Synthesis and characterization of hydrolytically degradable copolyester biomaterials based on glycolic acid,sebacic acid and ethylene glycol

Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthesized in different molar ratios (G: 0–100% and S: 100–0%) and their hydrolytic degradation was studied and correlated with their structures. Based on the FTIR spectra of the homopolyesters and copolyesters and the normalized peak intensity of the I₂₉₁₈, I₂₈₄₈ and I₁₀₈₇ for the corresponding wavenumbers, it is concluded that the I₂₉₁₈ and the I₂₈₄₈ are in accordance with the mean number degree of polymerization of ethylene sebacate units and the I₁₀₈₇ is in accordance with the mean number degree of polymerization of glycolate units. Based on the XRD diffractograms, poly(ethylene sebacate) and poly(glycolic acid) belong to the monoclinic and the orthorhombic crystal system, respectively and both have higher crystallinity than the copolyesters. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model and four-parameter model. Three regions can been distinguished for the hydrolytic degradation by decreasing the molar feed ratio of sebacic acid, which are correlated with the changes of crystallinity. Two copolyesters are proposed: first the copolyester with high amount of glycolate units (S10G90) having higher hydrolytic degradation than G100 and second the copolyester with equal amount of glycolate and ethylene sebacate units (S50G50), having lower hydrolytic degradation than G100. These hydrolytically degradable copolyesters are soluble in common organic solvents, opposite to poly(glycolic acid) and could have perspectives for biomedical applications.     

Synthesis and characterization of polyester copolymers based on poly(butylene succinate) and poly(ethylene glycol)

A series of polyester copolymers was synthesized from 1,4-succinic acid with 1,4-butanediol and poly(ethylene glycol) through a two-step process of esterification and polycondensation in this article. The composition and physical properties of copolyesters were investigated via GPC, ¹HNMR, DSC and PLM. The copolymer composition was in good agreement with that expected from the feed composition of the reactants. The melting temperature (T_m), crystallization temperature (T_c), and crystallinity (X_c) of these copolyesters decreased gradually as the content of PEG unit increased. Otherwise, experimental results also showed that the contents of PEG in copolymers had an effect on the molecular weight, distribution, thermal properties, hydrolysis degradation properties, and crystalline morphology of polyester copolymers.     

新型药物载体材料——端羟基聚(丙交酯-co-对二氧环己酮)的合成与表征

聚乳酸(PLA)作为药物载体材料存在因疏水性强而导致的药物释放速率难控以及在循环系统中停留时间短等问题.研究表明,在PLA中引入乙醇酸(GA)可提高材料降解速率,引入聚乙二醇(PEG)则可延长共聚物在循环系统中的停留时间.研究以丙交酯(LA)和对二氧环己酮(PDO)为主要原料,在辛酸亚锡-乙二醇共引发体系的存在下,通过熔融开环聚合制备出了端羟基聚(丙交酯-co-对二氧环己酮)(HO-P(LA-co-PDO)-OH).这种同时具有PLA、GA和EG结构单元的大分子二醇可望成为一种降解速率可控、在循环系统中停留时间可调的新型药物载体材料.采用DSC、~1H NMR、~(13)C NMR和GPC-MALLs等对其结构和热学性能进行了表征.分子量检测结果表明,HO-P(LA-co-PDO)-OH的分子量随原料中PDO/LA摩尔比的减小而增大.     

Synthesis, characterization, and thermal properties of biodegradable polyetheresteramide-based polyurethane

In this paper, a new kind of biodegradable polyetheresteramide-based polyurethane (PEEA-U) copolymers were prepared by melt polymerization from ε-caprolactone, 6-aminocaproic acid, poly(ethylene glycol), and toluene diisocyanate. The obtained polymers were characterized by ¹H NMR, FTIR, DSC, WAXD, and TGA/DTG. The water absorption, hydrolytic degradation, and alkaline degradation behavior of these copolymers were also studied in detail.     

