Poly(epsilon-caprolactone) (PCL)/chitin and PCL/chitosan blend films with compositional gradients were successfully fabricated by a dissolution/diffusion method; that is, repeatedly pouring the PCL/chitin (or PCL/chitosan) blend solutions, with variable composition, onto polysaccharide layers. The compositional gradient structure in the resulting films was characterized by polarized optic microscopy, ATR-FT-IR and trans-FT-IR microscopic spectroscopy. Enzymatic degradability of the PCL/chitin and PCL/chitosan blend films with compositional gradients in the presence of lysozyme was compared with those of homogeneous films and two-layer films. It was found that the degradation rate of PCL/chitin blend films with a compositional gradient was far lower than that of the neat chitin film, whereas the degradation rate of PCL/chitosan blend films with a compositional gradient was close to that of the neat chitosan film. The suppression of the chitosan crystallization, which accelerates the enzymatic degradation, at the surface of PCL/chitosan films with a compositional gradient was much more severe than that for PCL/chitin films with a compositional gradient. 相似文献
Star-shaped PCL with one to five arms were synthesized by ROP. They have the same crystal structure as linear PCL, indicating that the central cores are located in amorphous regions. The influence of arm length and number on crystallization and melting behavior were studied by DSC, POM, and through the Avrami equation. A model is proposed to analyze the enzymatic degradation process of star-shaped polymers. The multi-arm structure and the limitation of the central cores on the chain mobility of each arm are considered to be the primary factors influencing the characteristic crystallization and enzymatic degradation behavior of star-shaped PCLs. 相似文献
The effects of ionizing radiation (electron beam) on poly(epsilon-caprolactone) (PCL) were studied by analyzing changes in viscosity-average and weight-average molecular weight and radius of gyration, and by performing sol-gel analysis and swelling tests. Samples were irradiated under various conditions: solid and molten PCL in the presence or absence of air. The overall efficiency of crosslinking is higher for samples irradiated in the molten state than in the solid state, and is reduced in the presence of oxygen. Based on three kinds of experiments (molecular weight dependence on the dose in the pre-gelation region, sol-gel analysis, and swelling study), radiation-chemical yields of intermolecular crosslinking and scission were determined and are discussed in terms of the mechanism of radiation-induced reactions in PCL. Properties of the gels formed by high-dose irradiation and mechanical properties of irradiated PCL were analyzed. Irradiation causes an increase in the compression modulus of PCL. This process occurs at the pre-gelation stage and continues in the gel-containing system. We have demonstrated, for the first time, that irradiation of solid PCL is accompanied by a pronounced post-effect, which manifests itself by changes in the average molecular weight. EPR data indicate that this effect, at least in part, is caused by the presence of long-lived radicals trapped in the crystalline regions. Irradiation with the sterilizing dose does not cause a statistically significant change in the biocompatibility of PCL after subsequent storage for 79 d, as determined by preliminary osteoblast vitality tests. 相似文献
The micro construction of poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA) blend films fabricated by solution casting under microwave irradiation was investigated by selective enzymatic degradation and scanning electron microscopy (SEM). The results were totally different from the blends obtained by conventional methods. The blend was more homogeneous and the PCL continuous phase more compact as no spherulites and tiny zone separation were observed from the film surface and no PCL network was observed inside the film, and the degradation of a PCL plank by Pseudomonas lipase was significantly retarded. The distributed PLLA micro spheres were enlarged and amorphous. The thermal behavior of the blend by microwave heating revealed that PCL and PLLA underwent a melting process, which induced the variations of the PCL phase and PLLA spheres. The weight loss caused by degradation of the PCL/PLLA blend obtained by conventional methods (B50c) is greater than that of the blend obtained by microwave methods (B50m), which reflects the change in morphology from a loose PCL network (B50c) to a dense PCL plank (B50m). 相似文献
