Multifunctional Opioid-Derived Hybrids in Neuropathic Pain: Preclinical Evidence,Ideas and Challenges

When the first- and second-line therapeutics used to treat neuropathic pain (NP) fail to induce efficient analgesia—which is estimated to relate to more than half of the patients—opioid drugs are prescribed. Still, the pathological changes following the nerve tissue injury, i.a. pronociceptive neuropeptide systems activation, oppose the analgesic effects of opiates, enforcing the use of relatively high therapeutic doses in order to obtain satisfying pain relief. In parallel, the repeated use of opioid agonists is associated with burdensome adverse effects due to compensatory mechanisms that arise thereafter. Rational design of hybrid drugs, in which opioid ligands are combined with other pharmacophores that block the antiopioid action of pronociceptive systems, delivers the opportunity to ameliorate the NP-oriented opioid treatment via addressing neuropathological mechanisms shared both by NP and repeated exposition to opioids. Therewith, the new dually acting drugs, tailored for the specificity of NP, can gain in efficacy under nerve injury conditions and have an improved safety profile as compared to selective opioid agonists. The current review presents the latest ideas on opioid-comprising hybrid drugs designed to treat painful neuropathy, with focus on their biological action, as well as limitations and challenges related to this therapeutic approach.     

Angiopoietin-1 variant, COMP-Ang1 attenuates hydrogen peroxide-induced acute lung injury

Reactive oxygen species (ROS) play a crucial role in acute lung injury. Tissue inflammation, the increased vascular permeability, and plasma exudation are cardinal features of acute lung injury. Angiopoietin-1 (Ang1) has potential therapeutic applications in preventing vascular leakage and also has beneficial effects in several inflammatory disorders. Recently developed COMP-Ang1 is more potent than native Ang1 in phosphorylating tyrosine kinase with immunoglobulin and EGF homology domain 2 receptor in endothelial cells. However, there are no data on effects and related molecular mechanisms of COMP- Ang1 on ROS-induced acute lung injury. We used hydrogen peroxide (H2O2)-inhaled mice to evaluate the effect of COMP-Ang1 on pulmonary inflammation, bronchial hyper-responsiveness, and vascular leakage in acute lung injury. The results have revealed that VEGF expression, the levels of IL-4, TNF-alpha, IL-1beta, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in lungs, the levels of hypoxia-inducible factor-1alpha (HIF-1alpha) and NF-kappaB in nuclear protein extracts, phosphorylation of Akt, and vascular permeability were increased after inhalation of H2O2 and that the administration of COMP-Ang1 markedly reduced airway hyper-responsiveness, pulmonary inflammation, plasma extravasation, and the increases of cytokines, adhesion molecules, and VEGF in lungs treated with H2O2. We have also found that the activation of HIF-1a and NF-kB and the increase of phosphoinositide 3-kinase activity in lung tissues after H2O2 inhalation were decreased by the administration of COMP-Ang1. These results suggest that COMP-Ang1 ameliorates ROS-induced acute lung injury through attenuating vascular leakage and modulating inflammatory mediators.     

Effects of Photobiomodulation with Low-level Laser Therapy on Muscle Repair Following a Peripheral Nerve Injury in Wistar Rats

Peripheral nerve injury (PNI) can lead to sensory and/or motor impairment. As a treatment photobiomodulation (PBM) has demonstrated positive effects in terms of the maintenance of muscle activation and trophism. Wistar rats were divided into five groups: control, injury, injury + PBMn (irradiation over injured nerve), injury + PBMm (irradiation over affected muscle) and injury + PBMnm (irradiation over nerve and muscle). The left sciatic nerve was submitted to a crushing injury. Treatment was administered with low-level laser (780 nm, 0.04 cm², 1 W cm⁻², 3.2 J) over the injured nerve and/or the tibialis anterior muscle. The effects of PBM were favorable on muscle morphology and gene expression of calcineurin, myogenin and acetylcholine receptors. PBM led to an acceleration on muscle repair process, and effects were more evident in 2 weeks after PNI. Thus, PBM is indicated for the area over both the injured nerve and the affected muscle.     