Selectivity engineering in hydroxyalkoxylation of phenol by ethylene carbonate using calcined hydrotalcite

The high consumption of mono-ethylene glycol phenyl ether in various sectors requires clean and green synthesis. Herein, we report an efficient, selective and green route of hydroxylation using calcined hydrotalcite (CHT) for the preparation of mono-ethylene glycol phenyl ether. Various types of solid base catalysts were prepared and well characterized by TGA–DSC, FTIR, XRD, CO₂-TPD, NH₃-TPD, SEM and BET surface area. The catalyst CHT (3:1) possesses very high activity for hydroxyalkoxylation of phenol and ethylene glycol with 96% conversion at 180 °C in 2 h with catalyst loading of 0.03 g cm^?3. The insight of reaction reveals that it is kinetically controlled with second-order reaction and follows power law model. The apparent activation energy for the reaction is 21.3 kcal mol^?1. The catalyst is highly reusable and shows green chemistry prospective and gives excellent results up to four runs.     

Synthesis, characterization and hydrolytic degradation study of polyetheresteramide copolymers based on ε-caprolactone, 6-aminocaproic acid, and poly(ethylene glycol)

In this paper, a new kind of biodegradable aliphatic polyetheresteramide copolymers (PEEA) based on -caprolactone, 6-aminocaproic acid, and poly(ethylene glycol) (PEG) were synthesized by melt polymerization method. The obtained copolymers were characterized by ¹H-NMR. The thermal properties of PEEA copolymers were studied by DSC and TGA/DTA under nitrogen atmosphere. The water absorption and hydrolytic degradation behavior was also studied in detail. With the increase in PEG content or the decrease in caprolactone content, the water absorption of the copolymers increased accordingly. For the hydrolytic degradation behavior, with the increase in PEG content or caprolactone content, the degradation rate increased then.     

Synthesis and characterization of a novel multiblock copolyester containing poly(ethylene succinate) and poly(butylene succinate)

Multiblock copolyester (PBS-b-PES) containing poly(butylene succinate) (PBS) and poly(ethylene succinate) (PES) was successfully synthesized by chain-extension of dihydroxyl terminated PBS (HO-PBS-OH) and PES (HO-PES-OH) using 1,6-hexmethylene diisocyanate (HDI) as a chain extender. The chemical structures, molecular weights, crystallization behaviors, thermal and mechanical properties of the copolyesters were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), wide-angle X-ray diffraction (WAXD), tensile testing and hydrolytic degradation. High-molecular-weight copolyesters with M_w more than 2.0 × 10⁵ g mol⁻¹ were easily obtained through chain-extension. The copolyesters showed a single glass transition temperature (T_g) which increased with PES content. The melting point temperature (T_m) and relative degree of crystallinity (X_c) of the copolyesters decreased first and then increased with PES content. The copolyesters manifested excellent mechanical properties, for example, PBS₅-b-PES₅ had fracture stress of 61.8 MPa and fracture strain of 1173%. The chain-extension reaction provided a very effective way to produce high molecular weight multiblock copolyesters.     

Improved thermoelectric performance of PEDOT:PSS films prepared by polar-solvent vapor annealing method

To improve thermoelectric performance, polar-solvent vapor annealing (PSVA) method was introduced into the preparation of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films. The solvent vapors included dimethyl sulfoxide, ethylene glycol, N,N-dimethylformamide, N-methyl-2-pyrrolidone, and deionized water (H₂O). The PSVA-treated PEDOT:PSS films exhibited significantly enhanced electrical conductivity and the maximum value was up to 496 S cm^?1. Especially, utilizing the PSVA method, H₂O could also remarkably enhance the electrical conductivity of pristine PEDOT:PSS film from 0.2 to 57 S cm^?1. There was no distinct change for the Seebeck coefficient of PSVA-treated films with the significantly enhanced electrical conductivity, thereby a maximum power factor of 9.47 μW m^?1 K^?2 at room temperature was obtained. The effects of PSVA method on thermoelectric performance of PEDOT:PSS films were also investigated systematically by analyzing the changes in morphology, carrier mobility and carrier concentration. The results confirmed that PSVA-treated PEDOT:PSS films could obtain smoother morphologies and realize the simultaneous increase of carrier mobility and carrier concentration, which results in the improvement of the thermoelectric performance.     