A series of seven fast-biodegrading aliphatic polyesters were prepared from 1,3-propanediol and aliphatic diacids with increasing number of methylene units (x). Melting points decreased from PPSu to PPAd and then increased again to PPAz and PPSeb. Crystallization rates and thermal stability increased steadily with increasing x. Glass transition temperatures decreased steadily to PPPim and subsequently increased. Enzymatic degradation of the polymers in the presence of a mixture of Rhizopus delemar and Pseudomonas cepacia lipases was much faster than that of poly(epsilon-caprolactone). All the polyester specimens were almost disintegrated within 36 h. PPSub exhibited the fastest enzymatic hydrolysis rates, PPAd and PPSuc the slowest. 相似文献
Microspheres of amphiphilic multi-block poly(ester-ether)s (PEE)s and poly(ester-ether-amide)s (PEEA)s based on poly(epsilon-caprolactone) (PCL) were investigated as delivery systems for proteins. The interest was mainly focused on the effect of their molecular structure and composition on the overall properties of the microspheres, encapsulating bovine serum albumin (BSA) as a model protein. PEEs and PEEAs were prepared using a alpha,omega-dihydroxy-terminated PCL macromer (Mn= 2.0 kDa) as a hydrophobic component. Hydrophilic oxyethylene sequences were generated using poly(ethylene oxide)s (PEO)s of different molecular mass (Mn= 300-600 Da) in the case of PEEs, or 4,7,10-trioxa-1,13-tridecanediamine (Trioxy) and PEO150 (Mn= 150 Da) in the case of PEEAs. The copolymers showed a decrease of Tm and crystallinity values as compared with PCL. Within each class of copolymers, the bulk hydrophilicity increased with increasing the number of oxyethylene groups in the chain repeat unit. PEEAs were more hydrophilic than PEEs with a similar number of oxyethylene groups. Discrete spherical particles were prepared by both PEEs and PEEAs and their BSA encapsulation efficiency related to copolymer properties. Interestingly, the insertion of short hydrophilic segments is enough to significantly affect protein distribution inside microspheres and its release profiles, as compared to PCL microspheres. Different degradation rates and mechanisms were observed for copolymer microspheres, mainly depending on the distribution of oxyethylene units along the chain. The results highlight that a fine control over the structural parameters of amphiphilic PCL-based multi-block copolymers is a key factor for their application in the field of protein delivery. 相似文献
Poly(epsilon-caprolactone) (PCL) composite samples were prepared by polymerization and direct molding. The starting compound was epsilon-caprolactone monomer liquid combined with cellulose and inorganic fillers, using aluminium triflate as a catalyst at 80 degrees C, for 6 or 24 h. Cylinder-shaped PCL composite samples with a homogeneously dispersed cellulose filler were prepared with (-)M(n) = 4 600 ((-)M(w)/(-)M(n) = 2.9). The mechanical properties of the PCL composite samples were studied using compression test methods. The strength of a PCL composite with 50 wt.-% cellulose filler (10.8 MPa) was found to be lower than the PCL sample without fillers (19.2 MPa). The biobased content of the PCL composite with 50 wt.-% cellulose filler (51.67%) measured using accelerated mass spectrometry (AMS) was slightly higher than the carbon ratio of cellulose in the starting powder samples (41.3 mol-%). The biobased content of the polymer composite powders by AMS was found not to be affected by the presence of inorganic fillers, such as talc. The rate and extent of biodegradation, caused by Amano Lipase PS, of the PCL composite sample with cellulose filler (40% degradation in 4 d) was the same as that of a PCL sample without the cellulose filler. 相似文献
A novel preparation method for the core‐shell type biodegradable polyesters or biodegradable materials grafted with biodegradable polyesters was developed by alkaline surface treatment of biodegradable polyester films and subsequent enzymatic polymerization of aliphatic lactones, one example of which is shown in this study, i.e., the preparation of poly(L ‐lactide) (PLLA) film grafted with poly(ε‐caprolactone). It is revealed that only alkaline surface treatment or the combination of alkaline surface treatment and enzyme‐catalyzed grafting, the former and the latter, respectively accelerating and delaying the enzymatic degradation of PLLA, will give PLLA materials having a wide variety of biodegradability. Also, the specificity of the enzyme used for hydrolysis could be used to confirm the grafted chain species.
