显微镜和MTT实验对复合纤维支架的细胞相容性进行了评价。研究结果表明,层压复合纤维支架的直径和孔结构具有多样性,nHA能够提高PLLA/PCL层压纤维支架的亲水性,改善支架的细胞相容性,增加细胞的附着能力,提高细胞的存活率。

用辐射方法制备PCL/玻璃纤维布和PCL/碳纤维布复合材料以及它们的生物降解性研究

观察了聚已内酯 (PCL) /玻璃纤维布和PCL/碳纤维布的机械性能的变化 ,通过对辐射交联的方法制备出了可生物降解聚合物涂覆纤维布复合材料。结果表明 ,γ辐射提高了复合材料的机械性能 ,这是由于所涂覆聚合物交联所产生的凝胶所致。在过冷态下通过γ射线照射 2 70kGy的PCL/玻璃纤维布复合材料的弯曲强度是未辐照样品的 1.5倍 ,弯曲模量提高到 1.35倍。通过酶降解试验和土埋法降解实验的研究 ,可以观察到降解导致了样品的失重。在酶降解试验中2 3h后 ,对于未交联材料涂覆的PCL完全降解掉 ,而交联样品中的PCL有 5 4%的失重发生。同样 ,在土埋法降解实验中 ,交联和未交联样品在一定的土埋时间后 ,也产生了样品的失重。未交联样品的失重率大于交联样品 ,这是由于交联样品所含有的交联网络结构阻碍它的降解。

PLGA/PCL复合材料的制备及其性能研究

在聚乳酸-羟基乙酸(PLGA)中加入聚ε-己内酯(PCL)、柠檬酸三丁酯(TBC),通过溶液共混制备了PLGA/PCL共混聚合物,通过静电纺膜及涂膜法制备了不同比表面积的降解膜,并对共混材料力学性能和膜的降解性能进行了研究。结果表明:柠檬酸三丁酯作为增容剂对整个共混聚合物的韧性和强度有明显的影响;当聚乳酸-羟基乙酸和聚ε-己内酯的质量比为80/20、增容剂柠檬酸三丁酯的用量为6%时,所得共混聚合物的断裂伸长率达到130%、冲击强度达到9.55kJ·m-2。相同条件下加入聚ε-己内酯(PCL)的膜的降解性能优于单一的聚乳酸-羟基乙酸(PLGA)膜,静电纺丝膜降解性能优于流延法膜。

超临界CO_2中合成PCL及其共聚物的研究进展

主要介绍了超临界CO2中聚酯类生物医用材料合成的特点,详细介绍了聚己内酯(PCL)的合成及其共聚物的研究状况。并探讨了超临界CO2中聚酯类生物医用材料合成中存在的问题及研究发展方向。