Synthesis and characterization of MeO–PEG–PLGA–PEG–OMe copolymers as drug carriers and their degradation behavior in vitro

The objective of this study was to characterize the methylpoly (ethylene glycol)-poly (lacticacid-co-glycolicacid)-poly (ethylene-glycol) (MeO-PEG-PLGA-PEG-OMe, abbreviation as PELGE) copolymers as intravenous injection drug delivery carriers and their degradation behavior in vitro. A series of MeO-PEG-PLGA-PEG-OMe copolymers with various molar ratios of lactic to glycolic acid and various molecular weights and different MeO-PEG contents were synthesized by ring-opening polymerization in the presence of MeO-PEG with molar masses of 2000 and 5000, using stannous octoate as the catalyst. The hydrophilicity of PELGE copolymers, evaluated by contact angle measurements, was found to increase with an increase in their MeO-PEG contents. Methylpoly (ethylene glycol)-poly (lacticacid-co-glycolicacid) (MeO-PEG-PLGA, abbreviation as PELGA) nanoparticles and PELGE nanoparticles were prepared using the emulsion-solvent evaporation technique (o/w) with Pluronic F68 (Poloxamer 188 NF) as emulsifier in the external aqueous phase. The degradation behavior of the nanoparticles was evaluated by the lactate generation with time upon their in vitro incubation in PBS (pH 7.4). The rate of in vitro degradation of the PELGE or PELGA nanoparticles depended on their composition, increasing with an increase in the proportion of MeO-PEG or LA in the copolymer chains. The degradation rate was slower at higher lactide: glycolide ratio. The lower the molecular weight of PELGE; the higher the degradation rate of the nanoparticles.     

Influence of the synthesis methods on the physical and structural characteristics of 0.6TiO2·0.4Al2O3 catalytic supports

A series of 0.6TiO₂·0.4Al₂O₃ catalytic supports has been prepared by both non-hydrolytic route and hydrolytic sol-gel processes. Some synthesis variables, such as the use of ethylene glycol as complexing agent, the generation in situ of the hydrolysis water, or the separated hydrolysis of the respective alkoxides, have been studied for the samples prepared by the hydrolytic sol-gel method. The physical and structural characterisation of the samples has been carried out by different techniques. The textural results show that the surface area and the pore size distribution are influenced by the synthesis method, which also affects the thermal behaviour and the crystallization process of the samples. The distribution of acid sites is also different, depending on the synthesis conditions.     

Synthesis and optimization of P(MMA-BA-MAA)/PEG-based polymer gel electrolytes

A polymer gel electrolyte based on poly(methyl methacrylate-butyl acrylate-methacrylic acid)/polyethylene glycol 400 blend (P(MMA-BA-MAA)/PEG400) was successfully prepared by a simple and efficient procedure. The optimal ionic conductivity was achieved to be 3.12 mS cm^?1 at the temperature of 30 °C when the electrolyte has the composition of 20 wt% P(MMA-BA-MAA)/PEG400 blend, 0.6 M NaI, and 0.06 M I₂ in the solvent γ-butyrolactone (GBL). For tuning the ionic conductivity, various additives were introduced into the polymer gel electrolytes. The measured values of open circuit voltage, short circuit current, and total photovoltaic efficiency indicates that the adding of pyridine (PY) leads to better performance of the final dye-sensitized solar cells (DSSCs), while the adding of Guanidine thiocyante (GuSCN) leads to a worse one. 4-Tert-butylpyridine (TBP) additive takes a more complex effect on the performance of the final DSSCs. For polymer gel electrolyte with 0.5 M pyridine, the final fabricated dye-sensitized solar cell has overall energy conversion efficiency (η) of 3.63 % (0.16 cm² active area) under AM 1.5 at irradiation of 100 mW cm^?2, which reached the level of the liquid electrolyte based device (η = 3.83 % at 0.16 cm² active area). Meanwhile, this gel electrolyte exhibits well long-term stability. The mechanism analysis revealed the dependences of ionic conductivity on the concentration of polymer and NaI and the temperatures.     