A novel poly(epsilon-caprolactone)/calcium sulfate system was prepared and characterized in order to enhance calcium sulfate (gypsum) performance as bone graft substitute overcoming its brittleness and fast resorption rate. A poly(epsilon-caprolactone) (PCL) photo-crosslinkable derivative (PCLf) was synthesized by reaction of a low molecular weight PCL diol with methacryloyl chloride and confirmed by FT-IR and 1H NMR analyses. An injectable and easy mouldable mixture of PCLf and calcium sulfate hemi-hydrate (PCLf/CHS) was obtained. Thermal analyses and solvent extraction proved the occurrence of PCLf photo-crosslinking, even in the presence of CHS, in a time suitable for clinical applications. Swelling studies demonstrated that the encapsulation of the inorganic filler increases network hydrophilicity making it more permeable to water. Scanning electron microscopy, performed on crosslinked PCLf/CHS and on the same material after incubation in a PBS solution, showed the feasibility to obtain, in situ, gypsum entrapped into a degradable polymeric network. In vitro cytotoxicity tests, performed according to ISO 10993-5, proved that the developed system was not cytotoxic supporting its potential use in tissue engineering as a new, injectable, photocurable bone graft material. SEM micrograph of calcium sulfate di-hydrate (gypsum) entrapped in the PCL network. 相似文献
In this study, cross-linked materials were prepared using the branched macromonomer with different CL/LA molar ratios, and feasibility studies for tissue engineering were carried out. The thermal and mechanical properties of these materials depended on the CL/LA compositions; however, there was no change in the wettability of each material. The HeLa cells adhesion and growth on the CL-LA7030c were equal to that on the commercially available polystyrene dish. The protein absorption experiment using the FBS proteins revealed that the materials with well-grown cells showed better adhesion of the proteins. [photo: see text] 相似文献
Hydroxyl-group functional polylactones were prepared and converted to acid- terminated polyesters in a reaction with a series of alkenylsuccinic anhydrides containing 8, 12, or 18 carbons in their alkenyl chains. These polyester precursors were then linked into higher molecular weight poly(ester anhydrides) containing alkenyl moieties in their polyester blocks. The hydrolysis behaviour of the poly(ester anhydrides) was found to depend on the thermal properties of the polyester precursors. For poly(ester anhydrides) prepared from low molecular weight prepolymers with thermal transitions below 37 degrees C, the presence of hydrophobic alkenyl chains in the polyester precursors slowed the rate of weight loss. Poly(ester anhydrides) prepared from higher molecular weight prepolymers showed the opposite weight-loss behaviour; i.e., the crystallinity and thermal transitions of the alkenyl chain-containing poly(ester anhydrides) were low, and the weight loss was faster than for poly(ester anhydrides) without the alkenyl chains. The differences in length of the alkenyl chain, as such, had little effect on the hydrolysis behaviour and thermal properties of the poly(ester anhydrides). 相似文献
Poly(epsilon-caprolactone) (PCL) macromers (M(n) = 1.7-3.8 kDa) which contain one Z-protected -NH2 group per chain were synthesized by ring-opening polymerization of epsilon-caprolactone in the presence of Sn(oct)2 using as initiator a diamine prepared by condensation of N-Boc-1,6-hexanediamine and N(alpha)-Boc-N(epsilon)-Z-L-Lysine. The coupling of these macromers with -COCl end-capped poly(oxyethylene) (PEO), M(n) = 1.0 kDa, afforded amphiphilic multiblock poly(ether ester)s (PEEs) which have, along the chain, regularly spaced pendant protected amino groups. Deprotection, accomplished without chain degradation, yielded -NH2 groups available for further reactions. The molecular structure of macromers and PEEs was investigated by 1H NMR and SEC. DSC and WAXS analyses showed that macromers and copolymers were semicrystalline and their T(m) increased with increase in the molecular weight of PCL segments. The inherent viscosity values (0.25-0.30 dL x g(-1)), together with SEC analysis results, indicated moderate polymerization degrees. 相似文献