NLRP3 Inflammasome Inhibitors in Cardiovascular Diseases

Virtually all types of cardiovascular diseases are associated with pathological activation of the innate immune system. The NACHT, leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome is a protein complex that functions as a platform for rapid induction of the inflammatory response to infection or sterile injury. NLRP3 is an intracellular sensor that is sensitive to danger signals, such as ischemia and extracellular or intracellular alarmins during tissue injury. The NLRP3 inflammasome is regulated by the presence of damage-associated molecular patterns and initiates or amplifies inflammatory response through the production of interleukin-1β (IL-1β) and/or IL-18. NLRP3 activation regulates cell survival through the activity of caspase-1 and gasdermin-D. The development of NLRP3 inflammasome inhibitors has opened the possibility to targeting the deleterious effects of NLRP3. Here, we examine the scientific evidence supporting a role for NLRP3 and the effects of inhibitors in cardiovascular diseases.     

Extraction of Geniposide and Its Application in Anesthesiology

We tried to develop an efficient strategy to isolate geniposide from Gardenia fruit and use it to treat chronic pain. Eight extraction solvents and three extraction methods were respectively compared with each other for the efficiency of geniposide extraction from Gardenia fruit. Extraction with 80% ethanol under reflux was found to give the highest yield of geniposide. Orthogonal experiment was conducted to optimize the reflux conditions and the optimal conditions are a mass(of Gardenia jasminoides Ellis powder) to volume(of solvent, 80% ethanol) ratio of 1:7 and reflux twice for 60 min each. The geniposide obtained by the reflux method was tested on the rats with chronic constriction injury(CCI) for pain relief. The results show that geniposide can enhance pain threshold and relieve pain via repressing tumor necrosis factor-α(TNF-α) expression in either ipsilateral or contralateral dorsal root ganglion(DRG) cells. These results suggest that geniposide treatement may be an effective clinical method to relieve pain based on the mechanism of molecular biology at DRG due to nerve injury.     

Dynamic mechanical properties of random ethylene/1-octene copolymers prepared by rapid cooling

The dynamic mechanical properties of a well-characterized series of homogeneous ethylene/1-octene copolymers with different random hexyl branch contents and prepared using different cooling conditions have been examined using dynamic mechanical analysis (DMA). It was confirmed that the relaxation behavior of copolymers varied continuously with the branch content: the magnitude of the β relaxation increased with branch content while the intensity of the α relaxation decreased with the branch content; both relaxation temperatures decreasing with increasing branch level in the copolymers. Copolymers prepared at different cooling conditions were further examined and strikingly continuous changes were found for the first time. The β relaxation was shown to correlate to the amorphous region, while the α₁ and α₂ relaxations can be clearly differentiated for some samples and are assumed to be associated with the interlamellar slip and intra-crystalline c-shear processes respectively. With increasing cooling rate, the relative intensity of α₁ relaxation to α₂ relaxation was found to decrease while the β relaxation did not change. The most informative data is determined from deconvolution of tan δ spectra. In higher crystallinity polymers the α₁ and α₂ relaxations are closely related in activation energy but have different temperature locations. For lower crystallinity systems, where the α₁ relaxation cannot be observed, the α₂ and β relaxations are closely linked, with activation energies approaching one another. These results show very clearly that, although the observed relaxation data can be separated through deconvolution into three separate peaks, the behaviors are closely linked. Presumably, this a clear reflection of the role of tie molecules in binding phases together and in influencing dynamic mechanical behavior. A clear change of behavior has also been observed in the β relaxation when a distinct amorphous phase exists outside of the spherulites, confirming the general belief that the crystalline phase influences the amorphous phase when it is confined within a spherulite. Again, this behavior is reflecting the role of tie molecules in binding together the nanocomposite structure of a spherulite.     

Electroactive Composite of FeCl3‐Doped P3HT/PLGA with Adjustable Electrical Conductivity for Potential Application in Neural Tissue Engineering

Conducting polymers (CPs) is one of intelligent biomaterials with the specific properties of reversible redox states, which have a significant effects on the cell behaviors and nerve tissue regeneration. However, the effects of CPs with different electrical conductivity on the behaviors of nerve cells are rarely reported. Therefore, a kind of Poly(3‐hexylthiophene) (P3HT) with certain molecular weight is synthesized by Kumada catalyst transfer polymerization (KCTP) method and employed to prepare bioabsorbable and electroactive intelligent composites of Poly(3‐hexylthiophene)/Poly(glycolide‐lactide) (P3HT/PLGA). FeCl₃ doping electroactive membranes with different electrical conductivities are prepared to investigate the cell behaviors. On the substrate with higher electrical conductivity, the proliferation of rat adrenal pheochromocytoma cells (PC12 cells) is significantly promoted and neurite length is increased obviously. In particular, the most significant improvements are the neuron gene expression of Synapsin 1 and microtubule‐associated protein 2 (MAP2) by the composites with high conductivity. These results suggest that P3HT/PLGA with suitable electrical conductivity have a positive role in promoting neural growth and differentiation, which is promising for advancing potential application of nerve repair and regeneration.     