Bioresorbability and biocompatibility of aliphatic polyesters

The field of biodegradable polymers is a fast growing area of polymer science because of the interest of such compounds for temporary surgical and pharmacological applications. Aliphatic polyesters constitute the most attractive family among which poly(-hydroxy acids) have been extensively studied. In the past two decades, several excellent reviews have been published to present the general properties of aliphatic polyesters. The aim of this paper is to complete the information collected so far with a special attention to the complex phenomena of biodegradability and biocompatibility. Indeed, the degradation of a polymer leads to the delivery of low molecular weight degradation by-products whose effects on the host body have to be considered. The consequences of the absence of standard terminology are first discussed with respect to words such as biodegradable and bioresorbable. Poly(-hydroxy acids) derived from lactic and glycolic acids are then introduced in order to make easier the critical discussions of the following problems from literature data: biocompatibility, biodegradability, bioresorbability, mechanism of hydrolysis (enzymaticvs simple chemistry), polymodality of molecular weight distributions during degradation and the effects of the presence of oligomers. Finally, some specific comments are made on other aliphatic polyesters such as poly(hydroxy butyrate) and poly(-malic acid).     

Carrier properties of B atomic-layer-doped Si films grown by ECR Ar plasma-enhanced CVD without substrate heating

Abstract

The atomic-layer (AL) doping technique in epitaxy has attracted attention as a low-resistive ultrathin semiconductor film as well as a two-dimensional (2-D) carrier transport system. In this paper, we report carrier properties for B AL-doped Si films with suppressed thermal diffusion. B AL-doped Si films were formed on Si(100) by B AL formation followed by Si cap layer deposition in low-energy Ar plasma-enhanced chemical-vapor deposition without substrate heating. After fabrication of Hall-effect devices with the B AL-doped Si films on unstrained and 0.8%-tensile-strained Si(100)-on-insulator substrates (maximum process temperature 350°C), carrier properties were electrically measured at room temperature. Typically for the initial B amount of 2?×?10¹⁴ cm^?2 and 7?×?10¹⁴ cm^?2, B concentration depth profiles showed a clear decay slope as steep as 1.3 nm/decade. Dominant carrier was a hole and the maximum sheet carrier densities as high as 4?×?10¹³ cm^?2 and 2?×?10¹³ cm^?2 (electrical activity ratio of about 7% and 3.5%) were measured respectively for the unstrained and 0.8%-tensile-strained Si with Hall mobility around 10–13 cm² V^?1 s^?1. Moreover, mobility degradation was not observed even when sheet carrier density was increased by heat treatment at 500–700 °C. There is a possibility that the local carrier (ionized B atom) concentration around the B AL in Si reaches around 10²¹ cm^?3 and 2-D impurity-band formation with strong Coulomb interaction is expected. The behavior of carrier properties for heat treatment at 500–700 °C implies that thermal diffusion causes broadening of the B AL in Si and decrease of local B concentration.     

一种新型可降解共聚物薄膜的制备与性能研究

在氩气环境下,以丁二酸、己二酸、1,4-丁二醇和尿素为原料,通过高温熔融缩聚和扩链反应合成了一种新型可降解丁二酸/己二酸-1,4-丁二醇-尿素聚酯酰脲共聚物,并用压延成膜法制备了共聚物薄膜.采用红外光谱、热重分析、差示量热扫描及万能拉力机对共聚物薄膜的结构与性能进行了表征.结果表明,随着己二酸含量的增加,聚合物薄膜的熔点、结晶度和结晶温度均明显下降.当n（SA）∶n（AA）=1∶1时,共聚物大部分为无定形区域,结晶性能大大降低,水解速率最快,薄膜的降解性能最好.通过调节丁二酸与己二酸添加的物质的量之比,可使聚酯酰脲薄膜在热学性能、力学性能和降解性能之间达到一定程度的可控性.     

Effect of molecular weight on conformational changes of PEO: an infrared spectroscopic analysis

Effect of molecular weight on conformation, helix structure (H structure) and trans planar structure (T structure), of Poly(ethylene oxide) (PEO) has been investigated in detail by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimeter. Two main diffraction peaks at about 2θ = 19° and 23° are discovered, and XRD patterns reveal that the unit cell of crystalline PEO belongs to the monoclinic lattice. The crystallinity decreases from 93.82 to 59.62 %, and the deviation of crystalline temperature of PEO-0.5 is larger than those of the other three under four reheated cycles. From FTIR results, a red shift about 11 cm^?1 is observed in the stretching vibration of –C–O–C– with increasing molecular weight, suggesting the presence of chain–chain interactions to restrict the stretching vibration of -C–O–C– in main chains. Meanwhile, the bending region of –C–C–O– at about 533 cm^?1 sensitive to tension shifts to lower wavenumber, and a new peak at about 510 cm^?1 emerges with increasing molecular weight, which is the indicator of internal tension/strain and orientation. Furthermore, the peak intensity ratios of H structure decrease with increasing molecular weight. In contrast, T structure increases dramatically. Consequently, with respect to molecular weight, the possible interactions, entanglements and tie molecules, of PEO molecular chains to explain the difference between H and T structure is proposed, which is in agreement with the experimental observations quite well.     

聚(丁二酸丁二醇酯癸二酸丁二醇酯)的合成与表征

用熔融缩聚法合成了一系列聚(丁二酸丁二醇酯癸二酸丁二醇酯)的无规共聚物(PBSu-co-PBSe)。通过核磁共振(1H-NMR),差示扫描量热(DSC),热重分析(TGA),X射线衍射(XRD)和酶降解测试等方法表征了材料的结构与性能。XRD测试结果表明,共聚酯的晶体结构随着癸二酸含量的增加发生了改变,并产生了共结晶行为;DSC分析得出,随着PBSe组分在共聚酯中含量的增大,产物的熔点(Tm)由84.8℃降低至46.7℃,然后升高至55.9℃,玻璃化温度(Tg)单调降低至-58.7℃;TGA分析表明,癸二酸的引入提高了聚酯的热稳定性;酶降解测试得出产物具有良好的生物降解性,当PBSe占共聚酯含量的40%时,产物具有最快的降解速率。     

Bamboo-like,oxygen-doped carbon tubes with hierarchical pore structure derived from polymer tubes for supercapacitor applications

In this paper, bamboo-like, O-doped carbon tubes with hierarchical pore structure have been fabricated by the direct pyrolysis of dual cross-linked polydivinylbenzene (PDVB) tubes. The bamboo-like, cross-linked PDVB tubes are firstly synthesized by cationic polymerization of divinylbenzene in cyclohexane using BF₃/Et₂O complex as the initiator. After a secondary cross-linking being imposed by Friedel–Crafts reaction in CCl₄ using anhydrous AlCl₃ as the catalyst, the obtained dual cross-linked, carboxylic acid functionalized PDVB tubes are directly subjected to pyrolysis, yielding bamboo-like, O-doped porous carbons. The resultant O-doped porous carbon tubes (BCTF-900, pyrolyzed at 900 °C) exhibit a trimodal pore structure (micro-, meso-, and macropores) with a relatively high specific surface area of 595 m² g^?1 and a low total pore volume of 0.37 cm³ g^?1. Such bamboo-like carbon tubes display good volumetric capacitive performance (254 F cm^?3 at 0.5 A g^?1), moderate volumetric energy density (12.9 Wh L^?1 at 428 W L^?1), and excellent cycling stability (the capacitance retention has remained at 96.9% after 10000 cycles at 2 A g^?1). Due to their unique bamboo-like architecture and trimodal pore structure, the PDVB-derived carbon tubes should have widely application prospect.     