不同结构CoPt纳米棒磁学性能

运用电位置换结合化学还原方法制备了两种不同结构的CoPt纳米棒材料,一种为实心结构(CoPt-a),一种为空心结构(CoPt-b).采用透射电镜(TEM)和能量散射光谱(EDS)研究了其形貌和组成.在5和300K下测试了两种纳米棒的磁学性能.结果显示,CoPt-a和CoPt-b纳米棒在5K时的矫顽力分别为6.5和9.3A·m-1,温度升至300K时,两种结构CoPt纳米棒矫顽力均减小为0A·m-1.场冷曲线(FC)和零场冷曲线(ZFC)结果表明两种结构的CoPt纳米棒均表现出超顺磁性,阻塞温度(TB)分别为10.0和9.0K.两种CoPt纳米棒组成、结构等不同可能是引起其矫顽力、磁化强度和阻塞温度差异的主要原因.     

Enhanced antitumor chemo-immunotherapy by local co-delivery of chemotherapeutics,immune checkpoint blocking antibody and IDO inhibitor using an injectable polypeptide hydrogel

The efficiency of antitumor immunotherapy is usually limited by the immunosuppressive tumor microenvironment (TME). In this study, we developed a chemo-immunotherapy strategy that is able to improve the immunosuppressive TME for enhancing the antitumor efficacy. The chemo-immunotherapy was achieved by the topical co-delivery of a chemotherapeutic drug, Doxorubicin (DOX), an immune checkpoint blocking antibody targeting programmed cell death protein 1 (aPD-1), and an indoleamine-2,3-dioxygenase (IDO) inhibitor, 1-methyl-d -tryptophan (d -1MT) by using a thermosensitive polypeptide hydrogel. It was revealed that the sustained DOX release from the hydrogel caused the immunogenic cell death (ICD) of B16F10 cells in vitro, and the tumor cell lysates subsequently promoted the activation of dendritic cells (DCs). After intratumoral injection into B16F10 melanoma-bearing mice, the DOX/aPD-1/D-1MT co-loaded hydrogel exhibited enhanced tumor inhibition efficacy and prolonged animal survival time, compared to the DOX/aPD-1/D-1MT mixed solution, DOX-loaded hydrogel or DOX/aPD-1 co-loaded hydrogel. The improvement of immunosuppressive TME and enhancement of antitumor immune response after the local chemo-immunotherapy were demonstrated by the augmented activation of DCs and increased infiltration of CD8⁺ and CD4⁺ T cells, as well as enhanced secretion of pro-inflammatory cytokines. Therefore, the hydrogel-based local chemo-immunotherapy system holds great potential for effective antitumor treatment.     

Determination of Metabolites in the Cerebellum of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Exposed Mice by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin elicits many harmful effects in tissues. Metabolomic changes and the associated pathway alterations caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin in the cerebellum, an area thought to be less affected by environmental alterations, remain unknown. Here, metabolomics was performed to identify endogenous metabolites that were associated with 2,3,7,8-tetrachlorodibenzo-p-dioxin in the cerebellum of 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated mice using Fourier transform ion cyclotron resonance mass spectrometry. Distinct peaks were located in two mass ranges, 210 m/z–420 m/z and 450 m/z–570 m/z. In principal component space, the high-dose group was clearly separated from the control group. Six metabolites associated with 2,3,7,8-tetrachlorodibenzo-p-dioxin dose were identified. The metabolite 1-palmitoyl lysophosphatidic acid increased with increasing doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin, indicating activation of the rat sarcoma pathway. Biosynthesis of the unsaturated fatty acid 18-hydroxyoleate was inhibited upon 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure. The decrease in N-arachidonoyl taurine, implies that taurine increased, suggesting inhibition of neuronal signal transmission. A decrease in N-acetyl-aspartyl-glutamate has been associated with injury of the cerebellum through activation of N-methyl-D-aspartic acid receptors. An increase in glycerophosphoinositol suggests damage to blood–brain barrier function, and changes in purine metabolism were observed because inosine increased following 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure. These results suggest that 2,3,7,8-tetrachlorodibenzo-p-dioxin activates the rat sarcoma pathway, alters fatty acid biosynthesis and purine metabolism, inhibits neurotransmitter systems, and is harmful to blood–brain barrier function in the cerebellum.     