Degradation and compatibility behaviors of poly(glycolic acid) grafted chitosan

The films of poly(glycolic acid) grafted chitosan were prepared without using a catalyst to improve the degradable property of chitosan. The films were characterized by Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy (XPS). The degradation of the poly(glycolic acid) grafted chitosan films were investigated in the lysozyme solution. In vitro degradation tests revealed that the degradation rate of poly(glycolic acid) grafted chitosan films increased dramatically compared with chitosan. The degradation rate of poly(glycolic acid) grafted chitosan films gradually increased with the increasing of the molar ratio of glycolic acid to chitosan. Additionally, the poly(glycolic acid) grafted chitosan films have good biocompatibility, as demonstrated by in vitro cytotoxicity of the extraction fluids. The biocompatible and biodegradable poly(glycolic acid) grafted chitosan would be an effective material with controllable degradation rate to meet the diverse needs in biomedical fields.     

Injectable Conductive Hydrogels with Tunable Degradability as Novel Implantable Bioelectrodes

Bioelectrodes have been developed to efficiently mediate electrical signals of biological systems as stimulators and recording devices. Recently, conductive hydrogels have garnered great attention as emerging materials for bioelectrode applications because they can permit intimate/conformal contact with living tissues and tissue-like softness. However, administration and control over the in vivo lifetime of bioelectrodes remain challenges. Here, injectable conductive hydrogels (ICHs) with tunable degradability as implantable bioelectrodes are developed. ICHs were constructed via thiol-ene reactions using poly(ethylene glycol)-tetrathiol and thiol-functionalized reduced graphene oxide with either hydrolyzable poly(ethylene glycol)-diacrylate or stable poly(ethylene glycol)-dimaleimide, the resultant hydrogels of which are degradable and nondegradable, respectively. The ICH electrodes had conductivities of 21–22 mS cm⁻¹ and Young's moduli of 15–17 kPa, and showed excellent cell and tissue compatibility. The hydrolyzable conductive hydrogels disappeared 3 days after in vivo administration, while the stable conductive hydrogels maintained their shapes for up to 7 days. Our proof-of-concept studies reveal that electromyography signals with significantly improved sensitivity from rats could be obtained from the injected ICH electrodes compared to skin electrodes and injected nonconductive hydrogel electrodes. The ICHs, offering convenience in use, controllable degradation and excellent signal transmission, will have great potential to develop various bioelectronics devices.     

Application of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate in polymer heterojunction solar cells

In this study, p-type semiconducting polymer of acid, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), has been employed as a hole-transporting electrode to fabricate organic polymer heterojunction photovoltaic cells. The results showed that the resultant poly(3-hexylthiophene): C₆₀ derivatives [6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM)/PEDOT:PSS can significantly expand the light absorption range which was expected to enhance the sunlight excitation. The influences of annealing conditions and barrier layer on the photoelectric performances were investigated in detail, giving an optimized synthesis conditions: annealed temperature was at 120 °C for 90 min, the thickness of PEDOT:PSS film was approximately 3–4 μm, and the ratio of PCBM and P3HT was 1:2. The blended heterojunction consisting of PCBM and P3HT was used as charge carrier-transferring medium to replace I₃ ^?/I^? redox electrolyte, showing a short-circuit current of 4.30 mA cm^?2, an open-circuit voltage of 0.83 V, and a light-to-electric energy conversion efficiency of 2.37 % under a simulated solar light irradiation of 100 mW cm^?2. In addition, a solid-state polymer heterojunction photovoltaic cells with a short-circuit current of 3.59 mA cm^?2, an open-circuit voltage of 0.80 V, and a light-to-electric energy conversion efficiency of 1.9 % was successfully fabricated by simplifying the process.