Synaptic vesicle proteins under conditions of rest and activation: analysis by 2-D difference gel electrophoresis

Synaptic vesicles are organelles of the nerve terminal that secrete neurotransmitters by fusion with the presynaptic plasma membrane. Vesicle fusion is tightly controlled by depolarization of the plasma membrane and a set of proteins that may undergo post-translational modifications such as phosphorylation. In order to identify proteins that undergo modifications as a result of synaptic activation, we induced massive exocytosis and analysed the synaptic vesicle compartment by benzyldimethyl-n-hexadecylammonium chloride (BAC)/SDS-PAGE and difference gel electrophoresis (DIGE) followed by MALDI-TOF-MS. We identified eight proteins that revealed significant changes in abundance following nerve terminal depolarization. Of these, six were increased and two were decreased in abundance. Three of these proteins were phosphorylated as detected by Western blot analysis. In addition, we identified an unknown synaptic vesicle protein whose abundance increased on synaptic activation. Our results demonstrate that depolarization of the presynaptic compartment induces changes in the abundance of synaptic vesicle proteins and post-translational protein modification.     

Non-isothermal crystalliztion kinetics of poly(phenylene sulfide) with low crosslinking levels

Poly(phenylene sulfide) (PPS) with different crosslinking levels was successfully fabricated by means of high- temperature isothermal treatment (IT). The crosslinking degree of PPS was increased with IT time as revealed by Fourier-transform infrared spectroscopy and dynamic viscosity measurements. Its influence on the non-isothermal crystallization behaviors of PPS was studied by differential scanning calorimeter (DSC). The crystallization peak temperature of PPS with 6 h IT was 15 K higher than that of the one with 2 h IT at 30 K/min cooling rate. The non-isothermal crystallization data were also analyzed based on the Ozawa model. The Ozawa exponent m decreased from 3.5 to 2.2 at 232℃ with the increase of the IT time, suggestive of intensive thermal oxidative crosslinking reducing the crystallite dimension as PPS crystal grew. The reduced cooling crystallization function K(T) was indicative of the larger activation energy of crosslinked PPS chain diffusion into crystal lattice, resulting in a slow crystal growth rate. Additionally, the overall crystallization rate of PPS was also accelerated with the increase of crosslinking degree from the observation of polarized optical micrograph. These results indicated that the chemical crosslinked points and network structures formed during the high-temperature isothermal treatment acted as the effective nucleating sites, which greatly promoted the crystallization process of PPS and changed the type of nucleation and the geometry of crystal growth accordingly.     

Crystallization kinetics of polyethylene/paraffin oil blend sheets formed by thermally induced phase separation with different molecular weights of polyethylene

Polyethylene/paraffin oil blend sheets with different molecular weights of polyethylene were prepared by thermally induced phase separation. Isothermal and non-isothermal crystallization behaviors of blend sheets were investigated by differential scanning calorimetry (DSC). Isothermal DSC curves were analyzed by Avrami equation, whereas non-isothermal DSC curves were analyzed by Jeziorny method and Mo method. Effective activation energy (ΔE) of isothermal and non-isothermal crystallization was calculated by Friedman method. Under isothermal condition, value of n in Avrami equation hovered at 2.1, and lgZ increased with the decrease of crystallization temperature. lgZ and ΔE of blend sheets with a larger molecular weight of polyethylene was smaller than that of blend sheets with smaller molecular weight. Under non-isothermal condition, value of n obtained by Jeziorny method hovered at 2.4, close to n of isothermal condition. lgZ _c increased with the increase of cooling rate and decrease of molecular weight of polyethylene. ΔE of different blend sheets were close to each other. Crystal structures of blend sheets formed under non-isothermal condition were analyzed by X-ray diffraction (XRD) analysis. XRD analysis showed that molecular weight of polyethylene and cooling rate had slight influence on crystal structure and crystallinity of polyethylene/paraffin oil blend sheet.     

Inflammasome Regulation: Therapeutic Potential for Inflammatory Bowel Disease

Inflammasomes are multiprotein complexes formed to regulate the maturation of pro-inflammatory caspases, in response to intracellular or extracellular stimulants. Accumulating studies showed that the inflammasomes are implicated in the pathogenesis of inflammatory bowel disease (IBD), although their activation is not a decisive factor for the development of IBD. Inflammasomes and related cytokines play an important role in the maintenance of gut immune homeostasis, while its overactivation might induce excess immune responses and consequently cause tissue damage in the gut. Emerging studies provide evidence that some genetic abnormalities might induce enhanced NLRP3 inflammasome activation and cause colitis. In these cases, the colonic inflammation can be ameliorated by blocking NLRP3 activation or its downstream cytokine IL-1β. A number of natural products were shown to play a role in preventing colon inflammation in various experimental colitis models. On the other hand, lack of inflammasome function also causes intestinal abnormalities. Thus, an appropriate regulation of inflammasomes might be a promising therapeutic strategy for IBD intervention. This review aims at summarizing the main findings in these studies and provide an outline for further studies that might contribute to our understanding of the role of inflammasomes in the pathogenesis and therapeutic treatment of IBD.     

Spermidine Prevents Ethanol and Lipopolysaccharide-Induced Hepatic Injury in Mice

To date, there is no effective treatment for alcoholic liver disease, despite its prevalence world-wide. Because alcohol consumption is associated with oxidative stress-induced liver injury and pro-inflammatory responses, naturally occurring antioxidants and/or anti-inflammatories may be potential therapeutics. Spermidine is an abundant, ubiquitous polyamine that has been found to display strong antioxidant and anti-inflammatory properties. To further investigate whether spermidine is an effective intervention for alcohol-induced liver disease, we examined its hepatoprotective properties using a two-hit, chronic ethanol and acute lipopolysaccharide (LPS)-induced mouse model of liver injury. We determined that spermidine administration prevented ethanol and LPS-induced increases in liver injury using plasma ALT as a readout. Furthermore, histological analysis of tissue from control and treated animals revealed that the pathology associated with ethanol and LPS treatment was prevented in mice additionally treated with spermidine. As predicted, spermidine also prevented ethanol and LPS-induced oxidative stress by decreasing the levels of both reactive oxygen species (ROS) and lipid peroxidation. We further determined that spermidine treatment prevented the nuclear translocation of nuclear factor κB (NFκB) by blocking the phosphorylation of the inhibitory protein, IκB, thereby preventing expression of pro-inflammatory cytokines. Finally, by measuring expression of known markers of hepatic stellate cell activation and monitoring collagen deposition, we observed that spermidine also prevented alcohol and LPS-induced hepatic fibrosis. Together, our results indicate that spermidine is an antioxidant thereby conferring anti-inflammatory and anti-fibrotic effects associated with alcoholic liver injury.     

Activation of the IL-10 gene promoter following photodynamic therapy of murine keratinocytes

Photodynamic therapy (PDT), an anticancer treatment modality, has recently been shown to be an effective treatment for several autoimmune disease models including antigen-induced arthritis. PDT was found to induce the expression of IL-10 messenger RNA (mRNA) and protein in the skin, and this expression has similar kinetics to the appearance of PDT-induced suppression of skin-mediated immune responses such as the contract hypersensitivity (CHS) response. Some aspects of the UVB-induced suppression of the immune response have been linked to the induction of IL-10. IL-10 has been shown to inhibit the development and activation of Th1 cells, which are critical for many cell-mediated immune responses, including CHS. We have examined the effect of PDT and UVB irradiation on the activity of the IL-10 gene promoter and on IL-10 mRNA stability using the murine keratinocyte line, PAM 212. In vitro PDT induces IL-10 mRNA and protein expression from PAM 212 cells, which can be correlated with an increase in AP-1 DNA binding activity and activation of the IL-10 gene promoter by PDT. Deletion of an AP-1 response element from the IL-10 gene promoter was shown to abrogate the PDT-induced promoter activity indicating that the AP-1 response element is critical to IL-10 induction by PDT. In addition, PDT results in an increase in IL-10 mRNA stability, which may also contribute to the increased IL-10 expression in PAM 212 cells following PDT. In vitro UVB irradiation also results in activation of the IL-10 promoter. However, in contrast to PDT, UVB-induced activation of the IL-10 promoter is not AP-1 dependent and did not increase IL-10 mRNA stability.     

Two Coordination Polymers: Protective Activity On Nerve Injury by Increasing miR-219 and Reducing Inflammatory Response

Two novel transition metal coordination polymers (CPs) of {Cu(tdc)(Hdmea)₂ (1, Hdmea?=?N,N-dimethylethanolamine, tdc?=?2,5-thiopenedicarboxylate) and [Co₃(H₂O)₃(tdc)₃(dioxane)]·2(dioxane) (2) were prepared via the reaction of Co(NO₃)₂·6H₂O or Cu(NO₃)₂·3H₂O and H₂tdc with or without the template reagent Hdmea. The following experiments were carried out to determine the treatment activity for compounds against nerve injury. Firstly, the real time RT-PCR was carried out to determine the miR-219 relative expression in the nerve cells. Then the activation level of the AMPK signaling pathway in the nerve cells was measured with western blot. In addition to this, the ELISA detection was also used in this research, for the inflammatory cytokines’ evaluation. Finally, the inhibition of the compound 1 and compound 2 on the death of the nerve cells was determined with MTT assay.

     

Study of the physical aging of an epoxy/cycloaliphatic amine resin modified with abs

Using differential scanning calorimetry (DSC) we have studied the physical aging of an epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) modified by two different contents of an acrylonitrile-butadiene-styrene (ABS) and cured with 1,3-bisaminomethylcyclohexane (1,3-BAC). Samples fully cured were annealed at temperature of 125°C for periods of time of 72 and 120 h, to determine the process of physical aging. The apparent activation energy for the enthalpy relaxation, Dh*, is determined as the sample is heated at 10°C min^-1 following cooling at various rates through the glass transition region. DSC studies suggested that the presence of thermoplastic inhibits the process of relaxation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Vitamin B Complex Treatment on Macrophages to Schwann Cells Association during Neuroinflammation after Peripheral Nerve Injury

Peripheral nerve injury (PNI) triggers a complex multi-cellular response involving the injured neurons, Schwann cells (SCs), and immune cells, often resulting in poor functional recovery. The aim of this study was to investigate the effects of the treatment with vitamin B (B1, B2, B3, B5, B6, and B12) complex on the interaction between macrophages and SCs during the recovery period after PNI. Transection of the motor branch of the femoral nerve followed by reconstruction by termino-terminal anastomosis was used as an experimental model. Isolated nerves from the sham (S), operated (O), and operated groups treated with the B vitamins (OT group) were used for immunofluorescence analysis. The obtained data indicated that PNI modulates interactions between macrophages and SCs in a time-dependent manner. The treatment with B vitamins complex promoted the M1-to M2-macrophage polarization and accelerated the transition from the non-myelin to myelin-forming SCs, an indicative of SCs maturation. The effect of B vitamins complex on both cell types was accompanied with an increase in macrophage/SC interactions, all of which correlated with the regeneration of the injured nerve. Clearly, the capacity of B vitamins to modulate macrophages-SCs interaction may be promising for the treatment of PNI.     

Nonisothermal crystallization kinetics of poly(ε‐caprolactone) blocks in double crystalline triblock copolymers containing poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and poly(ε‐caprolactone) units

The poly(3‐hydroxbutyrate‐co‐3‐hydroxyvalerate)/poly(ε‐caprolactone) block copolymers (PHCLs) with three different weight ratios of PCL blocks (38%, named PHCL‐38; 53%, named PHCL‐53; and 60%, named PHCL‐60) were synthesized by using PHBV with two hydroxyl end groups to initiate ring‐opening polymerization of ε‐caprolactone. During DSC cooling process, melt crystallization of PHCL‐53 at relatively high cooling rates (9, 12, and 15 °C min^?1) and PHCL‐60 at all the selected cooling rates corresponded to PCL blocks so that PHCL‐53 and PHCL‐60 were used to study the nonisothermal crystallization behaviors of PCL blocks. The kinetics of PCL blocks in PHCL‐53 and PHCL‐60 under nonisothermal crystallization conditions were analyzed by Mo equation. Mo equation was successful in describing the nonisothermal crystallization kinetics of PCL blocks in PHCLs. Crystallization activation energy were estimated using Kissinger's method. The results of kinetic parameters showed that both blocks crystallized more difficultly than corresponding homopolymers. With the increase of PCL content, the crystallization rate of PCL block increased gradually. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010